101
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Hillen HS, Kokic G, Farnung L, Dienemann C, Tegunov D, Cramer P. Structure of replicating SARS-CoV-2 polymerase. Nature 2020; 584:154-156. [PMID: 32438371 DOI: 10.1038/s41586-020-2368-8] [Citation(s) in RCA: 523] [Impact Index Per Article: 130.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 05/15/2020] [Indexed: 01/18/2023]
Abstract
The new coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses an RNA-dependent RNA polymerase (RdRp) for the replication of its genome and the transcription of its genes1-3. Here we present a cryo-electron microscopy structure of the SARS-CoV-2 RdRp in an active form that mimics the replicating enzyme. The structure comprises the viral proteins non-structural protein 12 (nsp12), nsp8 and nsp7, and more than two turns of RNA template-product duplex. The active-site cleft of nsp12 binds to the first turn of RNA and mediates RdRp activity with conserved residues. Two copies of nsp8 bind to opposite sides of the cleft and position the second turn of RNA. Long helical extensions in nsp8 protrude along exiting RNA, forming positively charged 'sliding poles'. These sliding poles can account for the known processivity of RdRp that is required for replicating the long genome of coronaviruses3. Our results enable a detailed analysis of the inhibitory mechanisms that underlie the antiviral activity of substances such as remdesivir, a drug for the treatment of coronavirus disease 2019 (COVID-19)4.
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Affiliation(s)
- Hauke S Hillen
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Goran Kokic
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Lucas Farnung
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christian Dienemann
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dimitry Tegunov
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
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102
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Yin W, Mao C, Luan X, Shen DD, Shen Q, Su H, Wang X, Zhou F, Zhao W, Gao M, Chang S, Xie YC, Tian G, Jiang HW, Tao SC, Shen J, Jiang Y, Jiang H, Xu Y, Zhang S, Zhang Y, Xu HE. Structural basis for inhibition of the RNA-dependent RNA polymerase from SARS-CoV-2 by remdesivir. Science 2020; 368:1499-1504. [PMID: 32358203 PMCID: PMC7199908 DOI: 10.1126/science.abc1560] [Citation(s) in RCA: 803] [Impact Index Per Article: 200.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 04/28/2020] [Indexed: 01/18/2023]
Abstract
Understanding the inner workings of the virus that causes coronavirus disease 2019 (COVID-19) may help us to disrupt it. Yin et al. focused on the viral polymerase essential for replicating viral RNA. They determined a structure of the polymerase bound to RNA and to the drug remdesivir. Remdesivir mimics an RNA nucleotide building block and is covalently linked to the replicating RNA, which blocks further synthesis of RNA. The structure provides a template for designing improved therapeutics against the viral polymerase. Science, this issue p. 1499 The pandemic of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global crisis. Replication of SARS-CoV-2 requires the viral RNA-dependent RNA polymerase (RdRp) enzyme, a target of the antiviral drug remdesivir. Here we report the cryo–electron microscopy structure of the SARS-CoV-2 RdRp, both in the apo form at 2.8-angstrom resolution and in complex with a 50-base template-primer RNA and remdesivir at 2.5-angstrom resolution. The complex structure reveals that the partial double-stranded RNA template is inserted into the central channel of the RdRp, where remdesivir is covalently incorporated into the primer strand at the first replicated base pair, and terminates chain elongation. Our structures provide insights into the mechanism of viral RNA replication and a rational template for drug design to combat the viral infection.
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Affiliation(s)
- Wanchao Yin
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Chunyou Mao
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Xiaodong Luan
- School of Medicine, Tsinghua University, Haidian District, Beijing 100084, China.,Department of Cardiology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China.,Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Dan-Dan Shen
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Qingya Shen
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Haixia Su
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoxi Wang
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Fulai Zhou
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Wenfeng Zhao
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Minqi Gao
- WuxiBiortus Biosciences Co. Ltd., Jiangyin 214437, China
| | - Shenghai Chang
- Center of Cryo-Electron Microscopy, Zhejiang University School of Medicine, Hangzhou 310058, China.,Center of Diagnostic Electron Microscopy, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Yuan-Chao Xie
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Guanghui Tian
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - He-Wei Jiang
- Shanghai Center for Systems Biomedicine, Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, China
| | - Sheng-Ce Tao
- Shanghai Center for Systems Biomedicine, Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jingshan Shen
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Jiang
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hualiang Jiang
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yechun Xu
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. .,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuyang Zhang
- Department of Cardiology, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China. .,Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China.,School of Medicine, Tsinghua University, Haidian District, Beijing 100084, China
| | - Yan Zhang
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China. .,Key Laboratory of Immunity and Inflammatory Diseases of Zhejiang Province, Hangzhou 310058, China
| | - H Eric Xu
- The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. .,University of Chinese Academy of Sciences, Beijing 100049, China
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103
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Liu W, Zhang S, Nekhai S, Liu S. Depriving Iron Supply to the Virus Represents a Promising Adjuvant Therapeutic Against Viral Survival. CURRENT CLINICAL MICROBIOLOGY REPORTS 2020; 7:13-19. [PMID: 32318324 PMCID: PMC7169647 DOI: 10.1007/s40588-020-00140-w] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Purpose of the review The ongoing outbreak of novel coronavirus pneumonia (COVID-19) caused by the 2019 novel coronavirus (SARS-CoV-2) in China is lifting widespread concerns. Thus, therapeutic options are urgently needed, and will be discussed in this review. Recent findings Iron-containing enzymes are required for viruses most likely including coronaviruses (CoVs) to complete their replication process. Moreover, poor prognosis occurred in the conditions of iron overload for patients upon infections of viruses. Thus, limiting iron represents a promising adjuvant strategy in treating viral infection through oral uptake or venous injection of iron chelators, or through the manipulation of the key iron regulators. For example, treatment with iron chelator deferiprone has been shown to prolong the survival of acquired immunodeficiency syndrome (AIDS) patients. Increasing intracellular iron efflux via increasing iron exporter ferroportin expression also exhibits antiviral effect on human immunodeficiency virus (HIV). The implications of other metals besides iron are also briefly discussed. Summary For even though we know little about iron regulation in COVID-19 patients thus far, it could be deduced from other viral infections that iron chelation might be an alternative beneficial adjuvant in treating COVID-19.
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Affiliation(s)
- Wei Liu
- 1State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085 China.,2University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Shuping Zhang
- Department of Hematology, The First Affiliated Hospital of Shandong First Medical University, Jinan, 250062 China.,Shandong Medicinal Biotechnology Center, Jinan, 250062 China.,5University Creative Research Initiatives Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250062 China
| | - Sergei Nekhai
- 6Center for Sickle Cell Disease and Department of Medicine, College of Medicine, Howard University, Washington, DC 20059 USA
| | - Sijin Liu
- 1State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085 China.,2University of Chinese Academy of Sciences, Beijing, 100049 China
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104
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Chen Y, Liu Q, Guo D. Emerging coronaviruses: Genome structure, replication, and pathogenesis. J Med Virol 2020; 92:418-423. [PMID: 31967327 PMCID: PMC7167049 DOI: 10.1002/jmv.25681] [Citation(s) in RCA: 1774] [Impact Index Per Article: 443.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 01/21/2020] [Indexed: 12/11/2022]
Abstract
The recent emergence of a novel coronavirus (2019-nCoV), which is causing an outbreak of unusual viral pneumonia in patients in Wuhan, a central city in China, is another warning of the risk of CoVs posed to public health. In this minireview, we provide a brief introduction of the general features of CoVs and describe diseases caused by different CoVs in humans and animals. This review will help understand the biology and potential risk of CoVs that exist in richness in wildlife such as bats.
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Affiliation(s)
- Yu Chen
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life SciencesWuhan UniversityWuhanChina
| | - Qianyun Liu
- State Key Laboratory of Virology, Modern Virology Research Center, College of Life SciencesWuhan UniversityWuhanChina
| | - Deyin Guo
- Center for Infection and Immunity Study, School of MedicineSun Yat‐sen UniversityGuangzhouChina
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105
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Uchiumi F, Ogino Y, Sato A, Tanuma SI. Insights into the development of effective materials to suppress replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). AIMS BIOENGINEERING 2020. [DOI: 10.3934/bioeng.2020012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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106
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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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107
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Kirchdoerfer RN, Ward AB. Structure of the SARS-CoV nsp12 polymerase bound to nsp7 and nsp8 co-factors. Nat Commun 2019; 10:2342. [PMID: 31138817 PMCID: PMC6538669 DOI: 10.1038/s41467-019-10280-3] [Citation(s) in RCA: 568] [Impact Index Per Article: 113.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 05/02/2019] [Indexed: 12/12/2022] Open
Abstract
Recent history is punctuated by the emergence of highly pathogenic coronaviruses such as SARS- and MERS-CoV into human circulation. Upon infecting host cells, coronaviruses assemble a multi-subunit RNA-synthesis complex of viral non-structural proteins (nsp) responsible for the replication and transcription of the viral genome. Here, we present the 3.1 Å resolution structure of the SARS-CoV nsp12 polymerase bound to its essential co-factors, nsp7 and nsp8, using single particle cryo-electron microscopy. nsp12 possesses an architecture common to all viral polymerases as well as a large N-terminal extension containing a kinase-like fold and is bound by two nsp8 co-factors. This structure illuminates the assembly of the coronavirus core RNA-synthesis machinery, provides key insights into nsp12 polymerase catalysis and fidelity and acts as a template for the design of novel antiviral therapeutics.
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Affiliation(s)
- Robert N Kirchdoerfer
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, HZ-102, La Jolla, CA, 92037, USA.
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, HZ-102, La Jolla, CA, 92037, USA
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108
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Koonpaew S, Teeravechyan S, Frantz PN, Chailangkarn T, Jongkaewwattana A. PEDV and PDCoV Pathogenesis: The Interplay Between Host Innate Immune Responses and Porcine Enteric Coronaviruses. Front Vet Sci 2019; 6:34. [PMID: 30854373 PMCID: PMC6395401 DOI: 10.3389/fvets.2019.00034] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Accepted: 01/28/2019] [Indexed: 12/24/2022] Open
Abstract
Enteropathogenic porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV), members of the coronavirus family, account for the majority of lethal watery diarrhea in neonatal pigs in the past decade. These two viruses pose significant economic and public health burdens, even as both continue to emerge and reemerge worldwide. The ability to evade, circumvent or subvert the host’s first line of defense, namely the innate immune system, is the key determinant for pathogen virulence, survival, and the establishment of successful infection. Unfortunately, we have only started to unravel the underlying viral mechanisms used to manipulate host innate immune responses. In this review, we gather current knowledge concerning the interplay between these viruses and components of host innate immunity, focusing on type I interferon induction and signaling in particular, and the mechanisms by which virus-encoded gene products antagonize and subvert host innate immune responses. Finally, we provide some perspectives on the advantages gained from a better understanding of host-pathogen interactions. This includes their implications for the future development of PEDV and PDCoV vaccines and how we can further our knowledge of the molecular mechanisms underlying virus pathogenesis, virulence, and host coevolution.
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Affiliation(s)
- Surapong Koonpaew
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathumthani, Thailand
| | - Samaporn Teeravechyan
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathumthani, Thailand
| | - Phanramphoei Namprachan Frantz
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathumthani, Thailand
| | - Thanathom Chailangkarn
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathumthani, Thailand
| | - Anan Jongkaewwattana
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Pathumthani, Thailand
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109
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Abstract
Coronaviruses (CoVs) are a major group of viruses known to be responsible for wide spectrum of diseases in multiple species. The CoVs affecting human population are referred to as human coronaviruses (HCoVs). They lead to multiple respiratory diseases, such as common cold, pneumonia, bronchitis, severe acute respiratory syndrome, and Middle East respiratory syndrome. CoVs are RNA viruses that require RNA-dependent RNA polymerases (RdRPs) for various steps in their life cycle. Action of RdRP is needed in several steps in the life cycle of CoVs and thus RdRPs constitute potential targets for drugs and other therapeutic interventions for the treatment of diseases caused by CoVs. The chapter therefore presents a detailed discussion on the structure and functions of CoV polymerases and the development of their potential inhibitors.
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110
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Structural Basis for the Inhibition of Host Gene Expression by Porcine Epidemic Diarrhea Virus nsp1. J Virol 2018; 92:JVI.01896-17. [PMID: 29237834 DOI: 10.1128/jvi.01896-17] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 11/29/2017] [Indexed: 01/21/2023] Open
Abstract
Porcine epidemic diarrhea virus (PEDV), an enteropathogenic Alphacoronavirus, has caused enormous economic losses in the pork industry. Nonstructural protein 1 (nsp1) is a characteristic feature of alpha- and betacoronaviruses, which exhibits both functional conservation and mechanistic diversity in inhibiting host gene expression and antiviral responses. However, the detailed structure and molecular mechanisms underlying the Alphacoronavirus nsp1 inhibition of host gene expression remain unclear. Here, we report the first full-length crystal structure of Alphacoronavirus nsp1 from PEDV. The structure displays a six-stranded β-barrel fold in the middle of two α-helices. The core structure of PEDV nsp1 shows high similarity to those of severe acute respiratory syndrome coronavirus (SARS-CoV) nsp1 and transmissible gastroenteritis virus (TGEV) nsp1, despite its low degree of sequence homology. Using ribopuromycylation and Renilla luciferase reporter assays, we showed that PEDV nsp1 can dramatically inhibit general host gene expression. Furthermore, three motifs (amino acids [aa] 67 to 71, 78 to 85, and 103 to 110) of PEDV nsp1 create a stable functional region for inhibiting protein synthesis, differing considerably from Betacoronavirus nsp1. These results elucidate the detailed structural basis through which PEDV nsp1 inhibits host gene expression, providing insight into the development of a new attenuated vaccine with nsp1 modifications.IMPORTANCE Porcine epidemic diarrhea virus (PEDV) has led to tremendous economic losses in the global swine industry. PEDV nsp1 plays a crucial role in inhibiting host gene expression, but its functional mechanism remains unclear. Here, we report the full-length structure of PEDV nsp1, the first among coronaviruses to be reported. The 1.25-Å resolution crystal structure of PEDV nsp1 shows high similarity to severe acute respiratory syndrome coronavirus (SARS-CoV) nsp113-128 and transmissible gastroenteritis virus (TGEV) nsp11-104, despite a lack of sequence homology. Structural and biochemical characterization demonstrated that PEDV nsp1 possesses a stable functional region for inhibition of host protein synthesis, which is formed by loops at residues 67 to 71, 78 to 85, and 103 to 110. The different functional regions in PEDV nsp1 and SARS-CoV nsp1 may explain their distinct mechanisms. Importantly, our structural data are conducive to understanding the mechanism of PEDV nsp1 inhibition of the expression of host genes and may aid in the development of a new attenuated vaccine.
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111
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Posthuma CC, Te Velthuis AJW, Snijder EJ. Nidovirus RNA polymerases: Complex enzymes handling exceptional RNA genomes. Virus Res 2017; 234:58-73. [PMID: 28174054 PMCID: PMC7114556 DOI: 10.1016/j.virusres.2017.01.023] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 01/24/2017] [Accepted: 01/26/2017] [Indexed: 12/22/2022]
Abstract
Coronaviruses and arteriviruses are distantly related human and animal pathogens that belong to the order Nidovirales. Nidoviruses are characterized by their polycistronic plus-stranded RNA genome, the production of subgenomic mRNAs and the conservation of a specific array of replicase domains, including key RNA-synthesizing enzymes. Coronaviruses (26-34 kilobases) have the largest known RNA genomes and their replication presumably requires a processive RNA-dependent RNA polymerase (RdRp) and enzymatic functions that suppress the consequences of the typically high error rate of viral RdRps. The arteriviruses have significantly smaller genomes and form an intriguing package with the coronaviruses to analyse viral RdRp evolution and function. The RdRp domain of nidoviruses resides in a cleavage product of the replicase polyprotein named non-structural protein (nsp) 12 in coronaviruses and nsp9 in arteriviruses. In all nidoviruses, the C-terminal RdRp domain is linked to a conserved N-terminal domain, which has been coined NiRAN (nidovirus RdRp-associated nucleotidyl transferase). Although no structural information is available, the functional characterization of the nidovirus RdRp and the larger enzyme complex of which it is part, has progressed significantly over the past decade. In coronaviruses several smaller, non-enzymatic nsps were characterized that direct RdRp function, while a 3'-to-5' exoribonuclease activity in nsp14 was implicated in fidelity. In arteriviruses, the nsp1 subunit was found to maintain the balance between genome replication and subgenomic mRNA production. Understanding RdRp behaviour and interactions during RNA synthesis and subsequent processing will be key to rationalising the evolutionary success of nidoviruses and the development of antiviral strategies.
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Affiliation(s)
- Clara C Posthuma
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands.
| | - Aartjan J W Te Velthuis
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom; Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Eric J Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, the Netherlands
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112
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Abstract
Coronaviruses are animal and human pathogens that can cause lethal zoonotic infections like SARS and MERS. They have polycistronic plus-stranded RNA genomes and belong to the order Nidovirales, a diverse group of viruses for which common ancestry was inferred from the common principles underlying their genome organization and expression, and from the conservation of an array of core replicase domains, including key RNA-synthesizing enzymes. Coronavirus genomes (~ 26–32 kilobases) are the largest RNA genomes known to date and their expansion was likely enabled by acquiring enzyme functions that counter the commonly high error frequency of viral RNA polymerases. The primary functions that direct coronavirus RNA synthesis and processing reside in nonstructural protein (nsp) 7 to nsp16, which are cleavage products of two large replicase polyproteins translated from the coronavirus genome. Significant progress has now been made regarding their structural and functional characterization, stimulated by technical advances like improved methods for bioinformatics and structural biology, in vitro enzyme characterization, and site-directed mutagenesis of coronavirus genomes. Coronavirus replicase functions include more or less universal activities of plus-stranded RNA viruses, like an RNA polymerase (nsp12) and helicase (nsp13), but also a number of rare or even unique domains involved in mRNA capping (nsp14, nsp16) and fidelity control (nsp14). Several smaller subunits (nsp7–nsp10) act as crucial cofactors of these enzymes and contribute to the emerging “nsp interactome.” Understanding the structure, function, and interactions of the RNA-synthesizing machinery of coronaviruses will be key to rationalizing their evolutionary success and the development of improved control strategies.
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Affiliation(s)
- E J Snijder
- Leiden University Medical Center, Leiden, The Netherlands.
| | - E Decroly
- Aix-Marseille Université, AFMB UMR 7257, Marseille, France; CNRS, AFMB UMR 7257, Marseille, France
| | - J Ziebuhr
- Institute of Medical Virology, Justus Liebig University Giessen, Giessen, Germany.
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113
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Abstract
Replication of the coronavirus genome requires continuous RNA synthesis, whereas transcription is a discontinuous process unique among RNA viruses. Transcription includes a template switch during the synthesis of subgenomic negative-strand RNAs to add a copy of the leader sequence. Coronavirus transcription is regulated by multiple factors, including the extent of base-pairing between transcription-regulating sequences of positive and negative polarity, viral and cell protein-RNA binding, and high-order RNA-RNA interactions. Coronavirus RNA synthesis is performed by a replication-transcription complex that includes viral and cell proteins that recognize cis-acting RNA elements mainly located in the highly structured 5' and 3' untranslated regions. In addition to many viral nonstructural proteins, the presence of cell nuclear proteins and the viral nucleocapsid protein increases virus amplification efficacy. Coronavirus RNA synthesis is connected with the formation of double-membrane vesicles and convoluted membranes. Coronaviruses encode proofreading machinery, unique in the RNA virus world, to ensure the maintenance of their large genome size.
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Affiliation(s)
- Isabel Sola
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049 Madrid, Spain;
| | - Fernando Almazán
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049 Madrid, Spain;
| | - Sonia Zúñiga
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049 Madrid, Spain;
| | - Luis Enjuanes
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas (CNB-CSIC), 28049 Madrid, Spain;
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114
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Arterivirus RNA-dependent RNA polymerase: Vital enzymatic activity remains elusive. Virology 2015; 487:68-74. [PMID: 26499043 PMCID: PMC7111705 DOI: 10.1016/j.virol.2015.10.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 09/25/2015] [Accepted: 10/01/2015] [Indexed: 12/19/2022]
Abstract
All RNA viruses encode an RNA-dependent RNA polymerase (RdRp), which in arteriviruses is expressed as the C-terminal domain of nonstructural protein 9 (nsp9). Previously, potent primer-dependent RdRp activity has been demonstrated for the homologous polymerase subunit (nsp12) of the distantly related coronaviruses. The only previous study focusing on the in vitro activity of nsp9 of an arterivirus (equine arteritis virus; EAV) reported weak de novo polymerase activity on homopolymeric RNA templates. However, this activity was not retained when Mn2+ ions were omitted from the assay or when biologically relevant templates were supplied, which prompted us to revisit the biochemical properties of this polymerase. Based on the properties of active-site mutants, we conclude that the RNA-synthesizing activities observed in de novo and primer-dependent polymerase and terminal transferase assays cannot be attributed to recombinant EAV nsp9-RdRp. Our results illustrate the potential pitfalls of characterizing polymerases using highly sensitive biochemical assays. Several recombinant RdRp preparations of Equine arteritis virus (EAV) were purified. No primer-dependent or de novo RdRp or terminal transferase activity was shown. One RdRp preparation showed products resembling those of phage T7 RNA polymerase. Mutation of the RdRp active site aspartates to alanine crippled the EAV viability. Characterizing low activity RdRp in sensitive enzymatic assays requires extra care.
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115
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Lehmann KC, Gulyaeva A, Zevenhoven-Dobbe JC, Janssen GMC, Ruben M, Overkleeft HS, van Veelen PA, Samborskiy DV, Kravchenko AA, Leontovich AM, Sidorov IA, Snijder EJ, Posthuma CC, Gorbalenya AE. Discovery of an essential nucleotidylating activity associated with a newly delineated conserved domain in the RNA polymerase-containing protein of all nidoviruses. Nucleic Acids Res 2015; 43:8416-34. [PMID: 26304538 PMCID: PMC4787807 DOI: 10.1093/nar/gkv838] [Citation(s) in RCA: 170] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 08/08/2015] [Indexed: 11/13/2022] Open
Abstract
RNA viruses encode an RNA-dependent RNA polymerase (RdRp) that catalyzes the synthesis of their RNA(s). In the case of positive-stranded RNA viruses belonging to the order Nidovirales, the RdRp resides in a replicase subunit that is unusually large. Bioinformatics analysis of this non-structural protein has now revealed a nidoviral signature domain (genetic marker) that is N-terminally adjacent to the RdRp and has no apparent homologs elsewhere. Based on its conservation profile, this domain is proposed to have nucleotidylation activity. We used recombinant non-structural protein 9 of the arterivirus equine arteritis virus (EAV) and different biochemical assays, including irreversible labeling with a GTP analog followed by a proteomics analysis, to demonstrate the manganese-dependent covalent binding of guanosine and uridine phosphates to a lysine/histidine residue. Most likely this was the invariant lysine of the newly identified domain, named nidovirus RdRp-associated nucleotidyltransferase (NiRAN), whose substitution with alanine severely diminished the described binding. Furthermore, this mutation crippled EAV and prevented the replication of severe acute respiratory syndrome coronavirus (SARS-CoV) in cell culture, indicating that NiRAN is essential for nidoviruses. Potential functions supported by NiRAN may include nucleic acid ligation, mRNA capping and protein-primed RNA synthesis, possibilities that remain to be explored in future studies.
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Affiliation(s)
- Kathleen C Lehmann
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Anastasia Gulyaeva
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Jessika C Zevenhoven-Dobbe
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - George M C Janssen
- Department of Immunohematology and Blood transfusion, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Mark Ruben
- Leiden Institute of Chemistry, Leiden University, 2300 CC, Leiden, The Netherlands
| | - Hermen S Overkleeft
- Leiden Institute of Chemistry, Leiden University, 2300 CC, Leiden, The Netherlands
| | - Peter A van Veelen
- Department of Immunohematology and Blood transfusion, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Dmitry V Samborskiy
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119899 Moscow, Russia
| | - Alexander A Kravchenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119899 Moscow, Russia
| | - Andrey M Leontovich
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119899 Moscow, Russia
| | - Igor A Sidorov
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Eric J Snijder
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Clara C Posthuma
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands
| | - Alexander E Gorbalenya
- Department of Medical Microbiology, Leiden University Medical Center, Leiden, 2300 RC, Leiden, The Netherlands Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119899 Moscow, Russia Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119899 Moscow, Russia
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116
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Mutations in coronavirus nonstructural protein 10 decrease virus replication fidelity. J Virol 2015; 89:6418-26. [PMID: 25855750 DOI: 10.1128/jvi.00110-15] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 04/02/2015] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED Coronaviruses (CoVs) are unique in encoding a 3'→5' exoribonuclease within nonstructural protein 14 (nsp14-ExoN) that is required for high-fidelity replication, likely via proofreading. nsp14 associates with the CoV RNA-dependent RNA polymerase (nsp12-RdRp), and nsp14-ExoN activity is enhanced by binding nsp10, a small nonenzymatic protein. However, it is not known whether nsp10 functions in the regulation of CoV replication fidelity. To test this, we engineered single and double alanine substitution mutations into the genome of murine hepatitis virus (MHV-A59) containing ExoN activity [ExoN(+)] at positions within nsp10 known to disrupt the nsp10-nsp14 interaction in vitro. We show that an nsp10 mutant, R80A/E82A-ExoN(+), was five to ten times more sensitive to treatment with the RNA mutagen 5-fluorouracil (5-FU) than wild-type (WT)-ExoN(+), suggestive of decreased replication fidelity. This decreased-fidelity phenotype was confirmed using two additional nucleoside analogs, 5-azacytidine and ribavirin. R80A/E82A-ExoN(+) reached a peak titer similar to and demonstrated RNA synthesis kinetics comparable to those seen with WT-ExoN(+). No change in 5-FU sensitivity was observed for R80A/E82A-ExoN(-) relative to MHV-ExoN(-), indicating that the decreased-fidelity phenotype of R80A/E82A-ExoN(-) is linked to the presence of ExoN activity. Our results demonstrate that nsp10 is important for CoV replication fidelity and support the hypothesis that nsp10 functions to regulate nsp14-ExoN activity during virus replication. IMPORTANCE The adaptive capacity of CoVs, as well as all other RNA viruses, is partially attributed to the presence of extensive population genetic diversity. However, decreased fidelity is detrimental to CoV replication and virulence; mutant CoVs with decreased replication fidelity are attenuated and more sensitive to inhibition by RNA mutagens. Thus, identifying the viral protein determinants of CoV fidelity is important for understanding CoV replication, pathogenesis, and virulence. In this report, we show that nsp10, a small, nonenzymatic viral protein, contributes to CoV replication fidelity. Our data support the hypothesis that CoVs have evolved multiple proteins, in addition to nsp14-ExoN, that are responsible for maintaining the integrity of the largest known RNA genomes.
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117
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Smith EC, Sexton NR, Denison MR. Thinking Outside the Triangle: Replication Fidelity of the Largest RNA Viruses. Annu Rev Virol 2014; 1:111-32. [PMID: 26958717 DOI: 10.1146/annurev-virology-031413-085507] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
When judged by ubiquity, adaptation, and emergence of new diseases, RNA viruses are arguably the most successful biological organisms. This success has been attributed to a defect of sorts: high mutation rates (low fidelity) resulting in mutant swarms that allow rapid selection for fitness in new environments. Studies of viruses with small RNA genomes have identified fidelity determinants in viral RNA-dependent RNA polymerases and have shown that RNA viruses likely replicate within a limited fidelity range to maintain fitness. In this review we compare the fidelity of small RNA viruses with that of the largest RNA viruses, the coronaviruses. Coronaviruses encode the first known viral RNA proofreading exoribonuclease, a function that likely allowed expansion of the coronavirus genome and that dramatically increases replication fidelity and the range of tolerated variation. We propose models for regulation of coronavirus fidelity and discuss the implications of altered fidelity for RNA virus replication, pathogenesis, and evolution.
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Affiliation(s)
- Everett Clinton Smith
- Department of Pediatrics.,Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232;
| | - Nicole R Sexton
- Department of Pathology, Microbiology, and Immunology, and.,Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232;
| | - Mark R Denison
- Department of Pediatrics.,Department of Pathology, Microbiology, and Immunology, and.,Elizabeth B. Lamb Center for Pediatric Research, Vanderbilt University Medical Center, Nashville, Tennessee 37232;
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118
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Subissi L, Imbert I, Ferron F, Collet A, Coutard B, Decroly E, Canard B. SARS-CoV ORF1b-encoded nonstructural proteins 12-16: replicative enzymes as antiviral targets. Antiviral Res 2014; 101:122-30. [PMID: 24269475 PMCID: PMC7113864 DOI: 10.1016/j.antiviral.2013.11.006] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 10/22/2013] [Accepted: 11/11/2013] [Indexed: 12/17/2022]
Abstract
The SARS (severe acute respiratory syndrome) pandemic caused ten years ago by the SARS-coronavirus (SARS-CoV) has stimulated a number of studies on the molecular biology of coronaviruses. This research has provided significant new insight into many mechanisms used by the coronavirus replication-transcription complex (RTC). The RTC directs and coordinates processes in order to replicate and transcribe the coronavirus genome, a single-stranded, positive-sense RNA of outstanding length (∼27-32kilobases). Here, we review the up-to-date knowledge on SARS-CoV replicative enzymes encoded in the ORF1b, i.e., the main RNA-dependent RNA polymerase (nsp12), the helicase/triphosphatase (nsp13), two unusual ribonucleases (nsp14, nsp15) and RNA-cap methyltransferases (nsp14, nsp16). We also review how these enzymes co-operate with other viral co-factors (nsp7, nsp8, and nsp10) to regulate their activity. These last ten years of research on SARS-CoV have considerably contributed to unravel structural and functional details of one of the most fascinating replication/transcription machineries of the RNA virus world. This paper forms part of a series of invited articles in Antiviral Research on "From SARS to MERS: 10years of research on highly pathogenic human coronaviruses".
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Affiliation(s)
- Lorenzo Subissi
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France
| | - Isabelle Imbert
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France
| | - François Ferron
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France
| | - Axelle Collet
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France
| | - Bruno Coutard
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France
| | - Etienne Decroly
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France
| | - Bruno Canard
- Laboratoire Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257 - CNRS et Aix-Marseille Université, ESIL Case 925, 13288 Marseille, France.
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119
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Neuman BW, Chamberlain P, Bowden F, Joseph J. Atlas of coronavirus replicase structure. Virus Res 2013; 194:49-66. [PMID: 24355834 PMCID: PMC7114488 DOI: 10.1016/j.virusres.2013.12.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 12/03/2013] [Accepted: 12/05/2013] [Indexed: 12/13/2022]
Abstract
Complete and up to date coverage of replicase protein structures for SARS-CoV. Discusses SARS-CoV structure in the context of other coronavirus structures. Summarizes data from a variety of structural methods to illuminate protein function. Uses models and predictions to fill gaps in the SARS-CoV structure. Discusses the high percentage of novel protein folds among SARS-CoV proteins.
The international response to SARS-CoV has produced an outstanding number of protein structures in a very short time. This review summarizes the findings of functional and structural studies including those derived from cryoelectron microscopy, small angle X-ray scattering, NMR spectroscopy, and X-ray crystallography, and incorporates bioinformatics predictions where no structural data is available. Structures that shed light on the function and biological roles of the proteins in viral replication and pathogenesis are highlighted. The high percentage of novel protein folds identified among SARS-CoV proteins is discussed.
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Affiliation(s)
| | | | - Fern Bowden
- School of Biological Sciences, University of Reading, Reading, UK
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120
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Defects in base excision repair sensitize cells to manganese in S. cerevisiae. BIOMED RESEARCH INTERNATIONAL 2013; 2013:295635. [PMID: 24282812 PMCID: PMC3825218 DOI: 10.1155/2013/295635] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022]
Abstract
Manganese (Mn) is essential for normal physiologic functioning; therefore, deficiencies and excess intake of manganese can result in disease. In humans, prolonged exposure to manganese causes neurotoxicity characterized by Parkinson-like symptoms. Mn(2+) has been shown to mediate DNA damage possibly through the generation of reactive oxygen species. In a recent publication, we showed that Mn induced oxidative DNA damage and caused lesions in thymines. This study further investigates the mechanisms by which cells process Mn(2+)-mediated DNA damage using the yeast S. cerevisiae. The strains most sensitive to Mn(2+) were those defective in base excision repair, glutathione synthesis, and superoxide dismutase mutants. Mn(2+) caused a dose-dependent increase in the accumulation of mutations using the CAN1 and lys2-10A mutator assays. The spectrum of CAN1 mutants indicates that exposure to Mn results in accumulation of base substitutions and frameshift mutations. The sensitivity of cells to Mn(2+) as well as its mutagenic effect was reduced by N-acetylcysteine, glutathione, and Mg(2+). These data suggest that Mn(2+) causes oxidative DNA damage that requires base excision repair for processing and that Mn interferes with polymerase fidelity. The status of base excision repair may provide a biomarker for the sensitivity of individuals to manganese.
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