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Guo X, Zhang M, Liu X, Zhang Y, Wang C, Guo Y. Attachment, Entry, and Intracellular Trafficking of Classical Swine Fever Virus. Viruses 2023; 15:1870. [PMID: 37766277 PMCID: PMC10534341 DOI: 10.3390/v15091870] [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: 05/30/2023] [Revised: 08/29/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
Classical swine fever virus (CSFV), which is a positive-sense, single-stranded RNA virus with an envelope, is a member of the Pestivirus genus in the Flaviviridae family. CSFV causes a severe and highly contagious disease in pigs and is prevalent worldwide, threatening the pig farming industry. The detailed mechanisms of the CSFV life cycle have been reported, but are still limited. Some receptors and attachment factors of CSFV, including heparan sulfate (HS), laminin receptor (LamR), complement regulatory protein (CD46), MER tyrosine kinase (MERTK), disintegrin, and metalloproteinase domain-containing protein 17 (ADAM17), were identified. After attachment, CSFV internalizes via clathrin-mediated endocytosis (CME) and/or caveolae/raft-dependent endocytosis (CavME). After internalization, CSFV moves to early and late endosomes before uncoating. During this period, intracellular trafficking of CSFV relies on components of the endosomal sorting complex required for transport (ESCRT) and Rab proteins in the endosome dynamics, with a dependence on the cytoskeleton network. This review summarizes the data on the mechanisms of CSFV attachment, internalization pathways, and intracellular trafficking, and provides a general view of the early events in the CSFV life cycle.
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Affiliation(s)
| | | | | | | | | | - Yidi Guo
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Key Laboratory for Zoonosis Research of the Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun 130012, China
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Plante JA, Plante KS, Popov VL, Shinde DP, Widen SG, Buenemann M, Nogueira ML, Vasilakis N. Morphologic and Genetic Characterization of Ilheus Virus, a Potential Emergent Flavivirus in the Americas. Viruses 2023; 15:195. [PMID: 36680235 PMCID: PMC9866216 DOI: 10.3390/v15010195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 01/12/2023] Open
Abstract
Ilheus virus (ILHV) is a mosquito-borne flavivirus circulating throughout Central and South America and the Caribbean. It has been detected in several mosquito genera including Aedes and Culex, and birds are thought to be its primary amplifying and reservoir host. Here, we describe the genomic and morphologic characterization of ten ILHV strains. Our analyses revealed a high conservation of both the 5'- and 3'-untranslated regions but considerable divergence within the open reading frame. We also showed that ILHV displays a typical flavivirus structural and genomic organization. Our work lays the foundation for subsequent ILHV studies to better understand its transmission cycles, pathogenicity, and emergence potential.
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Affiliation(s)
- Jessica A. Plante
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- World Reference Center for Emerging Viruses and Arboviruses, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX 77555-0610, USA
| | - Kenneth S. Plante
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- World Reference Center for Emerging Viruses and Arboviruses, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX 77555-0610, USA
| | - Vsevolod L. Popov
- World Reference Center for Emerging Viruses and Arboviruses, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX 77555-0610, USA
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
| | - Divya P. Shinde
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- World Reference Center for Emerging Viruses and Arboviruses, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX 77555-0610, USA
| | - Steven G. Widen
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555-0679, USA
| | - Michaela Buenemann
- Department of Geography and Environmental Studies, New Mexico State University, Las Cruces, NM 88003-8801, USA
| | - Mauricio L. Nogueira
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Center for Vector-Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Department of Dermatological, Infectious and Parasitic Diseases, Faculdade de Medicina de São José do Rio Preto 15090-000, SP, Brazil
| | - Nikos Vasilakis
- World Reference Center for Emerging Viruses and Arboviruses, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, TX 77555-0610, USA
- Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
- Center for Vector-Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
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Proline to Threonine Mutation at Position 162 of NS5B of Classical Swine Fever Virus Vaccine C Strain Promoted Genome Replication and Infectious Virus Production by Facilitating Initiation of RNA Synthesis. Viruses 2021; 13:v13081523. [PMID: 34452387 PMCID: PMC8402891 DOI: 10.3390/v13081523] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/29/2021] [Accepted: 07/30/2021] [Indexed: 12/11/2022] Open
Abstract
The 3′untranslated region (3′UTR) and NS5B of classical swine fever virus (CSFV) play vital roles in viral genome replication. In this study, two chimeric viruses, vC/SM3′UTR and vC/b3′UTR, with 3′UTR substitution of CSFV Shimen strain or bovine viral diarrhea virus (BVDV) NADL strain, were constructed based on the infectious cDNA clone of CSFV vaccine C strain, respectively. After virus rescue, each recombinant chimeric virus was subjected to continuous passages in PK-15 cells. The representative passaged viruses were characterized and sequenced. Serial passages resulted in generation of mutations and the passaged viruses exhibited significantly increased genomic replication efficiency and infectious virus production compared to parent viruses. A proline to threonine mutation at position 162 of NS5B was identified in both passaged vC/SM3′UTR and vC/b3′UTR. We generated P162T mutants of two chimeras using the reverse genetics system, separately. The single P162T mutation in NS5B of vC/SM3′UTR or vC/b3′UTR played a key role in increased viral genome replication and infectious virus production. The P162T mutation increased vC/SM3′UTRP162T replication in rabbits. From RNA-dependent RNA polymerase (RdRp) assays in vitro, the NS5B containing P162T mutation (NS5BP162T) exhibited enhanced RdRp activity for different RNA templates. We further identified that the enhanced RdRp activity originated from increased initiation efficiency of RNA synthesis. These findings revealed a novel function for the NS5B residue 162 in modulating pestivirus replication.
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Bhatia S, Narayanan N, Nagpal S, Nair DT. Antiviral therapeutics directed against RNA dependent RNA polymerases from positive-sense viruses. Mol Aspects Med 2021; 81:101005. [PMID: 34311994 DOI: 10.1016/j.mam.2021.101005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 01/18/2023]
Abstract
Viruses with positive-sense single stranded RNA (+ssRNA) genomes are responsible for different diseases and represent a global health problem. In addition to developing new vaccines that protect against severe illness on infection, it is imperative to identify new antiviral molecules to treat infected patients. The genome of these RNA viruses generally codes for an enzyme with RNA dependent RNA polymerase (RdRP) activity. This molecule is centrally involved in the duplication of the RNA genome. Inhibition of this enzyme by small molecules will prevent duplication of the RNA genome and thus reduce the viral titer. An overview of the different therapeutic strategies used to inhibit RdRPs from +ssRNA viruses is provided, along with an analysis of these enzymes to highlight new binding sites for inhibitors.
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Affiliation(s)
- Sonam Bhatia
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India
| | - Naveen Narayanan
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India
| | - Shilpi Nagpal
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India; National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore, 560065, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India.
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Membrane Topology of Pestiviral Non-Structural Protein 2 and determination of the minimal autoprotease domain. J Virol 2021; 95:JVI.00154-21. [PMID: 33731461 PMCID: PMC8139697 DOI: 10.1128/jvi.00154-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pestiviruses like bovine viral diarrhea virus (BVDV) belong to the family Flaviviridae A distinctive feature of the Flaviviridae is the importance of non-structural (NS) proteins for RNA genome replication and virus morphogenesis. For pestiviruses, the NS2 protease-mediated release of NS3 is essential for RNA replication, whereas uncleaved NS2-3 is indispensable for producing viral progeny. Accordingly, in the pestiviral life cycle the switch from RNA replication to virion morphogenesis is temporally regulated by the extent of NS2-3 cleavage, which is catalyzed by the NS2 autoprotease. A detailed knowledge of the structural and functional properties of pestiviral NS2 and NS2-3 is mandatory for a better understanding of these processes.In the present study, we experimentally determined the membrane topology of NS2 of BVDV-1 strain NCP7 by the Substituted Cysteine Accessibility Method (SCAM) assay. According to the resulting model, the N terminus of NS2 resides in the ER lumen and is followed by three transmembrane segments (TM) and a cytoplasmic C-terminal protease domain. We used the resulting model for fine mapping of the minimal autoprotease domain. Only one TM segment was found to be essential for maintaining residual autoprotease activity. While the topology of pestiviral NS2 is overall comparable to the one of hepatitis C virus (HCV) NS2, our data also reveal potentially important differences between the two molecules. The improved knowledge about structural and functional properties of this protein will support future functional and structural studies on pestiviral NS2.ImportancePestiviral NS2 is central to the regulation of RNA replication and virion morphogenesis via its autoprotease activity. This activity is temporally regulated by the cellular DNAJC14 as a cofactor: while free NS3 is required for RNA replication as a component of the viral replicase, only uncleaved NS2-3 supports virion morphogenesis. For a better understanding of the underlying molecular interactions, topological and structural data are required. The topology-based determination of the minimal NS2-protease domain in the present study will facilitate future attempts to determine the structure of this unusual protease cofactor complex. In the hepatitis C virus system, NS2 functions as a hub in virion morphogenesis by interacting with structural as well as non-structural proteins. Our knowledge of the membrane topology will significantly support future detailed interaction studies for pestiviral NS2.
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A Sensitive Yellow Fever Virus Entry Reporter Identifies Valosin-Containing Protein (VCP/p97) as an Essential Host Factor for Flavivirus Uncoating. mBio 2020; 11:mBio.00467-20. [PMID: 32291299 PMCID: PMC7157815 DOI: 10.1128/mbio.00467-20] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Flaviviruses are an important group of RNA viruses that cause significant human disease. The mechanisms by which flavivirus nucleocapsids are disassembled during virus entry remain unclear. Here, we used a yellow fever virus entry reporter, which expresses a sensitive reporter enzyme but does not replicate, to show that nucleocapsid disassembly requires the cellular protein-disaggregating enzyme valosin-containing protein, also known as p97. While the basic mechanisms of flavivirus entry and fusion are understood, little is known about the postfusion events that precede RNA replication, such as nucleocapsid disassembly. We describe here a sensitive, conditionally replication-defective yellow fever virus (YFV) entry reporter, YFVΔSK/Nluc, to quantitively monitor the translation of incoming, virus particle-delivered genomes. We validated that YFVΔSK/Nluc gene expression can be neutralized by YFV-specific antisera and requires known flavivirus entry pathways and cellular factors, including clathrin- and dynamin-mediated endocytosis, endosomal acidification, YFV E glycoprotein-mediated fusion, and cellular LY6E and RPLP1 expression. The initial round of YFV translation was shown to require cellular ubiquitylation, consistent with recent findings that dengue virus capsid protein must be ubiquitylated in order for nucleocapsid uncoating to occur. Importantly, translation of incoming YFV genomes also required valosin-containing protein (VCP)/p97, a cellular ATPase that unfolds and extracts ubiquitylated client proteins from large complexes. RNA transfection and washout experiments showed that VCP/p97 functions at a postfusion, pretranslation step in YFV entry. Finally, VCP/p97 activity was required by other flaviviruses in mammalian cells and by YFV in mosquito cells. Together, these data support a critical role for VCP/p97 in the disassembly of incoming flavivirus nucleocapsids during a postfusion step in virus entry.
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Zhang T, Wang ML, Zhang GR, Liu W, Xiao XQ, Yang YS, Li JT, Xun ZM, Li DY, Chan PK. Recombinant DENV 2 NS5: An effective antigen for diagnosis of DENV infection. J Virol Methods 2019; 265:35-41. [DOI: 10.1016/j.jviromet.2018.12.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 12/13/2018] [Accepted: 12/15/2018] [Indexed: 12/12/2022]
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CRISPR/Cas9-Mediated Knockout of DNAJC14 Verifies This Chaperone as a Pivotal Host Factor for RNA Replication of Pestiviruses. J Virol 2019; 93:JVI.01714-18. [PMID: 30518653 DOI: 10.1128/jvi.01714-18] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 11/20/2018] [Indexed: 12/19/2022] Open
Abstract
Pestiviruses like bovine viral diarrhea virus (BVDV) are a threat to livestock. For pestiviruses, cytopathogenic (cp) and noncytopathogenic (noncp) strains are distinguished in cell culture. The noncp biotype of BVDV is capable of establishing persistent infections, which is a major problem in disease control. The noncp biotype rests on temporal control of viral RNA replication, mediated by regulated cleavage of nonstructural protein 2-3 (NS2-3). This cleavage is catalyzed by the autoprotease in NS2, the activity of which depends on its cellular cofactor, DNAJC14. Since this chaperone is available in small amounts and binds tightly to NS2, NS2-3 translated later in infection is no longer cleaved. As NS3 is an essential constituent of the viral replicase, this shift in polyprotein processing correlates with downregulation of RNA replication. In contrast, cp BVDV strains arising mostly by RNA recombination show highly variable genome structures and display unrestricted NS3 release. The functional importance of DNAJC14 for noncp pestiviruses has been established so far only for BVDV-1. It was therefore enigmatic whether replication of other noncp pestiviruses is also DNAJC14 dependent. By generating bovine and porcine DNAJC14 knockout cells, we could show that (i) replication of 6 distinct noncp pestivirus species (A to D, F, and G) depends on DNAJC14, (ii) the pestiviral replicase NS3-5B can assemble into functional complexes in the absence of DNAJC14, and (iii) all cp pestiviruses replicate their RNA and generate infectious progeny independent of host DNAJC14. Together, these findings confirm DNAJC14 as a pivotal cellular cofactor for the replication and maintenance of the noncp biotype of pestiviruses.IMPORTANCE Only noncp pestivirus strains are capable of establishing life-long persistent infections to generate the virus reservoir in the field. The molecular basis for this biotype is only partially understood and only investigated in depth for BVDV-1 strains. Temporal control of viral RNA replication correlates with the noncp biotype and is mediated by limiting amounts of cellular DNAJC14 that activate the viral NS2 protease to catalyze the release of the essential replicase component NS3. Here, we demonstrate that several species of noncp pestiviruses depend on DNAJC14 for their RNA replication. Moreover, all cp pestiviruses, in sharp contrast to their noncp counterparts, replicate independently of DNAJC14. The generation of a cp BVDV in the persistently infected animal is causative for onset of mucosal disease. Therefore, the observed strict biotype-specific difference in DNAJC14 dependency should be further examined for its role in cell type/tissue tropism and the pathogenesis of this lethal disease.
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Danilevicz MF, Moharana KC, Venancio TM, Franco LO, Cardoso SRS, Cardoso M, Thiebaut F, Hemerly AS, Prosdocimi F, Ferreira PCG. Copaifera langsdorffii Novel Putative Long Non-Coding RNAs: Interspecies Conservation Analysis in Adaptive Response to Different Biomes. Noncoding RNA 2018; 4:ncrna4040027. [PMID: 30297664 PMCID: PMC6316758 DOI: 10.3390/ncrna4040027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/26/2018] [Accepted: 09/28/2018] [Indexed: 12/20/2022] Open
Abstract
Long non-coding RNAs (lncRNAs) are involved in multiple regulatory pathways and its versatile form of action has disclosed a new layer in gene regulation. LncRNAs have their expression levels modulated during plant development, and in response to stresses with tissue-specific functions. In this study, we analyzed lncRNA from leaf samples collected from the legume Copaifera langsdorffii Desf. (copaíba) present in two divergent ecosystems: Cerrado (CER; Ecological Station of Botanical Garden in Brasília, Brazil) and Atlantic Rain Forest (ARF; Rio de Janeiro, Brazil). We identified 8020 novel lncRNAs, and they were compared to seven Fabaceae genomes and transcriptomes, to which 1747 and 2194 copaíba lncRNAs were mapped, respectively, to at least one species. The secondary structures of the lncRNAs that were conserved and differentially expressed between the populations were predicted using in silico methods. A few selected lncRNA were confirmed by RT-qPCR in the samples from both biomes; Additionally, the analysis of the lncRNA sequences predicted that some might act as microRNA (miRNA) targets or decoys. The emerging studies involving lncRNAs function and conservation have shown their involvement in several types of biotic and abiotic stresses. Thus, the conservation of lncRNAs among Fabaceae species considering their rapid turnover, suggests they are likely to have been under functional conservation pressure. Our results indicate the potential involvement of lncRNAs in the adaptation of C. langsdorffii in two different biomes.
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Affiliation(s)
- Monica F Danilevicz
- Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-599, Brazil.
| | - Kanhu C Moharana
- Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Rio de Janeiro 28013-602, Brazil.
| | - Thiago M Venancio
- Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Rio de Janeiro 28013-602, Brazil.
| | - Luciana O Franco
- Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Diretoria de Pesquisa Científica, Rio de Janeiro 22460-030, Brazil.
| | - Sérgio R S Cardoso
- Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Diretoria de Pesquisa Científica, Rio de Janeiro 22460-030, Brazil.
| | - Mônica Cardoso
- Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Diretoria de Pesquisa Científica, Rio de Janeiro 22460-030, Brazil.
| | - Flávia Thiebaut
- Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-599, Brazil.
| | - Adriana S Hemerly
- Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-599, Brazil.
| | - Francisco Prosdocimi
- Laboratório de Genômica e Biodiversidade, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-599, Brazil.
| | - Paulo C G Ferreira
- Laboratório de Biologia Molecular de Plantas, Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-599, Brazil.
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Crystal Structure of Classical Swine Fever Virus NS5B Reveals a Novel N-Terminal Domain. J Virol 2018; 92:JVI.00324-18. [PMID: 29720518 PMCID: PMC6026734 DOI: 10.1128/jvi.00324-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/23/2018] [Indexed: 01/07/2023] Open
Abstract
Classical swine fever virus (CSFV) is the cause of classical swine fever (CSF). Nonstructural protein 5B (NS5B) is an RNA-dependent RNA polymerase (RdRp) that is a key enzyme initiating viral RNA replication by a de novo mechanism. It is also an attractive target for the development of anti-CSFV drugs. To gain a better understanding of the mechanism of CSFV RNA synthesis, here, we solved the first crystal structure of CSFV NS5B. Our studies show that the CSFV NS5B RdRp contains the characteristic finger, palm, and thumb domains, as well as a unique N-terminal domain (NTD) that has never been observed. Mutagenesis studies on NS5B validated the importance of the NTD in the catalytic activity of this novel RNA-dependent RNA polymerase. Moreover, our results shed light on CSFV infection.IMPORTANCE Pigs are important domesticated animals. However, a highly contagious viral disease named classical swine fever (CSF) causes devastating economic losses. Classical swine fever virus (CSFV), the primary cause of CSF, is a positive-sense single-stranded RNA virus belonging to the genus Pestivirus, family Flaviviridae Genome replication of CSFV depends on an RNA-dependent RNA polymerase (RdRp) known as NS5B. However, the structure of CSFV NS5B has never been reported, and the mechanism of CSFV replication is poorly understood. Here, we solve the first crystal structure of CSFV NS5B and analyze the functions of the characteristic finger, palm, and thumb domains. Additionally, our structure revealed the presence of a novel N-terminal domain (NTD). Biochemical studies demonstrated that the NTD of CSFV NS5B is very important for RdRp activity. Collectively, our studies provide a structural basis for future rational design of anti-CSFV drugs, which is critically important, as no effective anti-CSFV drugs have been developed.
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Xu HT, Hassounah SA, Colby-Germinario SP, Oliveira M, Fogarty C, Quan Y, Han Y, Golubkov O, Ibanescu I, Brenner B, Stranix BR, Wainberg MA. Purification of Zika virus RNA-dependent RNA polymerase and its use to identify small-molecule Zika inhibitors. J Antimicrob Chemother 2017; 72:727-734. [PMID: 28069884 DOI: 10.1093/jac/dkw514] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 11/01/2016] [Indexed: 12/21/2022] Open
Abstract
Background The viral RNA-dependent RNA polymerase (RdRp) enzymes of the Flaviviridae family are essential for viral replication and are logically important targets for development of antiviral therapeutic agents. Zika virus (ZIKV) is a rapidly re-emerging human pathogen for which no vaccine or antiviral agent is currently available. Methods To facilitate development of ZIKV RdRp inhibitors, we have established an RdRp assay using purified recombinant ZIKV NS5 polymerase. Results We have shown that both the hepatitis C virus (HCV) nucleoside inhibitor sofosbuvir triphosphate and a pyridoxine-derived non-nucleoside small-molecule inhibitor, DMB213, can act against ZIKV RdRp activity at IC 50 s of 7.3 and 5.2 μM, respectively, in RNA synthesis reactions catalysed by recombinant ZIKV NS5 polymerase. Cell-based assays confirmed the anti-ZIKV activity of sofosbuvir and DMB213 with 50% effective concentrations (EC 50 s) of 8.3 and 4.6 μM, respectively. Control studies showed that DMB213 did not inhibit recombinant HIV-1 reverse transcriptase and showed only very weak inhibition of HIV-1 integrase strand-transfer activity. The S604T substitution in motif B of the ZIKV RdRp, which corresponds to the S282T substitution in motif B of HCV RdRp, which confers resistance to nucleotide inhibitors, also conferred resistance to sofosbuvir triphosphate, but not to DMB213. Enzyme assays showed that DMB213 appears to be competitive with natural nucleoside triphosphate (NTP) substrates. Conclusions Recombinant ZIKV RdRp assays can be useful tools for the screening of both nucleos(t)ide compounds and non-nucleotide metal ion-chelating agents that interfere with ZIKV replication.
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Affiliation(s)
- Hong-Tao Xu
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Said A Hassounah
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Susan P Colby-Germinario
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Maureen Oliveira
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Clare Fogarty
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Yudong Quan
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Yingshan Han
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Olga Golubkov
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Ilinca Ibanescu
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | - Bluma Brenner
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada
| | | | - Mark A Wainberg
- Jewish General Hospital, McGill University AIDS Centre, Lady Davis Institute for Medical Research, Montreal, Quebec, Canada.,Department of Medicine, McGill University, Montreal, Quebec, Canada.,Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
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Kleine Büning M, Meyer D, Austermann-Busch S, Roman-Sosa G, Rümenapf T, Becher P. Nonreplicative RNA Recombination of an Animal Plus-Strand RNA Virus in the Absence of Efficient Translation of Viral Proteins. Genome Biol Evol 2017; 9:817-829. [PMID: 28338950 PMCID: PMC5381556 DOI: 10.1093/gbe/evx046] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/08/2017] [Indexed: 12/27/2022] Open
Abstract
RNA recombination is a major driving force for the evolution of RNA viruses and is significantly implicated in the adaptation of viruses to new hosts, changes of virulence, as well as in the emergence of new viruses including drug-resistant and escape mutants. However, the molecular details of recombination in animal RNA viruses are only poorly understood. In order to determine whether viral RNA recombination depends on translation of viral proteins, a nonreplicative recombination system was established which is based on cotransfection of cells with synthetic bovine viral diarrhea virus (family Flaviviridae) RNA genome fragments either lacking the internal ribosome entry site required for cap-independent translation or lacking almost the complete polyprotein coding region. The emergence of a number of recombinant viruses demonstrated that IRES-mediated translation of viral proteins is dispensable for efficient recombination and suggests that RNA recombination can occur in the absence of viral proteins. Analyses of 58 independently emerged viruses led to the detection of recombinant genomes with duplications, deletions and insertions in the 5′ terminal region of the open reading frame, leading to enlarged core fusion proteins detectable by Western blot analysis. This demonstrates a remarkable flexibility of the pestivirus core protein. Further experiments with capped and uncapped genome fragments containing a luciferase gene for monitoring the level of protein translation revealed that even a ∼1,000-fold enhancement of translation of viral proteins did not increase the frequency of RNA recombination. Taken together, this study highlights that nonreplicative RNA recombination does not require translation of viral proteins.
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Affiliation(s)
- Maximiliane Kleine Büning
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Germany
| | - Denise Meyer
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Germany
| | - Sophia Austermann-Busch
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Germany
| | | | - Tillmann Rümenapf
- Department of Pathobiology, Institute of Virology, University of Veterinary Medicine Vienna, Austria
| | - Paul Becher
- Department of Infectious Diseases, Institute of Virology, University of Veterinary Medicine Hannover, Germany
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Amraiz D, Zaidi NUSS, Fatima M. Development of robust in vitro RNA-dependent RNA polymerase assay as a possible platform for antiviral drug testing against dengue. Enzyme Microb Technol 2016; 92:26-30. [PMID: 27542741 PMCID: PMC7112394 DOI: 10.1016/j.enzmictec.2016.06.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 06/16/2016] [Accepted: 06/16/2016] [Indexed: 12/16/2022]
Abstract
Successful expression of recombinant RNA dependent RNA polymerase (RdRp) of DENV-2 in E. coli cells. Two step purification of enzymatically active RdRp protein using Ni-NTA and size exclusion columns. High level production of RdRp with final yield of 6.5 mg protein from 1 L of culture. Demonstration of in vitro polymerase activity of RdRp using homopolymeric RNA template. Optimization of RdRp assay conditions such as protein concentration, GTP concentration and incubation time of the reaction.
NS5 is the largest and most conserved protein among the four dengue virus (DENV) serotypes. It has been the target of interest for antiviral drug development due to its major role in replication. NS5 consists of two domains, the N-terminal methyltransferase domain and C-terminal catalytic RNA-dependent RNA polymerase (RdRp) domain. It is an unstable protein and is prone to inactivation upon prolonged incubation at room temperature, thus affecting the inhibitor screening assays. In the current study, we expressed and purified DENV RdRp alone in Esherichia coli (E. coli) cells. The N-terminally His-tagged construct of DENV RdRp was transformed into E. coli expression strain BL-21 (DE3) pLysS cells. Protein expression was induced with isopropyl-β-D-thiogalactopyranoside (IPTG) at a final concentration of 0.4 mM. The induced cultures were then grown for 20 h at 18 °C and cells were harvested by centrifugation at 6000 x g for 15 min at 4 °C. The recombinant protein was purified using HisTrap affinity column (Ni-NTA) and then the sample was subjected to size exclusion chromatography, which successfully removed the degradation product obtained during the previous purification step. The in vitro polymerase activity of RdRp was successfully demonstrated using homopolymeric polycytidylic acid (poly(rC)) RNA template. This study describes the high level production of enzymatically active DENV RdRp protein which can be used to develop assays for testing large number of compounds in a high-throughput manner. RdRp has the de novo initiation activity and the in vitro polymerase assays for the protein provide a platform for highly robust and efficient antiviral compound screening systems.
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Affiliation(s)
- Deeba Amraiz
- Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan.
| | - Najam-Us-Sahar Sadaf Zaidi
- Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan.
| | - Munazza Fatima
- Atta-ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan.
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14
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Abstract
Pestiviruses are among the economically most important pathogens of livestock. The biology of these viruses is characterized by unique and interesting features that are both crucial for their success as pathogens and challenging from a scientific point of view. Elucidation of these features at the molecular level has made striking progress during recent years. The analyses revealed that major aspects of pestivirus biology show significant similarity to the biology of human hepatitis C virus (HCV). The detailed molecular analyses conducted for pestiviruses and HCV supported and complemented each other during the last three decades resulting in elucidation of the functions of viral proteins and RNA elements in replication and virus-host interaction. For pestiviruses, the analyses also helped to shed light on the molecular basis of persistent infection, a special strategy these viruses have evolved to be maintained within their host population. The results of these investigations are summarized in this chapter.
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Affiliation(s)
- Norbert Tautz
- Institute for Virology and Cell Biology, University of Lübeck, Lübeck, Germany
| | - Birke Andrea Tews
- Institut für Immunologie, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany.
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15
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The global ecology and epidemiology of West Nile virus. BIOMED RESEARCH INTERNATIONAL 2015; 2015:376230. [PMID: 25866777 PMCID: PMC4383390 DOI: 10.1155/2015/376230] [Citation(s) in RCA: 307] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 08/10/2014] [Indexed: 12/30/2022]
Abstract
Since its initial isolation in Uganda in 1937 through the present, West Nile virus (WNV) has become an important cause of human and animal disease worldwide. WNV, an enveloped virus of the genus Flavivirus, is naturally maintained in an enzootic cycle between birds and mosquitoes, with occasional epizootic spillover causing disease in humans and horses. The mosquito vectors for WNV are widely distributed worldwide, and the known geographic range of WNV transmission and disease has continued to increase over the past 77 years. While most human infections with WNV are asymptomatic, severe neurological disease may develop resulting in long-term sequelae or death. Surveillance and preventive measures are an ongoing need to reduce the public health impact of WNV in areas with the potential for transmission.
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16
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Kocabas F, Turan RD, Aslan GS. Fluorometric RdRp assay with self-priming RNA. Virus Genes 2015; 50:498-504. [PMID: 25749997 DOI: 10.1007/s11262-015-1187-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 02/27/2015] [Indexed: 10/23/2022]
Abstract
There is an outmost need for the identification of specific antiviral compounds. Current antivirals lack specificity, making them susceptible to off-target effects, and highlighting importance of development of assays to discover antivirals targeting viral specific proteins. Previous studies for identification of inhibitors of RNA-dependent RNA polymerase (RdRp) mostly relied on radioactive methods. This study describes a fluorometric approach to assess in vitro activity of viral RdRp for drug screening. Using readily available DNA- and RNA-specific fluorophores, we determined an optimum fluorometric approach that could be used in antiviral discovery specifically for RNA viruses by targeting RdRp. Here, we show that double-stranded RNA could be successfully distinguished from single-stranded RNA. In addition, we provide a strategy based on self-priming RNA to assess RdRp activity.
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Affiliation(s)
- Fatih Kocabas
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, 34755, Istanbul, Turkey,
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17
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Sheng C, Liu X, Jiang Q, Xu B, Zhou C, Wang Y, Chen J, Xiao M. Annexin A2 is involved in the production of classical swine fever virus infectious particles. J Gen Virol 2015; 96:1027-1032. [PMID: 25593157 DOI: 10.1099/vir.0.000048] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 01/09/2014] [Indexed: 12/20/2022] Open
Abstract
Annexin A2 (ANXA2) is an important host factor regulating several key processes in many viruses. To evaluate the potential involvement of ANXA2 in the life cycle of classical swine fever virus (CSFV), an RNA interference (RNAi) approach was utilized. Knockdown of ANXA2 did not impair CSFV RNA replication but significantly reduced CSFV production. A comparable reduction of extracellular and intracellular infectivity levels was detected, indicating that ANXA2 might play a role in CSFV assembly rather than in genome replication and virion release. Furthermore, ANXA2 was found to bind CSFV NS5A, an essential replicase component. Amino acids R338, N359, G378 of NS5A were revealed to be pivotal for the ANXA2-NS5A interaction. Substitutions of these amino acids had no effect on viral RNA replication but substantially reduced CSFV production, which might partly be due to these mutations destroying the ANXA2-NS5A interaction. These results suggested that ANXA2 might participate in CSFV production process by binding NS5A.
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Affiliation(s)
- Chun Sheng
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Xiaoxiang Liu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Qiuyue Jiang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Bin Xu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Chenhao Zhou
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Yujing Wang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Jun Chen
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
| | - Ming Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, PR China
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18
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Sheng C, Kou S, Jiang Q, Zhou C, Xiao J, Li J, Chen B, Zhao Y, Wang Y, Xiao M. Characterization of the C-terminal sequence of NS5A necessary for the assembly and production of classical swine fever virus infectious particles. Res Vet Sci 2014; 97:449-54. [PMID: 25218811 DOI: 10.1016/j.rvsc.2014.07.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 07/11/2014] [Accepted: 07/25/2014] [Indexed: 11/16/2022]
Abstract
Recent studies show that classical swine fever virus (CSFV) NS5A is an essential replicase component, but it is not known how NS5A participates in viral particle production. In this study, deletion and substitution mutations were introduced into the C-terminus of CSFV NS5A. The efficiency of Core protein release and extracellular and intracellular infectivity levels were assessed and NS5A-Core interaction was investigated. These results suggested that CSFV NS5A was a key factor for the assembly of infectious CSFV particles. The C-terminal sequence from amino acids 478 to 487 and amino acids S481 and T482 were necessary for CSFV assembly and production. The effect of NS5A on CSFV assembly and production might be related to NS5A-Core interaction. T482 was found to be conserved in the C-terminus of NS5A proteins of pestiviruses and hepatitis C virus (HCV), therefore suggesting that it might be important for these virus assembly and production.
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Affiliation(s)
- Chun Sheng
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Shumeng Kou
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Qiuyue Jiang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Chenhao Zhou
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Jing Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Jing Li
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Bing Chen
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Yu Zhao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Yujing Wang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China
| | - Ming Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai, 200234, China.
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19
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Castro EF, Campos RH, Cavallaro LV. Stability of the resistance to the thiosemicarbazone derived from 5,6-dimethoxy-1-indanone, a non-nucleoside polymerase inhibitor of bovine viral diarrhea virus. PLoS One 2014; 9:e100528. [PMID: 24950191 PMCID: PMC4065067 DOI: 10.1371/journal.pone.0100528] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 05/28/2014] [Indexed: 12/03/2022] Open
Abstract
Bovine viral diarrhea virus (BVDV) is the prototype Pestivirus. BVDV infection is distributed worldwide and causes serious problems for the livestock industry. The thiosemicarbazone of 5,6-dimethoxy-1-indanone (TSC) is a non-nucleoside polymerase inhibitor (NNI) of BVDV. All TSC-resistant BVDV variants (BVDV-TSCr T1–5) present an N264D mutation in the NS5B gene (RdRp) whereas the variant BVDV-TSCr T1 also presents an NS5B A392E mutation. In the present study, we carried out twenty passages of BVDV-TSCr T1–5 in MDBK cells in the absence of TSC to evaluate the stability of the resistance. The viral populations obtained (BVDV R1–5) remained resistant to the antiviral compound and conserved the mutations in NS5B associated with this phenotype. Along the passages, BVDV R2, R3 and R5 presented a delay in the production of cytopathic effect that correlated with a decrease in cell apoptosis and intracellular accumulation of viral RNA. The complete genome sequences that encode for NS2 to NS5B, Npro and Erns were analyzed. Additional mutations were detected in the NS5B of BVDV R1, R3 and R4. In both BVDV R2 and R3, most of the mutations found were localized in NS5A, whereas in BVDV R5, the only mutation fixed was NS5A V177A. These results suggest that mutations in NS5A could alter BVDV cytopathogenicity. In conclusion, the stability of the resistance to TSC may be due to the fixation of different compensatory mutations in each BVDV-TSCr. During their replication in a TSC-free medium, some virus populations presented a kind of interaction with the host cell that resembled a persistent infection: decreased cytopathogenicity and viral genome synthesis. This is the first report on the stability of antiviral resistance and on the evolution of NNI-resistant BVDV variants. The results obtained for BVDV-TSCr could also be applied for other NNIs.
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Affiliation(s)
- Eliana F. Castro
- Cátedra de Virología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Rodolfo H. Campos
- Cátedra de Virología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Lucía V. Cavallaro
- Cátedra de Virología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
- * E-mail:
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20
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Ambrose RL, Mackenzie JM. Flaviviral regulation of the unfolded protein response: can stress be beneficial? Future Virol 2013. [DOI: 10.2217/fvl.13.100] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Members of the Flaviviridae family remain some of the most significant human viral pathogens, with few vaccines or antivirals commercially available for therapeutic use. Thus, understanding the intracellular events of replication and how these viruses modulate signaling within an infected cell is of great importance. The ER is central to replication within the Flaviviridae family, as the site of viral protein translation and processing, as a source of membranes for replication complex formation and as a site of virus assembly. This places a large burden upon the organelle, resulting in the induction of ER stress responses, in particular the unfolded protein response. In turn, unfolded protein response signaling induced in infected cells is tightly modulated by the virus in order to maintain an optimal environment for replication. The loss of various components of the stress response can have either beneficial or detrimental effects, presenting intriguing targets for antiviral discovery.
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Affiliation(s)
- Rebecca L Ambrose
- Department of Microbiology & Immunology, University of Melbourne, Parkville, Melbourne, VIC, 3052, Australia
| | - Jason M Mackenzie
- Department of Microbiology & Immunology, University of Melbourne, Parkville, Melbourne, VIC, 3052, Australia
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21
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Functional characterization of bovine viral diarrhea virus nonstructural protein 5A by reverse genetic analysis and live cell imaging. J Virol 2013; 88:82-98. [PMID: 24131714 DOI: 10.1128/jvi.01957-13] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Nonstructural protein 5A (NS5A) of bovine viral diarrhea virus (BVDV) is a hydrophilic phosphoprotein with RNA binding activity and a critical component of the viral replicase. In silico analysis suggests that NS5A encompasses three domains interconnected by two low-complexity sequences (LCSs). While domain I harbors two functional determinants, an N-terminal amphipathic helix important for membrane association, and a Zn-binding site essential for RNA replication, the structure and function of the C-terminal half of NS5A are still ill defined. In this study, we introduced a panel of 10 amino acid deletions covering the C-terminal half of NS5A. In the context of a highly efficient monocistronic replicon, deletions in LCS I and the N-terminal part of domain II, as well as in domain III, were tolerated with regard to RNA replication. When introduced into a bicistronic replicon, only deletions in LCS I and the N-terminal part of domain II were tolerated. In the context of the viral full-length genome, these mutations allowed residual virion morphogenesis. Based on these data, a functional monocistronic BVDV replicon coding for an NS5A variant with an insertion of the fluorescent protein mCherry was constructed. Live cell imaging demonstrated that a fraction of NS5A-mCherry localizes to the surface of lipid droplets. Taken together, this study provides novel insights into the functions of BVDV NS5A. Moreover, we established the first pestiviral replicon expressing fluorescent NS5A-mCherry to directly visualize functional viral replication complexes by live cell imaging.
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22
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Chen Y, Xiao J, Xiao J, Sheng C, Wang J, Jia L, Zhi Y, Li G, Chen J, Xiao M. Classical swine fever virus NS5A regulates viral RNA replication through binding to NS5B and 3'UTR. Virology 2012; 432:376-88. [PMID: 22795973 DOI: 10.1016/j.virol.2012.04.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 03/30/2012] [Accepted: 04/23/2012] [Indexed: 12/01/2022]
Abstract
In this report, classical swine fever virus (CSFV) NS5A inhibit viral RNA replication when its concentration reached and surpassed the level of NS5B. Three amino acid fragments of CSFV NS5A, 137-172, 224-268 and 390-414 individually were shown to be essential to NS5B binding. The former two fragments were independently necessary for regulation of viral RNA replication and correlated with NS5B and 3'UTR binding activity. We also found that amino acids W143, V145, P227, T246, P257, K399, T401, E406 and L413 of CSFV NS5A were essential to NS5B binding activity. Furthermore, these amino acids were shown to be necessary for viral RNA replication and infection and conserved in NS5A proteins of CSFV, BDV, BVDV and HCV. These results indicated that NS5A may regulate viral RNA replication by binding to NS5B and 3'UTR. NS5A can still regulate viral RNA synthesis through binding to 3'UTR when binding to NS5B is not available.
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Affiliation(s)
- Yan Chen
- Biology Department, College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
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23
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Sheng C, Wang J, Xiao J, Xiao J, Chen Y, Jia L, Zhi Y, Li G, Xiao M. Classical swine fever virus NS5B protein suppresses the inhibitory effect of NS5A on viral translation by binding to NS5A. J Gen Virol 2012; 93:939-950. [DOI: 10.1099/vir.0.039495-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In order to investigate molecular mechanisms of internal ribosome entry site (IRES)-mediated translation in classical swine fever virus (CSFV), an important pathogen of pigs, the expression level of NS3 was evaluated in the context of genomic RNAs and reporter RNA fragments. All data showed that the NS5A protein has an inhibitory effect on IRES-mediated translation and that NS5B proteins suppress the inhibitory effect of NS5A on viral translation, but CSFV NS5B GDD mutants do not. Furthermore, glutathione S-transferase pull-down assay and immunoprecipitation analysis, associated with deletion and alanine-scanning mutations, were performed. Results showed that NS5B interacts with NS5A and that the region aa 390–414, located in the C-terminal half of NS5A, is important for binding of NS5B to NS5A. Furthermore, amino acids K399, T401, E406 and L413 in the region were found to be essential for NS5A–NS5B interaction, virus rescue and infection. The above-mentioned region and four amino acids were observed to overlap with the site responsible for inhibition of IRES-mediated translation by the NS5A protein. We also found that aa 63–72, aa 637–653 and the GDD motif of NS5B were necessary for the interaction between NS5A and NS5B. These findings suggest that the repression activity of the NS5B protein toward the role of NS5A in translation might be achieved by NS5A–NS5B interaction, for which aa 390–414 of NS5A and aa 63–72, aa 637–653 and the GDD motif of NS5B are indispensable. This is important for understanding the role of NS5A–NS5B interaction in the virus life cycle.
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Affiliation(s)
- Chun Sheng
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jing Wang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jing Xiao
- The First Clinical Medical College, Southern Medical University, Guangzhou 510515, PR China
| | - Jun Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Yan Chen
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Lin Jia
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Yimiao Zhi
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Guangyuan Li
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Ming Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
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24
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Sheng C, Chen Y, Xiao J, Xiao J, Wang J, Li G, Chen J, Xiao M. Classical swine fever virus NS5A protein interacts with 3'-untranslated region and regulates viral RNA synthesis. Virus Res 2012; 163:636-43. [PMID: 22261205 DOI: 10.1016/j.virusres.2012.01.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Revised: 01/02/2012] [Accepted: 01/04/2012] [Indexed: 12/22/2022]
Abstract
To investigate the function of classical swine fever virus (CSFV) NS5A protein, the experiments for viral RNA synthesis and viral replication were performed in the co-presence of NS5A and NS5B. Results showed that small concentrations of NS5A stimulated, large concentrations of NS5A inhibited, viral RNA synthesis and viral replication. Affinity chromatography experiments and UV-crosslinking assays revealed that CSFV NS5A and NS5B bound its cognate 3'UTR and that NS5A had higher affinity than NS5B protein in binding to 3'UTR. 200 ng of NS5A inhibited NS5B-3'UTR complex formation by about 95%. CSFV 3'UTR was found to contain two NS5A-binding sites, located in 3'UTRSL-1 (nt 161-231) and 3'UTRSL-2 (nt 90-160), respectively, a NS5B-binding site, also located in 3'UTRSL-1. The 3'UTRSL-1 is the common binding site for NS5A and NS5B. Furthermore, competitive electrophoretic mobility shift assays indicated that binding of CSFV NS5A to 3'UTRSL-1 is more efficiently than to 3'UTRSL-2. These results suggested that the different concentrations of NS5A, the different binding activities of NS5A and NS5B to 3'UTR and binding of NS5A to different regions of 3'UTR might contribute at least partially to modulation of CSFV replication.
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Affiliation(s)
- Chun Sheng
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
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25
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The F1 motif of dengue virus polymerase NS5 is involved in promoter-dependent RNA synthesis. J Virol 2011; 85:5745-56. [PMID: 21471248 DOI: 10.1128/jvi.02343-10] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The mechanism by which viral RNA-dependent RNA polymerases (RdRp) specifically amplify viral genomes is still unclear. In the case of flaviviruses, a model has been proposed that involves the recognition of an RNA element present at the viral 5' untranslated region, stem-loop A (SLA), that serves as a promoter for NS5 polymerase binding and activity. Here, we investigated requirements for specific promoter-dependent RNA synthesis of the dengue virus NS5 protein. Using mutated purified NS5 recombinant proteins and infectious viral RNAs, we analyzed the requirement of specific amino acids of the RdRp domain on polymerase activity and viral replication. A battery of 19 mutants was designed and analyzed. By measuring polymerase activity using nonspecific poly(rC) templates or specific viral RNA molecules, we identified four mutants with impaired polymerase activity. Viral full-length RNAs carrying these mutations were found to be unable to replicate in cell culture. Interestingly, one recombinant NS5 protein carrying the mutations K456A and K457A located in the F1 motif lacked RNA synthesis dependent on the SLA promoter but displayed high activity using a poly(rC) template. Promoter RNA binding of this NS5 mutant was unaffected while de novo RNA synthesis was abolished. Furthermore, the mutant maintained RNA elongation activity, indicating a role of the F1 region in promoter-dependent initiation. In addition, four NS5 mutants were selected to have polymerase activity in the recombinant protein but delayed or impaired virus replication when introduced into an infectious clone, suggesting a role of these amino acids in other functions of NS5. This work provides new molecular insights on the specific RNA synthesis activity of the dengue virus NS5 polymerase.
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26
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Characterisation of interaction between NS3 and NS5B protein of classical swine fever virus by deletion of terminal sequences of NS5B. Virus Res 2011; 156:98-106. [DOI: 10.1016/j.virusres.2011.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 01/01/2011] [Accepted: 01/04/2011] [Indexed: 11/23/2022]
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Xiao M, Wang Y, Zhu Z, Ding C, Yu J, Wan L, Chen J. Influence of the 5'-proximal elements of the 5'-untranslated region of classical swine fever virus on translation and replication. J Gen Virol 2011; 92:1087-1096. [PMID: 21307229 DOI: 10.1099/vir.0.027870-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The 5'-terminal sequence spanning nt 1-29 of the 5'-untranslated region of classical swine fever virus (CSFV) forms a 5'-proximal stem-loop structure known as domain Ia. Deletions and replacement mutations were performed to examine the role of this domain. Deletion of the 5'-proximal nucleotides and disruption of the stem-loop structure greatly increased internal ribosome entry site-mediated translation but abolished the replication of the replicons. Internal deletions resulting in a change in the size of the loop of domain Ia, and even removal of the entire domain, did not substantially change the translation activity, but reduced the replication of CSFV replicons provided the replicons contained the extreme 5'-GUAU terminal sequence. Internal replacements leading to a change in the nucleotide sequence of the loop did not alter the translation and replication activities of the CSFV RNA replicon, and did not influence the rescue of viruses and growth characteristics of new viruses. These results may be important for our understanding of the regulation of translation, replication and encapsidation in CSFV and other positive-sense RNA viruses.
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Affiliation(s)
- Ming Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Yujing Wang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Zailing Zhu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Chengli Ding
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jialin Yu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Lingzhu Wan
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jun Chen
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
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Phylogenetic analysis of NS5B gene of classical swine fever virus isolates indicates plausible Chinese origin of Indian subgroup 2.2 viruses. Virus Genes 2011; 44:104-8. [PMID: 21246270 DOI: 10.1007/s11262-011-0572-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 01/04/2011] [Indexed: 10/18/2022]
Abstract
Twenty-three CSFV isolates recovered from field outbreaks in various parts of India during 2006-2009 were used for genetic analysis in the NS5B region (409 nts). Seventeen of these were studied earlier [16] in the 5'UTR region. Phylogenetic analysis indicated the continued dominance of subgroup 1.1 strains in the country. Detailed analysis of a subgroup 2.2 virus indicated the plausible Chinese origin of this subgroup in India and provided indirect evidence of routes of CSFV movement within South East Asia region.
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Identification of an NTPase motif in classical swine fever virus NS4B protein. Virology 2011; 411:41-9. [PMID: 21236462 DOI: 10.1016/j.virol.2010.12.028] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 11/15/2010] [Accepted: 12/16/2010] [Indexed: 11/20/2022]
Abstract
Classical swine fever (CSF) is a highly contagious and often fatal disease of swine caused by CSF virus (CSFV), a positive-sense single-stranded RNA virus within the Pestivirus genus of the Flaviviridae family. Here, we have identified conserved sequence elements observed in nucleotide-binding motifs (NBM) that hydrolyze NTPs within the CSFV non-structural (NS) protein NS4B. Expressed NS4B protein hydrolyzes both ATP and GTP. Substitutions of critical residues within the identified NS4B NBM Walker A and B motifs significantly impair the ATPase and GTPase activities of expressed proteins. Similar mutations introduced into the genetic backbone of a full-length cDNA copy of CSFV strain Brescia rendered no infectious viruses or viruses with impaired replication capabilities, suggesting that this NTPase activity is critical for the CSFV cycle. Recovered mutant viruses retained a virulent phenotype, as parental strain Brescia, in infected swine. These results have important implications for developing novel antiviral strategies against CSFV infection.
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Zhu Z, Wang Y, Yu J, Wan L, Chen J, Xiao M. Classical swine fever virus NS3 is an IRES-binding protein and increases IRES-dependent translation. Virus Res 2010; 153:106-12. [PMID: 20637813 DOI: 10.1016/j.virusres.2010.07.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2010] [Revised: 07/06/2010] [Accepted: 07/08/2010] [Indexed: 10/19/2022]
Abstract
To get more evidences for understanding the role of NS3 in viral translation, we observed the promotive effect of CSFV NS3 on IRES-mediated translation by using dicistronic and monocistronic systems containing the precise segment comprising CSFV IRES. The results for affinity chromatography and UV-crosslinking assays indicated that NS3 bound CSFV IRES and that CSFV NS5A and NS5B could reduce the IRES-NS3 interaction. Further experiments showed that the NS5A also bound the IRES and that NS3 and NS5A bound the same binding sites of the IRES, suggesting that NS3 and NS5A competitively bind the same sites in IRES RNA sequence, thus hampering the interaction CSFV NS3 and IRES. But, CSFV NS5B was not found to interact with the IRES. The inhibitive effect of NS5B on binding of CSFV NS3 to IRES was supposed to result from the NS3-NS5B interaction which has been documented.
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Affiliation(s)
- Zailing Zhu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
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Sheng C, Zhu Z, Yu J, Wan L, Wang Y, Chen J, Gu F, Xiao M. Characterization of NS3, NS5A and NS5B of classical swine fever virus through mutation and complementation analysis. Vet Microbiol 2010; 140:72-80. [DOI: 10.1016/j.vetmic.2009.07.026] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Revised: 07/04/2009] [Accepted: 07/31/2009] [Indexed: 11/16/2022]
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Classical swine fever virus NS3 enhances RNA-dependent RNA polymerase activity by binding to NS5B. Virus Res 2009; 148:17-23. [PMID: 19951725 DOI: 10.1016/j.virusres.2009.11.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2009] [Revised: 11/24/2009] [Accepted: 11/25/2009] [Indexed: 11/20/2022]
Abstract
NS3 of pestiviruses contains a protease domain and a RNA helicase/NTPase domain. Contradictory results have been reported regarding NS3 in RNA synthesis. To investigate the effect of NS3 on classical swine fever virus (CSFV) NS5B RNA-dependent RNA polymerase activity (RdRp) activity and NS3-NS5B interaction, RdRp reactions, GST-pull-down assays and co-immunoprecipitation analyses containing NS5B and either of NS3 protein and the different truncated NS3 mutants were performed, respectively. We found that NS3 stimulated NS5B RdRp activity in a dose-dependent manner by binding to NS5 through a NS3 protease domain. Furthermore, mapping important regions of the NS3 protease domain was carried out by deletion mutagenesis, associated with RdRp reactions, GST-pull-down assays and co-immunoprecipitation analyses. Results showed that stimulation of CSFV NS5B RdRp activity was obtained by NS3 binding to NS5B through a 31-amino acid fragment at the N-terminal end of NS3 protease domain, which mediated a specific NS3-NS5B interaction.
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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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Xiao M, Wang Y, Zhu Z, Yu J, Wan L, Chen J. Influence of NS5A protein of classical swine fever virus (CSFV) on CSFV internal ribosome entry site-dependent translation. J Gen Virol 2009; 90:2923-2928. [PMID: 19710255 DOI: 10.1099/vir.0.014472-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An internal ribosome entry site (IRES) present in the 5' untranslated region (UTR) promotes translation of classical swine fever virus (CSFV) genomes. Using an in vitro system with monocistronic reporter RNA containing the CSFV 5'UTR, this study found that CSFV NS5A decreased CSFV IRES-mediated translation in a dose-dependent manner. Deletion analysis showed that the region responsible for repressing CSFV IRES activity might cover aa 390-414, located in the C-terminal half of CSFV NS5A. Triple and single alanine-scanning mutagenesis revealed that the inhibitory effect on CSFV IRES-directed translation mapped to the K399, T401, E406 and L413 residues of NS5A. These important amino acids were also found to be present in the NS5A proteins of bovine viral diarrhea virus (BVDV)-1, BVDV-2, border disease virus and hepatitis C virus, indicating that NS5A may play an important role in the switch from translation to replication in these viruses.
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Affiliation(s)
- Ming Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Yujing Wang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Zailing Zhu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jialin Yu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Lingzhu Wan
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jun Chen
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
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Liang D, Chen L, Ansari IH, Gil LH, Topliff CL, Kelling CL, Donis RO. A replicon trans-packaging system reveals the requirement of nonstructural proteins for the assembly of bovine viral diarrhea virus (BVDV) virion. Virology 2009; 387:331-40. [DOI: 10.1016/j.virol.2009.02.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 12/28/2008] [Accepted: 02/07/2009] [Indexed: 11/25/2022]
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Bougie I, Bisaillon M. Metal ion-binding studies highlight important differences between flaviviral RNA polymerases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1794:50-60. [PMID: 18930844 DOI: 10.1016/j.bbapap.2008.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 09/04/2008] [Accepted: 09/11/2008] [Indexed: 11/16/2022]
Abstract
West Nile virus (WNV) is a member of the Flaviviridae family which includes a number of important human pathogens. The WNV NS5 protein harbors an RNA-dependent RNA polymerase activity which is required both for replication and transcription of the viral genome. To extend our studies on the role of metal ions in the activity of flaviviral polymerases, we have used fluorescence spectroscopy, circular dichroism, and a combination of chemical and thermal denaturation assays to monitor the consequences of metal ion binding to the enzyme. We demonstrate that the binding of magnesium is not critical for the structural stabilization of the enzyme. Moreover, structural studies indicate that the protein does not undergo conformational change upon the binding of magnesium ions. Additional binding assays also indicate that the interaction of magnesium ions with the enzyme does not significantly stimulate the interaction with the RNA or NTP substrates. The inability of cobalt hexamine, an exchange-inert metal complex structurally analogous to magnesium hexahydrate, to support the catalytic activity also allowed us to demonstrate a direct role of magnesium ions in the catalytic activity of the enzyme. Finally, a three-dimensional structural model of the active center of the enzyme was generated which highlighted the importance of two aspartate residues involved in the coordination of two metal ions. Mutational analyses confirmed the importance of these two amino acids for the binding of magnesium ions. Our data provide further insight into the precise role of magnesium ions for the RNA polymerase activity of the protein, and more importantly, highlight key differences between the RNA polymerases of the Flaviviridae family.
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Affiliation(s)
- Isabelle Bougie
- Département de Biochimie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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Malet H, Massé N, Selisko B, Romette JL, Alvarez K, Guillemot JC, Tolou H, Yap TL, Vasudevan S, Lescar J, Canard B. The flavivirus polymerase as a target for drug discovery. Antiviral Res 2008; 80:23-35. [PMID: 18611413 DOI: 10.1016/j.antiviral.2008.06.007] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 06/06/2008] [Accepted: 06/10/2008] [Indexed: 02/06/2023]
Abstract
Flaviviruses are emerging pathogens of increasingly important public health concern in the world. For most flaviviruses such as dengue virus (DENV) and West Nile virus (WNV) neither vaccine nor antiviral treatment is available. The viral RNA-dependent RNA polymerase (RdRp) non-structural protein 5 (NS5) has no equivalent in the host cell and is essential for viral replication. Here, we give an overview of the current knowledge regarding Flavivirus RdRp function and structure as it represents an attractive target for drug design. Flavivirus RdRp exhibits primer-independent activity, thus initiating RNA synthesis de novo. Following initiation, a conformational change must occur to allow the elongation process. Structure-function studies of Flavivirus RdRp are now facilitated by the crystal structures of DENV (serotype 3) and WNV RdRp domains. Both adopt a classic viral RdRp fold and present a closed pre-initiation conformation. The so-called priming loop is thought to provide the initiation platform stabilizing the de novo initiation complex. A zinc-ion binding site at the hinge between two subdomains might be involved in opening up the RdRp structure towards a conformation for elongation. Using two different programs we predicted common potential allosteric inhibitor binding sites on both structures. We also review ongoing approaches of in vitro and cell-based screening programs aiming at the discovery of nucleosidic and non-nucleosidic inhibitors targeting Flavivirus RdRps.
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Affiliation(s)
- Hélène Malet
- Architecture et Fonction des Macromolécules Biologiques, CNRS and Universités d'Aix-Marseille I et II, UMR 6098, ESIL Case 925, 13288 Marseille, France
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38
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Xiao M, Bai Y, Xu H, Geng X, Chen J, Wang Y, Chen J, Li B. Effect of NS3 and NS5B proteins on classical swine fever virus internal ribosome entry site-mediated translation and its host cellular translation. J Gen Virol 2008; 89:994-999. [DOI: 10.1099/vir.0.83341-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A full-length NS3 (NS3F) and a truncated NS3 protein (NS3H) with an RNA helicase domain possess RNA helicase activity. Using an in vitro system with a monocistronic reporter RNA or DNA, containing the CSFV 5′-UTR, we observed that both NS3F and NS3H enhanced internal ribosome entry site (IRES)-mediated and cellular translation in a dose-dependent manner, but NS3 protease (NS3P) that lacks a helicase domain did not. NS3F was stronger than NS3H in promoting both translations. These results showed that viral RNA helicase could promote viral and cellular translation, and higher RNA helicase activity might be more efficient. The NS5B protein, the viral replicase, did not significantly affect the IRES-directed or cellular translation alone. NS5B significantly enhanced the stimulative effect of NS3F on both IRES-mediated and cellular translation, but did not affect that of NS3H or NS3P. This suggests that NS5B and NS3 interact via the protease domain during the enhancement of translation.
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Affiliation(s)
- Ming Xiao
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Yan Bai
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Hui Xu
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Xiaolu Geng
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jun Chen
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Yujing Wang
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, PR China
| | - Jiakuan Chen
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, PR China
| | - Bo Li
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, PR China
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Qi RF, Zhang L, Chi CW. Biological characteristics of dengue virus and potential targets for drug design. Acta Biochim Biophys Sin (Shanghai) 2008; 40:91-101. [PMID: 18235970 DOI: 10.1111/j.1745-7270.2008.00382.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Dengue infection is a major cause of morbidity in tropical and subtropical regions, bringing nearly 40% of the world population at risk and causing more than 20,000 deaths per year. But there is neither a vaccine for dengue disease nor antiviral drugs to treat the infection. In recent years, dengue infection has been particularly prevalent in India, Southeast Asia, Brazil, and Guangdong Province, China. In this article, we present a brief summary of the biological characteristics of dengue virus and associated flaviviruses, and outline the progress on studies of vaccines and drugs based on potential targets of the dengue virus.
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Affiliation(s)
- Rui-feng Qi
- Institute of Protein Research, Tongji University, Shanghai 200092, China
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40
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Biochemical characterization of a recombinant Japanese encephalitis virus RNA-dependent RNA polymerase. BMC Mol Biol 2007; 8:59. [PMID: 17623110 PMCID: PMC1934914 DOI: 10.1186/1471-2199-8-59] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Accepted: 07/11/2007] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Japanese encephalitis virus (JEV) NS5 is a viral nonstructural protein that carries both methyltransferase and RNA-dependent RNA polymerase (RdRp) domains. It is a key component of the viral RNA replicase complex that presumably includes other viral nonstructural and cellular proteins. The biochemical properties of JEV NS5 have not been characterized due to the lack of a robust in vitro RdRp assay system, and the molecular mechanisms for the initiation of RNA synthesis by JEV NS5 remain to be elucidated. RESULTS To characterize the biochemical properties of JEV RdRp, we expressed in Escherichia coli and purified an enzymatically active full-length recombinant JEV NS5 protein with a hexahistidine tag at the N-terminus. The purified NS5 protein, but not the mutant NS5 protein with an Ala substitution at the first Asp of the RdRp-conserved GDD motif, exhibited template- and primer-dependent RNA synthesis activity using a poly(A) RNA template. The NS5 protein was able to use both plus- and minus-strand 3'-untranslated regions of the JEV genome as templates in the absence of a primer, with the latter RNA being a better template. Analysis of the RNA synthesis initiation site using the 3'-end 83 nucleotides of the JEV genome as a minimal RNA template revealed that the NS5 protein specifically initiates RNA synthesis from an internal site, U81, at the two nucleotides upstream of the 3'-end of the template. CONCLUSION As a first step toward the understanding of the molecular mechanisms for JEV RNA replication and ultimately for the in vitro reconstitution of viral RNA replicase complex, we for the first time established an in vitro JEV RdRp assay system with a functional full-length recombinant JEV NS5 protein and characterized the mechanisms of RNA synthesis from nonviral and viral RNA templates. The full-length recombinant JEV NS5 will be useful for the elucidation of the structure-function relationship of this enzyme and for the development of anti-JEV agents.
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Sheng C, Xiao M, Geng X, Liu J, Wang Y, Gu F. Characterization of interaction of classical swine fever virus NS3 helicase with 3' untranslated region. Virus Res 2007; 129:43-53. [PMID: 17566586 DOI: 10.1016/j.virusres.2007.05.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2007] [Revised: 05/03/2007] [Accepted: 05/04/2007] [Indexed: 11/24/2022]
Abstract
The classical swine fever virus (CSFV) full-length NS3 protein (NS3F) and the truncated NS3 protein (NS3H) with postulated helicase domain were expressed and demonstrated to have helicase activity. Further, the electrophoretic mobility shift assays containing NS3H and the viral 3' terminal sequences showed that NS3H specifically bound to the plus- and minus-strand 3'UTR. The minus-strand 3'UTR had higher binding activity. The 21-nt fragments at the 3'-most terminal sequences of both 3'UTRs were essential to NS3H binding. A 12-nt insertion, CUUUUUUCUUUU, present in the 3'UTR of a CSFV live attenuated vaccine strain, was also found to be deleterious to helicase binding. Intact secondary structure of 3' terminal sequence of 3'UTR might be important in helicase binding. Our results show that interaction between the helicase and the viral 3'UTR is similar to that between the replicase and the 3'UTR, suggesting that NS3 helicase is important for CSFV genomic replication.
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Affiliation(s)
- Chun Sheng
- College of Life and Environment Sciences, Shanghai Normal University, Shanghai 200234, China
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42
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Mackenzie JM, Kenney MT, Westaway EG. West Nile virus strain Kunjin NS5 polymerase is a phosphoprotein localized at the cytoplasmic site of viral RNA synthesis. J Gen Virol 2007; 88:1163-1168. [PMID: 17374759 DOI: 10.1099/vir.0.82552-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Using West Nile virus strain Kunjin virus (WNV(KUN)) as a model system for flavivirus replication, we showed that the virus replication complex (RC) is associated with the dsRNA template located in induced membranes only in the cytoplasm. In this report we established for the first time that the RNA-dependent RNA polymerase NS5 is located in flavivirus-induced membranes, including the site of viral RNA replication. We found no evidence for nuclear localization of the essential RC components NS5 and its dsRNA template for WNV(KUN) or the closely related WNV strain Sarafend, by immuno-electron microscopy or by immunofluorescence. Metabolic radiolabelling with [(32)P]orthophosphate revealed that WNV(KUN) NS5 was phosphorylated and this was confirmed by Western blotting with antibodies specific for phosphorylated serine and threonine only. These observations of a cytoplasmic location for the WNV polymerase and its phosphorylation state correspond to the characteristics of the hepatitis C virus RNA polymerase NS5B.
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Affiliation(s)
- Jason M Mackenzie
- School of Molecular and Microbial Sciences, University of Queensland, St Lucia, QLD 4072, Australia
| | - Mark T Kenney
- Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital, and Clinical Medical Virology Centre, University of Queensland, Herston, Brisbane, QLD 4029, Australia
| | - Edwin G Westaway
- Sir Albert Sakzewski Virus Research Centre, Royal Children's Hospital, and Clinical Medical Virology Centre, University of Queensland, Herston, Brisbane, QLD 4029, Australia
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Moulin HR, Seuberlich T, Bauhofer O, Bennett LC, Tratschin JD, Hofmann MA, Ruggli N. Nonstructural proteins NS2-3 and NS4A of classical swine fever virus: essential features for infectious particle formation. Virology 2007; 365:376-89. [PMID: 17482232 DOI: 10.1016/j.virol.2007.03.056] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 02/13/2007] [Accepted: 03/29/2007] [Indexed: 11/17/2022]
Abstract
The nonstructural protein NS2-3 of pestiviruses undergoes tightly regulated processing. For bovine viral diarrhea virus it was shown that uncleaved NS2-3 is required for infectious particle formation while cleaved NS3 is essential for genome replication. To further investigate the functions of NS2-3 and NS4A in the pestivirus life cycle, we established T7 RNA polymerase-dependent trans-complementation for p7-NS2-3-4A of classical swine fever virus (CSFV). Expression of NS2-3 and NS4A in trans restored the production of infectious particles from genomes lacking NS2-3 expression. Co-expression of cleaved NS4A was essential. None of the enzymatic activities harbored by NS2-3 were required for infectious particle formation. Importantly, expression of uncleavable NS2-3 together with NS4A rescued infectious particles from a genome lacking NS2, demonstrating that cleaved NS2 per se has no additional essential function. These data indicate that NS2-3 and NS3, each in association with NS4A, have independent functions in the CSFV life cycle.
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Affiliation(s)
- Hervé R Moulin
- Institute of Virology and Immunoprophylaxis, Sensemattstrasse 293, CH-3147 Mittelhäusern, Switzerland.
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Yap TL, Xu T, Chen YL, Malet H, Egloff MP, Canard B, Vasudevan SG, Lescar J. Crystal structure of the dengue virus RNA-dependent RNA polymerase catalytic domain at 1.85-angstrom resolution. J Virol 2007; 81:4753-65. [PMID: 17301146 PMCID: PMC1900186 DOI: 10.1128/jvi.02283-06] [Citation(s) in RCA: 318] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Dengue fever, a neglected emerging disease for which no vaccine or antiviral agents exist at present, is caused by dengue virus, a member of the Flavivirus genus, which includes several important human pathogens, such as yellow fever and West Nile viruses. The NS5 protein from dengue virus is bifunctional and contains 900 amino acids. The S-adenosyl methionine transferase activity resides within its N-terminal domain, and residues 270 to 900 form the RNA-dependent RNA polymerase (RdRp) catalytic domain. Viral replication begins with the synthesis of minus-strand RNA from the dengue virus positive-strand RNA genome, which is subsequently used as a template for synthesizing additional plus-strand RNA genomes. This essential function for the production of new viral particles is catalyzed by the NS5 RdRp. Here we present a high-throughput in vitro assay partly recapitulating this activity and the crystallographic structure of an enzymatically active fragment of the dengue virus RdRp refined at 1.85-A resolution. The NS5 nuclear localization sequences, previously thought to fold into a separate domain, form an integral part of the polymerase subdomains. The structure also reveals the presence of two zinc ion binding motifs. In the absence of a template strand, a chain-terminating nucleoside analogue binds to the priming loop site. These results should inform and accelerate the structure-based design of antiviral compounds against dengue virus.
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Affiliation(s)
- Thai Leong Yap
- Novartis Institute for Tropical Diseases, 05-01 Chromos, 10 Biopolis Road, Singapore 138670, Singapore
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Malet H, Egloff MP, Selisko B, Butcher RE, Wright PJ, Roberts M, Gruez A, Sulzenbacher G, Vonrhein C, Bricogne G, Mackenzie JM, Khromykh AA, Davidson AD, Canard B. Crystal structure of the RNA polymerase domain of the West Nile virus non-structural protein 5. J Biol Chem 2007; 282:10678-89. [PMID: 17287213 DOI: 10.1074/jbc.m607273200] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Viruses of the family Flaviviridae are important human and animal pathogens. Among them, the Flaviviruses dengue (DENV) and West Nile (WNV) cause regular outbreaks with fatal outcomes. The RNA-dependent RNA polymerase (RdRp) activity of the non-structural protein 5 (NS5) is a key activity for viral RNA replication. In this study, crystal structures of enzymatically active and inactive WNV RdRp domains were determined at 3.0- and 2.35-A resolution, respectively. The determined structures were shown to be mostly similar to the RdRps of the Flaviviridae members hepatitis C and bovine viral diarrhea virus, although with unique elements characteristic for the WNV RdRp. Using a reverse genetic system, residues involved in putative interactions between the RNA-cap methyltransferase (MTase) and the RdRp domain of Flavivirus NS5 were identified. This allowed us to propose a model for the structure of the full-length WNV NS5 by in silico docking of the WNV MTase domain (modeled from our previously determined structure of the DENV MTase domain) onto the RdRp domain. The Flavivirus RdRp domain structure determined here should facilitate both the design of anti-Flavivirus drugs and structure-function studies of the Flavivirus replication complex in which the multifunctional NS5 protein plays a central role.
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Affiliation(s)
- Hélène Malet
- Architecture et Fonction des Macromolécules Biologiques, CNRS, and Universités d'Aix-Marseille I et II, UMR 6098, ESIL Case 925, 13288 Marseille, France
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Tellinghuisen TL, Paulson MS, Rice CM. The NS5A protein of bovine viral diarrhea virus contains an essential zinc-binding site similar to that of the hepatitis C virus NS5A protein. J Virol 2006; 80:7450-8. [PMID: 16840325 PMCID: PMC1563740 DOI: 10.1128/jvi.00358-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The recent demonstration that the NS5A protein of hepatitis C virus (HCV) contains an unconventional zinc-binding site with the format Cx(17)CxCx(20)C and the presence of a similar sequence element in the NS5A proteins of members of the Pestivirus genus has led to the hypothesis that the NS5A protein of the pestivirus bovine viral diarrhea virus (BVDV) is a zinc-binding protein. A method for the expression and partial purification of BVDV NS5A was developed, and the partially purified protein was analyzed for zinc content by atomic absorption spectroscopy. BVDV NS5A was found to coordinate a single zinc atom per protein molecule. Mutation of any of the four cysteines of the predicted zinc-binding motif eliminated zinc coordination. Furthermore, analysis of mutations at these cysteine residues in the context of a BVDV replicon system indicated that these residues were absolutely essential for RNA replication. The recently determined crystal structure of the N-terminal zinc-binding domain of the HCV NS5A protein, combined with secondary structure predictions of the region surrounding the mapped BVDV zinc-binding region, indicates that the BVDV zinc-binding motif fits the general template Cx(22)CxCx(24)C and likely comprises a three-stranded antiparallel beta-sheet fold. These data highlight the similarities between the Hepacivirus and Pestivirus NS5A proteins and suggest that both proteins perform a not-yet-defined function in RNA replication that requires coordination of a single zinc atom.
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Affiliation(s)
- Timothy L Tellinghuisen
- Laboratory of Virology and Infectious Disease, Center for the Study of Hepatitis C, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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Selisko B, Dutartre H, Guillemot JC, Debarnot C, Benarroch D, Khromykh A, Desprès P, Egloff MP, Canard B. Comparative mechanistic studies of de novo RNA synthesis by flavivirus RNA-dependent RNA polymerases. Virology 2006; 351:145-58. [PMID: 16631221 DOI: 10.1016/j.virol.2006.03.026] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 02/22/2006] [Accepted: 03/16/2006] [Indexed: 01/09/2023]
Abstract
Flavivirus protein NS5 harbors the RNA-dependent RNA polymerase (RdRp) activity. In contrast to the RdRps of hepaci- and pestiviruses, which belong to the same family of Flaviviridae, NS5 carries two activities, a methyltransferase (MTase) and a RdRp. RdRp domains of Dengue virus (DV) and West Nile virus (WNV) NS5 were purified in high yield relative to full-length NS5 and showed full RdRp activity. Steady-state enzymatic parameters were determined on homopolymeric template poly(rC). The presence of the MTase domain does not affect the RdRp activity. Flavivirus RdRp domains might bear more than one GTP binding site displaying positive cooperativity. The kinetics of RNA synthesis by four Flaviviridae RdRps were compared. In comparison to Hepatitis C RdRp, DV and WNV as well as Bovine Viral Diarrhea virus RdRps show less rate limitation by early steps of short-product formation. This suggests that they display a higher conformational flexibility upon the transition from initiation to elongation.
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Affiliation(s)
- Barbara Selisko
- Centre National de la Recherche Scientifique and Universités d'Aix-Marseille I et II, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, AFMB-CNRS-ESIL, 13288 Marseille Cedex 9, France
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48
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Xiao M, Li H, Wang Y, Wang X, Wang W, Peng J, Chen J, Li B. Characterization of the N-terminal domain of classical swine fever virus RNA-dependent RNA polymerase. J Gen Virol 2006; 87:347-356. [PMID: 16432021 DOI: 10.1099/vir.0.81385-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To investigate RNA-dependent RNA polymerase (RdRp) further, mutational analysis of the N-terminal domain of the NS5B protein of Classical swine fever virus was performed. Results show that the N-terminal domain (positions 1–300) of the protein might be divided artificially into four different regions, N1–N4. The N1 region (positions 1–61) contained neither conserved lysine nor conserved arginine residues. NS5B protein with deletion of the N1 region has the capacity for elongative RNA synthesis, but not for de novo RNA synthesis on natural templates. All substitutions of the conserved lysines and arginines in the N2 region (positions 63–216) destroyed RdRp activity completely. Substitutions of the conserved arginines in the N3 region (positions 217–280) seriously reduced RdRp activity. However, all substitutions of the conserved lysines in this region enhanced RNA synthesis and made the mutants synthesize RNA on any template. Substitutions of the conserved arginines in the N4 region (positions 281–300) reduced elongative synthesis and destroyed de novo RNA synthesis. In contrast, substitutions of lysines in this region did not affect RdRp activity significantly. These data indicate that the N3 region might be related to the enzymic specificity for templates, and the conserved lysines and arginines in different regions have different effects on RdRp activity. In combination with the published crystal structure of bovine viral diarrhea virus NS5B, these results define the important role of the N-terminal domain of NS5B for template recognition and de novo RNA synthesis.
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Affiliation(s)
- Ming Xiao
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, China
- College of Life and Environment Sciences, Biology Department, Shanghai Normal University, Shanghai 200234, China
| | - Huaibo Li
- College of Life and Environment Sciences, Biology Department, Shanghai Normal University, Shanghai 200234, China
| | - Yujing Wang
- College of Life and Environment Sciences, Biology Department, Shanghai Normal University, Shanghai 200234, China
| | - Xiaohui Wang
- College of Life and Environment Sciences, Biology Department, Shanghai Normal University, Shanghai 200234, China
| | - Wei Wang
- College of Life and Environment Sciences, Biology Department, Shanghai Normal University, Shanghai 200234, China
| | - Jun Peng
- College of Life and Environment Sciences, Biology Department, Shanghai Normal University, Shanghai 200234, China
| | - Jiakuan Chen
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, China
| | - Bo Li
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, China
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Horiuchi H, Fukuhara T. Putative Replication Intermediates in Endornavirus, a Novel Genus of Plant dsRNA Viruses. Virus Genes 2004; 29:365-75. [PMID: 15550778 DOI: 10.1007/s11262-004-7441-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Oryza sativa endornavirus (OSV) belongs to a new genus (Endornavirus) and family (Endoviridae) with members containing large double-stranded RNA (dsRNA) replicons with plasmid-like properties. Analysis of products obtained from in vitro reaction of the OSV RNA-dependent RNA polymerase revealed a rapid increase of a population of the non-coding strand RNA molecules with a head-to-tail composition. Northern hybridization of total RNA from OSV-carrier cells with riboprobes specific for the coding strand RNA, revealed two types of RNA molecules (i) with a site specific nick and (ii) full-length unnicked molecules. Quantitative analyses of these RNAs showed about 50-fold higher amounts of full-length unnicked molecules in cultured cells in which the OSV copy number increases compared with those found in the seedling cells. Both the head-to-tail linked non-coding strand and the full-length coding strand molecules were also found in wild rice and broad beans infected with other endornaviruses indicating that the presence of these unique types of RNA molecules should be considered as a characteristic feature of Endoviridae .
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Affiliation(s)
- Hideki Horiuchi
- Department of Applied Biological Sciences, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Tokyo, Japan
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Xiao M, Gao J, Wang W, Wang Y, Chen J, Chen J, Li B. Specific interaction between the classical swine fever virus NS5B protein and the viral genome. ACTA ACUST UNITED AC 2004; 271:3888-96. [PMID: 15373834 DOI: 10.1111/j.1432-1033.2004.04325.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The NS5B protein of the classical swine fever virus (CSFV) is the RNA-dependent RNA polymerase of the virus and is able to catalyze the viral genome replication. The 3' untranslated region is most likely involved in regulation of the Pestivirus genome replication. However, little is known about the interaction between the CSFV NS5B protein and the viral genome. We used different RNA templates derived from the plus-strand viral genome, or the minus-strand viral genome and the CSFV NS5B protein obtained from the Escherichia coli expression system to address this problem. We first showed that the viral NS5B protein formed a complex with the plus-strand genome through the genomic 3' UTR and that the NS5B protein was also able to bind the minus-strand 3' UTR. Moreover, it was found that viral NS5B protein bound the minus-strand 3' UTR more efficiently than the plus-strand 3' UTR. Further, we observed that the plus-strand 3' UTR with deletion of CCCGG or 21 continuous nucleotides at its 3' terminal had no binding activity and also lost the activity for initiation of minus-strand RNA synthesis, which similarly occurred in the minus-strand 3' UTR with CATATGCTC or the 21 nucleotide fragment deleted from the 3' terminal. Therefore, it is indicated that the 3' CCCGG sequence of the plus-strand 3' UTR, and the 3' CATATGCTC fragment of the minus-strand are essential to in vitro synthesis of the minus-strand RNA and the plus-strand RNA, respectively. The same conclusion is also appropriate for the 3' 21 nucleotide terminal site of both the 3' UTRs.
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Affiliation(s)
- Ming Xiao
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, Shanghai 200433, China
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