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Deng J, Gong F, Li Y, Tan X, Liu X, Yang S, Chen X, Wang H, Liu Q, Shen C, Zhou L, Chen Y. Structural and functional insights into the 2'-O-methyltransferase of SARS-CoV-2. Virol Sin 2024; 39:619-631. [PMID: 38969340 DOI: 10.1016/j.virs.2024.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 07/02/2024] [Indexed: 07/07/2024] Open
Abstract
A unique feature of coronaviruses is their utilization of self-encoded nonstructural protein 16 (nsp16), 2'-O-methyltransferase (2'-O-MTase), to cap their RNAs through ribose 2'-O-methylation modification. This process is crucial for maintaining viral genome stability, facilitating efficient translation, and enabling immune escape. Despite considerable advances in the ultrastructure of SARS-CoV-2 nsp16/nsp10, insights into its molecular mechanism have so far been limited. In this study, we systematically characterized the 2'-O-MTase activity of nsp16 in SARS-CoV-2, focusing on its dependence on nsp10 stimulation. We observed cross-reactivity between nsp16 and nsp10 in various coronaviruses due to a conserved interaction interface. However, a single residue substitution (K58T) in SARS-CoV-2 nsp10 restricted the functional activation of MERS-CoV nsp16. Furthermore, the cofactor nsp10 effectively enhanced the binding of nsp16 to the substrate RNA and the methyl donor S-adenosyl-l-methionine (SAM). Mechanistically, His-80, Lys-93, and Gly-94 of nsp10 interacted with Asp-102, Ser-105, and Asp-106 of nsp16, respectively, thereby effectively stabilizing the SAM binding pocket. Lys-43 of nsp10 interacted with Lys-38 and Gly-39 of nsp16 to dynamically regulate the RNA binding pocket and facilitate precise binding of RNA to the nsp16/nsp10 complex. By assessing the conformational epitopes of nsp16/nsp10 complex, we further determined the critical residues involved in 2'-O-MTase activity. Additionally, we utilized an in vitro biochemical platform to screen potential inhibitors targeting 2'-O-MTase activity. Overall, our results significantly enhance the understanding of viral 2'-O methylation process and mechanism, providing valuable targets for antiviral drug development.
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Affiliation(s)
- Jikai Deng
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Feiyu Gong
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Yingjian Li
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Xue Tan
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Xuemei Liu
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Shimin Yang
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Xianying Chen
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Hongyun Wang
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Qianyun Liu
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Chao Shen
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China
| | - Li Zhou
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China; Animal Bio-Safety Level III Laboratory/Institute for Vaccine Research, Wuhan University School of Medicine, Wuhan, 430071, China
| | - Yu Chen
- State Key Laboratory of Virology, RNA Institute, College of Life Sciences and Frontier Science Center for Immunology and Metabolism, Wuhan University, Wuhan, 430072, China; Animal Bio-Safety Level III Laboratory/Institute for Vaccine Research, Wuhan University School of Medicine, Wuhan, 430071, China.
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2
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Mack AH, Menzies G, Southgate A, Jones DD, Connor TR. A Proofreading Mutation with an Allosteric Effect Allows a Cluster of SARS-CoV-2 Viruses to Rapidly Evolve. Mol Biol Evol 2023; 40:msad209. [PMID: 37738143 PMCID: PMC10553922 DOI: 10.1093/molbev/msad209] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 09/06/2023] [Accepted: 09/19/2023] [Indexed: 09/24/2023] Open
Abstract
The RNA-dependent RNA polymerase of the severe acute respiratory syndrome coronavirus 2 virus is error prone, with errors being corrected by the exonuclease (NSP14) proofreading mechanism. However, the mutagenesis and subsequent evolutionary trajectory of the virus is mediated by the delicate interplay of replicase fidelity and environmental pressures. Here, we have shown that a single, distal mutation (F60S) in NSP14 can have a profound impact upon proofreading with an increased accumulation of mutations and elevated evolutionary rate being observed. Understanding the implications of these changes is crucial, as these underlying mutational processes may have important implications for understanding the population-wide evolution of the virus. This study underscores the urgent need for continued research into the replicative mechanisms of this virus to combat its continued impact on global health, through the re-emergence of immuno-evasive variants.
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Affiliation(s)
- Andrew H Mack
- Molecular Biosciences Division, School of Biosciences, Cardiff University, UK
| | - Georgina Menzies
- Molecular Biosciences Division, School of Biosciences, Cardiff University, UK
| | - Alex Southgate
- Molecular Biosciences Division, School of Biosciences, Cardiff University, UK
| | - D Dafydd Jones
- Molecular Biosciences Division, School of Biosciences, Cardiff University, UK
| | - Thomas R Connor
- Molecular Biosciences Division, School of Biosciences, Cardiff University, UK
- Pathogen Genomics Unit, Public Health Wales NHS Trust, Cardiff, UK
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3
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Yuyukina SK, Zharkov DO. Mechanisms of Coronavirus Genome Stability As Potential Targets for Antiviral Drugs. HERALD OF THE RUSSIAN ACADEMY OF SCIENCES 2022; 92:470-478. [PMID: 36091852 PMCID: PMC9447942 DOI: 10.1134/s1019331622040256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 02/25/2022] [Accepted: 03/14/2022] [Indexed: 06/15/2023]
Abstract
The COVID-19 pandemic has made it necessary to create antivirals active against the SARS-CoV-2 coronavirus. One of the widely used strategies to fight off viral infections is the use of modified nucleoside analogues that inhibit viral replication by incorporating DNA or RNA into the growing chain, thus stopping its synthesis. The difficulty of using this method of treatment in the case of SARS-CoV-2 is that coronaviruses have an effective mechanism for maintaining genome stability. Its central element is the nsp14 protein, which is characterized by exonuclease activity, due to which incorrectly included and noncanonical nucleotides are removed from the 3' end of the growing RNA chain. Inhibitors of nsp14 exonuclease and nucleoside analogues resistant to its action are viewed as potential targets for anticoronavirus therapy.
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Affiliation(s)
- S. K. Yuyukina
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
| | - D. O. Zharkov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
- Novosibirsk State University, Novosibirsk, Russia
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4
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Proteolytic Processing of the Coronavirus Replicase Nonstructural Protein 14 Exonuclease Is Not Required for Virus Replication but Alters RNA Synthesis and Viral Fitness. J Virol 2022; 96:e0084122. [PMID: 35924922 PMCID: PMC9400476 DOI: 10.1128/jvi.00841-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Coronaviruses (CoVs) initiate replication by translation of the positive-sense RNA genome into the replicase polyproteins connecting 16 nonstructural protein domains (nsp1-16), which are subsequently processed by viral proteases to yield mature nsp. For the betacoronavirus murine hepatitis virus (MHV), total inhibition of translation or proteolytic processing of replicase polyproteins results in rapid cessation of RNA synthesis. The nsp5-3CLpro (Mpro) processes nsps7-16, which assemble into functional replication-transcription complexes (RTCs), including the enzymatic nsp12-RdRp and nsp14-exoribonuclease (ExoN)/N7-methyltransferase. The nsp14-ExoN activity mediates RNA-dependent RNA proofreading, high-fidelity RNA synthesis, and replication. To date, the solved partial RTC structures, biochemistry, and models use or assume completely processed, mature nsp. Here, we demonstrate that in MHV, engineered deletion of the cleavage sites between nsp13-14 and nsp14-15 allowed recovery of replication-competent virus. Compared to wild-type (WT) MHV, the nsp13-14 and nsp14-15 cleavage deletion mutants demonstrated delayed replication kinetics, impaired genome production, altered abundance and patterns of recombination, and impaired competitive fitness. Further, the nsp13-14 and nsp14-15 mutant viruses demonstrated mutation frequencies that were significantly higher than with the WT. The results demonstrate that cleavage of nsp13-14 or nsp14-15 is not required for MHV viability and that functions of the RTC/nsp14-ExoN are impaired when assembled with noncleaved intermediates. These data will inform future genetic, structural, biochemical, and modeling studies of coronavirus RTCs and nsp 13, 14, and 15 and may reveal new approaches for inhibition or attenuation of CoV infection. IMPORTANCE Coronavirus replication requires proteolytic maturation of the nonstructural replicase proteins to form the replication-transcription complex. Coronavirus replication-transcription complex models assume mature subunits; however, mechanisms of coronavirus maturation and replicase complex formation have yet to be defined. Here, we show that for the coronavirus murine hepatitis virus, cleavage between the nonstructural replicase proteins nsp13-14 and nsp14-15 is not required for replication but does alter RNA synthesis and recombination. These results shed new light on the requirements for coronavirus maturation and replication-transcription complex assembly, and they may reveal novel therapeutic targets and strategies for attenuation.
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5
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Uppal T, Tuffo K, Khaiboullina S, Reganti S, Pandori M, Verma SC. Screening of SARS-CoV-2 antivirals through a cell-based RNA-dependent RNA polymerase (RdRp) reporter assay. CELL INSIGHT 2022; 1:100046. [PMID: 37192863 PMCID: PMC9239919 DOI: 10.1016/j.cellin.2022.100046] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 11/29/2022]
Abstract
COVID-19 (Coronavirus Disease 2019) caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome CoronaVirus-2) continues to pose an international public health threat and thus far, has resulted in greater than 6.4 million deaths worldwide. Vaccines are critical tools to limit COVID-19 spread, but antiviral drug development is an ongoing global priority due to fast-spreading COVID-19 variants that may elude vaccine efficacies. The RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 is an essential enzyme of viral replication and transcription machinery complex. Therefore, the RdRp is an attractive target for the development of effective anti-COVID-19 therapeutics. In this study, we developed a cell-based assay to determine the enzymatic activity of SARS-CoV-2 RdRp through a luciferase reporter system. The SARS-CoV-2 RdRp reporter assay was validated using known inhibitors of RdRp polymerase, remdesivir along with other anti-virals including ribavirin, penciclovir, rhoifolin, 5′CT, and dasabuvir. Dasabuvir (an FDA-approved drug) exhibited promising RdRp inhibitory activity among these inhibitors. Anti-viral activity of dasabuvir was also tested on the replication of SARS-CoV-2 through infection of Vero E6 cells. Dasabuvir inhibited the replication of SARS-CoV-2, USA-WA1/2020 as well as B.1.617.2 (delta variant) in Vero E6 cells in a dose-dependent manner with EC50 values 9.47 μM and 10.48 μM, for USA-WA1/2020 and B.1.617.2 variants, respectively. Our results suggest that dasabuvir can be further evaluated as a therapeutic drug for COVID-19. Importantly, this system provides a robust, target-specific, and high-throughput screening compatible (z- and z’-factors of >0.5) platforms that will be a valuable tool for screening SARS-CoV-2 RdRp inhibitors.
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6
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Wright LR, Wright DL, Weller SK. Viral Nucleases from Herpesviruses and Coronavirus in Recombination and Proofreading: Potential Targets for Antiviral Drug Discovery. Viruses 2022; 14:v14071557. [PMID: 35891537 PMCID: PMC9324378 DOI: 10.3390/v14071557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 07/08/2022] [Accepted: 07/11/2022] [Indexed: 02/05/2023] Open
Abstract
In this review, we explore recombination in two very different virus families that have become major threats to human health. The Herpesviridae are a large family of pathogenic double-stranded DNA viruses involved in a range of diseases affecting both people and animals. Coronaviridae are positive-strand RNA viruses (CoVs) that have also become major threats to global health and economic stability, especially in the last two decades. Despite many differences, such as the make-up of their genetic material (DNA vs. RNA) and overall mechanisms of genome replication, both human herpes viruses (HHVs) and CoVs have evolved to rely heavily on recombination for viral genome replication, adaptation to new hosts and evasion of host immune regulation. In this review, we will focus on the roles of three viral exonucleases: two HHV exonucleases (alkaline nuclease and PolExo) and one CoV exonuclease (ExoN). We will review the roles of these three nucleases in their respective life cycles and discuss the state of drug discovery efforts against these targets.
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Affiliation(s)
- Lee R. Wright
- Department of Pharmaceutical Sciences, University of Connecticut School of Pharmacy, Storrs, CT 06269, USA; (L.R.W.); (D.L.W.)
| | - Dennis L. Wright
- Department of Pharmaceutical Sciences, University of Connecticut School of Pharmacy, Storrs, CT 06269, USA; (L.R.W.); (D.L.W.)
| | - Sandra K. Weller
- Department of Molecular Biology and Biophysics, University of Connecticut School of Medicine, 263 Farmington Ave., Farmington, CT 06030, USA
- Correspondence: ; Tel.: +1-(860)-679-2310; Fax: +1-(860)-679-1239
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7
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Wang X, Tao C, Morozova I, Kalachikov S, Li X, Kumar S, Russo JJ, Ju J. Identifying Structural Features of Nucleotide Analogues to Overcome SARS-CoV-2 Exonuclease Activity. Viruses 2022; 14:1413. [PMID: 35891393 PMCID: PMC9324094 DOI: 10.3390/v14071413] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 01/27/2023] Open
Abstract
With the recent global spread of new SARS-CoV-2 variants, there remains an urgent need to develop effective and variant-resistant oral drugs. Recently, we reported in vitro results validating the use of combination drugs targeting both the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) and proofreading exonuclease (ExoN) as potential COVID-19 therapeutics. For the nucleotide analogues to be efficient SARS-CoV-2 inhibitors, two properties are required: efficient incorporation by RdRp and substantial resistance to excision by ExoN. Here, we have selected and evaluated nucleotide analogues with a variety of structural features for resistance to ExoN removal when they are attached at the 3' RNA terminus. We found that dideoxynucleotides and other nucleotides lacking both 2'- and 3'-OH groups were most resistant to ExoN excision, whereas those possessing both 2'- and 3'-OH groups were efficiently removed. We also found that the 3'-OH group in the nucleotide analogues was more critical than the 2'-OH for excision by ExoN. Since the functionally important sequences in Nsp14/10 are highly conserved among all SARS-CoV-2 variants, these identified structural features of nucleotide analogues offer invaluable insights for designing effective RdRp inhibitors that can be simultaneously efficiently incorporated by the RdRp and substantially resist ExoN excision. Such newly developed RdRp terminators would be good candidates to evaluate their ability to inhibit SARS-CoV-2 in cell culture and animal models, perhaps combined with additional exonuclease inhibitors to increase their overall effectiveness.
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Affiliation(s)
- Xuanting Wang
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Chuanjuan Tao
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Irina Morozova
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Sergey Kalachikov
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Xiaoxu Li
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Shiv Kumar
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - James J. Russo
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
| | - Jingyue Ju
- Center for Genome Technology and Biomolecular Engineering, Columbia University, New York, NY 10027, USA; (X.W.); (C.T.); (I.M.); (S.K.); (X.L.); (S.K.); (J.J.R.)
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University, New York, NY 10032, USA
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8
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Chen Y, Liu Q, Zhou L, Zhou Y, Yan H, Lan K. Emerging SARS-CoV-2 variants: Why, how, and what's next? CELL INSIGHT 2022; 1:100029. [PMID: 37193049 PMCID: PMC9057926 DOI: 10.1016/j.cellin.2022.100029] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 04/27/2022] [Accepted: 04/27/2022] [Indexed: 01/18/2023]
Abstract
The emergence of the SARS-CoV-2 Omicron variant poses a striking threat to human society. More than 30 mutations in the Spike protein of the Omicron variant severely compromised the protective immunity elicited by either vaccination or prior infection. The persistent viral evolutionary trajectory generates Omicron-associated lineages, such as BA.1 and BA.2. Moreover, the virus recombination upon Delta and Omicron co-infections has been reported lately, although the impact remains to be assessed. This minireview summarizes the characteristics, evolution and mutation control, and immune evasion mechanisms of SARS-CoV-2 variants, which will be helpful for the in-depth understanding of the SARS-CoV-2 variants and policy-making related to COVID-19 pandemic control.
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Affiliation(s)
- Yu Chen
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Qianyun Liu
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Li Zhou
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - You Zhou
- Systems Immunity University Research Institute and Division of Infection and Immunity, Cardiff University, Cardiff, UK
| | - Huan Yan
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Ke Lan
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life Sciences, Wuhan University, Wuhan, 430072, China
- Department of Infectious Diseases, Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan, 430071, China
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9
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Martínez-González B, Soria ME, Vázquez-Sirvent L, Ferrer-Orta C, Lobo-Vega R, Mínguez P, de la Fuente L, Llorens C, Soriano B, Ramos R, Cortón M, López-Rodríguez R, García-Crespo C, Gallego I, de Ávila AI, Gómez J, Enjuanes L, Salar-Vidal L, Esteban J, Fernandez-Roblas R, Gadea I, Ayuso C, Ruíz-Hornillos J, Verdaguer N, Domingo E, Perales C. SARS-CoV-2 Point Mutation and Deletion Spectra and Their Association with Different Disease Outcomes. Microbiol Spectr 2022; 10:e0022122. [PMID: 35348367 PMCID: PMC9045161 DOI: 10.1128/spectrum.00221-22] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 02/25/2022] [Indexed: 12/15/2022] Open
Abstract
Mutant spectra of RNA viruses are important to understand viral pathogenesis and response to selective pressures. There is a need to characterize the complexity of mutant spectra in coronaviruses sampled from infected patients. In particular, the possible relationship between SARS-CoV-2 mutant spectrum complexity and disease associations has not been established. In the present study, we report an ultradeep sequencing (UDS) analysis of the mutant spectrum of amplicons from the nsp12 (polymerase)- and spike (S)-coding regions of 30 nasopharyngeal isolates (diagnostic samples) of SARS-CoV-2 of the first COVID-19 pandemic wave (Madrid, Spain, April 2020) classified according to the severity of ensuing COVID-19. Low-frequency mutations and deletions, counted relative to the consensus sequence of the corresponding isolate, were overwhelmingly abundant. We show that the average number of different point mutations, mutations per haplotype, and several diversity indices was significantly higher in SARS-CoV-2 isolated from patients who developed mild disease than in those associated with moderate or severe disease (exitus). No such bias was observed with RNA deletions. Location of amino acid substitutions in the three-dimensional structures of nsp12 (polymerase) and S suggest significant structural or functional effects. Thus, patients who develop mild symptoms may be a richer source of genetic variants of SARS-CoV-2 than patients with moderate or severe COVID-19. IMPORTANCE The study shows that mutant spectra of SARS-CoV-2 from diagnostic samples differ in point mutation abundance and complexity and that significantly larger values were observed in virus from patients who developed mild COVID-19 symptoms. Mutant spectrum complexity is not a uniform trait among isolates. The nature and location of low-frequency amino acid substitutions present in mutant spectra anticipate great potential for phenotypic diversification of SARS-CoV-2.
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Affiliation(s)
- Brenda Martínez-González
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - María Eugenia Soria
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Lucía Vázquez-Sirvent
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Cristina Ferrer-Orta
- Structural Biology Department, Institut de Biología Molecular de Barcelona CSIC, Barcelona, Spain
| | - Rebeca Lobo-Vega
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Pablo Mínguez
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Bioinformatics Unit, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Lorena de la Fuente
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
- Bioinformatics Unit, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Carlos Llorens
- Biotechvana, “Scientific Park”, Universidad de Valencia, Valencia, Spain
| | - Beatriz Soriano
- Biotechvana, “Scientific Park”, Universidad de Valencia, Valencia, Spain
| | - Ricardo Ramos
- Unidad de Genómica, “Scientific Park of Madrid”, Campus de Cantoblanco, Madrid, Spain
| | - Marta Cortón
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Rosario López-Rodríguez
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Carlos García-Crespo
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Isabel Gallego
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain
| | - Ana Isabel de Ávila
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Jordi Gómez
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain
- Instituto de Parasitología y Biomedicina ‘López-Neyra’ (CSIC), Parque Tecnológico Ciencias de la Salud, Granada, Spain
| | - Luis Enjuanes
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Llanos Salar-Vidal
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Jaime Esteban
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Ricardo Fernandez-Roblas
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Ignacio Gadea
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
| | - Carmen Ayuso
- Department of Genetics & Genomics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centre for Biomedical Network Research on Rare Diseases (CIBERER), Instituto de Salud Carlos III, Madrid, Spain
| | - Javier Ruíz-Hornillos
- Allergy Unit, Hospital Infanta Elena, Valdemoro, Madrid, Spain
- Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Faculty of Medicine, Universidad Francisco de Vitoria, Madrid, Spain
| | - Nuria Verdaguer
- Structural Biology Department, Institut de Biología Molecular de Barcelona CSIC, Barcelona, Spain
| | - Esteban Domingo
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain
| | - Celia Perales
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Madrid, Spain
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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10
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Zaffagni M, Harris JM, Patop IL, Pamudurti NR, Nguyen S, Kadener S. SARS-CoV-2 Nsp14 mediates the effects of viral infection on the host cell transcriptome. eLife 2022; 11:71945. [PMID: 35293857 PMCID: PMC9054133 DOI: 10.7554/elife.71945] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 03/10/2022] [Indexed: 11/15/2022] Open
Abstract
Viral infection involves complex set of events orchestrated by multiple viral proteins. To identify functions of SARS-CoV-2 proteins, we performed transcriptomic analyses of cells expressing individual viral proteins. Expression of Nsp14, a protein involved in viral RNA replication, provoked a dramatic remodeling of the transcriptome that strongly resembled that observed following SARS-CoV-2 infection. Moreover, Nsp14 expression altered the splicing of more than 1000 genes and resulted in a dramatic increase in the number of circRNAs, which are linked to innate immunity. These effects were independent of the Nsp14 exonuclease activity and required the N7-guanine-methyltransferase domain of the protein. Activation of the NFkB pathway and increased expression of CXCL8 occurred early upon Nsp14 expression. We identified IMPDH2, which catalyzes the rate-limiting step of guanine nucleotides biosynthesis, as a key mediator of these effects. Nsp14 expression caused an increase in GTP cellular levels, and the effect of Nsp14 was strongly decreased in the presence of IMPDH2 inhibitors. Together, our data demonstrate an unknown role for Nsp14 with implications for therapy. Viruses are parasites, relying on the cells they infect to make more of themselves. In doing so they change how an infected cell turns its genes on and off, forcing it to build new virus particles and turning off the immune surveillance that would allow the body to intervene. This is how SARS-CoV-2, the virus that causes COVID, survives with a genome that carries instructions to make just 29 proteins. One of these proteins, known as Nsp14, is involved in both virus reproduction and immune escape. Previous work has shown that it interacts with IMPDH2, the cellular enzyme that controls the production of the building blocks of the genetic code. The impact of this interaction is not clear. To find out more, Zaffagni et al. introduced 26 of the SARS-CoV-2 proteins into human cells one at a time. Nsp14 had the most dramatic effect, dialing around 4,000 genes up or down and changing how the cell interprets over 1,000 genes. Despite being just one protein, it mimicked the genetic changes seen during real SARS-CoV-2 infection. Blocking IMPDH2 partially reversed the effects, which suggests that the interaction of Nsp14 with the enzyme might be responsible for the effects of SARS-CoV-2 on the genes of the cell. Understanding how viral proteins affect cells can explain what happens during infection. This could lead to the discovery of new treatments designed to counteract the effects of the virus. Further work could investigate whether interfering with Nsp14 helps cells to overcome infection.
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Affiliation(s)
- Michela Zaffagni
- Department of Biology, Brandeis University, Waltham, United States
| | - Jenna M Harris
- Department of Biology, Brandeis University, Waltham, United States
| | - Ines L Patop
- Department of Biology, Brandeis University, Waltham, United States
| | | | - Sinead Nguyen
- Department of Biology, Brandeis University, Waltham, United States
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11
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Zaffagni M, Harris JM, Patop IL, Pamudurti NR, Nguyen S, Kadener S. SARS-CoV-2 Nsp14 mediates the effects of viral infection on the host cell transcriptome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2022:2021.07.02.450964. [PMID: 35194610 PMCID: PMC8863146 DOI: 10.1101/2021.07.02.450964] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Viral infection involves complex set of events orchestrated by multiple viral proteins. To identify functions of SARS-CoV-2 proteins, we performed transcriptomic analyses of cells expressing individual viral proteins. Expression of Nsp14, a protein involved in viral RNA replication, provoked a dramatic remodeling of the transcriptome that strongly resembled that observed following SARS-CoV-2 infection. Moreover, Nsp14 expression altered the splicing of more than 1,000 genes and resulted in a dramatic increase in the number of circRNAs, which are linked to innate immunity. These effects were independent of the Nsp14 exonuclease activity and required the N7-guanine-methyltransferase domain of the protein. Activation of the NFkB pathway and increased expression of CXCL8 occurred early upon Nsp14 expression. We identified IMPDH2, which catalyzes the rate-limiting step of guanine nucleotides biosynthesis, as a key mediator of these effects. Nsp14 expression caused an increase in GTP cellular levels, and the effect of Nsp14 was strongly decreased in presence of IMPDH2 inhibitors. Together, our data demonstrate an unknown role for Nsp14 with implications for therapy.
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12
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Domingo E, García-Crespo C, Lobo-Vega R, Perales C. Mutation Rates, Mutation Frequencies, and Proofreading-Repair Activities in RNA Virus Genetics. Viruses 2021; 13:1882. [PMID: 34578463 PMCID: PMC8473064 DOI: 10.3390/v13091882] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/06/2021] [Accepted: 09/17/2021] [Indexed: 12/29/2022] Open
Abstract
The error rate displayed during template copying to produce viral RNA progeny is a biologically relevant parameter of the replication complexes of viruses. It has consequences for virus-host interactions, and it represents the first step in the diversification of viruses in nature. Measurements during infections and with purified viral polymerases indicate that mutation rates for RNA viruses are in the range of 10-3 to 10-6 copying errors per nucleotide incorporated into the nascent RNA product. Although viruses are thought to exploit high error rates for adaptation to changing environments, some of them possess misincorporation correcting activities. One of them is a proofreading-repair 3' to 5' exonuclease present in coronaviruses that may decrease the error rate during replication. Here we review experimental evidence and models of information maintenance that explain why elevated mutation rates have been preserved during the evolution of RNA (and some DNA) viruses. The models also offer an interpretation of why error correction mechanisms have evolved to maintain the stability of genetic information carried out by large viral RNA genomes such as the coronaviruses.
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Affiliation(s)
- Esteban Domingo
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain;
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Carlos García-Crespo
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain;
| | - Rebeca Lobo-Vega
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Av. Reyes Católicos 2, 28040 Madrid, Spain;
| | - Celia Perales
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Consejo Superior de Investigaciones Científicas (CSIC), Campus de Cantoblanco, 28049 Madrid, Spain;
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, 28029 Madrid, Spain
- Department of Clinical Microbiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Av. Reyes Católicos 2, 28040 Madrid, Spain;
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13
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Bhavaniramya S, Ramar V, Vishnupriya S, Palaniappan R, Sibiya A, Baskaralingam V. Comprehensive analysis of SARS-COV-2 drug targets and pharmacological aspects in treating the COVID-19. Curr Mol Pharmacol 2021; 15:393-417. [PMID: 34382513 DOI: 10.2174/1874467214666210811120635] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/27/2021] [Accepted: 02/22/2021] [Indexed: 11/22/2022]
Abstract
Corona viruses are enveloped, single-stranded RNA (Ribonucleic acid) viruses and they cause pandemic diseases having a devastating effect on both human healthcare and the global economy. To date, six corona viruses have been identified as pathogenic organisms which are significantly responsible for the infection and also cause severe respiratory diseases. Among them, the novel SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) caused a major outbreak of corona virus diseases 2019 (COVID-19). Coronaviridae family members can affects both humans and animals. In human, corona viruses cause severe acute respiratory syndrome with mild to severe outcomes. Several structural and genomics have been investigated, and the genome encodes about 28 proteins most of them with unknown function though it shares remarkable sequence identity with other proteins. There is no potent and licensed vaccine against SARS-CoV-2 and several trials are underway to investigate the possible therapeutic agents against viral infection. However, some of the antiviral drugs that have been investigated against SARS-CoV-2 are under clinical trials. In the current review we comparatively emphasize the emergence and pathogenicity of the SARS-CoV-2 and their infection and discuss the various putative drug targets of both viral and host receptors for developing effective vaccines and therapeutic combinations to overcome the viral outbreak.
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Affiliation(s)
- Sundaresan Bhavaniramya
- Biomaterials and Biotechnology in Animal Health Lab, Department of Animal Health and Management, Alagappa University, Karaikudi 630004, Tamil Nadu. India
| | - Vanajothi Ramar
- Department of Biomedical Science, Bharathidasan University, Tiruchirappalli, Tamil Nadu, 620024. India
| | - Selvaraju Vishnupriya
- College of Food and Dairy Technology, Tamil Nadu Veterinary and Animal Sciences University, Chennai 600052. India
| | - Ramasamy Palaniappan
- Research and Development Wing, Sree Balaji Medical College and Hospital, Bharath Institute of Higher Education (BIHER), Chennai-600044, Tamilnadu. India
| | - Ashokkumar Sibiya
- Biomaterials and Biotechnology in Animal Health Lab, Department of Animal Health and Management, Alagappa University, Karaikudi 630004, Tamil Nadu. India
| | - Vaseeharan Baskaralingam
- Biomaterials and Biotechnology in Animal Health Lab, Department of Animal Health and Management, Alagappa University, Karaikudi 630004, Tamil Nadu. India
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14
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Canal B, McClure AW, Curran JF, Wu M, Ulferts R, Weissmann F, Zeng J, Bertolin AP, Milligan JC, Basu S, Drury LS, Deegan TD, Fujisawa R, Roberts EL, Basier C, Labib K, Beale R, Howell M, Diffley JF. Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of nsp14/nsp10 exoribonuclease. Biochem J 2021; 478:2445-2464. [PMID: 34198326 PMCID: PMC8286829 DOI: 10.1042/bcj20210198] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/05/2021] [Accepted: 05/10/2021] [Indexed: 01/18/2023]
Abstract
SARS-CoV-2 is a coronavirus that emerged in 2019 and rapidly spread across the world causing a deadly pandemic with tremendous social and economic costs. Healthcare systems worldwide are under great pressure, and there is an urgent need for effective antiviral treatments. The only currently approved antiviral treatment for COVID-19 is remdesivir, an inhibitor of viral genome replication. SARS-CoV-2 proliferation relies on the enzymatic activities of the non-structural proteins (nsp), which makes them interesting targets for the development of new antiviral treatments. With the aim to identify novel SARS-CoV-2 antivirals, we have purified the exoribonuclease/methyltransferase (nsp14) and its cofactor (nsp10) and developed biochemical assays compatible with high-throughput approaches to screen for exoribonuclease inhibitors. We have screened a library of over 5000 commercial compounds and identified patulin and aurintricarboxylic acid (ATA) as inhibitors of nsp14 exoribonuclease in vitro. We found that patulin and ATA inhibit replication of SARS-CoV-2 in a VERO E6 cell-culture model. These two new antiviral compounds will be valuable tools for further coronavirus research as well as potentially contributing to new therapeutic opportunities for COVID-19.
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Affiliation(s)
- Berta Canal
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Allison W. McClure
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Joseph F. Curran
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Mary Wu
- High Throughput Screening, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Rachel Ulferts
- Cell Biology of Infection Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Florian Weissmann
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Jingkun Zeng
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Agustina P. Bertolin
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Jennifer C. Milligan
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Souradeep Basu
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Lucy S. Drury
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Tom D. Deegan
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Ryo Fujisawa
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Emma L. Roberts
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Clovis Basier
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Karim Labib
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Rupert Beale
- Cell Biology of Infection Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Michael Howell
- High Throughput Screening, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - John F.X. Diffley
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
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15
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The Baltimore Classification of Viruses 50 Years Later: How Does It Stand in the Light of Virus Evolution? Microbiol Mol Biol Rev 2021; 85:e0005321. [PMID: 34259570 DOI: 10.1128/mmbr.00053-21] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Fifty years ago, David Baltimore published a brief conceptual paper delineating the classification of viruses by the routes of genome expression. The six "Baltimore classes" of viruses, with a subsequently added 7th class, became the conceptual framework for the development of virology during the next five decades. During this time, it became clear that the Baltimore classes, with relatively minor additions, indeed cover the diversity of virus genome expression schemes that also define the replication cycles. Here, we examine the status of the Baltimore classes 50 years after their advent and explore their links with the global ecology and biology of the respective viruses. We discuss an extension of the Baltimore scheme and why many logically admissible expression-replication schemes do not appear to be realized in nature. Recent phylogenomic analyses allow tracing the complex connections between the Baltimore classes and the monophyletic realms of viruses. The five classes of RNA viruses and reverse-transcribing viruses share an origin, whereas both the single-stranded DNA viruses and double-stranded DNA (dsDNA) viruses evolved on multiple independent occasions. Most of the Baltimore classes of viruses probably emerged during the earliest era of life evolution, at the stage of the primordial pool of diverse replicators, and before the advent of modern-like cells with large dsDNA genomes. The Baltimore classes remain an integral part of the conceptual foundation of biology, providing the essential structure for the logical space of information transfer processes, which is nontrivially connected with the routes of evolution of viruses and other replicators.
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16
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Devkota K, Schapira M, Perveen S, Khalili Yazdi A, Li F, Chau I, Ghiabi P, Hajian T, Loppnau P, Bolotokova A, Satchell KJF, Wang K, Li D, Liu J, Smil D, Luo M, Jin J, Fish PV, Brown PJ, Vedadi M. Probing the SAM Binding Site of SARS-CoV-2 Nsp14 In Vitro Using SAM Competitive Inhibitors Guides Developing Selective Bisubstrate Inhibitors. SLAS DISCOVERY 2021; 26:1200-1211. [PMID: 34192965 PMCID: PMC8458670 DOI: 10.1177/24725552211026261] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The COVID-19 pandemic has clearly brought the healthcare systems worldwide to a breaking point, along with devastating socioeconomic consequences. The SARS-CoV-2 virus, which causes the disease, uses RNA capping to evade the human immune system. Nonstructural protein (nsp) 14 is one of the 16 nsps in SARS-CoV-2 and catalyzes the methylation of the viral RNA at N7-guanosine in the cap formation process. To discover small-molecule inhibitors of nsp14 methyltransferase (MTase) activity, we developed and employed a radiometric MTase assay to screen a library of 161 in-house synthesized S-adenosylmethionine (SAM) competitive MTase inhibitors and SAM analogs. Among six identified screening hits, SS148 inhibited nsp14 MTase activity with an IC50 value of 70 ± 6 nM and was selective against 20 human protein lysine MTases, indicating significant differences in SAM binding sites. Interestingly, DS0464 with an IC50 value of 1.1 ± 0.2 µM showed a bisubstrate competitive inhibitor mechanism of action. DS0464 was also selective against 28 out of 33 RNA, DNA, and protein MTases. The structure-activity relationship provided by these compounds should guide the optimization of selective bisubstrate nsp14 inhibitors and may provide a path toward a novel class of antivirals against COVID-19, and possibly other coronaviruses.
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Affiliation(s)
- Kanchan Devkota
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Matthieu Schapira
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada.,Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
| | - Sumera Perveen
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | | | - Fengling Li
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Irene Chau
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Pegah Ghiabi
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Taraneh Hajian
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Peter Loppnau
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Albina Bolotokova
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Northwestern University, Center for Structural Genomics of Infectious Diseases, Feinberg School of Medicine, Chicago, IL, USA
| | - Ke Wang
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.,Program of Pharmacology, Weill Cornell Medical College of Cornell University, New York, NY, USA
| | - Deyao Li
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.,Program of Pharmacology, Weill Cornell Medical College of Cornell University, New York, NY, USA
| | - Jing Liu
- Departments of Pharmacological Sciences and Oncological Sciences, Mount Sinai Center for Therapeutics Discovery, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - David Smil
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Minkui Luo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.,Program of Pharmacology, Weill Cornell Medical College of Cornell University, New York, NY, USA
| | - Jian Jin
- Departments of Pharmacological Sciences and Oncological Sciences, Mount Sinai Center for Therapeutics Discovery, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Paul V Fish
- Alzheimer's Research UK UCL Drug Discovery Institute, University College London, London, UK
| | - Peter J Brown
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada
| | - Masoud Vedadi
- Structural Genomics Consortium, University of Toronto, Toronto, ON, Canada.,Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
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17
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Lin S, Chen H, Chen Z, Yang F, Ye F, Zheng Y, Yang J, Lin X, Sun H, Wang L, Wen A, Dong H, Xiao Q, Deng D, Cao Y, Lu G. Crystal structure of SARS-CoV-2 nsp10 bound to nsp14-ExoN domain reveals an exoribonuclease with both structural and functional integrity. Nucleic Acids Res 2021; 49:5382-5392. [PMID: 33956156 PMCID: PMC8136770 DOI: 10.1093/nar/gkab320] [Citation(s) in RCA: 78] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/08/2021] [Accepted: 04/21/2021] [Indexed: 02/05/2023] Open
Abstract
The emergence of SARS-CoV-2 infection has posed unprecedented threat to global public health. The virus-encoded non-structural protein 14 (nsp14) is a bi-functional enzyme consisting of an exoribonuclease (ExoN) domain and a methyltransferase (MTase) domain and plays a pivotal role in viral replication. Here, we report the structure of SARS-CoV-2 nsp14-ExoN domain bound to its co-factor nsp10 and show that, compared to the SARS-CoV nsp10/nsp14-full-length complex, SARS-CoV-2 nsp14-ExoN retains an integral exoribonuclease fold and preserves an active configuration in the catalytic center. Analysis of the nsp10/nsp14-ExoN interface reveals a footprint in nsp10 extensively overlapping with that observed in the nsp10/nsp16 structure. A marked difference in the co-factor when engaging nsp14 and nsp16 lies in helix-α1′, which is further experimentally ascertained to be involved in nsp14-binding but not in nsp16-engagement. Finally, we also show that nsp10/nsp14-ExoN is enzymatically active despite the absence of nsp14-MTase domain. These data demonstrate that SARS-CoV-2 nsp10/nsp14-ExoN functions as an exoribonuclease with both structural and functional integrity.
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Affiliation(s)
- Sheng Lin
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Hua Chen
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Zimin Chen
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Fanli Yang
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Fei Ye
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Yue Zheng
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Jing Yang
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Xi Lin
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Honglu Sun
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Lingling Wang
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Ao Wen
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China
| | - Haohao Dong
- Laboratory of Aging Research and Cancer Drug Target, State Key Laboratory of Biotherapy and Cancer Center, National Clinical Research Center for Geriatrics, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Qingjie Xiao
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan 610041, China.,National Facility for Protein Science in Shanghai, Shanghai Advanced Research Institute (Zhangjiang Laboratory), Chinese Academy of Sciences, Shanghai 201210, China
| | - Dong Deng
- Department of Obstetrics, Key Laboratory of Birth Defects and Related Disease of Women and Children of MOE, State Key Laboratory of Biotherapy, West China Second Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Yu Cao
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China.,Disaster Medicine Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China
| | - Guangwen Lu
- West China Hospital Emergency Department (WCHED), State Key Laboratory of Biotherapy and Cancer Center, West China Hospital and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu, Sichuan 610041, China.,WestVac Biopharma Co., Ltd, Chengdu, Sichuan 610000, China
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18
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Bhatt PR, Scaiola A, Loughran G, Leibundgut M, Kratzel A, Meurs R, Dreos R, O'Connor KM, McMillan A, Bode JW, Thiel V, Gatfield D, Atkins JF, Ban N. Structural basis of ribosomal frameshifting during translation of the SARS-CoV-2 RNA genome. Science 2021; 372:1306-1313. [PMID: 34029205 PMCID: PMC8168617 DOI: 10.1126/science.abf3546] [Citation(s) in RCA: 150] [Impact Index Per Article: 50.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 02/24/2021] [Accepted: 05/07/2021] [Indexed: 12/22/2022]
Abstract
Programmed ribosomal frameshifting is a key event during translation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA genome that allows synthesis of the viral RNA-dependent RNA polymerase and downstream proteins. Here, we present the cryo-electron microscopy structure of a translating mammalian ribosome primed for frameshifting on the viral RNA. The viral RNA adopts a pseudoknot structure that lodges at the entry to the ribosomal messenger RNA (mRNA) channel to generate tension in the mRNA and promote frameshifting, whereas the nascent viral polyprotein forms distinct interactions with the ribosomal tunnel. Biochemical experiments validate the structural observations and reveal mechanistic and regulatory features that influence frameshifting efficiency. Finally, we compare compounds previously shown to reduce frameshifting with respect to their ability to inhibit SARS-CoV-2 replication, establishing coronavirus frameshifting as a target for antiviral intervention.
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Affiliation(s)
- Pramod R Bhatt
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland.,School of Biochemistry and Cell Biology, University College Cork, Cork T12 XF62, Ireland.,School of Microbiology, University College Cork, Cork T12 K8AF, Ireland
| | - Alain Scaiola
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork T12 XF62, Ireland
| | - Marc Leibundgut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Annika Kratzel
- Institute of Virology and Immunology, University of Bern, Bern, Switzerland.,Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Romane Meurs
- Center for Integrative Genomics, Génopode, University of Lausanne, 1015 Lausanne, Switzerland
| | - René Dreos
- Center for Integrative Genomics, Génopode, University of Lausanne, 1015 Lausanne, Switzerland
| | - Kate M O'Connor
- School of Biochemistry and Cell Biology, University College Cork, Cork T12 XF62, Ireland
| | - Angus McMillan
- Laboratorium für Organische Chemie, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - Jeffrey W Bode
- Laboratorium für Organische Chemie, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
| | - Volker Thiel
- Institute of Virology and Immunology, University of Bern, Bern, Switzerland.,Department of Infectious Diseases and Pathobiology, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - David Gatfield
- Center for Integrative Genomics, Génopode, University of Lausanne, 1015 Lausanne, Switzerland
| | - John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork T12 XF62, Ireland. .,School of Microbiology, University College Cork, Cork T12 K8AF, Ireland.,MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Nenad Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland.
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19
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Fang P, Hong Y, Xia S, Zhang J, Ren J, Zhou Y, Fang L, Xiao S. Porcine deltacoronavirus nsp10 antagonizes interferon-β production independently of its zinc finger domains. Virology 2021; 559:46-56. [PMID: 33813212 DOI: 10.1016/j.virol.2021.03.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 11/18/2022]
Abstract
Porcine deltacoronavirus (PDCoV) is a novel swine enteropathogenic coronavirus that causes serious vomiting and diarrhea in piglets. Previous work demonstrated that PDCoV infection inhibits type I interferon (IFN) production. Here, we found that ectopic expression of PDCoV nsp10 significantly inhibited Sendai virus (SeV)-induced IFN-β production by impairing the phosphorylation and nuclear translocation of two transcription factors, IRF3 and NF-κB p65 subunit. Interestingly, experiments with truncated mutants and site-directed mutagenesis revealed that PDCoV nsp10 mutants with missing or destroyed zinc fingers (ZFs) domains also impeded SeV-induced IFN-β production, suggesting that nsp10 does not require its ZF domains to antagonize IFN-β production. Further work found that co-expression of nsp10 with nsp14 or nsp16, two replicative enzymes, significantly enhanced the inhibitory effects of nsp10 on IFN-β. Taken together, our results demonstrate that PDCoV nsp10 antagonizes IFN via a ZF-independent mechanism and has a synergistic effect with nsp14 and nsp16 on inhibiting IFN-β production.
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Affiliation(s)
- Puxian Fang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Yingying Hong
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Sijin Xia
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Jiansong Zhang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Jie Ren
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Yanrong Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Liurong Fang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
| | - Shaobo Xiao
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China; Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, 430070, China
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20
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James AM, Seal SE, Bailey AM, Foster GD. Viral inosine triphosphatase: A mysterious enzyme with typical activity, but an atypical function. MOLECULAR PLANT PATHOLOGY 2021; 22:382-389. [PMID: 33471956 PMCID: PMC7865087 DOI: 10.1111/mpp.13021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/22/2020] [Accepted: 10/23/2020] [Indexed: 05/03/2023]
Abstract
Plant viruses typically have highly condensed genomes, yet the plant-pathogenic viruses Cassava brown streak virus, Ugandan cassava brown streak virus, and Euphorbia ringspot virus are unusual in encoding an enzyme not yet found in any other virus, the "house-cleaning" enzyme inosine triphosphatase. Inosine triphosphatases (ITPases) are highly conserved enzymes that occur in all kingdoms of life and perform a house-cleaning function by hydrolysing the noncanonical nucleotide inosine triphosphate to inosine monophosphate. The ITPases encoded by cassava brown streak virus and Ugandan cassava brown streak virus have been characterized biochemically and are shown to have typical ITPase activity. However, their biological role in virus infection has yet to be elucidated. Here we review what is known of viral-encoded ITPases and speculate on potential roles in infection with the aim of generating a greater understanding of cassava brown streak viruses, a group of the world's most devastating viruses.
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Affiliation(s)
- Amy M. James
- School of Biological SciencesLife Sciences BuildingUniversity of BristolBristolUK
| | - Susan E. Seal
- Natural Resources Institute, Chatham MaritimeGillinghamUK
| | - Andy M. Bailey
- School of Biological SciencesLife Sciences BuildingUniversity of BristolBristolUK
| | - Gary D. Foster
- School of Biological SciencesLife Sciences BuildingUniversity of BristolBristolUK
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21
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Devkota K, Schapira M, Perveen S, Yazdi AK, Li F, Chau I, Ghiabi P, Hajian T, Loppnau P, Bolotokova A, Satchell KJF, Wang K, Li D, Liu J, Smil D, Luo M, Jin J, Fish PV, Brown PJ, Vedadi M. Probing the SAM Binding Site of SARS-CoV-2 nsp14 in vitro Using SAM Competitive Inhibitors Guides Developing Selective bi-substrate Inhibitors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2021:2021.02.19.424337. [PMID: 33619486 PMCID: PMC7899450 DOI: 10.1101/2021.02.19.424337] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The COVID-19 pandemic has clearly brought the healthcare systems world-wide to a breaking point along with devastating socioeconomic consequences. The SARS-CoV-2 virus which causes the disease uses RNA capping to evade the human immune system. Non-structural protein (nsp) 14 is one of the 16 nsps in SARS-CoV-2 and catalyzes the methylation of the viral RNA at N7-guanosine in the cap formation process. To discover small molecule inhibitors of nsp14 methyltransferase (MT) activity, we developed and employed a radiometric MT assay to screen a library of 161 in house synthesized S-adenosylmethionine (SAM) competitive methyltransferase inhibitors and SAM analogs. Among seven identified screening hits, SS148 inhibited nsp14 MT activity with an IC 50 value of 70 ± 6 nM and was selective against 20 human protein lysine methyltransferases indicating significant differences in SAM binding sites. Interestingly, DS0464 with IC 50 value of 1.1 ± 0.2 μM showed a bi-substrate competitive inhibitor mechanism of action. Modeling the binding of this compound to nsp14 suggests that the terminal phenyl group extends into the RNA binding site. DS0464 was also selective against 28 out of 33 RNA, DNA, and protein methyltransferases. The structure-activity relationship provided by these compounds should guide the optimization of selective bi-substrate nsp14 inhibitors and may provide a path towards a novel class of antivirals against COVID-19, and possibly other coronaviruses.
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22
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Gorgulla C, Padmanabha Das KM, Leigh KE, Cespugli M, Fischer PD, Wang ZF, Tesseyre G, Pandita S, Shnapir A, Calderaio A, Gechev M, Rose A, Lewis N, Hutcheson C, Yaffe E, Luxenburg R, Herce HD, Durmaz V, Halazonetis TD, Fackeldey K, Patten J, Chuprina A, Dziuba I, Plekhova A, Moroz Y, Radchenko D, Tarkhanova O, Yavnyuk I, Gruber C, Yust R, Payne D, Näär AM, Namchuk MN, Davey RA, Wagner G, Kinney J, Arthanari H. A multi-pronged approach targeting SARS-CoV-2 proteins using ultra-large virtual screening. iScience 2021; 24:102021. [PMID: 33426509 PMCID: PMC7783459 DOI: 10.1016/j.isci.2020.102021] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 10/28/2020] [Accepted: 12/29/2020] [Indexed: 02/07/2023] Open
Abstract
The unparalleled global effort to combat the continuing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic over the last year has resulted in promising prophylactic measures. However, a need still exists for cheap, effective therapeutics, and targeting multiple points in the viral life cycle could help tackle the current, as well as future, coronaviruses. Here, we leverage our recently developed, ultra-large-scale in silico screening platform, VirtualFlow, to search for inhibitors that target SARS-CoV-2. In this unprecedented structure-based virtual campaign, we screened roughly 1 billion molecules against each of 40 different target sites on 17 different potential viral and host targets. In addition to targeting the active sites of viral enzymes, we also targeted critical auxiliary sites such as functionally important protein-protein interactions.
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Affiliation(s)
- Christoph Gorgulla
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
- Department of Physics, Faculty of Arts and Sciences, Harvard University, Cambridge, MA 02138, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Krishna M. Padmanabha Das
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Kendra E. Leigh
- Max Planck Institute of Biophysics, Frankfurt am Main, Hessen 60438, Germany
| | | | - Patrick D. Fischer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Saarbrücken, Saarland 66123, Germany
| | - Zi-Fu Wang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
| | | | | | | | - Anthony Calderaio
- VirtualFlow Organization, https://virtual-flow.org/, Boston, MA 02115, USA
| | | | - Alexander Rose
- Mol∗ Consortium, https://molstar.org, San Diego, CA 92109, USA
| | | | | | | | | | - Henry D. Herce
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | | | | | - Konstantin Fackeldey
- Zuse Institute Berlin (ZIB), Berlin 14195, Germany
- Institute of Mathematics, Technical University Berlin, Berlin 10587, Germany
| | - J.J. Patten
- Department of Microbiology, Boston University Medical School, Boston University, Boston, MA 02118, USA
| | | | | | | | - Yurii Moroz
- Chemspace, Kyiv 02094, Ukraine
- Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine
| | - Dmytro Radchenko
- Enamine, Kyiv 02094, Ukraine
- Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine
| | | | | | - Christian Gruber
- Innophore GmbH, Graz 8010, Austria
- Institute of Molecular Biosciences, University of Graz, Graz 8010, Austria
| | - Ryan Yust
- Google, Mountain View, CA 94043, USA
| | | | - Anders M. Näär
- Department of Nutritional Sciences & Toxicology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Mark N. Namchuk
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
| | - Robert A. Davey
- Department of Microbiology, Boston University Medical School, Boston University, Boston, MA 02118, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
| | | | - Haribabu Arthanari
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, MA 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
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23
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Selkrig J, Stanifer M, Mateus A, Mitosch K, Barrio‐Hernandez I, Rettel M, Kim H, Voogdt CGP, Walch P, Kee C, Kurzawa N, Stein F, Potel C, Jarzab A, Kuster B, Bartenschlager R, Boulant S, Beltrao P, Typas A, Savitski MM. SARS-CoV-2 infection remodels the host protein thermal stability landscape. Mol Syst Biol 2021; 17:e10188. [PMID: 33590968 PMCID: PMC7885171 DOI: 10.15252/msb.202010188] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 12/15/2022] Open
Abstract
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global threat to human health and has compromised economic stability. In addition to the development of an effective vaccine, it is imperative to understand how SARS-CoV-2 hijacks host cellular machineries on a system-wide scale so that potential host-directed therapies can be developed. In situ proteome-wide abundance and thermal stability measurements using thermal proteome profiling (TPP) can inform on global changes in protein activity. Here we adapted TPP to high biosafety conditions amenable to SARS-CoV-2 handling. We discovered pronounced temporal alterations in host protein thermostability during infection, which converged on cellular processes including cell cycle, microtubule and RNA splicing regulation. Pharmacological inhibition of host proteins displaying altered thermal stability or abundance during infection suppressed SARS-CoV-2 replication. Overall, this work serves as a framework for expanding TPP workflows to globally important human pathogens that require high biosafety containment and provides deeper resolution into the molecular changes induced by SARS-CoV-2 infection.
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Affiliation(s)
- Joel Selkrig
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Megan Stanifer
- Department of Infectious DiseasesMolecular VirologyHeidelberg University HospitalHeidelbergGermany
| | - André Mateus
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Karin Mitosch
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | | | - Mandy Rettel
- Proteomics Core FacilityEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Heeyoung Kim
- Department of Infectious DiseasesMolecular VirologyHeidelberg University HospitalHeidelbergGermany
| | - Carlos G P Voogdt
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Philipp Walch
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
- Faculty of BiosciencesEMBL and Heidelberg UniversityHeidelbergGermany
| | - Carmon Kee
- Department of Infectious DiseasesMolecular VirologyHeidelberg University HospitalHeidelbergGermany
| | - Nils Kurzawa
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
- Faculty of BiosciencesEMBL and Heidelberg UniversityHeidelbergGermany
| | - Frank Stein
- Proteomics Core FacilityEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Clément Potel
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Anna Jarzab
- Proteomics and BioanalyticsTechnical University of MunichFreisingGermany
| | - Bernhard Kuster
- Proteomics and BioanalyticsTechnical University of MunichFreisingGermany
| | - Ralf Bartenschlager
- Department of Infectious DiseasesMolecular VirologyHeidelberg University HospitalHeidelbergGermany
- Division “Virus‐associated Carcinogenesis”German Cancer Research Center (DKFZ)HeidelbergGermany
- German Center for Infection ResearchHeidelberg Partner siteHeidelbergGermany
| | - Steeve Boulant
- Department of Infectious Diseases, VirologyHeidelberg University HospitalHeidelbergGermany
- Research Group “Cellular Polarity and Viral Infection”German Cancer Research Center (DKFZ)HeidelbergGermany
| | - Pedro Beltrao
- European Bioinformatics Institute (EMBL‐EBI)HinxtonUK
| | - Athanasios Typas
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
| | - Mikhail M Savitski
- Genome Biology UnitEuropean Molecular Biology Laboratory (EMBL)HeidelbergGermany
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24
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Liu J, Li K, Cheng L, Shao J, Yang S, Zhang W, Zhou G, de Vries AAF, Yu Z. A high-throughput drug screening strategy against coronaviruses. Int J Infect Dis 2020; 103:300-304. [PMID: 33333250 PMCID: PMC7832824 DOI: 10.1016/j.ijid.2020.12.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/03/2020] [Accepted: 12/10/2020] [Indexed: 01/08/2023] Open
Abstract
The emergence and re-emergence of coronaviruses (CoV) continually cause circulating epidemics and pandemics worldwide, such as the on-going outbreak of the novel coronavirus SARS-CoV-2. The resultant disease, coronavirus disease 2019 (COVID-19), has rapidly developed into a worldwide pandemic, leading to severe health and economic burdens. Although the recently announced vaccines against COVID-19 has rekindled hope, there is still a major challenge to urgently meet the global need for rapid treatment of the pandemic. Given the urgency of the CoV outbreak, we propose a strategy to screen potential broad-spectrum drugs against CoV in a high-throughput manner, particularly against SARS-CoV-2. Since the essential functional domains of CoV are extensively homologous, the availability of two types of mild CoV, HCoV-OC43 and MHV, should provide a valuable tool for the rapid identification of promising drugs against CoV without the drawbacks of level three biological confinements. The luciferase reporter gene is introduced into HCoV-OC43 and MHV to indicate viral activity, and hence the antiviral efficiency of screened drugs can be quantified by luciferase activity. Compounds with antiviral activity against both HCoV-OC43 and MHV are further evaluated in SARS-CoV-2 after structural optimizations. This system allows large-scale compounds to be screened to search for broad-spectrum drugs against CoV in a high-throughput manner, providing potential alternatives for clinical management of SARS-CoV-2 or other CoV.
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Affiliation(s)
- Jia Liu
- Central Laboratory, Longgang Distract People's Hospital of Shenzhen & The Third Affiliated Hospital (Provisional) of The Chinese University of Hong Kong, Shenzhen, China
| | - Kang Li
- Central Laboratory, Longgang Distract People's Hospital of Shenzhen & The Third Affiliated Hospital (Provisional) of The Chinese University of Hong Kong, Shenzhen, China
| | - Lin Cheng
- Shenzhen Key Laboratory of Infection and Immunity, Guangdong Key Laboratory of Emerging Infectious Diseases, Shenzhen Third People's Hospital, Shenzhen, China
| | - Jingjin Shao
- Central Laboratory, Longgang Distract People's Hospital of Shenzhen & The Third Affiliated Hospital (Provisional) of The Chinese University of Hong Kong, Shenzhen, China
| | - Shukun Yang
- Central Laboratory, Longgang Distract People's Hospital of Shenzhen & The Third Affiliated Hospital (Provisional) of The Chinese University of Hong Kong, Shenzhen, China
| | - Wei Zhang
- Department of Emergency, People's Hospital of Leling, Dezhou, Shandong, China
| | - Guangqian Zhou
- Department of Medical Cell Biology and Genetics, Guangdong Key Laboratory of Genome Stability & Disease Prevention, Shenzhen Key Laboratory for Anti-ageing and Regenerative Medicine, Health Science Center, Shenzhen University, Shenzhen, China
| | - Antoine A F de Vries
- Laboratory of Experimental Cardiology, Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Zhiyi Yu
- Department of Medicinal Chemistry, School of Pharmaceutical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, 250100, Shandong, China.
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25
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Wang Y, Grunewald M, Perlman S. Coronaviruses: An Updated Overview of Their Replication and Pathogenesis. Methods Mol Biol 2020; 2203:1-29. [PMID: 32833200 DOI: 10.1007/978-1-0716-0900-2_1] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Coronaviruses (CoVs), enveloped positive-sense RNA viruses, are characterized by club-like spikes that project from their surface, an unusually large RNA genome, and a unique replication strategy. CoVs cause a variety of diseases in mammals and birds ranging from enteritis in cows and pigs, and upper respiratory tract and kidney disease in chickens to lethal human respiratory infections. Most recently, the novel coronavirus, SARS-CoV-2, which was first identified in Wuhan, China in December 2019, is the cause of a catastrophic pandemic, COVID-19, with more than 8 million infections diagnosed worldwide by mid-June 2020. Here we provide a brief introduction to CoVs discussing their replication, pathogenicity, and current prevention and treatment strategies. We will also discuss the outbreaks of the highly pathogenic Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV), which are relevant for understanding COVID-19.
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Affiliation(s)
- Yuhang Wang
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA
| | - Matthew Grunewald
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA
| | - Stanley Perlman
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, USA.
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26
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Hartenian E, Nandakumar D, Lari A, Ly M, Tucker JM, Glaunsinger BA. The molecular virology of coronaviruses. J Biol Chem 2020; 295:12910-12934. [PMID: 32661197 PMCID: PMC7489918 DOI: 10.1074/jbc.rev120.013930] [Citation(s) in RCA: 302] [Impact Index Per Article: 75.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/13/2020] [Indexed: 12/14/2022] Open
Abstract
Few human pathogens have been the focus of as much concentrated worldwide attention as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of COVID-19. Its emergence into the human population and ensuing pandemic came on the heels of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), two other highly pathogenic coronavirus spillovers, which collectively have reshaped our view of a virus family previously associated primarily with the common cold. It has placed intense pressure on the collective scientific community to develop therapeutics and vaccines, whose engineering relies on a detailed understanding of coronavirus biology. Here, we present the molecular virology of coronavirus infection, including its entry into cells, its remarkably sophisticated gene expression and replication mechanisms, its extensive remodeling of the intracellular environment, and its multifaceted immune evasion strategies. We highlight aspects of the viral life cycle that may be amenable to antiviral targeting as well as key features of its biology that await discovery.
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Affiliation(s)
- Ella Hartenian
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Divya Nandakumar
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
| | - Azra Lari
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
| | - Michael Ly
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Jessica M Tucker
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
| | - Britt A Glaunsinger
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA; Department of Plant and Microbial Biology, University of California, Berkeley, California, USA; Howard Hughes Medical Institute, University of California, Berkeley, California, USA.
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27
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Gorgulla C, Padmanabha Das KM, Leigh KE, Cespugli M, Fischer PD, Wang ZF, Tesseyre G, Pandita S, Shnapir A, Calderaio A, Gechev M, Rose A, Lewis N, Hutcheson C, Yaffe E, Luxenburg R, Herce HD, Durmaz V, Halazonetis TD, Fackeldey K, Patten JJ, Chuprina A, Dziuba I, Plekhova A, Moroz Y, Radchenko D, Tarkhanova O, Yavnyuk I, Gruber C, Yust R, Payne D, Näär AM, Namchuk MN, Davey RA, Wagner G, Kinney J, Arthanari H. A Multi-Pronged Approach Targeting SARS-CoV-2 Proteins Using Ultra-Large Virtual Screening. CHEMRXIV : THE PREPRINT SERVER FOR CHEMISTRY 2020:12682316. [PMID: 33200116 PMCID: PMC7668741 DOI: 10.26434/chemrxiv.12682316] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Revised: 07/24/2020] [Indexed: 11/23/2022]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), previously known as 2019 novel coronavirus (2019-nCoV), has spread rapidly across the globe, creating an unparalleled global health burden and spurring a deepening economic crisis. As of July 7th, 2020, almost seven months into the outbreak, there are no approved vaccines and few treatments available. Developing drugs that target multiple points in the viral life cycle could serve as a strategy to tackle the current as well as future coronavirus pandemics. Here we leverage the power of our recently developed in silico screening platform, VirtualFlow, to identify inhibitors that target SARS-CoV-2. VirtualFlow is able to efficiently harness the power of computing clusters and cloud-based computing platforms to carry out ultra-large scale virtual screens. In this unprecedented structure-based multi-target virtual screening campaign, we have used VirtualFlow to screen an average of approximately 1 billion molecules against each of 40 different target sites on 17 different potential viral and host targets in the cloud. In addition to targeting the active sites of viral enzymes, we also target critical auxiliary sites such as functionally important protein-protein interaction interfaces. This multi-target approach not only increases the likelihood of finding a potent inhibitor, but could also help identify a collection of anti-coronavirus drugs that would retain efficacy in the face of viral mutation. Drugs belonging to different regimen classes could be combined to develop possible combination therapies, and top hits that bind at highly conserved sites would be potential candidates for further development as coronavirus drugs. Here, we present the top 200 in silico hits for each target site. While in-house experimental validation of some of these compounds is currently underway, we want to make this array of potential inhibitor candidates available to researchers worldwide in consideration of the pressing need for fast-tracked drug development.
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Affiliation(s)
- Christoph Gorgulla
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
- Department of Physics, Faculty of Arts and Sciences, Harvard University, Cambridge, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, USA
| | - Krishna M. Padmanabha Das
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, USA
| | | | | | - Patrick D. Fischer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, USA
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Saarbrücken, Germany
| | - Zi-Fu Wang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
| | | | | | | | | | | | | | | | | | | | | | - Henry D. Herce
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, USA
| | | | | | - Konstantin Fackeldey
- Zuse Institute Berlin (ZIB), Berlin, Germany
- Institute of Mathematics, Technical University Berlin, Berlin, Germany
| | - Justin J. Patten
- Department of Microbiology, Boston University Medical School, Boston University, Boston, USA
| | | | | | | | - Yurii Moroz
- Chemspace, Kyiv, Ukraine
- Taras Shevchenko National University of Kyiv, Ukraine
| | - Dmytro Radchenko
- Enamine, Kyiv, Ukraine
- Taras Shevchenko National University of Kyiv, Ukraine
| | | | | | - Christian Gruber
- Innophore GmbH, Graz, Austria
- Institute of Molecular Biosciences, University of Graz, Austria
| | | | | | - Anders M. Näär
- Department of Nutritional Sciences & Toxicology, University of California Berkeley, USA
| | - Mark N. Namchuk
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
| | - Robert A. Davey
- Department of Microbiology, Boston University Medical School, Boston University, Boston, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
| | | | - Haribabu Arthanari
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Harvard University, Boston, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, USA
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Abstract
Since the end of 2019, the global COVID-19 outbreak has once again made coronaviruses a hot topic. Vaccines are hoped to be an effective way to stop the spread of the virus. However, there are no clinically approved vaccines available for coronavirus infections. Reverse genetics technology can realize the operation of RNA virus genomes at the DNA level and provide new ideas and strategies for the development of new vaccines. In this review, we systematically describe the role of reverse genetics technology in studying the effects of coronavirus proteins on viral virulence and innate immunity, cell and tissue tropism and antiviral drug screening. An efficient reverse genetics platform is useful for obtaining the ideal attenuated strain to prepare an attenuated live vaccine.
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5-Fluorouracil in combination with deoxyribonucleosides and deoxyribose as possible therapeutic options for the Coronavirus, COVID-19 infection. Med Hypotheses 2020; 142:109754. [PMID: 32438240 PMCID: PMC7194918 DOI: 10.1016/j.mehy.2020.109754] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 04/21/2020] [Indexed: 12/11/2022]
Abstract
The recent global pandemic created by the Coronavirus SARS-CoV-2, started in Wuhan, China in December 2019, has generated panic, both in term of human death (4–5% of infected patients identified through testing) and the global economy. Human sufferings seem to be continuing, and it is not clear how long this will continue and how much more destruction it is going to cause until complete control is achieved. One of the most disturbing issues is Covid-19 treatment; although a large number of medications, previously used successfully with other viruses (including Chinese herbal medicines and anti-malaria drugs), are under consideration, there remain questions as to whether they can play a satisfactory role for this disease. Global attempts are ongoing to find the drugs for the treatment of this virus but none of the antiviral drugs used for treatment of other human viral infection is working and hence attempts to find new drugs are continuing. Here the author is proposing that 5-Fluorouracil (5-FU) which when used on its own is failing as an antiviral agent due to the removal of this compound by proof reading ability exceptionally found in Coronaviruses. The author here is proposing to test 5-FU in combination with a number of deoxynucleosides on animal models infected with this Covid-19. Should encouraging results ensue, therapies could then be tried on patients.
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Quasispecies dynamics in disease prevention and control. VIRUS AS POPULATIONS 2020. [PMCID: PMC7153035 DOI: 10.1016/b978-0-12-816331-3.00008-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Medical interventions to prevent and treat viral disease constitute evolutionary forces that may modify the genetic composition of viral populations that replicate in an infected host and influence the genomic composition of those viruses that are transmitted and progress at the epidemiological level. Given the adaptive potential of viruses in general and the RNA viruses in particular, the selection of viral mutants that display some degree of resistance to inhibitors or vaccines is a tangible challenge. Mutant selection may jeopardize control of the viral disease. Strategies intended to minimize vaccination and treatment failures are proposed and justified based on fundamental features of viral dynamics explained in the preceding chapters. The recommended use of complex, multiepitopic vaccines, and combination therapies as early as possible after initiation of infection falls under the general concept that complexity cannot be combated with simplicity. It also follows that sociopolitical action to interrupt virus replication and spread as soon as possible is as important as scientifically sound treatment designs to control viral disease on a global scale.
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Fitness Barriers Limit Reversion of a Proofreading-Deficient Coronavirus. J Virol 2019; 93:JVI.00711-19. [PMID: 31341046 PMCID: PMC6798108 DOI: 10.1128/jvi.00711-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 07/05/2019] [Indexed: 12/28/2022] Open
Abstract
Coronaviruses encode an exoribonuclease (ExoN) that is important for viral replication, fitness, and virulence, yet coronaviruses with a defective ExoN (ExoN-AA) have not reverted under diverse experimental conditions. In this study, we identify multiple impediments to MHV-ExoN-AA reversion. We show that ExoN-AA reversion is possible but evolutionarily unfavorable. Instead, compensatory mutations outside ExoN-AA motif I are more accessible and beneficial than partial reversion. We also show that coevolution between replicase proteins over long-term passage partially compensates for ExoN-AA motif I but renders the virus inhospitable to a reverted ExoN. Our results reveal the evolutionary basis for the genetic stability of ExoN-inactivating mutations, illuminate complex functional and evolutionary relationships between coronavirus replicase proteins, and identify potential mechanisms for stabilization of ExoN-AA coronavirus mutants. The 3′-to-5′ exoribonuclease in coronavirus (CoV) nonstructural protein 14 (nsp14-ExoN) mediates RNA proofreading during genome replication. ExoN catalytic residues are arranged in three motifs: I (DE), II (E), and III (D). Alanine replacement of the motif I residues (AA-E-D; four nucleotide substitutions) in murine hepatitis virus (MHV) and severe acute respiratory syndrome (SARS)-CoV yields viable mutants with impaired replication and fitness, increased mutation rates, and attenuated virulence in vivo. Despite these impairments, MHV- and SARS-CoV ExoN motif I AA mutants (ExoN-AA) have not reverted at motif I in diverse in vitro and in vivo environments, suggesting that profound fitness barriers prevent motif I reversion. To test this hypothesis, we engineered MHV-ExoN-AA with 1, 2, or 3 nucleotide mutations along genetic pathways to AA-to-DE reversion. We show that engineered intermediate revertants were viable but had no increased replication or competitive fitness compared to that of MHV-ExoN-AA. In contrast, a low-passage-number (passage 10 [P10]) MHV-ExoN-AA showed increased replication and competitive fitness without reversion of ExoN-AA. Finally, engineered reversion of ExoN-AA to ExoN-DE in the presence of ExoN-AA passage-adaptive mutations resulted in significant fitness loss. These results demonstrate that while reversion is possible, at least one alternative adaptive pathway is more rapidly advantageous than intermediate revertants and may alter the genetic background to render reversion detrimental to fitness. Our results provide an evolutionary rationale for lack of ExoN-AA reversion, illuminate potential multiprotein replicase interactions and coevolution, and support future studies aimed at stabilizing attenuated CoV ExoN-AA mutants. IMPORTANCE Coronaviruses encode an exoribonuclease (ExoN) that is important for viral replication, fitness, and virulence, yet coronaviruses with a defective ExoN (ExoN-AA) have not reverted under diverse experimental conditions. In this study, we identify multiple impediments to MHV-ExoN-AA reversion. We show that ExoN-AA reversion is possible but evolutionarily unfavorable. Instead, compensatory mutations outside ExoN-AA motif I are more accessible and beneficial than partial reversion. We also show that coevolution between replicase proteins over long-term passage partially compensates for ExoN-AA motif I but renders the virus inhospitable to a reverted ExoN. Our results reveal the evolutionary basis for the genetic stability of ExoN-inactivating mutations, illuminate complex functional and evolutionary relationships between coronavirus replicase proteins, and identify potential mechanisms for stabilization of ExoN-AA coronavirus mutants.
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Ogando NS, Ferron F, Decroly E, Canard B, Posthuma CC, Snijder EJ. The Curious Case of the Nidovirus Exoribonuclease: Its Role in RNA Synthesis and Replication Fidelity. Front Microbiol 2019; 10:1813. [PMID: 31440227 PMCID: PMC6693484 DOI: 10.3389/fmicb.2019.01813] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 07/23/2019] [Indexed: 12/20/2022] Open
Abstract
Among RNA viruses, the order Nidovirales stands out for including viruses with the largest RNA genomes currently known. Nidoviruses employ a complex RNA-synthesizing machinery comprising a variety of non-structural proteins (nsps). One of the postulated drivers of the expansion of nidovirus genomes is the presence of a proofreading 3′-to-5′ exoribonuclease (ExoN) belonging to the DEDDh family. ExoN may enhance the fidelity of RNA synthesis by correcting nucleotide incorporation errors made by the RNA-dependent RNA polymerase. Here, we review our current understanding of ExoN evolution, structure, and function. Most experimental data are derived from studies of the ExoN domain of coronaviruses (CoVs), which were triggered by the bioinformatics-based identification of ExoN in the genome of severe acute respiratory syndrome coronavirus (SARS-CoV) and its relatives in 2003. Although convincing data supporting the proofreading hypothesis have been obtained, from biochemical assays and studies with CoV mutants lacking ExoN functionality, the features of ExoN from most other nidovirus families remain to be characterized. Remarkably, viable ExoN knockout mutants were obtained only for two CoVs, mouse hepatitis virus (MHV) and SARS-CoV, whose RNA synthesis and replication kinetics were mildly affected by the lack of ExoN function. In several other CoV species, ExoN inactivation was not tolerated, and knockout mutants could not be rescued when launched using a reverse genetics system. This suggests that ExoN is also critical for primary viral RNA synthesis, a property that poorly matches the profile of an enzyme that would merely boost long-term replication fidelity. In CoVs, ExoN resides in a bifunctional replicase subunit (nsp14) whose C-terminal part has (N7-guanine)-methyltransferase activity. The crystal structure of SARS-CoV nsp14 has shed light on the interplay between these two domains, and on nsp14’s interactions with nsp10, a co-factor that strongly enhances ExoN activity in vitro assays. Further elucidation of the structure-function relationships of ExoN and its interactions with other (viral and/or host) members of the CoV replication machinery will be key to understanding the enzyme’s role in viral RNA synthesis and pathogenesis, and may contribute to the design of new approaches to combat emerging nidoviruses.
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Affiliation(s)
- Natacha S Ogando
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Francois Ferron
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France.,European Virus Bioinformatics Center, Jena, Germany
| | - Etienne Decroly
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
| | - Bruno Canard
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Aix-Marseille Université, Marseille, France
| | - Clara C Posthuma
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - Eric J Snijder
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
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34
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Durzynska I, Sauerwald M, Karl N, Madhugiri R, Ziebuhr J. Characterization of a bafinivirus exoribonuclease activity. J Gen Virol 2018; 99:1253-1260. [PMID: 30058998 DOI: 10.1099/jgv.0.001120] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
White bream virus (WBV), a poorly characterized plus-strand RNA virus infecting freshwater fish of the Cyprinidae family, is the prototype species of the genus Bafinivirus in the subfamily Torovirinae (family Coronaviridae, order Nidovirales). In common with other nidoviruses featuring >20 kilobase genomes, bafiniviruses have been predicted to encode an exoribonuclease (ExoN) in their replicase gene. Here, we used information on the substrate specificity of bafinivirus 3C-like proteases to express WBV ExoN in an active form in Escherichia coli. The 374-residue protein displayed robust 3'-to-5' exoribonuclease activity in the presence of Mg2+ ions and, unlike its coronavirus homologues, did not require a protein cofactor for activity. Characterization of mutant forms of ExoN provided support for predictions on putative active-site and conserved zinc-binding residues. WBV ExoN was revealed to be most active on double-stranded RNA substrates containing one or two non-paired 3'-terminal nucleotides, supporting its presumed role in increasing the fidelity of the bafinivirus RNA-dependent RNA polymerase.
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Affiliation(s)
- Izabela Durzynska
- 1Centre for Infection and Immunity, Queen's University, Belfast, UK.,†Present address: Department of Cancer Biology, Dana Farber Cancer Institute, Boston, USA.,‡Present address: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, USA
| | - Marc Sauerwald
- 2Institute of Medical Virology, Justus Liebig University, Giessen, Germany
| | - Nadja Karl
- 1Centre for Infection and Immunity, Queen's University, Belfast, UK.,2Institute of Medical Virology, Justus Liebig University, Giessen, Germany
| | | | - John Ziebuhr
- 2Institute of Medical Virology, Justus Liebig University, Giessen, Germany.,1Centre for Infection and Immunity, Queen's University, Belfast, UK
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35
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Abstract
Reproduction of RNA viruses is typically error-prone due to the infidelity of their replicative machinery and the usual lack of proofreading mechanisms. The error rates may be close to those that kill the virus. Consequently, populations of RNA viruses are represented by heterogeneous sets of genomes with various levels of fitness. This is especially consequential when viruses encounter various bottlenecks and new infections are initiated by a single or few deviating genomes. Nevertheless, RNA viruses are able to maintain their identity by conservation of major functional elements. This conservatism stems from genetic robustness or mutational tolerance, which is largely due to the functional degeneracy of many protein and RNA elements as well as to negative selection. Another relevant mechanism is the capacity to restore fitness after genetic damages, also based on replicative infidelity. Conversely, error-prone replication is a major tool that ensures viral evolvability. The potential for changes in debilitated genomes is much higher in small populations, because in the absence of stronger competitors low-fit genomes have a choice of various trajectories to wander along fitness landscapes. Thus, low-fit populations are inherently unstable, and it may be said that to run ahead it is useful to stumble. In this report, focusing on picornaviruses and also considering data from other RNA viruses, we review the biological relevance and mechanisms of various alterations of viral RNA genomes as well as pathways and mechanisms of rehabilitation after loss of fitness. The relationships among mutational robustness, resilience, and evolvability of viral RNA genomes are discussed.
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36
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Graepel KW, Lu X, Case JB, Sexton NR, Smith EC, Denison MR. Proofreading-Deficient Coronaviruses Adapt for Increased Fitness over Long-Term Passage without Reversion of Exoribonuclease-Inactivating Mutations. mBio 2017; 8:e01503-17. [PMID: 29114026 PMCID: PMC5676041 DOI: 10.1128/mbio.01503-17] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 10/10/2017] [Indexed: 12/31/2022] Open
Abstract
The coronavirus (CoV) RNA genome is the largest among the single-stranded positive-sense RNA viruses. CoVs encode a proofreading 3'-to-5' exoribonuclease within nonstructural protein 14 (nsp14-ExoN) that is responsible for CoV high-fidelity replication. Alanine substitution of ExoN catalytic residues [ExoN(-)] in severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and murine hepatitis virus (MHV) disrupts ExoN activity, yielding viable mutant viruses with defective replication, up to 20-fold-decreased fidelity, and increased susceptibility to nucleoside analogues. To test the stability of the ExoN(-) genotype and phenotype, we passaged MHV-ExoN(-) 250 times in cultured cells (P250), in parallel with wild-type MHV (WT-MHV). Compared to MHV-ExoN(-) P3, MHV-ExoN(-) P250 demonstrated enhanced replication and increased competitive fitness without reversion at the ExoN(-) active site. Furthermore, MHV-ExoN(-) P250 was less susceptible than MHV-ExoN(-) P3 to multiple nucleoside analogues, suggesting that MHV-ExoN(-) was under selection for increased replication fidelity. We subsequently identified novel amino acid changes within the RNA-dependent RNA polymerase and nsp14 of MHV-ExoN(-) P250 that partially accounted for the reduced susceptibility to nucleoside analogues. Our results suggest that increased replication fidelity is selected in ExoN(-) CoVs and that there may be a significant barrier to ExoN(-) reversion. These results also support the hypothesis that high-fidelity replication is linked to CoV fitness and indicate that multiple replicase proteins could compensate for ExoN functions during replication.IMPORTANCE Uniquely among RNA viruses, CoVs encode a proofreading exoribonuclease (ExoN) in nsp14 that mediates high-fidelity RNA genome replication. Proofreading-deficient CoVs with disrupted ExoN activity [ExoN(-)] either are nonviable or have significant defects in replication, RNA synthesis, fidelity, fitness, and virulence. In this study, we showed that ExoN(-) murine hepatitis virus can adapt during long-term passage for increased replication and fitness without reverting the ExoN-inactivating mutations. Passage-adapted ExoN(-) mutants also demonstrate increasing resistance to nucleoside analogues that is explained only partially by secondary mutations in nsp12 and nsp14. These data suggest that enhanced resistance to nucleoside analogues is mediated by the interplay of multiple replicase proteins and support the proposed link between CoV fidelity and fitness.
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Affiliation(s)
- Kevin W Graepel
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Xiaotao Lu
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - James Brett Case
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Nicole R Sexton
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Everett Clinton Smith
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Biology, the University of the South, Sewanee, Tennessee, USA
| | - Mark R Denison
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Rai DK, Diaz-San Segundo F, Campagnola G, Keith A, Schafer EA, Kloc A, de Los Santos T, Peersen O, Rieder E. Attenuation of Foot-and-Mouth Disease Virus by Engineered Viral Polymerase Fidelity. J Virol 2017; 91:e00081-17. [PMID: 28515297 PMCID: PMC5651715 DOI: 10.1128/jvi.00081-17] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 05/03/2017] [Indexed: 12/21/2022] Open
Abstract
Foot-and-mouth disease virus (FMDV) RNA-dependent RNA polymerase (RdRp) (3Dpol) catalyzes viral RNA synthesis. Its characteristic low fidelity and absence of proofreading activity allow FMDV to rapidly mutate and adapt to dynamic environments. In this study, we used the structure of FMDV 3Dpol in combination with previously reported results from similar picornaviral polymerases to design point mutations that would alter replication fidelity. In particular, we targeted Trp237 within conserved polymerase motif A because of the low reversion potential inherent in the single UGG codon. Using biochemical and genetic tools, we show that the replacement of tryptophan 237 with phenylalanine imparts higher fidelity, but replacements with isoleucine and leucine resulted in lower-fidelity phenotypes. Viruses containing these W237 substitutions show in vitro growth kinetics and plaque morphologies similar to those of the wild-type (WT) A24 Cruzeiro strain in BHK cells, and both high- and low-fidelity variants retained fitness during coinfection with the wild-type virus. The higher-fidelity W237F (W237FHF) mutant virus was more resistant to the mutagenic nucleoside analogs ribavirin and 5-fluorouracil than the WT virus, whereas the lower-fidelity W237I (W237ILF) and W237LLF mutant viruses exhibited lower ribavirin resistance. Interestingly, the variant viruses showed heterogeneous and slightly delayed growth kinetics in primary porcine kidney cells, and they were significantly attenuated in mouse infection experiments. These data demonstrate, for a single virus, that either increased or decreased RdRp fidelity attenuates virus growth in animals, which is a desirable feature for the development of safer and genetically more stable vaccine candidates.IMPORTANCE Foot-and-mouth disease (FMD) is the most devastating disease affecting livestock worldwide. Here, using structural and biochemical analyses, we have identified FMDV 3Dpol mutations that affect polymerase fidelity. Recombinant FMDVs containing substitutions at 3Dpol tryptophan residue 237 were genetically stable and displayed plaque phenotypes and growth kinetics similar to those of the wild-type virus in cell culture. We further demonstrate that viruses harboring either a W237FHF substitution or W237ILF and W237LLF mutations were highly attenuated in animals. Our study shows that obtaining 3Dpol fidelity variants by protein engineering based on polymerase structure and function could be exploited for the development of attenuated FMDV vaccine candidates that are safer and more stable than strains obtained by selective pressure via mutagenic nucleotides or adaptation approaches.
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Affiliation(s)
- Devendra K Rai
- Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, USA
- University of Connecticut, Storrs, Connecticut, USA
| | - Fayna Diaz-San Segundo
- Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, USA
- University of Connecticut, Storrs, Connecticut, USA
| | - Grace Campagnola
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Anna Keith
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Elizabeth A Schafer
- Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, USA
| | - Anna Kloc
- Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, USA
- Oak Ridge Institute for Science and Education, Plum Island Animal Disease Center Research Participation Program, Oak Ridge, Tennessee, USA
| | - Teresa de Los Santos
- Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, USA
| | - Olve Peersen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Elizabeth Rieder
- Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, USA
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38
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Smith EC. The not-so-infinite malleability of RNA viruses: Viral and cellular determinants of RNA virus mutation rates. PLoS Pathog 2017; 13:e1006254. [PMID: 28448634 PMCID: PMC5407569 DOI: 10.1371/journal.ppat.1006254] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Everett Clinton Smith
- Department of Biology, Sewanee: The University of the South, Sewanee, Tennessee, United States of America
- * E-mail:
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39
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In Situ Tagged nsp15 Reveals Interactions with Coronavirus Replication/Transcription Complex-Associated Proteins. mBio 2017; 8:mBio.02320-16. [PMID: 28143984 PMCID: PMC5285509 DOI: 10.1128/mbio.02320-16] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Coronavirus (CoV) replication and transcription are carried out in close proximity to restructured endoplasmic reticulum (ER) membranes in replication/transcription complexes (RTC). Many of the CoV nonstructural proteins (nsps) are required for RTC function; however, not all of their functions are known. nsp15 contains an endoribonuclease domain that is conserved in the CoV family. While the enzymatic activity and crystal structure of nsp15 are well defined, its role in replication remains elusive. nsp15 localizes to sites of RNA replication, but whether it acts independently or requires additional interactions for its function remains unknown. To begin to address these questions, we created an in situ tagged form of nsp15 using the prototypic CoV, mouse hepatitis virus (MHV). In MHV, nsp15 contains the genomic RNA packaging signal (P/S), a 95-bp RNA stem-loop structure that is not required for viral replication or nsp15 function. Utilizing this knowledge, we constructed an internal hemagglutinin (HA) tag that replaced the P/S. We found that nsp15-HA was localized to discrete perinuclear puncta and strongly colocalized with nsp8 and nsp12, both well-defined members of the RTC, but not the membrane (M) protein, involved in virus assembly. Finally, we found that nsp15 interacted with RTC-associated proteins nsp8 and nsp12 during infection, and this interaction was RNA independent. From this, we conclude that nsp15 localizes and interacts with CoV proteins in the RTC, suggesting it plays a direct or indirect role in virus replication. Furthermore, the use of in situ epitope tags could be used to determine novel nsp-nsp interactions in coronaviruses. IMPORTANCE Despite structural and biochemical data demonstrating that the coronavirus nsp15 protein contains an endoribonuclease domain, its precise function during coronavirus infection remains unknown. In this work, we created a novel in situ tagged form of nsp15 to study interactions and localization during infection. This in situ tag was tolerated by MHV and did not affect viral replication. Utilizing this tag, we established that nsp15 localized to sites of replication but not sites of assembly throughout infection. Furthermore, we found that nsp15 interacted with the putative viral primase nsp8 and polymerase nsp12 during CoV infection. The strong association of nsp15 with replication complexes and interactions with replicative CoV enzymes suggest nsp15 is involved in CoV replication. These data and tools developed in this study help elucidate the function of nsp15 during infection and may be used to uncover other novel viral protein interactions.
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Sexton NR, Smith EC, Blanc H, Vignuzzi M, Peersen OB, Denison MR. Homology-Based Identification of a Mutation in the Coronavirus RNA-Dependent RNA Polymerase That Confers Resistance to Multiple Mutagens. J Virol 2016; 90:7415-7428. [PMID: 27279608 PMCID: PMC4984655 DOI: 10.1128/jvi.00080-16] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 05/27/2016] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Positive-sense RNA viruses encode RNA-dependent RNA polymerases (RdRps) essential for genomic replication. With the exception of the large nidoviruses, such as coronaviruses (CoVs), RNA viruses lack proofreading and thus are dependent on RdRps to control nucleotide selectivity and fidelity. CoVs encode a proofreading exonuclease in nonstructural protein 14 (nsp14-ExoN), which confers a greater-than-10-fold increase in fidelity compared to other RNA viruses. It is unknown to what extent the CoV polymerase (nsp12-RdRp) participates in replication fidelity. We sought to determine whether homology modeling could identify putative determinants of nucleotide selectivity and fidelity in CoV RdRps. We modeled the CoV murine hepatitis virus (MHV) nsp12-RdRp structure and superimposed it on solved picornaviral RdRp structures. Fidelity-altering mutations previously identified in coxsackie virus B3 (CVB3) were mapped onto the nsp12-RdRp model structure and then engineered into the MHV genome with [nsp14-ExoN(+)] or without [nsp14-ExoN(-)] ExoN activity. Using this method, we identified two mutations conferring resistance to the mutagen 5-fluorouracil (5-FU): nsp12-M611F and nsp12-V553I. For nsp12-V553I, we also demonstrate resistance to the mutagen 5-azacytidine (5-AZC) and decreased accumulation of mutations. Resistance to 5-FU, and a decreased number of genomic mutations, was effectively masked by nsp14-ExoN proofreading activity. These results indicate that nsp12-RdRp likely functions in fidelity regulation and that, despite low sequence conservation, some determinants of RdRp nucleotide selectivity are conserved across RNA viruses. The results also indicate that, with regard to nucleotide selectivity, nsp14-ExoN is epistatic to nsp12-RdRp, consistent with its proposed role in a multiprotein replicase-proofreading complex. IMPORTANCE RNA viruses have evolutionarily fine-tuned replication fidelity to balance requirements for genetic stability and diversity. Responsibility for replication fidelity in RNA viruses has been attributed to the RNA-dependent RNA polymerases, with mutations in RdRps for multiple RNA viruses shown to alter fidelity and attenuate virus replication and virulence. Coronaviruses (CoVs) are the only known RNA viruses to encode a proofreading exonuclease (nsp14-ExoN), as well as other replicase proteins involved in regulation of fidelity. This report shows that the CoV RdRp (nsp12) likely functions in replication fidelity; that residue determinants of CoV RdRp nucleotide selectivity map to similar structural regions of other, unrelated RNA viral polymerases; and that for CoVs, the proofreading activity of the nsp14-ExoN is epistatic to the function of the RdRp in fidelity.
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Affiliation(s)
- Nicole R Sexton
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Everett Clinton Smith
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Hervé Blanc
- Institut Pasteur, Centre National de la Recherche Scientifique UMR 3569, Paris, France
| | - Marco Vignuzzi
- Institut Pasteur, Centre National de la Recherche Scientifique UMR 3569, Paris, France
| | - Olve B Peersen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Mark R Denison
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Mutagenesis of S-Adenosyl-l-Methionine-Binding Residues in Coronavirus nsp14 N7-Methyltransferase Demonstrates Differing Requirements for Genome Translation and Resistance to Innate Immunity. J Virol 2016; 90:7248-7256. [PMID: 27252528 PMCID: PMC4984653 DOI: 10.1128/jvi.00542-16] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 05/24/2016] [Indexed: 12/23/2022] Open
Abstract
UNLABELLED Eukaryotic mRNAs possess a methylated 5'-guanosine cap that is required for RNA stability, efficient translation, and protection from cell-intrinsic defenses. Many viruses use 5' caps or other mechanisms to mimic a cap structure to limit detection of viral RNAs by intracellular innate sensors and to direct efficient translation of viral proteins. The coronavirus (CoV) nonstructural protein 14 (nsp14) is a multifunctional protein with N7-methyltransferase (N7-MTase) activity. The highly conserved S-adenosyl-l-methionine (SAM)-binding residues of the DxG motif are required for nsp14 N7-MTase activity in vitro However, the requirement for CoV N7-MTase activity and the importance of the SAM-binding residues during viral replication have not been determined. Here, we engineered mutations in murine hepatitis virus (MHV) nsp14 N7-MTase at residues D330 and G332 and determined the effects of these mutations on viral replication, sensitivity to mutagen, inhibition by type I interferon (IFN), and translation efficiency. Virus encoding a G332A substitution in nsp14 displayed delayed replication kinetics and decreased peak titers relative to wild-type (WT) MHV. In addition, replication of nsp14 G332A virus was diminished following treatment of cells with IFN-β, and nsp14 G332A genomes were translated less efficiently both in vitro and during viral infection. In contrast, substitution of alanine at MHV nsp14 D330 did not affect viral replication, sensitivity to mutagen, or inhibition by IFN-β compared to WT MHV. Our results demonstrate that the conserved MHV N7-MTase SAM-binding-site residues are not required for MHV viability and suggest that the determinants of CoV N7-MTase activity differ in vitro and during virus infection. IMPORTANCE Human coronaviruses, most notably severe acute respiratory syndrome (SARS)-CoV and Middle East respiratory syndrome (MERS)-CoV, cause severe and lethal human disease. Since specific antiviral therapies are not available for the treatment of human coronavirus infections, it is essential to understand the functions of conserved CoV proteins in viral replication. Here, we show that substitution of alanine at G332 in the N7-MTase domain of nsp14 impairs viral replication, enhances sensitivity to the innate immune response, and reduces viral RNA translation efficiency. Our data support the idea that coronavirus RNA capping could be targeted for development of antiviral therapeutics.
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Agudo R, de la Higuera I, Arias A, Grande-Pérez A, Domingo E. Involvement of a joker mutation in a polymerase-independent lethal mutagenesis escape mechanism. Virology 2016; 494:257-66. [PMID: 27136067 PMCID: PMC7111656 DOI: 10.1016/j.virol.2016.04.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 04/20/2016] [Accepted: 04/21/2016] [Indexed: 02/05/2023]
Abstract
We previously characterized a foot-and-mouth disease virus (FMDV) with three amino acid replacements in its polymerase (3D) that conferred resistance to the mutagenic nucleoside analogue ribavirin. Here we show that passage of this mutant in the presence of high ribavirin concentrations resulted in selection of viruses with the additional replacement I248T in 2C. This 2C substitution alone (even in the absence of replacements in 3D) increased FMDV fitness mainly in the presence of ribavirin, prevented an incorporation bias in favor of A and U associated with ribavirin mutagenesis, and conferred the ATPase activity of 2C decreased sensitivity to ribavirin-triphosphate. Since in previous studies we described that 2C with I248T was selected under different selective pressures, this replacement qualifies as a joker substitution in FMDV evolution. The results have identified a role of 2C in nucleotide incorporation, and have unveiled a new polymerase-independent mechanism of virus escape to lethal mutagenesis. A replacement in FMDV protein 2C confers reduced sensitivity to the mutagen ribavirin. The effect of the replacement is to prevent a mutational bias evoked by ribavirin. 2C has an effect in nucleotide incorporation by the FMDV polymerase. We describe a new molecular mechanism of escape to ribavirin-mediated extinction.
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Affiliation(s)
- Rubén Agudo
- Centro de Biologia Molecular "Severo Ochoa" (CSIC-UAM), Cantoblanco, E-28049 Madrid, Spain
| | - Ignacio de la Higuera
- Centro de Biologia Molecular "Severo Ochoa" (CSIC-UAM), Cantoblanco, E-28049 Madrid, Spain
| | - Armando Arias
- Centro de Biologia Molecular "Severo Ochoa" (CSIC-UAM), Cantoblanco, E-28049 Madrid, Spain
| | - Ana Grande-Pérez
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Universidad de Málaga - Consejo Superior de Investigaciones Científicas, (IHSM-UMA-CSIC) Área de Genética, Campus de Teatinos, 29071 Málaga, Spain
| | - Esteban Domingo
- Centro de Biologia Molecular "Severo Ochoa" (CSIC-UAM), Cantoblanco, E-28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Barcelona, Spain.
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Chen Y, Guo D. Molecular mechanisms of coronavirus RNA capping and methylation. Virol Sin 2016; 31:3-11. [PMID: 26847650 PMCID: PMC7091378 DOI: 10.1007/s12250-016-3726-4] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 01/25/2016] [Indexed: 12/17/2022] Open
Abstract
The 5′-cap structures of eukaryotic mRNAs are important for RNA stability, pre-mRNA splicing, mRNA export, and protein translation. Many viruses have evolved mechanisms for generating their own cap structures with methylation at the N7 position of the capped guanine and the ribose 2′-Oposition of the first nucleotide, which help viral RNAs escape recognition by the host innate immune system. The RNA genomes of coronavirus were identified to have 5′-caps in the early 1980s. However, for decades the RNA capping mechanisms of coronaviruses remained unknown. Since 2003, the outbreak of severe acute respiratory syndrome coronavirus has drawn increased attention and stimulated numerous studies on the molecular virology of coronaviruses. Here, we review the current understanding of the mechanisms adopted by coronaviruses to produce the 5′-cap structure and methylation modification of viral genomic RNAs.![]()
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Affiliation(s)
- Yu Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430070, China.
| | - Deyin Guo
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430070, China.
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Abstract
Despite having very limited coding capacity, RNA viruses are able to withstand challenge of antiviral drugs, cause epidemics in previously exposed human populations, and, in some cases, infect multiple host species. They are able to achieve this by virtue of their ability to multiply very rapidly, coupled with their extraordinary degree of genetic heterogeneity. RNA viruses exist not as single genotypes, but as a swarm of related variants, and this genomic diversity is an essential feature of their biology. RNA viruses have a variety of mechanisms that act in combination to determine their genetic heterogeneity. These include polymerase fidelity, error-mitigation mechanisms, genomic recombination, and different modes of genome replication. RNA viruses can vary in their ability to tolerate mutations, or “genetic robustness,” and several factors contribute to this. Finally, there is evidence that some RNA viruses exist close to a threshold where polymerase error rate has evolved to maximize the possible sequence space available, while avoiding the accumulation of a lethal load of deleterious mutations. We speculate that different viruses have evolved different error rates to complement the different “life-styles” they possess.
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Affiliation(s)
- J.N. Barr
- University of Leeds, Leeds, United Kingdom
| | - R. Fearns
- Boston University School of Medicine, Boston, MA, United States
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Trends in Antiviral Strategies. VIRUS AS POPULATIONS 2016. [PMCID: PMC7149557 DOI: 10.1016/b978-0-12-800837-9.00009-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Viral populations are true moving targets regarding the genomic sequences to be targeted in antiviral designs. Experts from different fields have expressed the need of new paradigms for antiviral interventions and viral disease control. This chapter reviews several strategies that aim at counteracting the adaptive capacity of viral quasispecies. The proposed designs are based on combinations of different antiviral drugs and immune modulators, or in the administration of virus-specific mutagenic agents, in an approach termed lethal mutagenesis of viruses. It consists of decreasing viral fitness by an excess of mutations that render viral proteins sub-optimal or non-functional. Viral extinction by lethal mutagenesis involves several sequential, overlapping steps that recapitulate the major concepts of intra-population interactions and genetic information stability discussed in preceding chapters. Despite the magnitude of the challenge, the chapter closes with some optimistic prospects for an effective control of viruses displaying error-prone replication, based on the combined targeting of replication fidelity and the induction of the innate immune response.
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Han Z, Zhang T, Xu Q, Gao M, Chen Y, Wang Q, Zhao Y, Shao Y, Li H, Kong X, Liu S. Altered pathogenicity of a tl/CH/LDT3/03 genotype infectious bronchitis coronavirus due to natural recombination in the 5'- 17kb region of the genome. Virus Res 2015; 213:140-148. [PMID: 26616599 PMCID: PMC7114521 DOI: 10.1016/j.virusres.2015.11.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 11/19/2015] [Accepted: 11/19/2015] [Indexed: 12/20/2022]
Abstract
An infectious bronchitis coronavirus, designated as ck/CH/LGX/130530, was isolated from an IBV strain H120-vaccinated chicken in this study. Analysis of the S1 gene showed that isolate ck/CH/LGX/130530 was a tl/CH/LDT3/03-like virus, with a nucleotide sequence similarity of 99%. However, a complete genomic sequence analysis showed that ck/CH/LGX/130530 was more closely related to a Massachusetts type strain (95% similarity to strain H120) than to the tl/CH/LDT3/03 strain (86%), suggesting that recombination might have occurred during the origin of the virus. A SimPlot analysis of the complete genomic sequence confirmed this hypothesis, and it showed that isolate ck/CH/LGX/130530 emerged from a recombination event between parental IBV H120 strain and pathogenic tl/CH/LDT3/03-like virus. The results obtained from the pairwise comparison and nucleotide similarity showed that the recombination breakpoint was located in the nsp14 gene at nucleotides 17055-17083. In line with the high S1 gene sequence similarity, the ck/CH/LGX/130530 isolate was serotypically close to that of the tl/CH/LDT3/03 strain (73% antigenic relatedness). Furthermore, vaccination with the LDT3-A vaccine, which was derived from the tl/CH/LDT3/03 strain by serial passaging in chicken eggs, provided good protection against challenge with the tl/CH/LDT3/03 strain, in contrast to the poor protection offered with the H120 vaccine. Interestingly, isolate ck/CH/LGX/130530 exhibited low pathogenicity toward specific-pathogen-free chickens compared with the nephropathogenic tl/CH/LDT3/03 strain, which was likely due to natural recombination in the 5' 17-kb region of the genome. Our results also indicate that the replicase gene of IBV isolate ck/CH/LGX/130530 is associated with viral pathogenicity.
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Affiliation(s)
- Zongxi Han
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Tingting Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Qianqian Xu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Mengying Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Yuqiu Chen
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Qiuling Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Yan Zhao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Yuhao Shao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Huixin Li
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Xiangang Kong
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China
| | - Shengwang Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Harbin 150001, People's Republic of China.
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Kilianski A, Nuzzo JB, Modjarrad K. Gain-of-Function Research and the Relevance to Clinical Practice. J Infect Dis 2015; 213:1364-9. [PMID: 26416657 PMCID: PMC7107371 DOI: 10.1093/infdis/jiv473] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/02/2015] [Indexed: 11/13/2022] Open
Abstract
The ongoing moratorium on gain-of-function (GOF) research with highly pathogenic avian influenza virus, severe acute respiratory syndrome coronavirus, and Middle East respiratory syndrome coronavirus has drawn attention to the current debate on these research practices and the potential benefits and risks they present. While much of the discussion has been steered by members of the microbiology and policy communities, additional input from medical practitioners will be highly valuable toward developing a broadly inclusive policy that considers the relative value and harm of GOF research. This review attempts to serve as a primer on the topic for the clinical community by providing a historical context for GOF research, summarizing concerns about its risks, and surveying the medical products that it has yielded.
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Affiliation(s)
- Andy Kilianski
- BioDefense Branch, Biosciences Division, Edgewood Chemical Biological Center, Aberdeen Proving Ground
| | - Jennifer B Nuzzo
- University of Pittsburgh Medical Center-Center for Health Security, Baltimore
| | - Kayvon Modjarrad
- US Military HIV Research Program, Walter Reed Army Institute for Research, Silver Spring, Maryland
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Viral Polymerase-Helicase Complexes Regulate Replication Fidelity To Overcome Intracellular Nucleotide Depletion. J Virol 2015; 89:11233-44. [PMID: 26311883 PMCID: PMC4645662 DOI: 10.1128/jvi.01553-15] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 08/20/2015] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED To date, the majority of work on RNA virus replication fidelity has focused on the viral RNA polymerase, while the potential role of other viral replicase proteins in this process is poorly understood. Previous studies used resistance to broad-spectrum RNA mutagens, such as ribavirin, to identify polymerases with increased fidelity that avoid misincorporation of such base analogues. We identified a novel variant in the alphavirus viral helicase/protease, nonstructural protein 2 (nsP2) that operates in concert with the viral polymerase nsP4 to further alter replication complex fidelity, a functional linkage that was conserved among the alphavirus genus. Purified chikungunya virus nsP2 presented delayed helicase activity of the high-fidelity enzyme, and yet purified replication complexes manifested stronger RNA polymerization kinetics. Because mutagenic nucleoside analogs such as ribavirin also affect intracellular nucleotide pools, we addressed the link between nucleotide depletion and replication fidelity by using purine and pyrimidine biosynthesis inhibitors. High-fidelity viruses were more resistant to these conditions, and viral growth could be rescued by the addition of exogenous nucleosides, suggesting that mutagenesis by base analogues requires nucleotide pool depletion. This study describes a novel function for nsP2, highlighting the role of other components of the replication complex in regulating viral replication fidelity, and suggests that viruses can alter their replication complex fidelity to overcome intracellular nucleotide-depleting conditions. IMPORTANCE Previous studies using the RNA mutagen ribavirin to select for drug-resistant variants have highlighted the essential role of the viral RNA-dependent RNA polymerase in regulating replication fidelity. However, the role of other viral replicase components in replication fidelity has not been studied in detail. We identified here an RNA mutagen-resistant variant of the nsP2 helicase/protease that conferred increased fidelity and yet could not operate in the same manner as high-fidelity polymerases. We show that the alphavirus helicase is a key component of the fidelity-regulating machinery. Our data show that the RNA mutagenic activity of compounds such as ribavirin is coupled to and potentiated by nucleotide depletion and that RNA viruses can fine-tune their replication fidelity when faced with an intracellular environment depleted of nucleotides.
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Structural basis and functional analysis of the SARS coronavirus nsp14-nsp10 complex. Proc Natl Acad Sci U S A 2015; 112:9436-41. [PMID: 26159422 DOI: 10.1073/pnas.1508686112] [Citation(s) in RCA: 331] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nonstructural protein 14 (nsp14) of coronaviruses (CoV) is important for viral replication and transcription. The N-terminal exoribonuclease (ExoN) domain plays a proofreading role for prevention of lethal mutagenesis, and the C-terminal domain functions as a (guanine-N7) methyl transferase (N7-MTase) for mRNA capping. The molecular basis of both these functions is unknown. Here, we describe crystal structures of severe acute respiratory syndrome (SARS)-CoV nsp14 in complex with its activator nonstructural protein10 (nsp10) and functional ligands. One molecule of nsp10 interacts with ExoN of nsp14 to stabilize it and stimulate its activity. Although the catalytic core of nsp14 ExoN is reminiscent of proofreading exonucleases, the presence of two zinc fingers sets it apart from homologs. Mutagenesis studies indicate that both these zinc fingers are essential for the function of nsp14. We show that a DEEDh (the five catalytic amino acids) motif drives nucleotide excision. The N7-MTase domain exhibits a noncanonical MTase fold with a rare β-sheet insertion and a peripheral zinc finger. The cap-precursor guanosine-P3-adenosine-5',5'-triphosphate and S-adenosyl methionine bind in proximity in a highly constricted pocket between two β-sheets to accomplish methyl transfer. Our studies provide the first glimpses, to our knowledge, into the architecture of the nsp14-nsp10 complex involved in RNA viral proofreading.
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