1
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Thai QM, Phung HTT, Pham NQA, Horng JT, Tran PT, Tung NT, Ngo ST. Natural compounds inhibit Monkeypox virus methyltransferase VP39 in silico studies. J Biomol Struct Dyn 2024:1-9. [PMID: 38419271 DOI: 10.1080/07391102.2024.2321509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 02/15/2024] [Indexed: 03/02/2024]
Abstract
VP39, an essential 2'-O-RNA methyltransferase enzyme discovered in Monkeypox virus (MPXV), plays a vital role in viral RNA replication and transcription. Inhibition of the enzyme may prevent viral replication. In this context, using a combination of molecular docking and molecular dynamics (MDs) simulations, the inhibitory ability of NCI Diversity Set VII natural compounds to VP39 protein was investigated. It should be noted that the computed binding free energy of ligand via molecular docking and linear interaction energy (LIE) approaches are in good agreement with the corresponding experiments with coefficients of R = 0.72 and 0.75, respectively. NSC 319990, NSC 196515 and NSC 376254 compounds were demonstrated that can inhibit MPVX methyltransferase VP39 protein with the similar affinity compared to available inhibitor sinefungin. Moreover, nine residues involving Gln39, Gly68, Gly72, Asp95, Arg97, Val116, Asp138, Arg140 and Asn156 may be argued that they play an important role in binding process of inhibitors to VP39.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Quynh Mai Thai
- Laboratory of Biophysics, Institute for Advanced Study in Technology, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Pharmacy, Ton Duc Thang University, Ho Chi Minh City, Vietnam
| | - Huong T T Phung
- NTT Hi-Tech Institute, Nguyen Tat Thanh University, Ho Chi Minh City, Vietnam
| | - Ngoc Quynh Anh Pham
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, ROC
| | - Jim-Tong Horng
- Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, ROC
| | - Phuong-Thao Tran
- Department of Pharmaceutical Chemistry, Hanoi University of Pharmacy, Hanoi, Vietnam
| | - Nguyen Thanh Tung
- Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi, Vietnam
- Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - Son Tung Ngo
- Laboratory of Biophysics, Institute for Advanced Study in Technology, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Pharmacy, Ton Duc Thang University, Ho Chi Minh City, Vietnam
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2
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Wang DP, Zhao R, Wang HF, Wang MY, Hu WS, Lin MM, Shu W, Sun YJ, Cao JM, Cui W, Zhou X. Crystal structure of mRNA cap (guanine-N7) methyltransferase E12 subunit from monkeypox virus and discovery of its inhibitors. Int J Biol Macromol 2023; 253:127565. [PMID: 37866584 DOI: 10.1016/j.ijbiomac.2023.127565] [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: 05/02/2023] [Revised: 09/12/2023] [Accepted: 10/18/2023] [Indexed: 10/24/2023]
Abstract
In July 2022, the World Health Organization announced monkeypox as a public health emergency of international concern (PHEIC), and over 85,000 global cases have been reported currently. However, preventive and therapeutic treatments for the monkeypox virus (MPXV) remain limited. MPXV mRNA cap N7 methyltransferase (MTase) is composed of two subunits (E1 C-terminal domain (E1CTD) and E12) which are essential for the replication of MPXV. Here, we solved a 2.16 Å crystal structure of E12. We also docked the D1CTD of the vaccinia virus (VACV) corresponding to the E1CTD in MPXV with E12 and found critical residues at their interface. These residues were further used for drug screening. After virtual screening, the top 347 compounds were screened out and a list of top 20 potential MPXV E12 inhibitors were discovered, including Rutin, Quercitrin, Epigallocatechin, Rosuvastatin, 5-hydroxy-L-Tryptophan, and Deferasirox, etc., which were potential E12 inhibitors. Taking the advantage of the previously unrecognized special structure of MPXV MTase composing of E1CTD and E12 heterodimer, we screened for inhibitors targeting MTase for the first time based on the interface between the heterodimer of MPXV MTase. Our study may provide insights into the development of anti-MPXV drugs.
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Affiliation(s)
- De-Ping Wang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Rong Zhao
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Hao-Feng Wang
- School of Life Sciences, Tianjin University, Tianjin, China
| | - Mei-Yue Wang
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Wen-Shu Hu
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Meng-Meng Lin
- Institute of Life Sciences, Chongqing Medical University, Chongqing, China
| | - Wen Shu
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Yao-Jun Sun
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China
| | - Ji-Min Cao
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China.
| | - Wen Cui
- Institute of Life Sciences, Chongqing Medical University, Chongqing, China.
| | - Xin Zhou
- Key Laboratory of Cellular Physiology at Shanxi Medical University, Ministry of Education, Department of Physiology, Shanxi Medical University, Taiyuan, China.
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3
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Silhan J, Klima M, Otava T, Skvara P, Chalupska D, Chalupsky K, Kozic J, Nencka R, Boura E. Discovery and structural characterization of monkeypox virus methyltransferase VP39 inhibitors reveal similarities to SARS-CoV-2 nsp14 methyltransferase. Nat Commun 2023; 14:2259. [PMID: 37080993 PMCID: PMC10116469 DOI: 10.1038/s41467-023-38019-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 04/06/2023] [Indexed: 04/22/2023] Open
Abstract
Monkeypox is a disease with pandemic potential. It is caused by the monkeypox virus (MPXV), a double-stranded DNA virus from the Poxviridae family, that replicates in the cytoplasm and must encode for its own RNA processing machinery including the capping machinery. Here, we present crystal structures of its 2'-O-RNA methyltransferase (MTase) VP39 in complex with the pan-MTase inhibitor sinefungin and a series of inhibitors that were discovered based on it. A comparison of this 2'-O-RNA MTase with enzymes from unrelated single-stranded RNA viruses (SARS-CoV-2 and Zika) reveals a conserved sinefungin binding mode, implicating that a single inhibitor could be used against unrelated viral families. Indeed, several of our inhibitors such as TO507 also inhibit the coronaviral nsp14 MTase.
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Affiliation(s)
- Jan Silhan
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
| | - Martin Klima
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
| | - Tomas Otava
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
- Faculty of Food and Biochemical Technology, University of Chemistry and Technology, Prague 6, Czech Republic
| | - Petr Skvara
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
| | - Dominika Chalupska
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
| | - Karel Chalupsky
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
| | - Jan Kozic
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic
| | - Radim Nencka
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic.
| | - Evzen Boura
- Institute of Organic Chemistry and Biochemistry AS CR, Prague 6, Czech Republic.
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4
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Sutto-Ortiz P, Eléouët JF, Ferron F, Decroly E. Biochemistry of the Respiratory Syncytial Virus L Protein Embedding RNA Polymerase and Capping Activities. Viruses 2023; 15:v15020341. [PMID: 36851554 PMCID: PMC9960070 DOI: 10.3390/v15020341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/12/2023] [Accepted: 01/21/2023] [Indexed: 01/27/2023] Open
Abstract
The human respiratory syncytial virus (RSV) is a negative-sense, single-stranded RNA virus. It is the major cause of severe acute lower respiratory tract infection in infants, the elderly population, and immunocompromised individuals. There is still no approved vaccine or antiviral treatment against RSV disease, but new monoclonal prophylactic antibodies are yet to be commercialized, and clinical trials are in progress. Hence, urgent efforts are needed to develop efficient therapeutic treatments. RSV RNA synthesis comprises viral transcription and replication that are catalyzed by the large protein (L) in coordination with the phosphoprotein polymerase cofactor (P), the nucleoprotein (N), and the M2-1 transcription factor. The replication/transcription is orchestrated by the L protein, which contains three conserved enzymatic domains: the RNA-dependent RNA polymerase (RdRp), the polyribonucleotidyl transferase (PRNTase or capping), and the methyltransferase (MTase) domain. These activities are essential for the RSV replicative cycle and are thus considered as attractive targets for the development of therapeutic agents. In this review, we summarize recent findings about RSV L domains structure that highlight how the enzymatic activities of RSV L domains are interconnected, discuss the most relevant and recent antivirals developments that target the replication/transcription complex, and conclude with a perspective on identified knowledge gaps that enable new research directions.
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Affiliation(s)
| | - Jean-François Eléouët
- Unité de Virologie et Immunologie Moléculaires, INRAE, Université Paris Saclay, F78350 Jouy en Josas, France
| | - François Ferron
- Aix Marseille Université, CNRS, AFMB, UMR, 7257 Marseille, France
- European Virus Bioinformatics Center, Leutragraben 1, 07743 Jena, Germany
| | - Etienne Decroly
- Aix Marseille Université, CNRS, AFMB, UMR, 7257 Marseille, France
- Correspondence:
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5
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Yadav P, El-Kafrawy SA, El-Day MM, Alghafari WT, Faizo AA, Jha SK, Dwivedi VD, Azhar EI. Discovery of Small Molecules from Echinacea angustifolia Targeting RNA-Dependent RNA Polymerase of Japanese Encephalitis Virus. Life (Basel) 2022; 12:life12070952. [PMID: 35888042 PMCID: PMC9324244 DOI: 10.3390/life12070952] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/13/2022] [Accepted: 06/20/2022] [Indexed: 05/28/2023] Open
Abstract
The Japanese encephalitis virus (JEV), a mosquito-borne flavivirus that causes viral encephalitis leading to neural damage, is a major threat in most Asian countries. The RNA-dependent RNA polymerase (RdRp) present in the viral genome is the key component for genome replication, making it an attractive target for antiviral drug development. In this study, the natural products from Echinacea angustifolia were retrieved for structure-based virtual screening against JEV-RdRp. The top six compounds (Echinacoside, Echinacin, Rutin, Cynaroside, Quercetagetin 7-glucoside, and Kaempferol-3-glucoside) were obtained based on the highest negative docking score, ADMET (absorption, distribution, metabolism, excretion, and toxicity), and molecular interaction. The computational analysis of these selected compounds against the co-crystallized ligands, i.e., ATP and GTP, were performed. Further, 100 ns molecular dynamic simulation and post-free binding energy calculation of all the selected compounds complexed with JEV-RdRP were performed to check the stability of the complexes. The obtained results showed considerable stability and intermolecular interaction with native ligand-binding site residues of JEV-RdRp. Hence, selected natural compounds are admissible inhibitors of JEV-RdRp protein and can be considered for future antiviral drug development studies.
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Affiliation(s)
- Pardeep Yadav
- Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida 201310, India; (P.Y.); (S.K.J.)
- Center for Bioinformatics, Computational and Systems Biology, Pathfinder Research and Training Foundation, Greater Noida 201308, India
| | - Sherif A. El-Kafrawy
- Special Infectious Agents Unit-BSL-3, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21362, Saudi Arabia; (S.A.E.-K.); (M.M.E.-D.); (W.T.A.); (A.A.F.)
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21362, Saudi Arabia
| | - Mai M. El-Day
- Special Infectious Agents Unit-BSL-3, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21362, Saudi Arabia; (S.A.E.-K.); (M.M.E.-D.); (W.T.A.); (A.A.F.)
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21362, Saudi Arabia
| | - Wejdan T. Alghafari
- Special Infectious Agents Unit-BSL-3, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21362, Saudi Arabia; (S.A.E.-K.); (M.M.E.-D.); (W.T.A.); (A.A.F.)
- Clinical Nutrition Department, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21362, Saudi Arabia
| | - Arwa A. Faizo
- Special Infectious Agents Unit-BSL-3, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21362, Saudi Arabia; (S.A.E.-K.); (M.M.E.-D.); (W.T.A.); (A.A.F.)
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21362, Saudi Arabia
| | - Saurabh Kumar Jha
- Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida 201310, India; (P.Y.); (S.K.J.)
- Department of Biotechnology Engineering and Food Technology, Chandigarh University, Mohali 140413, India
- Department of Biotechnology, School of Applied & Life Sciences (SALS), Uttaranchal University, Dehradun 248007, India
| | - Vivek Dhar Dwivedi
- Center for Bioinformatics, Computational and Systems Biology, Pathfinder Research and Training Foundation, Greater Noida 201308, India
- Institute of Advanced Materials, IAAM, 59053 Ulrika, Sweden
| | - Esam I. Azhar
- Special Infectious Agents Unit-BSL-3, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21362, Saudi Arabia; (S.A.E.-K.); (M.M.E.-D.); (W.T.A.); (A.A.F.)
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21362, Saudi Arabia
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6
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Zhao Y, Rai J, Yu H, Li H. CryoEM structures of pseudouridine-free ribosome suggest impacts of chemical modifications on ribosome conformations. Structure 2022; 30:983-992.e5. [PMID: 35489333 DOI: 10.1016/j.str.2022.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 10/07/2021] [Accepted: 04/04/2022] [Indexed: 10/18/2022]
Abstract
Pseudouridine, the most abundant form of RNA modification, is known to play important roles in ribosome function. Mutations in human DKC1, the pseudouridine synthase responsible for catalyzing the ribosome RNA modification, cause translation deficiencies and are associated with a complex cancer predisposition. The structural basis for how pseudouridine impacts ribosome function remains uncharacterized. Here, we characterized structures and conformations of a fully modified and a pseudouridine-free ribosome from Saccharomyces cerevisiae in the absence of ligands or when bound with translocation inhibitor cycloheximide by electron cryomicroscopy. In the modified ribosome, the rearranged N1 atom of pseudouridine is observed to stabilize key functional motifs by establishing predominately water-mediated close contacts with the phosphate backbone. The pseudouridine-free ribosome, however, is devoid of such interactions and displays conformations reflective of abnormal inter-subunit movements. The erroneous motions of the pseudouridine-free ribosome may explain its observed deficiencies in translation.
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Affiliation(s)
- Yu Zhao
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Jay Rai
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Hongguo Yu
- Biological Science Department, Florida State University, Tallahassee, FL 32306, USA
| | - Hong Li
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA.
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7
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Yu D, Dai N, Wolf EJ, Corrêa IR, Zhou J, Wu T, Blumenthal RM, Zhang X, Cheng X. Enzymatic characterization of mRNA cap adenosine-N6 methyltransferase PCIF1 activity on uncapped RNAs. J Biol Chem 2022; 298:101751. [PMID: 35189146 PMCID: PMC8931429 DOI: 10.1016/j.jbc.2022.101751] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 02/15/2022] [Accepted: 02/16/2022] [Indexed: 02/08/2023] Open
Abstract
The phosphorylated RNA polymerase II CTD interacting factor 1 (PCIF1) is a methyltransferase that adds a methyl group to the N6-position of 2′O-methyladenosine (Am), generating N6, 2′O-dimethyladenosine (m6Am) when Am is the cap-proximal nucleotide. In addition, PCIF1 has ancillary methylation activities on internal adenosines (both A and Am), although with much lower catalytic efficiency relative to that of its preferred cap substrate. The PCIF1 preference for 2′O-methylated Am over unmodified A nucleosides is due mainly to increased binding affinity for Am. Importantly, it was recently reported that PCIF1 can methylate viral RNA. Although some viral RNA can be translated in the absence of a cap, it is unclear what roles PCIF1 modifications may play in the functionality of viral RNAs. Here we show, using in vitro assays of binding and methyltransfer, that PCIF1 binds an uncapped 5′-Am oligonucleotide with approximately the same affinity as that of a cap analog (KM = 0.4 versus 0.3 μM). In addition, PCIF1 methylates the uncapped 5′-Am with activity decreased by only fivefold to sixfold compared with its preferred capped substrate. We finally discuss the relationship between PCIF1-catalyzed RNA methylation, shown here to have broader substrate specificity than previously appreciated, and that of the RNA demethylase fat mass and obesity-associated protein (FTO), which demonstrates PCIF1-opposing activities on capped RNAs.
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Affiliation(s)
- Dan Yu
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Nan Dai
- New England Biolabs, Inc, Ipswich, Massachusetts, USA
| | - Eric J Wolf
- New England Biolabs, Inc, Ipswich, Massachusetts, USA
| | - Ivan R Corrêa
- New England Biolabs, Inc, Ipswich, Massachusetts, USA
| | - Jujun Zhou
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Tao Wu
- Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Robert M Blumenthal
- Department of Medical Microbiology and Immunology, and Program in Bioinformatics, The University of Toledo College of Medicine and Life Sciences, Toledo, Ohio, USA
| | - Xing Zhang
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
| | - Xiaodong Cheng
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
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8
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Enzymatic characterization of three human RNA adenosine methyltransferases reveals diverse substrate affinities and reaction optima. J Biol Chem 2021; 296:100270. [PMID: 33428944 PMCID: PMC7948815 DOI: 10.1016/j.jbc.2021.100270] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/06/2021] [Accepted: 01/07/2021] [Indexed: 11/22/2022] Open
Abstract
RNA methylations of varied RNA species (mRNA, tRNA, rRNA, non-coding RNA) generate a range of modified nucleotides, including N6-methyladenosine. Here we study the enzymology of three human RNA methyltransferases that methylate the adenosine amino group in diverse contexts, when it is: the first transcribed nucleotide after the mRNA cap (PCIF1), at position 1832 of 18S rRNA (MettL5-Trm112 complex), and within a hairpin in the 3′ UTR of the S-adenosyl-l-methionine synthetase (MettL16). Among these three enzymes, the catalytic efficiency ranges from PCIF1, with the fastest turnover rate of >230 h−1 μM−1 on mRNA cap analog, down to MettL16, which has the lowest rate of ∼3 h−1 μM−1 acting on an RNA hairpin. Both PCIF1 and MettL5 have a binding affinity (Km) of ∼1 μM or less for both substrates of SAM and RNA, whereas MettL16 has significantly lower binding affinities for both (Km >0.4 mM for SAM and ∼10 μM for RNA). The three enzymes are active over a wide pH range (∼5.4–9.4) and have different preferences for ionic strength. Sodium chloride at 200 mM markedly diminished methylation activity of MettL5-Trm112 complex, whereas MettL16 had higher activity in the range of 200 to 500 mM NaCl. Zinc ion inhibited activities of all three enzymes. Together, these results illustrate the diversity of RNA adenosine methyltransferases in their enzymatic mechanisms and substrate specificities and underline the need for assay optimization in their study.
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9
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Functional and computational identification of a rescue mutation near the active site of an mRNA methyltransferase. Sci Rep 2020; 10:21841. [PMID: 33318548 PMCID: PMC7736282 DOI: 10.1038/s41598-020-79026-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 12/03/2020] [Indexed: 11/08/2022] Open
Abstract
RNA-based drugs are an emerging class of therapeutics combining the immense potential of DNA gene-therapy with the absence of genome integration-associated risks. While the synthesis of such molecules is feasible, large scale in vitro production of humanised mRNA remains a biochemical and economical challenge. Human mRNAs possess two post-transcriptional modifications at their 5' end: an inverted methylated guanosine and a unique 2'O-methylation on the ribose of the penultimate nucleotide. One strategy to precisely methylate the 2' oxygen is to use viral mRNA methyltransferases that have evolved to escape the host's cell immunity response following virus infection. However, these enzymes are ill-adapted to industrial processes and suffer from low turnovers. We have investigated the effects of homologous and orthologous active-site mutations on both stability and transferase activity, and identified new functional motifs in the interaction network surrounding the catalytic lysine. Our findings suggest that despite their low catalytic efficiency, the active-sites of viral mRNA methyltransferases have low mutational plasticity, while mutations in a defined third shell around the active site have strong effects on folding, stability and activity in the variant enzymes, mostly via network-mediated effects.
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10
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Pelletier J, Schmeing TM, Sonenberg N. The multifaceted eukaryotic cap structure. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 12:e1636. [PMID: 33300197 DOI: 10.1002/wrna.1636] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 10/16/2020] [Accepted: 11/03/2020] [Indexed: 12/13/2022]
Abstract
The 5' cap structure is added onto RNA polymerase II transcripts soon after initiation of transcription and modulates several post-transcriptional regulatory events involved in RNA maturation. It is also required for stimulating translation initiation of many cytoplasmic mRNAs and serves to protect mRNAs from degradation. These functional properties of the cap are mediated by several cap binding proteins (CBPs) involved in nuclear and cytoplasmic gene expression steps. The role that CBPs play in gene regulation, as well as the biophysical nature by which they recognize the cap, is quite intricate. Differences in mechanisms of capping as well as nuances in cap recognition speak to the potential of targeting these processes for drug development. In this review, we focus on recent findings concerning the cap epitranscriptome, our understanding of cap binding by different CBPs, and explore therapeutic targeting of CBP-cap interaction. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Processing > Capping and 5' End Modifications Translation > Translation Mechanisms.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Department of Oncology, McGill University, Montreal, Quebec, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montreal, Quebec, Canada
| | - T Martin Schmeing
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Centre de Recherche en Biologie Structurale, McGill University, Montreal, Quebec, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
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11
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Structure-Based Deep Mining Reveals First-Time Annotations for 46 Percent of the Dark Annotation Space of the 9,671-Member Superproteome of the Nucleocytoplasmic Large DNA Viruses. J Virol 2020; 94:JVI.00854-20. [PMID: 32999026 DOI: 10.1128/jvi.00854-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 09/16/2020] [Indexed: 12/20/2022] Open
Abstract
We conducted an exhaustive search for three-dimensional structural homologs to the proteins of 20 key phylogenetically distinct nucleocytoplasmic DNA viruses (NCLDV). Structural matches covered 429 known protein domain superfamilies, with the most highly represented being ankyrin repeat, P-loop NTPase, F-box, protein kinase, and membrane occupation and recognition nexus (MORN) repeat. Domain superfamily diversity correlated with genome size, but a diversity of around 200 superfamilies appeared to correlate with an abrupt switch to paralogization. Extensive structural homology was found across the range of eukaryotic RNA polymerase II subunits and their associated basal transcription factors, with the coordinated gain and loss of clusters of subunits on a virus-by-virus basis. The total number of predicted endonucleases across the 20 NCLDV was nearly quadrupled from 36 to 132, covering much of the structural and functional diversity of endonucleases throughout the biosphere in DNA restriction, repair, and homing. Unexpected findings included capsid protein-transcription factor chimeras; endonuclease chimeras; enzymes for detoxification; antimicrobial peptides and toxin-antitoxin systems associated with symbiosis, immunity, and addiction; and novel proteins for membrane abscission and protein turnover.IMPORTANCE We extended the known annotation space for the NCLDV by 46%, revealing high-probability structural matches for fully 45% of the 9,671 query proteins and confirming up to 98% of existing annotations per virus. The most prevalent protein families included ankyrin repeat- and MORN repeat-containing proteins, many of which included an F-box, suggesting extensive host cell modulation among the NCLDV. Regression suggested a minimum requirement for around 36 protein structural superfamilies for a viable NCLDV, and beyond around 200 superfamilies, genome expansion by the acquisition of new functions was abruptly replaced by paralogization. We found homologs to herpesvirus surface glycoprotein gB in cytoplasmic viruses. This study provided the first prediction of an endonuclease in 10 of the 20 viruses examined; the first report in a virus of a phenolic acid decarboxylase, proteasomal subunit, or cysteine knot (defensin) protein; and the first report of a prokaryotic-type ribosomal protein in a eukaryotic virus.
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12
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Roy P. Bluetongue virus assembly and exit pathways. Adv Virus Res 2020; 108:249-273. [PMID: 33837718 DOI: 10.1016/bs.aivir.2020.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Bluetongue virus (BTV) is an insect-vectored emerging pathogen of wild ruminants and livestock in many parts of the world. The virion particle is a complex structure of consecutive layers of protein surrounding a genome of 10 double-stranded (ds) RNA segments. BTV has been studied extensively as a model system for large, nonenveloped dsRNA viruses. A combination of recombinant proteins and particles together with reverse genetics, high-resolution structural analysis by X-ray crystallography and cryo-electron microscopy techniques have been utilized to provide an order for the assembly of the capsid shell and the protein sequestration required for it. Further, a reconstituted in vitro assembly system and RNA-RNA interaction assay, have defined the individual steps required for the assembly and packaging of the 10-segmented RNA genome. In addition, various microscopic techniques have been utilized to illuminate the stages of virus maturation and its egress via multiple pathways. These findings have not only given an overall understanding of BTV assembly and morphogenesis but also indicated that similar assembly and egress pathways are likely to be used by related viruses and provided an informed starting point for intervention or prevention.
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Affiliation(s)
- Polly Roy
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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13
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Viswanathan T, Arya S, Chan SH, Qi S, Dai N, Misra A, Park JG, Oladunni F, Kovalskyy D, Hromas RA, Martinez-Sobrido L, Gupta YK. Structural basis of RNA cap modification by SARS-CoV-2. Nat Commun 2020; 11:3718. [PMID: 32709886 PMCID: PMC7381649 DOI: 10.1038/s41467-020-17496-8] [Citation(s) in RCA: 151] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 07/04/2020] [Indexed: 02/06/2023] Open
Abstract
The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of COVID-19 illness, has caused millions of infections worldwide. In SARS coronaviruses, the non-structural protein 16 (nsp16), in conjunction with nsp10, methylates the 5'-end of virally encoded mRNAs to mimic cellular mRNAs, thus protecting the virus from host innate immune restriction. We report here the high-resolution structure of a ternary complex of SARS-CoV-2 nsp16 and nsp10 in the presence of cognate RNA substrate analogue and methyl donor, S-adenosyl methionine (SAM). The nsp16/nsp10 heterodimer is captured in the act of 2'-O methylation of the ribose sugar of the first nucleotide of SARS-CoV-2 mRNA. We observe large conformational changes associated with substrate binding as the enzyme transitions from a binary to a ternary state. This induced fit model provides mechanistic insights into the 2'-O methylation of the viral mRNA cap. We also discover a distant (25 Å) ligand-binding site unique to SARS-CoV-2, which can alternatively be targeted, in addition to RNA cap and SAM pockets, for antiviral development.
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Affiliation(s)
- Thiruselvam Viswanathan
- Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, 8403 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Shailee Arya
- Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, 8403 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Siu-Hong Chan
- New England Biolabs, 240 County Road, Ipswich, MA, 01938, USA
| | - Shan Qi
- Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, 8403 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Nan Dai
- New England Biolabs, 240 County Road, Ipswich, MA, 01938, USA
| | - Anurag Misra
- Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, 8403 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Jun-Gyu Park
- Texas Biomedical Research Institute, San Antonio, TX, 78227, USA
| | - Fatai Oladunni
- Texas Biomedical Research Institute, San Antonio, TX, 78227, USA
| | - Dmytro Kovalskyy
- Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, 8403 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Robert A Hromas
- Division of Hematology and Oncology, Department of Medicine, University of Texas Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | | | - Yogesh K Gupta
- Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, 8403 Floyd Curl Drive, San Antonio, TX, 78229, USA.
- Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA.
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14
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Wu J, Ye HQ, Zhang QY, Lu G, Zhang B, Gong P. A conformation-based intra-molecular initiation factor identified in the flavivirus RNA-dependent RNA polymerase. PLoS Pathog 2020; 16:e1008484. [PMID: 32357182 PMCID: PMC7219791 DOI: 10.1371/journal.ppat.1008484] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 05/13/2020] [Accepted: 03/18/2020] [Indexed: 12/26/2022] Open
Abstract
The flaviviruses pose serious threats to human health. Being a natural fusion of a methyltransferase (MTase) and an RNA-dependent RNA polymerase (RdRP), NS5 is the most conserved flavivirus protein and an important antiviral target. Previously reported NS5 structures represented by those from the Japanese encephalitis virus (JEV) and Dengue virus serotype 3 (DENV3) exhibit two apparently different global conformations, defining two sets of intra-molecular MTase-RdRP interactions. However, whether these NS5 conformations are conserved in flaviviruses and their specific functions remain elusive. Here we report two forms of DENV serotype 2 (DENV2) NS5 crystal structures representing two conformational states with defined analogies to the JEV-mode and DENV3-mode conformations, respectively, demonstrating the conservation of both conformation modes and providing clues for how different conformational states may be interconnected. Data from in vitro polymerase assays further demonstrate that perturbing the JEV-mode but not the DENV3-mode intra-molecular interactions inhibits catalysis only at initiation, while the cell-based virological analysis suggests that both modes of interactions are important for virus proliferation. Our work highlights the role of MTase as a unique intra-molecular initiation factor specifically only through the JEV-mode conformation, providing an example of conformation-based crosstalk between naturally fused protein functional modules.
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Affiliation(s)
- Jiqin Wu
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, China
- University of Chinese Academy of Sciences, Beijing, China
- Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Han-Qing Ye
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Qiu-Yan Zhang
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Guoliang Lu
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bo Zhang
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Peng Gong
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, Hubei, China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, China
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15
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Viswanathan T, Arya S, Chan SH, Qi S, Dai N, Hromas RA, Park JG, Oladunni F, Martinez-Sobrido L, Gupta YK. Structural Basis of RNA Cap Modification by SARS-CoV-2 Coronavirus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020:2020.04.26.061705. [PMID: 32511383 PMCID: PMC7263512 DOI: 10.1101/2020.04.26.061705] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The novel severe acute respiratory syndrome coronoavirus-2 (SARS-CoV-2), the causative agent of COVID-19 illness, has caused over 2 million infections worldwide in four months. In SARS coronaviruses, the non-structural protein 16 (nsp16) methylates the 5'-end of virally encoded mRNAs to mimic cellular mRNAs, thus protecting the virus from host innate immune restriction. We report here the high-resolution structure of a ternary complex of full-length nsp16 and nsp10 of SARS-CoV-2 in the presence of cognate RNA substrate and a methyl donor, S-adenosyl methionine. The nsp16/nsp10 heterodimer was captured in the act of 2'-O methylation of the ribose sugar of the first nucleotide of SARS-CoV-2 mRNA. We reveal large conformational changes associated with substrate binding as the enzyme transitions from a binary to a ternary state. This structure provides new mechanistic insights into the 2'-O methylation of the viral mRNA cap. We also discovered a distantly located ligand-binding site unique to SARS-CoV-2 that may serve as an alternative target site for antiviral development.
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Affiliation(s)
- Thiruselvam Viswanathan
- Greehey Children’s Cancer Research Institute, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Shailee Arya
- Greehey Children’s Cancer Research Institute, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
| | | | - Shan Qi
- Greehey Children’s Cancer Research Institute, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Nan Dai
- New England Biolabs, Ipswich, MA
| | - Robert A. Hromas
- Division of Hematology and Oncology, Department of Medicine, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
| | - Jun-Gyu Park
- Texas Biomedical Research Institute, San Antonio, TX
| | | | | | - Yogesh K. Gupta
- Greehey Children’s Cancer Research Institute, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, 8403 Floyd Curl Drive, San Antonio, TX 78229, USA
- Lead contact
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16
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Manning M, Jiang Y, Wang R, Liu L, Rode S, Bonahoom M, Kim S, Yang ZQ. Pan-cancer analysis of RNA methyltransferases identifies FTSJ3 as a potential regulator of breast cancer progression. RNA Biol 2020; 17:474-486. [PMID: 31957540 PMCID: PMC7237164 DOI: 10.1080/15476286.2019.1708549] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
RNA methylation, catalysed by a set of RNA methyltransferases (RNMTs), modulates RNA structures, properties, and biological functions. RNMTs are increasingly documented to be dysregulated in various human diseases, particularly developmental disorders and cancer. However, the genomic and transcriptomic alterations of RNMTs, as well as their functional roles in human cancer, are limited. In this study, we utilized an unbiased approach to examine copy number alterations and mutation rates of 58 RNMTs in more than 10,000 clinical samples across 32 human cancer types. We also investigated these alterations and RNMT expression level as they related to clinical features such as tumour subtype, grade, and survival in a large cohort of tumour samples, focusing on breast cancer. Loss-of-function analysis was performed to examine RNMT candidates with important roles in growth and viability of breast cancer cells. We identified a subset of RNMTs, notably TRMT12, NSUN2, TARBP1, and FTSJ3, that were amplified or mutated in a subset of human cancers. Several RNMTs were significantly associated with breast cancer aggressiveness and poor prognosis. Loss-of-function analysis indicated FTSJ3, a 2'-O-Me methyltransferase, as a candidate RNMT with functional roles in promoting cancer growth and survival. A subset of RNMTs, like FTSJ3, represents promising novel targets for anticancer drug discovery. Our findings provide a framework for further study of the functional consequences of RNMT alterations in human cancer and for developing therapies that target cancer-promoting RNMTs in the future.
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Affiliation(s)
- Morenci Manning
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Yuanyuan Jiang
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Rui Wang
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA.,Department of Diagnostics of Chinese Medicine, Hebei University of Chinese Medicine, Hebei, China
| | - Lanxin Liu
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Shomita Rode
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Madison Bonahoom
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Seongho Kim
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA.,Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, MI, USA
| | - Zeng-Quan Yang
- Department of Oncology, Wayne State University School of Medicine, Detroit, MI, USA.,Molecular Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Detroit, MI, USA
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17
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FTSJ3 is an RNA 2'-O-methyltransferase recruited by HIV to avoid innate immune sensing. Nature 2019; 565:500-504. [PMID: 30626973 DOI: 10.1038/s41586-018-0841-4] [Citation(s) in RCA: 138] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 12/04/2018] [Indexed: 11/08/2022]
Abstract
In mammals, 2'-O-methylation of RNA is a molecular signature by which the cellular innate immune system distinguishes endogenous from exogenous messenger RNA1-3. However, the molecular functions of RNA 2'-O-methylation are not well understood. Here we have purified TAR RNA-binding protein (TRBP) and its interacting partners and identified a DICER-independent TRBP complex containing FTSJ3, a putative 2'-O-methyltransferase (2'O-MTase). In vitro and ex vivo experiments show that FTSJ3 is a 2'O-MTase that is recruited to HIV RNA through TRBP. Using RiboMethSeq analysis4, we identified predominantly FTSJ3-dependent 2'-O-methylations at specific residues on the viral genome. HIV-1 viruses produced in FTSJ3 knockdown cells show reduced 2'-O-methylation and trigger expression of type 1 interferons (IFNs) in human dendritic cells through the RNA sensor MDA5. This induction of IFN-α and IFN-β leads to a reduction in HIV expression. We have identified an unexpected mechanism used by HIV-1 to evade innate immune recognition: the recruitment of the TRBP-FTSJ3 complex to viral RNA and its 2'-O-methylation.
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18
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Chatrin C, Talapatra SK, Canard B, Kozielski F. The structure of the binary methyltransferase-SAH complex from Zika virus reveals a novel conformation for the mechanism of mRNA capping. Oncotarget 2017; 9:3160-3171. [PMID: 29423037 PMCID: PMC5790454 DOI: 10.18632/oncotarget.23223] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 11/15/2017] [Indexed: 11/25/2022] Open
Abstract
Zika virus, a flavivirus like Dengue and West Nile viruses, poses a significant risk as a pathogen in the category of emerging infectious diseases. Zika infections typically cause nonspecific, mild symptoms, but can also manifest as a neurological disorder like Guillain-Barré syndrome. Infection in pregnant women is linked to microcephaly in newborn infants. The methyltransferase domain of the non-structural protein 5 is responsible for two sequential methylations of the 5′-RNA cap. This is crucial for genome stability, efficient translation, and escape from the host immune response. Here we present the crystal structures of the Zika methyltransferase domain in complex with the methyl-donor SAM and its by-product SAH. The methyltransferase-SAH binary complex presents a new conformation of a “closed” or “obstructed” state that would restrict the binding of new RNA for capping. The combination and comparison of our new structures with recently published Zika methyltransferase structures provide a first glimpse into the structural mechanism of Zika virus mRNA capping.
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Affiliation(s)
- Chatrin Chatrin
- Department of Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, WC1N 1AX, London, United Kingdom
| | - Sandeep K Talapatra
- Department of Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, WC1N 1AX, London, United Kingdom
| | - Bruno Canard
- CNRS, Aix Marseille University, AFMB UMR7257, Marseille, France
| | - Frank Kozielski
- Department of Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, WC1N 1AX, London, United Kingdom
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19
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Decroly E, Canard B. Biochemical principles and inhibitors to interfere with viral capping pathways. Curr Opin Virol 2017; 24:87-96. [PMID: 28527860 PMCID: PMC7185569 DOI: 10.1016/j.coviro.2017.04.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 04/07/2017] [Accepted: 04/10/2017] [Indexed: 12/16/2022]
Abstract
Many viruses cap their mRNAs with their own enzymes. The latter have significantly different structures and mechanisms from cellular capping enzymes. Unique active-site architecture and mechanisms should expedite inhibitor design. Capping enzymes and/or cap-methyltransferases are designated antiviral targets.
Messenger RNAs are decorated by a cap structure, which is essential for their translation into proteins. Many viruses have developed strategies in order to cap their mRNAs. The cap is either synthetized by a subset of viral or cellular enzymes, or stolen from capped cellular mRNAs by viral endonucleases (‘cap-snatching’). Reverse genetic studies provide evidence that inhibition of viral enzymes belonging to the capping pathway leads to inhibition of virus replication. The replication defect results from reduced protein synthesis as well as from detection of incompletely capped RNAs by cellular innate immunity sensors. Thus, it is now admitted that capping enzymes are validated antiviral targets, as their inhibition will support an antiviral response in addition to the attenuation of viral mRNA translation. In this review, we describe the different viral enzymes involved in mRNA capping together with relevant inhibitors, and their biochemical features useful in inhibitor discovery.
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Affiliation(s)
- Etienne Decroly
- CNRS, Aix Marseille University, AFMB UMR7257, Marseille, France.
| | - Bruno Canard
- CNRS, Aix Marseille University, AFMB UMR7257, Marseille, France.
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20
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Batra M, Sharma R, Malik A, Dhindwal S, Kumar P, Tomar S. Crystal structure of pentapeptide-independent chemotaxis receptor methyltransferase (CheR) reveals idiosyncratic structural determinants for receptor recognition. J Struct Biol 2016; 196:364-374. [PMID: 27544050 DOI: 10.1016/j.jsb.2016.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 08/10/2016] [Accepted: 08/17/2016] [Indexed: 01/08/2023]
Abstract
Chemotactic methyltransferase, CheR catalyse methylation of specific glutamate residues in the cytoplasmic domain of methyl-accepting chemotactic protein receptors (MCPRs). The methylation of MCPRs is essential for the chemical sensing and chemotactic bacterial mobility towards favorable chemicals or away from unfavorable ones. In this study, crystal structure of B. subtilis CheR (BsCheR) in complex with S-adenosyl-l-homocysteine (SAH) has been determined to 1.8Å resolution. This is the first report of crystal structure belonging to the pentapeptide-independent CheR (PICheR) class. Till date, only one crystal structure of CheR from S. typhimurium (StCheR) belonging to pentapeptide-dependent CheR (PDCheR) class is available. Structural analysis of BsCheR reveals a helix-X-helix motif (HXH) with Asp53 as the linker residue in the N-terminal domain. The key structural features of the PDCheR β-subdomain involved in the formation of a tight complex with the pentapeptide binding motif in MCPRs were found to be absent in the structure of BsCheR. Additionally, isothermal titration calorimetry (ITC) experiments were performed to investigate S-adenosyl-(l)-methionine (SAM) binding affinity and KD was determined to be 0.32mM. The structure of BsCheR reveals that mostly residues of the large C-terminal domain contribute to SAH binding, with contributions of few residues from the linker region and the N-terminal domain. Structural investigations and sequence analysis carried out in this study provide critical insights into the distinct receptor recognition mechanism of the PDCheR and PICheR methyltransferase classes.
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Affiliation(s)
- Monu Batra
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India
| | - Rajesh Sharma
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India
| | - Anjali Malik
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India
| | - Sonali Dhindwal
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India
| | - Pravindra Kumar
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India
| | - Shailly Tomar
- Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee 247667, India.
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21
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Paesen GC, Collet A, Sallamand C, Debart F, Vasseur JJ, Canard B, Decroly E, Grimes JM. X-ray structure and activities of an essential Mononegavirales L-protein domain. Nat Commun 2015; 6:8749. [PMID: 26549102 PMCID: PMC4659945 DOI: 10.1038/ncomms9749] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 09/28/2015] [Indexed: 12/15/2022] Open
Abstract
The L protein of mononegaviruses harbours all catalytic activities for genome replication and transcription. It contains six conserved domains (CR-I to -VI; Fig. 1a). CR-III has been linked to polymerase and polyadenylation activity, CR-V to mRNA capping and CR-VI to cap methylation. However, how these activities are choreographed is poorly understood. Here we present the 2.2-Å X-ray structure and activities of CR-VI+, a portion of human Metapneumovirus L consisting of CR-VI and the poorly conserved region at its C terminus, the +domain. The CR-VI domain has a methyltransferase fold, which besides the typical S-adenosylmethionine-binding site ((SAM)P) also contains a novel pocket ((NS)P) that can accommodate a nucleoside. CR-VI lacks an obvious cap-binding site, and the (SAM)P-adjoining site holding the nucleotides undergoing methylation ((SUB)P) is unusually narrow because of the overhanging +domain. CR-VI+ sequentially methylates caps at their 2'O and N7 positions, and also displays nucleotide triphosphatase activity.
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Affiliation(s)
- Guido C. Paesen
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, OX3 7BN UK
| | - Axelle Collet
- AFMB, CNRS, Aix-Marseille University, UMR 7257, Case 925, 163 Avenue de Luminy, Marseille, 13288 France
| | - Corinne Sallamand
- Department of Nucleic Acids, IBMM, UMR 5247, CNRS, Université Montpellier, ENSCM, Campus Triolet, Place E. Bataillon, Montpellier, 34095 France
| | - Françoise Debart
- Department of Nucleic Acids, IBMM, UMR 5247, CNRS, Université Montpellier, ENSCM, Campus Triolet, Place E. Bataillon, Montpellier, 34095 France
| | - Jean-Jacques Vasseur
- Department of Nucleic Acids, IBMM, UMR 5247, CNRS, Université Montpellier, ENSCM, Campus Triolet, Place E. Bataillon, Montpellier, 34095 France
| | - Bruno Canard
- AFMB, CNRS, Aix-Marseille University, UMR 7257, Case 925, 163 Avenue de Luminy, Marseille, 13288 France
| | - Etienne Decroly
- AFMB, CNRS, Aix-Marseille University, UMR 7257, Case 925, 163 Avenue de Luminy, Marseille, 13288 France
| | - Jonathan M. Grimes
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, OX3 7BN UK
- Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE UK
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22
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Byszewska M, Śmietański M, Purta E, Bujnicki JM. RNA methyltransferases involved in 5' cap biosynthesis. RNA Biol 2015; 11:1597-607. [PMID: 25626080 PMCID: PMC4615557 DOI: 10.1080/15476286.2015.1004955] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
In eukaryotes and viruses that infect them, the 5′ end of mRNA molecules, and also many other functionally important RNAs, are modified to form a so-called cap structure that is important for interactions of these RNAs with many nuclear and cytoplasmic proteins. The RNA cap has multiple roles in gene expression, including enhancement of RNA stability, splicing, nucleocytoplasmic transport, and translation initiation. Apart from guanosine addition to the 5′ end in the most typical cap structure common to transcripts produced by RNA polymerase II (in particular mRNA), essentially all cap modifications are due to methylation. The complexity of the cap structure and its formation can range from just a single methylation of the unprocessed 5′ end of the primary transcript, as in mammalian U6 and 7SK, mouse B2, and plant U3 RNAs, to an elaborate m7Gpppm6,6AmpAmpCmpm3Um structure at the 5′ end of processed RNA in trypanosomes, which are formed by as many as 8 methylation reactions. While all enzymes responsible for methylation of the cap structure characterized to date were found to belong to the same evolutionarily related and structurally similar Rossmann Fold Methyltransferase superfamily, that uses the same methyl group donor, S-adenosylmethionine; the enzymes also exhibit interesting differences that are responsible for their distinct functions. This review focuses on the evolutionary classification of enzymes responsible for cap methylation in RNA, with a focus on the sequence relationships and structural similarities and dissimilarities that provide the basis for understanding the mechanism of biosynthesis of different caps in cellular and viral RNAs. Particular attention is paid to the similarities and differences between methyltransferases from human cells and from human pathogens that may be helpful in the development of antiviral and antiparasitic drugs.
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23
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Yu X, Jiang J, Sun J, Zhou ZH. A putative ATPase mediates RNA transcription and capping in a dsRNA virus. eLife 2015; 4:e07901. [PMID: 26240998 PMCID: PMC4522710 DOI: 10.7554/elife.07901] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Accepted: 06/19/2015] [Indexed: 11/13/2022] Open
Abstract
mRNA transcription in dsRNA viruses is a highly regulated process but the mechanism of this regulation is not known. Here, by nucleoside triphosphatase (NTPase) assay and comparisons of six high-resolution (2.9-3.1 Å) cryo-electron microscopy structures of cytoplasmic polyhedrosis virus with bound ligands, we show that the large sub-domain of the guanylyltransferase (GTase) domain of the turret protein (TP) also has an ATP-binding site and is likely an ATPase. S-adenosyl-L-methionine (SAM) acts as a signal and binds the methylase-2 domain of TP to induce conformational change of the viral capsid, which in turn activates the putative ATPase. ATP binding/hydrolysis leads to an enlarged capsid for efficient mRNA synthesis, an open GTase domain for His217-mediated guanylyl transfer, and an open methylase-1 domain for SAM binding and methyl transfer. Taken together, our data support a role of the putative ATPase in mediating the activation of mRNA transcription and capping within the confines of the virus.
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Affiliation(s)
- Xuekui Yu
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Jiansen Jiang
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Jingchen Sun
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, United States
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Functional insights from molecular modeling, docking, and dynamics study of a cypoviral RNA dependent RNA polymerase. J Mol Graph Model 2015; 61:160-74. [PMID: 26264734 DOI: 10.1016/j.jmgm.2015.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/27/2015] [Accepted: 07/18/2015] [Indexed: 11/20/2022]
Abstract
Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) contains 11 double stranded RNA genome segments and infects tasar silkworm A. mylitta. RNA-dependent RNA polymerase (RdRp) is reported as a key enzyme responsible for propagation of the virus in the host cell but its structure function relationship still remains elusive. Here a computational approach has been taken to compare sequence and secondary structure of AmCPV RdRp with other viral RdRps to identify consensus motifs. Then a reliable pairwise sequence alignment of AmCPV RdRp with its closest sequence structure homologue λ3 RdRp is done to predict three dimensional structure of AmCPV RdRp. After comparing with other structurally known viral RdRps, important sequence and/or structural features involved in substrate entry or binding, polymerase reaction and the product release events have been identified. A conserved RNA pentanucleotide (5'-AGAGC-3') at the 3'-end of virus genome is predicted as cis-acting signal for RNA synthesis and its docking and simulation study along with the model of AmCPV RdRp has allowed to predict mode of template binding by the viral polymerase. It is found that template RNA enters into the catalytic center through nine sequence-independent and two sequence-dependent interactions with the specific amino acid residues. However, number of sequence dependent interactions remains almost same during 10 nano-second simulation time while total number of interactions decreases. Further, docking of N(7)-methyl-GpppG (mRNA cap) on the model as well as prediction of RNA secondary structure has shown the template entry process in the active site. These findings have led to postulate the mechanism of RNA-dependent RNA polymerization process by AmCPV RdRp. To our knowledge, this is the first report to evaluate structure function relationship of a cypoviral RdRp.
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Priet S, Lartigue A, Debart F, Claverie JM, Abergel C. mRNA maturation in giant viruses: variation on a theme. Nucleic Acids Res 2015; 43:3776-88. [PMID: 25779049 PMCID: PMC4402537 DOI: 10.1093/nar/gkv224] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 03/03/2015] [Accepted: 03/04/2015] [Indexed: 12/02/2022] Open
Abstract
Giant viruses from the Mimiviridae family replicate entirely in their host cytoplasm where their genes are transcribed by a viral transcription apparatus. mRNA polyadenylation uniquely occurs at hairpin-forming palindromic sequences terminating viral transcripts. Here we show that a conserved gene cluster both encode the enzyme responsible for the hairpin cleavage and the viral polyA polymerases (vPAP). Unexpectedly, the vPAPs are homodimeric and uniquely self-processive. The vPAP backbone structures exhibit a symmetrical architecture with two subdomains sharing a nucleotidyltransferase topology, suggesting that vPAPs originate from an ancestral duplication. A Poxvirus processivity factor homologue encoded by Megavirus chilensis displays a conserved 5'-GpppA 2'O methyltransferase activity but is also able to internally methylate the mRNAs' polyA tails. These findings elucidate how the arm wrestling between hosts and their viruses to access the translation machinery is taking place in Mimiviridae.
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Affiliation(s)
- Stéphane Priet
- Architecture et Fonction des Macromolécules Biologiques, CNRS UMR 7257, Aix-Marseille Université, 163 Avenue de Luminy, Case 932, 13288 Marseille cedex 9, France
| | - Audrey Lartigue
- Structural and Genomic Information Laboratory, UMR 7256 (IMM FR 3479) CNRS Aix-Marseille Université, 163 Avenue de Luminy, Case 934, 13288 Marseille cedex 9, France
| | - Françoise Debart
- IBMM, UMR 5247, CNRS-UM1-UM2, Université Montpellier 2, Place Eugène Bataillon, 34095 Montpellier, France
| | - Jean-Michel Claverie
- Structural and Genomic Information Laboratory, UMR 7256 (IMM FR 3479) CNRS Aix-Marseille Université, 163 Avenue de Luminy, Case 934, 13288 Marseille cedex 9, France APHM, FR-13385 Marseille, France
| | - Chantal Abergel
- Structural and Genomic Information Laboratory, UMR 7256 (IMM FR 3479) CNRS Aix-Marseille Université, 163 Avenue de Luminy, Case 934, 13288 Marseille cedex 9, France
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26
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Morelli M, Ogden KM, Patton JT. Silencing the alarms: Innate immune antagonism by rotavirus NSP1 and VP3. Virology 2015; 479-480:75-84. [PMID: 25724417 PMCID: PMC4940189 DOI: 10.1016/j.virol.2015.01.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 12/23/2014] [Accepted: 01/05/2015] [Indexed: 12/22/2022]
Abstract
The innate immune response involves a broad array of pathogen sensors that stimulate the production of interferons (IFNs) to induce an antiviral state. Rotavirus, a significant cause of childhood gastroenteritis and a member of the Reoviridae family of segmented, double-stranded RNA viruses, encodes at least two direct antagonists of host innate immunity: NSP1 and VP3. NSP1, a putative E3 ubiquitin ligase, mediates the degradation of cellular factors involved in both IFN induction and downstream signaling. VP3, the viral capping enzyme, utilizes a 2H-phosphodiesterase domain to prevent activation of the cellular oligoadenylate synthase (OAS)/RNase L pathway. Computational, molecular, and biochemical studies have provided key insights into the structural and mechanistic basis of innate immune antagonism by NSP1 and VP3 of group A rotaviruses (RVA). Future studies with non-RVA isolates will be essential to understand how other rotavirus species evade host innate immune responses. Rotavirus NSP1 and VP3 directly antagonize host innate immune pathways. NSP1, a putative E3 ubiquitin ligase, mediates turnover of multiple immune factors. VP3, the viral capping enzyme, has phosphodiesterase activity to block OAS/RNase L.
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Affiliation(s)
- Marco Morelli
- Rotavirus Molecular Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kristen M Ogden
- Rotavirus Molecular Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John T Patton
- Rotavirus Molecular Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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27
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Hyde JL, Diamond MS. Innate immune restriction and antagonism of viral RNA lacking 2׳-O methylation. Virology 2015; 479-480:66-74. [PMID: 25682435 PMCID: PMC4424151 DOI: 10.1016/j.virol.2015.01.019] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/22/2015] [Indexed: 01/31/2023]
Abstract
N-7 and 2′-O methylation of host cell mRNA occurs in the nucleus and results in the generation of cap structures (cap 0, m7GpppN; cap 1, m7GpppNm) that control gene expression by modulating nuclear export, splicing, turnover, and protein synthesis. Remarkably, RNA cap modification also contributes to mammalian cell host defense as viral RNA lacking 2′-O methylation is sensed and inhibited by IFIT1, an interferon (IFN) stimulated gene (ISG). Accordingly, pathogenic viruses that replicate in the cytoplasm have evolved mechanisms to circumvent IFIT1 restriction and facilitate infection of mammalian cells. These include: (a) generating cap 1 structures on their RNA through cap-snatching or virally-encoded 2′-O methyltransferases, (b) using cap-independent means of translation, or (c) using RNA secondary structural motifs to antagonize IFIT1 binding. This review will discuss new insights as to how specific modifications at the 5′-end of viral RNA modulate host pathogen recognition responses to promote infection and disease.
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Affiliation(s)
- Jennifer L Hyde
- Departments of Medicine, Washington University School of Medicine, St Louis., MO 63110, USA
| | - Michael S Diamond
- Departments of Medicine, Washington University School of Medicine, St Louis., MO 63110, USA; Molecular Microbiology, Washington University School of Medicine, St Louis., MO 63110 USA; Pathology & Immunology, Washington University School of Medicine, St Louis., MO 63110, USA; The Center for Human Immunology and Immunotherapy Programs, Washington University School of Medicine, St Louis., MO 63110, USA.
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28
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Sevajol M, Subissi L, Decroly E, Canard B, Imbert I. Insights into RNA synthesis, capping, and proofreading mechanisms of SARS-coronavirus. Virus Res 2014; 194:90-9. [PMID: 25451065 PMCID: PMC7114481 DOI: 10.1016/j.virusres.2014.10.008] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 10/06/2014] [Accepted: 10/06/2014] [Indexed: 10/30/2022]
Abstract
The successive emergence of highly pathogenic coronaviruses (CoVs) such as the Severe Acute Respiratory Syndrome (SARS-CoV) in 2003 and the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in 2012 has stimulated a number of studies on the molecular biology. This research has provided significant new insight into functions and activities of the replication/transcription multi-protein complex. The latter directs both continuous and discontinuous RNA synthesis to replicate and transcribe the large coronavirus genome made of a single-stranded, positive-sense RNA of ∼30 kb. In this review, we summarize our current understanding of SARS-CoV enzymes involved in RNA biochemistry, such as the in vitro characterization of a highly active and processive RNA polymerase complex which can associate with methyltransferase and 3'-5' exoribonuclease activities involved in RNA capping, and RNA proofreading, respectively. The recent discoveries reveal fascinating RNA-synthesizing machinery, highlighting the unique position of coronaviruses in the RNA virus world.
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Affiliation(s)
- Marion Sevajol
- Centre National de la Recherche Scientifique, Aix-Marseille Université, UMR 7257, AFMB, 163 Avenue de Luminy, 13288 Marseille, France
| | - Lorenzo Subissi
- Centre National de la Recherche Scientifique, Aix-Marseille Université, UMR 7257, AFMB, 163 Avenue de Luminy, 13288 Marseille, France
| | - Etienne Decroly
- Centre National de la Recherche Scientifique, Aix-Marseille Université, UMR 7257, AFMB, 163 Avenue de Luminy, 13288 Marseille, France
| | - Bruno Canard
- Centre National de la Recherche Scientifique, Aix-Marseille Université, UMR 7257, AFMB, 163 Avenue de Luminy, 13288 Marseille, France
| | - Isabelle Imbert
- Centre National de la Recherche Scientifique, Aix-Marseille Université, UMR 7257, AFMB, 163 Avenue de Luminy, 13288 Marseille, France.
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29
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Noble CG, Li SH, Dong H, Chew SH, Shi PY. Crystal structure of dengue virus methyltransferase without S-adenosyl-L-methionine. Antiviral Res 2014; 111:78-81. [PMID: 25241250 PMCID: PMC7113791 DOI: 10.1016/j.antiviral.2014.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/03/2014] [Accepted: 09/09/2014] [Indexed: 01/03/2023]
Abstract
Flavivirus methyltransferase is a genetically-validated antiviral target. Crystal structures of almost all available flavivirus methyltransferases contain S-adenosyl-L-methionine (SAM), the methyl donor molecule that co-purifies with the enzymes. This raises a possibility that SAM is an integral structural component required for the folding of dengue virus (DENV) methyltransferase. Here we exclude this possibility by solving the crystal structure of DENV methyltransferase without SAM. The SAM ligand was removed from the enzyme through a urea-mediated denaturation-and-renaturation protocol. The crystal structure of the SAM-depleted enzyme exhibits a vacant SAM-binding pocket, with a conformation identical to that of the SAM-enzyme co-crystal structure. Functionally, equivalent enzymatic activities (N-7 methylation, 2'-O methylation, and GMP-enzyme complex formation) were detected for the SAM-depleted and SAM-containing recombinant proteins. These results clearly indicate that the SAM molecule is not an essential component for the correct folding of DENV methyltransferase. Furthermore, the results imply a potential antiviral approach to search for inhibitors that can bind to the SAM-binding pocket and compete against SAM binding. To demonstrate this potential, we have soaked crystals of DENV methyltransferase without a bound SAM with the natural product Sinefungin and show that preformed crystals are capable of binding ligands in this pocket.
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Affiliation(s)
- Christian G Noble
- Novartis Institute for Tropical Diseases, 10 Biopolis Road, 05-01 Chromos, Singapore 138670, Singapore
| | - Shi-Hua Li
- Novartis Institute for Tropical Diseases, 10 Biopolis Road, 05-01 Chromos, Singapore 138670, Singapore
| | - Hongping Dong
- Novartis Institute for Tropical Diseases, 10 Biopolis Road, 05-01 Chromos, Singapore 138670, Singapore
| | - Sock Hui Chew
- Novartis Institute for Tropical Diseases, 10 Biopolis Road, 05-01 Chromos, Singapore 138670, Singapore
| | - Pei-Yong Shi
- Novartis Institute for Tropical Diseases, 10 Biopolis Road, 05-01 Chromos, Singapore 138670, Singapore.
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30
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Biswas P, Kundu A, Ghosh AK. Genome segment 4 of Antheraea mylitta cytoplasmic polyhedrosis virus encodes RNA triphosphatase and methyltransferases. J Gen Virol 2014; 96:95-105. [PMID: 25228490 DOI: 10.1099/vir.0.069716-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cloning and sequencing of Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) genome segment S4 showed that it consists of 3410 nt with a single ORF of 1110 aa which could encode a protein of ~127 kDa (p127). Bioinformatics analysis showed the presence of a 5' RNA triphosphatase (RTPase) domain (LRDR), a S-adenosyl-l-methionine (SAM)-binding (GxGxG) motif and the KDKE tetrad of 2'-O-methyltransferase (MTase), which suggested that S4 may encode RTPase and MTase. The ORF of S4 was expressed in Escherichia coli as a His-tagged fusion protein and purified by nickel-nitrilotriacetic acid affinity chromatography. Biochemical analysis of recombinant p127 showed its RTPase as well as SAM-dependent guanine N(7)-and ribose 2'-O-MTase activities. A MTase assay using in vitro transcribed AmCPV S2 RNA having a 5' G*pppG end showed that guanine N(7) methylation occurred prior to the ribose 2'-O methylation to yield a m(7)GpppG/m(7)GpppGm RNA cap. Mutagenesis of the SAM-binding (GxGxG) motif (G831A) completely abolished N(7)- and 2'-O-MTase activities, indicating the importance of these residues for capping. From the kinetic analysis, the Km values of N(7)-MTase for SAM and RNA were calculated as 4.41 and 0.39 µM, respectively. These results suggested that AmCPV S4-encoded p127 catalyses RTPase and two cap methylation reactions for capping the 5' end of viral RNA.
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Affiliation(s)
- Poulomi Biswas
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Anirban Kundu
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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31
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Rational design of human metapneumovirus live attenuated vaccine candidates by inhibiting viral mRNA cap methyltransferase. J Virol 2014; 88:11411-29. [PMID: 25056882 DOI: 10.1128/jvi.00876-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The paramyxoviruses human respiratory syncytial virus (hRSV), human metapneumovirus (hMPV), and human parainfluenza virus type 3 (hPIV3) are responsible for the majority of pediatric respiratory diseases and inflict significant economic loss, health care costs, and emotional burdens. Despite major efforts, there are no vaccines available for these viruses. The conserved region VI (CR VI) of the large (L) polymerase proteins of paramyxoviruses catalyzes methyltransferase (MTase) activities that typically methylate viral mRNAs at positions guanine N-7 (G-N-7) and ribose 2'-O. In this study, we generated a panel of recombinant hMPVs carrying mutations in the S-adenosylmethionine (SAM) binding site in CR VI of L protein. These recombinant viruses were specifically defective in ribose 2'-O methylation but not G-N-7 methylation and were genetically stable and highly attenuated in cell culture and viral replication in the upper and lower respiratory tracts of cotton rats. Importantly, vaccination of cotton rats with these recombinant hMPVs (rhMPVs) with defective MTases triggered a high level of neutralizing antibody, and the rats were completely protected from challenge with wild-type rhMPV. Collectively, our results indicate that (i) amino acid residues in the SAM binding site in the hMPV L protein are essential for 2'-O methylation and (ii) inhibition of mRNA cap MTase can serve as a novel target to rationally design live attenuated vaccines for hMPV and perhaps other paramyxoviruses, such as hRSV and hPIV3. IMPORTANCE Human paramyxoviruses, including hRSV, hMPV, and hPIV3, cause the majority of acute upper and lower respiratory tract infections in humans, particularly in infants, children, the elderly, and immunocompromised individuals. Currently, there is no licensed vaccine available. A formalin-inactivated vaccine is not suitable for these viruses because it causes enhanced lung damage upon reinfection with the same virus. A live attenuated vaccine is the most promising vaccine strategy for human paramyxoviruses. However, it remains a challenge to identify an attenuated virus strain that has an optimal balance between attenuation and immunogenicity. Using reverse genetics, we generated a panel of recombinant hMPVs that were specifically defective in ribose 2'-O methyltransferase (MTase) but not G-N-7 MTase. These MTase-defective hMPVs were genetically stable and sufficiently attenuated but retained high immunogenicity. This work highlights a critical role of 2'-O MTase in paramyxovirus replication and pathogenesis and a new avenue for the development of safe and efficacious live attenuated vaccines for hMPV and other human paramyxoviruses.
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32
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Predicted structure and domain organization of rotavirus capping enzyme and innate immune antagonist VP3. J Virol 2014; 88:9072-85. [PMID: 24899176 DOI: 10.1128/jvi.00923-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED Rotaviruses and orbiviruses are nonturreted Reoviridae members. The rotavirus VP3 protein is a multifunctional capping enzyme and antagonist of the interferon-induced cellular oligoadenylate synthetase-RNase L pathway. Despite mediating important processes, VP3 is the sole protein component of the rotavirus virion whose structure remains unknown. In the current study, we used sequence alignment and homology modeling to identify features common to nonturreted Reoviridae capping enzymes and to predict the domain organization, structure, and active sites of rotavirus VP3. Our results suggest that orbivirus and rotavirus capping enzymes share a domain arrangement similar to that of the bluetongue virus capping enzyme. Sequence alignments revealed conserved motifs and suggested that rotavirus and orbivirus capping enzymes contain a variable N-terminal domain, a central guanine-N7-methyltransferase domain that contains an additional inserted domain, and a C-terminal guanylyltransferase and RNA 5'-triphosphatase domain. Sequence conservation and homology modeling suggested that the insertion in the guanine-N7-methyltransferase domain is a ribose-2'-O-methyltransferase domain for most rotavirus species. Our analyses permitted putative identification of rotavirus VP3 active-site residues, including those that form the ribose-2'-O-methyltransferase catalytic tetrad, interact with S-adenosyl-l-methionine, and contribute to autoguanylation. Previous reports have indicated that group A rotavirus VP3 contains a C-terminal 2H-phosphodiesterase domain that can cleave 2'-5' oligoadenylates, thereby preventing RNase L activation. Our results suggest that a C-terminal phosphodiesterase domain is present in the capping enzymes from two additional rotavirus species. Together, these findings provide insight into a poorly understood area of rotavirus biology and are a springboard for future biochemical and structural studies of VP3. IMPORTANCE Rotaviruses are an important cause of severe diarrheal disease. The rotavirus VP3 protein caps viral mRNAs and helps combat cellular innate antiviral defenses, but little is known about its structure or enzymatic mechanisms. In this study, we used sequence- and structure-based alignments with related proteins to predict the structure of VP3 and identify enzymatic domains and active sites therein. This work provides insight into the mechanisms of rotavirus transcription and evasion of host innate immune defenses. An improved understanding of these processes may aid our ability to develop rotavirus vaccines and therapeutics.
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33
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Zhu B, Yang C, Liu H, Cheng L, Song F, Zeng S, Huang X, Ji G, Zhu P. Identification of the active sites in the methyltransferases of a transcribing dsRNA virus. J Mol Biol 2014; 426:2167-74. [PMID: 24690366 PMCID: PMC7094362 DOI: 10.1016/j.jmb.2014.03.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 03/24/2014] [Accepted: 03/25/2014] [Indexed: 11/28/2022]
Abstract
Many double-stranded RNA (dsRNA) viruses are capable of transcribing and capping RNA within a stable icosahedral viral capsid. The turret of turreted dsRNA viruses belonging to the family Reoviridae is formed by five copies of the turret protein, which contains domains with both 7-N-methyltransferase and 2′-O-methyltransferase activities, and serves to catalyze the methylation reactions during RNA capping. Cypovirus of the family Reoviridae provides a good model system for studying the methylation reactions in dsRNA viruses. Here, we present the structure of a transcribing cypovirus to a resolution of ~ 3.8 Å by cryo-electron microscopy. The binding sites for both S-adenosyl-l-methionine and RNA in the two methyltransferases of the turret were identified. Structural analysis of the turret in complex with RNA revealed a pathway through which the RNA molecule reaches the active sites of the two methyltransferases before it is released into the cytoplasm. The pathway shows that RNA capping reactions occur in the active sites of different turret protein monomers, suggesting that RNA capping requires concerted efforts by at least three turret protein monomers. Thus, the turret structure provides novel insights into the precise mechanisms of RNA methylation. Structure of methyltransferases (MTases) and RNA in a transcribing dsRNA virus. S-Adenosyl-l-methionine/S-adenosyl-l-homocysteine was observed in the two MTases. A pathway was identified through which RNA reaches active sites of the two MTase. Methylation reactions require concerted efforts by turret protein monomers.
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Affiliation(s)
- Bin Zhu
- College of Physics and Information Science, Hunan Normal University, 36 Lushan Road, Changsha, Hunan 410081, China
| | - Chongwen Yang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hongrong Liu
- College of Physics and Information Science, Hunan Normal University, 36 Lushan Road, Changsha, Hunan 410081, China.
| | - Lingpeng Cheng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
| | - Feng Song
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Songjun Zeng
- College of Physics and Information Science, Hunan Normal University, 36 Lushan Road, Changsha, Hunan 410081, China
| | - Xiaojun Huang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Gang Ji
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
| | - Ping Zhu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
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34
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The molecular biology of Bluetongue virus replication. Virus Res 2013; 182:5-20. [PMID: 24370866 DOI: 10.1016/j.virusres.2013.12.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/10/2013] [Accepted: 12/11/2013] [Indexed: 01/17/2023]
Abstract
The members of Orbivirus genus within the Reoviridae family are arthropod-borne viruses which are responsible for high morbidity and mortality in ruminants. Bluetongue virus (BTV) which causes disease in livestock (sheep, goat, cattle) has been in the forefront of molecular studies for the last three decades and now represents the best understood orbivirus at a molecular and structural level. The complex nature of the virion structure has been well characterised at high resolution along with the definition of the virus encoded enzymes required for RNA replication; the ordered assembly of the capsid shell as well as the protein and genome sequestration required for it; and the role of host proteins in virus entry and virus release. More recent developments of Reverse Genetics and Cell-Free Assembly systems have allowed integration of the accumulated structural and molecular knowledge to be tested at meticulous level, yielding higher insight into basic molecular virology, from which the rational design of safe efficacious vaccines has been possible. This article is centred on the molecular dissection of BTV with a view to understanding the role of each protein in the virus replication cycle. These areas are important in themselves for BTV replication but they also indicate the pathways that related viruses, which includes viruses that are pathogenic to man and animals, might also use providing an informed starting point for intervention or prevention.
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35
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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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Li H, Li C, Zhou S, Poulos TL, Gershon PD. Domain-level rocking motion within a polymerase that translocates on single-stranded nucleic acid. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:617-24. [PMID: 23519670 PMCID: PMC3606039 DOI: 10.1107/s0907444913000346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Accepted: 01/04/2013] [Indexed: 11/10/2022]
Abstract
Vaccinia virus poly(A) polymerase (VP55) is the only known polymerase that can translocate independently with respect to single-stranded nucleic acid (ssNA). Previously, its structure has only been solved in the context of the VP39 processivity factor. Here, a crystal structure of unliganded monomeric VP55 has been solved to 2.86 Å resolution, showing the first backbone structural isoforms among either VP55 or its processivity factor (VP39). Backbone differences between the two molecules of VP55 in the asymmetric unit indicated that unliganded monomeric VP55 can undergo a `rocking' motion of the N-terminal domain with respect to the other two domains, which may be `rigidified' upon VP39 docking. This observation is consistent with previously demonstrated experimental molecular dynamics of the monomer during translocation with respect to nucleic acid and with different mechanisms of translocation in the presence and absence of processivity factor VP39. Side-chain conformational changes in the absence of ligand were observed at a key primer contact site and at the catalytic center of VP55. The current structure completes the trio of possible structural forms for VP55 and VP39, namely the VP39 monomer, the VP39-VP55 heterodimer and the VP55 monomer.
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Affiliation(s)
- Huiyung Li
- Department of Molecular Biology and Biochemistry, Xinxiang Medical University, Xinxiang, Henan 453003, People’s Republic of China
| | - Changzheng Li
- Department of Molecular Biology and Biochemistry, Xinxiang Medical University, Xinxiang, Henan 453003, People’s Republic of China
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, USA
| | - Sufeng Zhou
- Department of Molecular Biology and Biochemistry, Xinxiang Medical University, Xinxiang, Henan 453003, People’s Republic of China
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, USA
| | - Thomas L. Poulos
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, USA
- Department of Pharmaceutical Sciences, UC-Irvine, Irvine, USA
- Department of Chemistry, UC-Irvine, Irvine, USA
| | - Paul David Gershon
- Department of Molecular Biology and Biochemistry, UC-Irvine, Irvine, USA
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Bouvet M, Ferron F, Imbert I, Gluais L, Selisko B, Coutard B, Canard B, Decroly E. [Capping strategies in RNA viruses]. Med Sci (Paris) 2012; 28:423-9. [PMID: 22549871 DOI: 10.1051/medsci/2012284021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Most viruses use the mRNA-cap dependent cellular translation machinery to translate their mRNAs into proteins. The addition of a cap structure at the 5' end of mRNA is therefore an essential step for the replication of many virus families. Additionally, the cap protects the viral RNA from degradation by cellular nucleases and prevents viral RNA recognition by innate immunity mechanisms. Viral RNAs acquire their cap structure either by using cellular capping enzymes, by stealing the cap of cellular mRNA in a process named "cap snatching", or using virus-encoded capping enzymes. Many viral enzymes involved in this process have recently been structurally and functionally characterized. These studies have revealed original cap synthesis mechanisms and pave the way towards the development of specific inhibitors bearing antiviral drug potential.
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Affiliation(s)
- Mickaël Bouvet
- Laboratoire CNRS - Architecture et fonction des macromolécules biologiques (AFMB), UMR 7257, groupe réplication virale, structures, mécanismes et drug-design, école supérieure d'ingénieurs de Luminy (ESIL) - Case 925, 163, avenue de Luminy, 13288 Marseille Cedex 09, France
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38
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Dong H, Chang DC, Hua MHC, Lim SP, Chionh YH, Hia F, Lee YH, Kukkaro P, Lok SM, Dedon PC, Shi PY. 2'-O methylation of internal adenosine by flavivirus NS5 methyltransferase. PLoS Pathog 2012; 8:e1002642. [PMID: 22496660 PMCID: PMC3320599 DOI: 10.1371/journal.ppat.1002642] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Accepted: 02/27/2012] [Indexed: 01/20/2023] Open
Abstract
RNA modification plays an important role in modulating host-pathogen interaction. Flavivirus NS5 protein encodes N-7 and 2′-O methyltransferase activities that are required for the formation of 5′ type I cap (m7GpppAm) of viral RNA genome. Here we reported, for the first time, that flavivirus NS5 has a novel internal RNA methylation activity. Recombinant NS5 proteins of West Nile virus and Dengue virus (serotype 4; DENV-4) specifically methylates polyA, but not polyG, polyC, or polyU, indicating that the methylation occurs at adenosine residue. RNAs with internal adenosines substituted with 2′-O-methyladenosines are not active substrates for internal methylation, whereas RNAs with adenosines substituted with N6-methyladenosines can be efficiently methylated, suggesting that the internal methylation occurs at the 2′-OH position of adenosine. Mass spectroscopic analysis further demonstrated that the internal methylation product is 2′-O-methyladenosine. Importantly, genomic RNA purified from DENV virion contains 2′-O-methyladenosine. The 2′-O methylation of internal adenosine does not require specific RNA sequence since recombinant methyltransferase of DENV-4 can efficiently methylate RNAs spanning different regions of viral genome, host ribosomal RNAs, and polyA. Structure-based mutagenesis results indicate that K61-D146-K181-E217 tetrad of DENV-4 methyltransferase forms the active site of internal methylation activity; in addition, distinct residues within the methyl donor (S-adenosyl-L-methionine) pocket, GTP pocket, and RNA-binding site are critical for the internal methylation activity. Functional analysis using flavivirus replicon and genome-length RNAs showed that internal methylation attenuated viral RNA translation and replication. Polymerase assay revealed that internal 2′-O-methyladenosine reduces the efficiency of RNA elongation. Collectively, our results demonstrate that flavivirus NS5 performs 2′-O methylation of internal adenosine of viral RNA in vivo and host ribosomal RNAs in vitro. We report that flavivirus NS5 has a novel internal RNA methylation activity. Recombinant proteins of NS5 and its N-terminal methyltransferase domain of West Nile virus and Dengue virus (DENV) specifically methylates polyA, but not polyG, polyC, or polyU. RNAs with internal adenosines substituted with 2′-O-methyladenosines are not active substrates for internal methylation, suggesting that the internal methylation occurs at the 2′-OH position of adenosine. Mass spectroscopic analysis confirmed that the internal methylation product is 2′-O-methyladenosine. Furthermore, the 2′-O-methyladenosine could also be detected in DENV genomic RNA. The 2′-O methylation of internal adenosine does not require specific RNA sequence context because the DENV methyltransferase can methylate RNAs spanning different regions of viral genome and host ribosomal RNAs at equal efficiencies. Mutagenesis analysis showed that K61-D146-K181-E217 motif of the DENV methyltransferase forms the active site of internal methylation activity; in addition, distinct residues on the surface of the enzyme are critical for the internal methylation activity. Functional analysis showed that internal methylation attenuated viral RNA translation and replication. Overall, our results demonstrate that flavivirus NS5 performs 2′-O methylation of internal adenosine of viral RNA in vivo and host ribosomal RNA in vitro. Such 2′-O-methyladenosine modification may modulate virus-host interaction.
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Affiliation(s)
- Hongping Dong
- Novartis Institute for Tropical Diseases, Singapore
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | | | - Maggie Ho Chia Hua
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore
| | | | - Yok Hian Chionh
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore
| | - Fabian Hia
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore
| | - Yie Hou Lee
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore
| | | | | | - Peter C. Dedon
- Singapore-MIT Alliance for Research and Technology (SMART) Centre, Singapore
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Pei-Yong Shi
- Novartis Institute for Tropical Diseases, Singapore
- Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- * E-mail:
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Decroly E, Ferron F, Lescar J, Canard B. Conventional and unconventional mechanisms for capping viral mRNA. Nat Rev Microbiol 2011; 10:51-65. [PMID: 22138959 PMCID: PMC7097100 DOI: 10.1038/nrmicro2675] [Citation(s) in RCA: 328] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
mRNAs are protected at their 5′ ends by a cap structure consisting of an N7-methylated GTP molecule linked to the first transcribed nucleotide by a 5′–5′ triphosphate bond. The cap structure is essential for RNA splicing, export and stability, and allows the ribosomal complex to recognize mRNAs and ensure their efficient translation. Uncapped RNA molecules are degraded in cytoplasmic granular compartments called processing bodies and may be detected as 'non-self' by the host cell, triggering antiviral innate immune responses through the production of interferons. Conventional RNA capping (that is, of mRNAs from the host cell and from DNA viruses) requires hydrolysis of the 5′ γ-phosphate of RNA by an RNA triphosphatase, transfer of a GMP molecule onto the 5′-end of RNA by a guanylyltransferase, and methylation of this guanosine by an (guanine-N7)-methyltransferase. Subsequent methylations on the first and second transcribed nucleotides by (nucleoside-2′-O)-methyltransferases form cap-1 and cap-2 structures. Viruses have evolved highly diverse capping mechanisms to acquire cap structures using their own or cellular capping machineries, or by stealing cap structures from cellular mRNAs. Virally encoded RNA-capping machineries are diverse in terms of their genetic components, protein domain organization, enzyme structures, and reaction mechanisms and pathways, making viral RNA capping an attractive target for antiviral-drug design.
Capping the 5′ end of eukaryotic mRNAs with a 7-methylguanosine moiety enables efficient splicing, nuclear export and translation of mRNAs, and also limits their degradation by cellular exonucleases. Here, Canard and colleagues describe how viruses synthesize their own mRNA cap structures or steal them from host mRNAs, allowing efficient synthesis of viral proteins and avoidance of host innate immune responses. In the eukaryotic cell, capping of mRNA 5′ ends is an essential structural modification that allows efficient mRNA translation, directs pre-mRNA splicing and mRNA export from the nucleus, limits mRNA degradation by cellular 5′–3′ exonucleases and allows recognition of foreign RNAs (including viral transcripts) as 'non-self'. However, viruses have evolved mechanisms to protect their RNA 5′ ends with either a covalently attached peptide or a cap moiety (7-methyl-Gppp, in which p is a phosphate group) that is indistinguishable from cellular mRNA cap structures. Viral RNA caps can be stolen from cellular mRNAs or synthesized using either a host- or virus-encoded capping apparatus, and these capping assemblies exhibit a wide diversity in organization, structure and mechanism. Here, we review the strategies used by viruses of eukaryotic cells to produce functional mRNA 5′-caps and escape innate immunity.
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Affiliation(s)
- Etienne Decroly
- Centre National de Recherche Scientifique and Aix-Marseille Université, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, 163 avenue de Luminy, 13288 Marseille cedex 09, France
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40
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Decroly E, Debarnot C, Ferron F, Bouvet M, Coutard B, Imbert I, Gluais L, Papageorgiou N, Sharff A, Bricogne G, Ortiz-Lombardia M, Lescar J, Canard B. Crystal structure and functional analysis of the SARS-coronavirus RNA cap 2'-O-methyltransferase nsp10/nsp16 complex. PLoS Pathog 2011; 7:e1002059. [PMID: 21637813 PMCID: PMC3102710 DOI: 10.1371/journal.ppat.1002059] [Citation(s) in RCA: 258] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 03/23/2011] [Indexed: 12/20/2022] Open
Abstract
Cellular and viral S-adenosylmethionine-dependent methyltransferases are involved in many regulated processes such as metabolism, detoxification, signal transduction, chromatin remodeling, nucleic acid processing, and mRNA capping. The Severe Acute Respiratory Syndrome coronavirus nsp16 protein is a S-adenosylmethionine-dependent (nucleoside-2′-O)-methyltransferase only active in the presence of its activating partner nsp10. We report the nsp10/nsp16 complex structure at 2.0 Å resolution, which shows nsp10 bound to nsp16 through a ∼930 Å2 surface area in nsp10. Functional assays identify key residues involved in nsp10/nsp16 association, and in RNA binding or catalysis, the latter likely through a SN2-like mechanism. We present two other crystal structures, the inhibitor Sinefungin bound in the S-adenosylmethionine binding pocket and the tighter complex nsp10(Y96F)/nsp16, providing the first structural insight into the regulation of RNA capping enzymes in (+)RNA viruses. A novel coronavirus emerged in 2003 and was identified as the etiological agent of the deadly disease called Severe Acute Respiratory Syndrome. This coronavirus replicates and transcribes its giant genome using sixteen non-structural proteins (nsp1-16). Viral RNAs are capped to ensure stability, efficient translation, and evading the innate immunity system of the host cell. The nsp16 protein is a RNA cap modifying enzyme only active in the presence of its activating partner nsp10. We have crystallized the nsp10/16 complex and report its crystal structure at atomic resolution. Nsp10 binds to nsp16 through a ∼930 Å2 activation surface area in nsp10, and the resulting complex exhibits RNA cap (nucleoside-2′-O)-methyltransferase activity. We have performed mutational and functional assays to identify key residues involved in catalysis and/or in RNA binding, and in the association of nsp10 to nsp16. We present two additional crystal structures, that of the known inhibitor Sinefungin bound in the SAM binding pocket, and that of a tighter complex made of the mutant nsp10(Y96F) bound to nsp16. Our study provides a basis for antiviral drug design as well as the first structural insight into the regulation of RNA capping enzymes in (+)RNA viruses.
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Affiliation(s)
- Etienne Decroly
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
- * E-mail: (ED); (BC)
| | - Claire Debarnot
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - François Ferron
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Mickael Bouvet
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Bruno Coutard
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Isabelle Imbert
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Laure Gluais
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Nicolas Papageorgiou
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Andrew Sharff
- Global Phasing Ltd., Sheraton House, Castle Park, Cambridge, United Kingdom
| | - Gérard Bricogne
- Global Phasing Ltd., Sheraton House, Castle Park, Cambridge, United Kingdom
| | - Miguel Ortiz-Lombardia
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
| | - Julien Lescar
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore
| | - Bruno Canard
- Centre National de la Recherche Scientifique and Université de la Méditerranée, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, Marseille, France
- * E-mail: (ED); (BC)
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Agarwal V, Metlitskaya A, Severinov K, Nair SK. Structural basis for microcin C7 inactivation by the MccE acetyltransferase. J Biol Chem 2011; 286:21295-303. [PMID: 21507941 DOI: 10.1074/jbc.m111.226282] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The antibiotic microcin C7 (McC) acts as a bacteriocide by inhibiting aspartyl-tRNA synthetase and stalling the protein translation machinery. McC is synthesized as a heptapeptide-nucleotide conjugate, which is processed by cellular peptidases within target strains to yield the biologically active compound. As unwanted processing of intact McC can result in self-toxicity, producing strains utilize multiple mechanisms for autoimmunity against processed McC. We have shown previously that the mccE gene within the biosynthetic cluster can inactivate processed McC by acetylating the antibiotic. Here, we present the characterization of this acetylation mechanism through biochemical and structural biological studies of the MccE acetyltransferase domain (MccE(AcTase)). We have also determined five crystal structures of the MccE-acetyl-CoA complex with bound substrates, inhibitor, and reaction product. The structural data reveal an unexpected mode of substrate recognition through π-stacking interactions similar to those found in cap-binding proteins and nucleotidyltransferases. These studies provide a rationale for the observation that MccE(AcTase) can detoxify a range of aminoacylnucleotides, including those that are structurally distinct from microcin C7.
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Affiliation(s)
- Vinayak Agarwal
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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42
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Lim SP, Sonntag LS, Noble C, Nilar SH, Ng RH, Zou G, Monaghan P, Chung KY, Dong H, Liu B, Bodenreider C, Lee G, Ding M, Chan WL, Wang G, Jian YL, Chao AT, Lescar J, Yin Z, Vedananda TR, Keller TH, Shi PY. Small molecule inhibitors that selectively block dengue virus methyltransferase. J Biol Chem 2011; 286:6233-40. [PMID: 21147775 PMCID: PMC3057852 DOI: 10.1074/jbc.m110.179184] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 11/23/2010] [Indexed: 01/16/2023] Open
Abstract
Crystal structure analysis of Flavivirus methyltransferases uncovered a flavivirus-conserved cavity located next to the binding site for its cofactor, S-adenosyl-methionine (SAM). Chemical derivatization of S-adenosyl-homocysteine (SAH), the product inhibitor of the methylation reaction, with substituents that extend into the identified cavity, generated inhibitors that showed improved and selective activity against dengue virus methyltransferase (MTase), but not related human enzymes. Crystal structure of dengue virus MTase with a bound SAH derivative revealed that its N6-substituent bound in this cavity and induced conformation changes in residues lining the pocket. These findings demonstrate that one of the major hurdles for the development of methyltransferase-based therapeutics, namely selectivity for disease-related methyltransferases, can be overcome.
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Affiliation(s)
- Siew Pheng Lim
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | | | - Christian Noble
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Shahul H. Nilar
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Ru Hui Ng
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Gang Zou
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Paul Monaghan
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Ka Yan Chung
- the School of Biological Sciences, Nanyang Technological University, Singapore, and
| | - Hongping Dong
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Boping Liu
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | | | - Gladys Lee
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Mei Ding
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Wai Ling Chan
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Gang Wang
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Yap Li Jian
- the School of Biological Sciences, Nanyang Technological University, Singapore, and
| | | | - Julien Lescar
- the School of Biological Sciences, Nanyang Technological University, Singapore, and
| | - Zheng Yin
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - T. R. Vedananda
- the Novartis Institutes for BioMedical Research, Cambridge, Massachusetts 02139
| | - Thomas H. Keller
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
| | - Pei-Yong Shi
- From the Novartis Institute for Tropical Diseases, 05-01 Chromos, Singapore
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Hu RH, Lin MC, Hsu YH, Meng M. Mutational effects of the consensus aromatic residues in the mRNA capping domain of Bamboo mosaic virus on GTP methylation and virus accumulation. Virology 2011; 411:15-24. [PMID: 21227477 DOI: 10.1016/j.virol.2010.12.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 10/29/2010] [Accepted: 12/14/2010] [Indexed: 10/18/2022]
Abstract
RNA viruses classified in the alphavirus-like superfamily possess a distinct capping domain, catalyzing GTP methylation and subsequent transfer of the m(7)GMP moiety from m(7)GTP to the 5'-diphosphate end of viral RNA. The H68A mutation in the capping domain of Bamboo mosaic virus enhanced GTP methylation but disabled the following transguanylation, making it possible to characterize the enzyme's methyltransferase activity separately. To explore the involvement of aromatic amino acids in substrate recognition, consensus aromatic residues in the viral domain were subjected to mutational analysis in the background of H68A. Several residues, including Y126, F144, F161, Y192, Y203, Y213, and W222, were found to be critical for GTP methylation and S-adenosylmethionine (AdoMet) binding. These mutations, except for Y213, also adversely affected the GTP binding, but less extensively. In general, the mutations decreasing the activity for GTP methylation also had correspondingly detrimental effects on virus accumulation.
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Affiliation(s)
- Rei-Hsing Hu
- Graduate Institute of Biotechnology, National Chung Hsing University, 250 Kuo-Kuang Rd, Taichung, Taiwan 40227, ROC
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Zhang X, Wei Y, Ma Y, Hu S, Li J. Identification of aromatic amino acid residues in conserved region VI of the large polymerase of vesicular stomatitis virus is essential for both guanine-N-7 and ribose 2'-O methyltransferases. Virology 2010; 408:241-52. [PMID: 20961592 PMCID: PMC7111938 DOI: 10.1016/j.virol.2010.09.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 08/23/2010] [Accepted: 09/17/2010] [Indexed: 10/25/2022]
Abstract
Non-segmented negative-sense RNA viruses possess a unique mechanism for mRNA cap methylation. For vesicular stomatitis virus, conserved region VI in the large (L) polymerase protein catalyzes both guanine-N-7 (G-N-7) and ribose 2'-O (2'-O) methyltransferases, and the two methylases share a binding site for the methyl donor S-adenosyl-l-methionine. Unlike conventional mRNA cap methylation, the 2'-O methylation of VSV precedes subsequent G-N-7 methylation. In this study, we found that individual alanine substitutions in two conserved aromatic residues (Y1650 and F1691) in region VI of L protein abolished both G-N-7 and 2'-O methylation. However, replacement of one aromatic residue with another aromatic residue did not significantly affect the methyltransferase activities. Our studies provide genetic and biochemical evidence that conserved aromatic residues in region VI of L protein essential for both G-N-7 and 2'-O methylations. In combination with the structural prediction, our results suggest that these aromatic residues may participate in RNA recognition.
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Affiliation(s)
- Xiaodong Zhang
- College of Animal Science, Zhejiang University, Hangzhou, Zhejiang, China
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45
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Abstract
Many flaviviruses are significant human pathogens. The plus-strand RNA genome of a flavivirus contains a 5' terminal cap 1 structure (m(7)GpppAmG). The flavivirus encodes one methyltransferase (MTase), located at the N-terminal portion of the NS5 RNA-dependent RNA polymerase (RdRp). Here we review recent advances in our understanding of flaviviral capping machinery and the implications for drug development. The NS5 MTase catalyzes both guanine N7 and ribose 2'-OH methylations during viral cap formation. Representative flavivirus MTases, from dengue, yellow fever, and West Nile virus (WNV), sequentially generate GpppA → m(7)GpppA → m(7)GpppAm. Despite the existence of two distinct methylation activities, the crystal structures of flavivirus MTases showed a single binding site for S-adenosyl-L-methionine (SAM), the methyl donor. This finding indicates that the substrate GpppA-RNA must be repositioned to accept the N7 and 2'-O methyl groups from SAM during the sequential reactions. Further studies demonstrated that distinct RNA elements are required for the methylations of guanine N7 on the cap and of ribose 2'-OH on the first transcribed nucleotide. Mutant enzymes with different methylation defects can trans complement one another in vitro, demonstrating that separate molecules of the enzyme can independently catalyze the two cap methylations in vitro. In the context of the infectious virus, defects in both methylations, or a defect in the N7 methylation alone, are lethal to WNV. However, viruses defective solely in 2'-O methylation are attenuated and can protect mice from later wild-type WNV challenge. The results demonstrate that the N7 methylation activity is essential for the WNV life cycle and, thus, methyltransferase represents a novel and promising target for flavivirus therapy.
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46
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Dong H, Chang DC, Xie X, Toh YX, Chung KY, Zou G, Lescar J, Lim SP, Shi PY. Biochemical and genetic characterization of dengue virus methyltransferase. Virology 2010; 405:568-78. [PMID: 20655081 DOI: 10.1016/j.virol.2010.06.039] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 05/29/2010] [Accepted: 06/22/2010] [Indexed: 01/13/2023]
Abstract
We report that dengue virus (DENV) methyltransferase sequentially methylates the guanine N-7 and ribose 2'-O positions of viral RNA cap (GpppA-->m(7)GpppA-->m(7)GpppAm). The order of two methylations is determined by the preference of 2'-O methylation for substrate m(7)GpppA-RNA to GpppA-RNA, and the 2'-O methylation is not absolutely dependent on the prior N-7 methylation. A mutation that completely abolished the 2'-O methylation attenuated DENV replication in cell culture, whereas another mutation that abolished both methylations was lethal for viral replication, suggesting that N-7 methylation is more important than 2'-O methylation in viral replication. The latter mutant with lethal replication could be rescued by trans complementation using a wild-type DENV replicon. Furthermore, we found that chimeric DENVs containing the West Nile virus methyltransferase, polymerase, or full-length NS5 were nonreplicative, but the replication defect could also be rescued through trans complementation using the wild-type DENV replicon.
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Affiliation(s)
- Hongping Dong
- Novartis Institute for Tropical Diseases, Chromos, Singapore 138670, Singapore.
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47
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Li CZ, Koter M, Ye X, Zhou SF, Chou W, Luo R, Gershon PD. Widespread but Small-Scale Changes in the Structural and Dynamic Properties of Vaccinia Virus Poly(A) Polymerase upon Association with Its Processivity Factor in Solution. Biochemistry 2010; 49:6247-62. [DOI: 10.1021/bi100166x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- C.-Z. Li
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - M. Koter
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - X. Ye
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - S.-F. Zhou
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - W. Chou
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - R. Luo
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
| | - P. D. Gershon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697
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Ghosh A, Lima CD. Enzymology of RNA cap synthesis. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:152-72. [PMID: 21956912 DOI: 10.1002/wrna.19] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The 5' guanine-N7 methyl cap is unique to cellular and viral messenger RNA (mRNA) and is the first co-transcriptional modification of mRNA. The mRNA cap plays a pivotal role in mRNA biogenesis and stability, and is essential for efficient splicing, mRNA export, and translation. Capping occurs by a series of three enzymatic reactions that results in formation of N7-methyl guanosine linked through a 5'-5' inverted triphosphate bridge to the first nucleotide of a nascent transcript. Capping of cellular mRNA occurs co-transcriptionally and in vivo requires that the capping apparatus be physically associated with the RNA polymerase II elongation complex. Certain capped mRNAs undergo further methylation to generate distinct cap structures. Although mRNA capping is conserved among viruses and eukaryotes, some viruses have adopted strategies for capping mRNA that are distinct from the cellular mRNA capping pathway.
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Affiliation(s)
- Agnidipta Ghosh
- Structural Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
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Abstract
Studies of the functional proteins encoded by the poxvirus genome provide information about the composition of the virus as well as individual virus-virus protein and virus-host protein interactions, which provides insight into viral pathogenesis and drug discovery. Widely used proteomic techniques to identify and characterize specific protein-protein interactions include yeast two-hybrid studies and coimmunoprecipitations. Recently, various mass spectrometry techniques have been employed to identify viral protein components of larger complexes. These methods, combined with structural studies, can provide new information about the putative functions of viral proteins as well as insights into virus-host interaction dynamics. For viral proteins of unknown function, identification of either viral or host binding partners provides clues about their putative function. In this review, we discuss poxvirus proteomics, including the use of proteomic methodologies to identify viral components and virus-host protein interactions. High-throughput global protein expression studies using protein chip technology as well as new methods for validating putative protein-protein interactions are also discussed.
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Abstract
Disease caused by flavivirus infections is an increasing world health problem. Flavivirus nonstructural protein 5 (NS5) possesses enzymatic activities required for capping and synthesis of the viral RNA genome and is essential for virus replication. NS5 is comprised of two domains. The N-terminal domain binds GTP and can perform two biochemically distinct methylation reactions required for RNA cap formation. The C-terminal domain contains RNA-dependent RNA polymerase activity. As such, NS5 is an interesting target against which antiviral drugs could be developed and research toward this goal has accelerated our understanding of NS5 structure and function in recent years. The production and purification of recombinant versions of either the full-length NS5 or the two individual NS5 domains has led to detailed enzymatic studies on NS5 and the determination of structures of the two NS5 domains. In turn, studies using a combination of structural, biochemical, and reverse genetic approaches are revealing how NS5 performs its multifunctional roles in genome replication. Aside from its localization in the membrane-bound replication complex, NS5 can be found free in the cytoplasm and for some flaviviruses in the nucleus of virus-infected cells. NS5 is phosphorylated which may potentially regulate NS5 function and trafficking. Recently, NS5 of a number of flaviviruses has been shown to interact with cellular pathways involved in the host immune response, suggesting that NS5 may play a role in viral pathogenesis. This chapter reviews recent advances in our understanding of the multifunctional roles played by NS5 in the virus lifecycle.
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