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Fellenberg J, Dubrau D, Isken O, Tautz N. Packaging defects in pestiviral NS4A can be compensated by mutations in NS2 and NS3. J Virol 2023; 97:e0057223. [PMID: 37695056 PMCID: PMC10537661 DOI: 10.1128/jvi.00572-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 07/18/2023] [Indexed: 09/12/2023] Open
Abstract
The non-structural (NS) proteins of the Flaviviridae members play a dual role in genome replication and virion morphogenesis. For pestiviruses, like bovine viral diarrhea virus, the NS2-3 region and its processing by the NS2 autoprotease is of particular importance. While uncleaved NS2-3 in complex with NS4A is essential for virion assembly, it cannot replace free NS3/4A in the viral replicase. Furthermore, surface interactions between NS3 and the C-terminal cytosolic domain of NS4A were shown to serve as a molecular switch between RNA replication and virion morphogenesis. To further characterize the functionality of NS4A, we performed an alanine-scanning mutagenesis of two NS4A regions, a short highly conserved cytoplasmic linker downstream of the transmembrane domain and the C-terminal domain. NS4A residues critical for polyprotein processing, RNA replication, and/or virion morphogenesis were identified. Three double-alanine mutants, two in the linker region and one close to the C-terminus of NS4A, showed a selective effect on virion assembly. All three packaging defective mutants could be rescued by a selected set of two second-site mutations, located in NS2 and NS3, respectively. This phenotype was additionally confirmed by complementation studies providing the NS2-3/4A packaging molecules containing the rescue mutations in trans. This indicates that the linker region and the cytosolic C-terminal part of NS4A are critical for the formation of protein complexes required for virion morphogenesis. The ability of the identified sets of second-site mutations in NS2-3 to compensate for diverse NS4A defects highlights a surprising functional flexibility for pestiviral NS proteins. IMPORTANCE Positive-strand RNA viruses have a limited coding capacity due to their rather small genome size. To overcome this constraint, viral proteins often exhibit multiple functions that come into play at different stages during the viral replication cycle. The molecular basis for this multifunctionality is often unknown. For the bovine viral diarrhea virus, the non-structural protein (NS) 4A functions as an NS3 protease cofactor, a replicase building block, and a component in virion morphogenesis. Here, we identified the critical amino acids of its C-terminal cytosolic region involved in those processes and show that second-site mutations in NS2 and NS3 can compensate for diverse NS4A defects in virion morphogenesis. The ability to evolve alternative functional solutions by gain-of-function mutations highlights the astounding plasticity of the pestiviral system.
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Affiliation(s)
- Jonas Fellenberg
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
| | - Danilo Dubrau
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
| | - Olaf Isken
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
| | - Norbert Tautz
- Institute of Virology and Cell Biology, University of Luebeck, Luebeck, Germany
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2
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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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3
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Kobayashi S, Fukuda Y, Yoshii K, Thammahakin P, Maezono K, Eyer L, Růžek D, Kariwa H. Development of recombinant West Nile virus expressing mCherry reporter protein. J Virol Methods 2023; 317:114744. [PMID: 37119976 DOI: 10.1016/j.jviromet.2023.114744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/30/2023] [Accepted: 04/27/2023] [Indexed: 05/01/2023]
Abstract
West Nile virus (WNV) is transmitted to humans and animals by a mosquito and enters the central nervous system, leading to lethal encephalitis. Reporter viruses expressing fluorescent proteins enable detection of infected cells in vitro and in vivo, facilitating evaluation of the dynamics of viral infection, and the development of diagnostic or therapeutic methods. In this study, we developed a method for production of a recombinant replication-competent WNV expressing mCherry fluorescent protein. The expression of mCherry was observed in viral antigen-positive cells in vitro and in vivo, but the growth of the reporter WNV was reduced as compared to the parental WNV. The expression of mCherry was stable during 5 passages in reporter WNV-infected culture cells. Neurological symptoms were observed in mice inoculated intracranially with the reporter WNV. The reporter WNV expressing mCherry will facilitate research into WNV replication in mouse brains.
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Affiliation(s)
- Shintaro Kobayashi
- Laboratory of Public Health, Faculty of Veterinary medicine, Hokkaido University, Sapporo, Japan.
| | - Yukine Fukuda
- Laboratory of Public Health, Faculty of Veterinary medicine, Hokkaido University, Sapporo, Japan
| | - Kentaro Yoshii
- National Research Center for the Control and Prevention of Infectious diseases (CCPID), Nagasaki University, Nagasaki, Japan
| | - Passawat Thammahakin
- Laboratory of Public Health, Faculty of Veterinary medicine, Hokkaido University, Sapporo, Japan
| | - Keisuke Maezono
- Laboratory of Public Health, Faculty of Veterinary medicine, Hokkaido University, Sapporo, Japan
| | - Luděk Eyer
- Department of Virology, Veterinary Research Institute, Brno, Czech Republic; Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Ceske Budejovice, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University
| | - Daniel Růžek
- Department of Virology, Veterinary Research Institute, Brno, Czech Republic; Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, Ceske Budejovice, Czech Republic; Department of Experimental Biology, Faculty of Science, Masaryk University
| | - Hiroaki Kariwa
- Laboratory of Public Health, Faculty of Veterinary medicine, Hokkaido University, Sapporo, Japan
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4
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The NS4A Protein of Classical Swine Fever Virus Suppresses RNA Silencing in Mammalian Cells. J Virol 2022; 96:e0187421. [PMID: 35867575 PMCID: PMC9364796 DOI: 10.1128/jvi.01874-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
RNA interference (RNAi) is a significant posttranscriptional gene silencing mechanism and can function as an antiviral immunity in eukaryotes. However, numerous viruses can evade this antiviral RNAi by encoding viral suppressors of RNA silencing (VSRs). Classical swine fever virus (CSFV), belonging to the genus Pestivirus, is the cause of classical swine fever (CSF), which has an enormous impact on animal health and the pig industry. Notably, little is known about how Pestivirus blocks RNAi in their host. In this paper, we uncovered that CSFV NS4A protein can antagonize RNAi efficiently in mammalian cells by binding to double-stranded RNA and small interfering RNA. In addition, the VSR activity of CSFV NS4A was conserved among Pestivirus. Furthermore, the replication of VSR-deficient CSFV was attenuated but could be restored by the deficiency of RNAi in mammalian cells. In conclusion, our studies uncovered that CSFV NS4A is a novel VSR that suppresses RNAi in mammalian cells and shed new light on knowledge about CSFV and other Pestivirus. IMPORTANCE It is well known that RNAi is an important posttranscriptional gene silencing mechanism that is also involved in the antiviral response in mammalian cells. While numerous viruses have evolved to block this antiviral immunity by encoding VSRs. Our data demonstrated that the NS4A protein of CSFV exhibited a potent VSR activity through binding to dsRNA and siRNA in the context of CSFV infection in mammalian cells, which are a conservative feature among Pestivirus. In addition, the replication of VSR-deficient CSFV was attenuated but could be restored by the deficiency of RNAi, providing a theoretical basis for the development of other important attenuated Pestivirus vaccines.
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Abstract
Bovine viral diarrhea virus (BVDV) belongs to the family Flaviviridae genus pestivirus. The viral genome is a single-stranded, positive-sense RNA that encodes four structural proteins (i.e., C, Erns, E1, and E2) and eight non-structural proteins (NSPs) (i.e., Npro, p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B). Cattle infected with BVDV exhibit a number of different clinical signs including diarrhea, abortion, and other reproductive disorders which have a serious impact on the cattle industry worldwide. Research on BVDV mainly focuses on its structural protein, however, progress in understanding the functions of the NSPs of BVDV has also been made in recent decades. The knowledge gained on the BVDV non-structural proteins is helpful to more fully understand the viral replication process and the molecular mechanism of viral persistent infection. This review focuses on the functions of BVDV NSPs and provides references for the identification of BVDV, the diagnosis and prevention of Bovine viral diarrhea mucosal disease (BVD-MD), and the development of vaccines.
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Luo J, Zhang J, Ni J, Jiang S, Xia N, Guo Y, Shao Q, Cao Q, Zheng W, Chen N, Zhang Q, Chen H, Chen Q, Zhu H, Meurens F, Zhu J. The African swine fever virus protease pS273R inhibits DNA sensing cGAS-STING pathway by targeting IKKε. Virulence 2022; 13:740-756. [PMID: 35437104 PMCID: PMC9067533 DOI: 10.1080/21505594.2022.2065962] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
African swine fever virus (ASFV), a large and complex cytoplasmic double-stranded DNA virus, has developed multiple strategies to evade the antiviral innate immune responses. Cytosolic DNA arising from invading ASFV is mainly detected by the cyclic GMP-AMP synthase (cGAS) and then triggers a series of innate immune responses to prevent virus invasion. However, the immune escape mechanism of ASFV remains to be fully clarified. The pS273R of ASFV is a member of the SUMO-1-specific protease family and is crucial for valid virus replication. In this study, we identified pS273R as a suppressor of cGAS-STING pathway mediated type I interferon (IFN) production by ASFV genomic open reading frame screening. The pS273R was further confirmed as an inhibitor of IFN production as well as its downstream antiviral genes in cGAS-STING pathway. Mechanistically, pS273R greatly decreased the cGAS-STING signaling by targeting IKKε but not TBK1, and pS273R was found to disturb the interaction between IKKε and STING through its interaction with IKKε. Further, mutational analyses revealed that pS273R antagonized the cGAS-STING pathway by enzyme catalytic activity, which might affect the IKKε sumoylation state required for the interaction with STING. In summary, our results revealed for the first time that pS273R acts as an obvious negative regulator of cGAS-STING pathway by targeting IKKε via its enzymatic activity, which shows a new immune evasion mechanism of ASFV.
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Affiliation(s)
- Jia Luo
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Jiajia Zhang
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Jinghua Ni
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Sen Jiang
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Nengwen Xia
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Yiwen Guo
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Qi Shao
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Qi Cao
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Wanglong Zheng
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Nanhua Chen
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Quan Zhang
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Hongjun Chen
- Shanghai Veterinary Research Institute, Chinese Academy of Agriculture Sciences, Shanghai, China
| | - Qing Chen
- College of Bioscience and Resource Environment, Beijing University of Agriculture, Beijing, China
| | - Hongfei Zhu
- Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
| | - François Meurens
- BIOEPAR, INRAE, Oniris, Nantes, France.,Department of Veterinary Microbiology and Immunology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Jianzhong Zhu
- College Veterinary Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, Yangzhou University, Yangzhou, China.,Comparative Medicine Research Institute, Yangzhou University, Yangzhou, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
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7
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Walther T, Bruhn B, Isken O, Tautz N. A novel NS3/4A protease dependent cleavage site within pestiviral NS2. J Gen Virol 2021; 102. [PMID: 34676824 DOI: 10.1099/jgv.0.001666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pestiviruses like bovine viral diarrhoea virus (BVDV) and classical swine fever virus (CSFV) belong to the family Flaviviridae. A special feature of the Flaviviridae is the importance of nonstructural (NS) proteins for both genome replication and virion morphogenesis. The NS2-3-4A region and its regulated processing by the NS2 autoprotease and the NS3/4A protease plays a central role in the pestiviral life cycle. We report the identification and characterization of a novel internal cleavage in BVDV NS2, which is mediated by the NS3/4A protease. Further mapping using the NS2 of BVDV-1 strain NCP7 showed that cleavage occurs between L188 and G189. This cleavage site represents a novel sequence motif recognized by the NS3/4A protease and is conserved between the pestivirus species A, B and D. Inhibition of this internal NS2 cleavage by mutating the cleavage site did not cause obvious effects on RNA replication or virion morphogenesis in cultured cell lines. Accordingly, this novel internal NS2 cleavage adds an additional layer to the already complex polyprotein processing of Pestiviruses and might further extend the repertoires of the multifunctional NS2. However, unravelling of the functional relevance of this novel processing event in NS2, therefore, awaits future in vivo studies.
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Affiliation(s)
- Thomas Walther
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany.,Present address: EUROIMMUN AG, Luebeck, Germany
| | - Barbara Bruhn
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany
| | - Olaf Isken
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany
| | - Norbert Tautz
- University of Luebeck, Institute of Virology and Cell Biology, Luebeck, Germany
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8
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Viral Manipulation of the Host Epigenome as a Driver of Virus-Induced Oncogenesis. Microorganisms 2021; 9:microorganisms9061179. [PMID: 34070716 PMCID: PMC8227491 DOI: 10.3390/microorganisms9061179] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/24/2021] [Accepted: 05/26/2021] [Indexed: 12/13/2022] Open
Abstract
Tumorigenesis due to viral infection accounts for a high fraction of the total global cancer burden (15–20%) of all human cancers. A comprehensive understanding of the mechanisms by which viral infection leads to tumor development is extremely important. One of the main mechanisms by which viruses induce host cell proliferation programs is through controlling the host’s epigenetic machinery. In this review, we dissect the epigenetic pathways through which oncogenic viruses can integrate their genome into host cell chromosomes and lead to tumor progression. In addition, we highlight the potential use of drugs based on histone modifiers in reducing the global impact of cancer development due to viral infection.
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9
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Nishi T, Fukai K, Kato T, Sawai K, Yamamoto T. Genome variability of classical swine fever virus during the 2018-2020 epidemic in Japan. Vet Microbiol 2021; 258:109128. [PMID: 34058522 DOI: 10.1016/j.vetmic.2021.109128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 05/20/2021] [Indexed: 11/18/2022]
Abstract
Although RNA viruses exhibit extensive sequence diversity, the mutation rate must be limited to ensure protein functions that maintain the viral life cycle. Here, we compared the whole genome sequences of 150 isolates of classical swine fever virus (CSFV), obtained from a single epidemic that occurred in Japan during 2018-2020. After the detection of the first case, the disease spread among both farm pigs and wild boars and caused severe impact on the pig industry. To evaluate the diversification of the CSFV genome that eliminated mutations negatively affecting viral transmission, the substitution sets inherited by at least two isolates were separately evaluated as shared single nucleotide variants (SNVs) or shared single amino acid variants (SAVs). Comparisons of 12 protein-coding regions indicated that the percentages of SNVs and SAVs in the multifunctional nonstructural protein NS3 were the lowest, and shared SAVs were not detected in another nonstructural protein, NS4A. This demonstrated purifying negative selection suppressing changes in the protein sequences of NS3 and NS4A during virus transmission in the field. In contrast, a high possibility of nonsynonymous substitution among shared SNVs was detected only in genes encoding the secreted protein Erns and the nonstructural protein NS2, suggesting positive selection during the epidemic. Mapping of shared SAVs to the three-dimensional structure of Erns revealed that shared SAVs were not present in the substrate-binding sites but were instead localized to the peripheral region of the protein. These data will support efforts toward the development of diagnostic methods, recombinant vaccines, and antiviral agents targeting conserved and indispensable viral genes.
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Affiliation(s)
- Tatsuya Nishi
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Tokyo, Japan
| | - Katsuhiko Fukai
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Tokyo, Japan
| | - Tomoko Kato
- Exotic Disease Research Unit, Division of Transboundary Animal Diseases, National Institute of Animal Health, National Agriculture and Food Research Organization, Kodaira, Tokyo, Japan
| | - Kotaro Sawai
- Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan
| | - Takehisa Yamamoto
- Epidemiology Research Unit, Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture Research Organization, Tsukuba, Ibaraki, Japan.
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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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11
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Zheng F, Yi W, Liu W, Zhu H, Gong P, Pan Z. A positively charged surface patch on the pestivirus NS3 protease module plays an important role in modulating NS3 helicase activity and virus production. Arch Virol 2021; 166:1633-1642. [PMID: 33787991 DOI: 10.1007/s00705-021-05055-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 02/08/2021] [Indexed: 10/21/2022]
Abstract
Pestivirus nonstructural protein 3 (NS3) is a multifunctional protein with protease and helicase activities that are essential for virus replication. In this study, we used a combination of biochemical and genetic approaches to investigate the relationship between a positively charged patch on the protease module and NS3 function. The surface patch is composed of four basic residues, R50, K74 and K94 in the NS3 protease domain and H24 in the structurally integrated cofactor NS4APCS. Single-residue or simultaneous four-residue substitutions in the patch to alanine or aspartic acid had little effect on ATPase activity. However, single substitutions of R50, K94 or H24 or a simultaneous four-residue substitution resulted in apparent changes in the helicase activity and RNA-binding ability of NS3. When these mutations were introduced into a classical swine fever virus (CSFV) cDNA clone, a single substitution at K94 or a simultaneous four-residue substitution (Qua_A or Qua_D) impaired the production of infectious virus. Furthermore, the replication efficiency of the CSFV variants was partially correlated with the helicase activity of NS3 in vitro. Our results suggest that the conserved positively charged patch on NS3 plays an important role in modulating the NS3 helicase activity in vitro and CSFV production.
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Affiliation(s)
- Fengwei Zheng
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Weicheng Yi
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Weichi Liu
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Hongchang Zhu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Peng Gong
- Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
| | - Zishu Pan
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
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12
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Downstream Sequences Control the Processing of the Pestivirus E rns-E1 Precursor. J Virol 2020; 95:JVI.01905-20. [PMID: 33028718 DOI: 10.1128/jvi.01905-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 09/30/2020] [Indexed: 02/06/2023] Open
Abstract
Like other enveloped viruses, pestiviruses employ cellular proteases for processing of their structural proteins. While typical signal peptidase cleavage motifs are present at the carboxy terminus of the signal sequence preceding Erns and the E1/E2 and E2/P7 sites, the Erns-E1 precursor is cleaved by signal peptidase at a highly unusual structure, in which the transmembrane sequence upstream of the cleavage site is replaced by an amphipathic helix. As shown before, the integrity of the amphipathic helix is crucial for efficient processing. The data presented here demonstrate that the E1 sequence downstream of this cleavage site is also important for the cleavage. Carboxy-terminal truncation of the E1 moiety as well as internal deletions in E1 reduced the cleavage efficiency to less than 30% of the wild-type (wt) level. Moreover, the C-terminal truncation by more than 30 amino acids resulted in strong secretion of the uncleaved fusion proteins. The reduced processing and increased secretion were even observed when 10 to 5 amino-terminal residues of E1 were left, whereas extensions by 1 or 3 E1 residues resulted in reduced processing but no significantly increased secretion. In contrast to the E1 sequences, a 10-amino-acid c-myc tag fused to the Erns C terminus had only marginal effect on secretion but was also not processed efficiently. Mutation of the von Heijne sequence upstream of E2 not only blocked the cleavage between E1 and E2 but also prevented the processing between Erns and E2. Thus, processing at the Erns-E1 site is a highly regulated process.IMPORTANCE Cellular signal peptidase (SPase) cleavage represents an important step in maturation of viral envelope proteins. Fine tuning of this system allows for establishment of concerted folding and processing processes in different enveloped viruses. We report here on SPase processing of the Erns-E1-E2 glycoprotein precursor of pestiviruses. Erns-E1 cleavage is delayed and only executed efficiently when the complete E1 sequence is present. C-terminal truncation of the Erns-E1 precursor impairs processing and leads to significant secretion of the protein. The latter is not detected when internal deletions preserving the E1 carboxy terminus are introduced, but also these constructs show impaired processing. Moreover, Erns-E1 is only processed after cleavage at the E1/E2 site. Thus, processing of the pestiviral glycoprotein precursor by SPase is done in an ordered way and depends on the integrity of the proteins for efficient cleavage. The functional importance of this processing scheme is discussed in the paper.
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West Nile Virus: An Update on Pathobiology, Epidemiology, Diagnostics, Control and "One Health" Implications. Pathogens 2020; 9:pathogens9070589. [PMID: 32707644 PMCID: PMC7400489 DOI: 10.3390/pathogens9070589] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 07/16/2020] [Accepted: 07/16/2020] [Indexed: 02/06/2023] Open
Abstract
West Nile virus (WNV) is an important zoonotic flavivirus responsible for mild fever to severe, lethal neuroinvasive disease in humans, horses, birds, and other wildlife species. Since its discovery, WNV has caused multiple human and animal disease outbreaks in all continents, except Antarctica. Infections are associated with economic losses, mainly due to the cost of treatment of infected patients, control programmes, and loss of animals and animal products. The pathogenesis of WNV has been extensively investigated in natural hosts as well as in several animal models, including rodents, lagomorphs, birds, and reptiles. However, most of the proposed pathogenesis hypotheses remain contentious, and much remains to be elucidated. At the same time, the unavailability of specific antiviral treatment or effective and safe vaccines contribute to the perpetuation of the disease and regular occurrence of outbreaks in both endemic and non-endemic areas. Moreover, globalisation and climate change are also important drivers of the emergence and re-emergence of the virus and disease. Here, we give an update of the pathobiology, epidemiology, diagnostics, control, and “One Health” implications of WNV infection and disease.
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Li G, Liu X, Yang M, Zhang G, Wang Z, Guo K, Gao Y, Jiao P, Sun J, Chen C, Wang H, Deng W, Xiao H, Li S, Wu H, Wang Y, Cao L, Jia Z, Shang L, Yang C, Guo Y, Rao Z. Crystal Structure of African Swine Fever Virus pS273R Protease and Implications for Inhibitor Design. J Virol 2020; 94:e02125-19. [PMID: 32075933 PMCID: PMC7199414 DOI: 10.1128/jvi.02125-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 02/11/2020] [Indexed: 01/21/2023] Open
Abstract
African swine fever (ASF) is a highly contagious hemorrhagic viral disease of domestic and wild pigs that is responsible for serious economic and production losses. It is caused by the African swine fever virus (ASFV), a large and complex icosahedral DNA virus of the Asfarviridae family. Currently, there is no effective treatment or approved vaccine against the ASFV. pS273R, a specific SUMO-1 cysteine protease, catalyzes the maturation of the pp220 and pp62 polyprotein precursors into core-shell proteins. Here, we present the crystal structure of the ASFV pS273R protease at a resolution of 2.3 Å. The overall structure of the pS273R protease is represented by two domains named the "core domain" and the N-terminal "arm domain." The "arm domain" contains the residues from M1 to N83, and the "core domain" contains the residues from N84 to A273. A structure analysis reveals that the "core domain" shares a high degree of structural similarity with chlamydial deubiquitinating enzyme, sentrin-specific protease, and adenovirus protease, while the "arm domain" is unique to ASFV. Further, experiments indicated that the "arm domain" plays an important role in maintaining the enzyme activity of ASFV pS273R. Moreover, based on the structural information of pS273R, we designed and synthesized several peptidomimetic aldehyde compounds at a submolar 50% inhibitory concentration, which paves the way for the design of inhibitors to target this severe pathogen.IMPORTANCE African swine fever virus, a large and complex icosahedral DNA virus, causes a deadly infection in domestic pigs. In addition to Africa and Europe, countries in Asia, including China, Vietnam, and Mongolia, were negatively affected by the hazards posed by ASFV outbreaks in 2018 and 2019, at which time more than 30 million pigs were culled. Until now, there has been no vaccine for protection against ASFV infection or effective treatments to cure ASF. Here, we solved the high-resolution crystal structure of the ASFV pS273R protease. The pS273R protease has a two-domain structure that distinguishes it from other members of the SUMO protease family, while the unique "arm domain" has been proven to be essential for its hydrolytic activity. Moreover, the peptidomimetic aldehyde compounds designed to target the substrate binding pocket exert prominent inhibitory effects and can thus be used in a potential lead for anti-ASFV drug development.
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Affiliation(s)
- Guobang Li
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Xiaoxia Liu
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
| | - Mengyuan Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Guangshun Zhang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Zhengyang Wang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
| | - Kun Guo
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
| | - Yuxue Gao
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Peng Jiao
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
| | - Jixue Sun
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
| | - Cheng Chen
- School of Life Sciences, Tianjin University, Tianjin, People's Republic of China
| | - Hao Wang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Weilong Deng
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Huihe Xiao
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
| | - Sizheng Li
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
| | - Haoru Wu
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Ying Wang
- Tianjin Crops Research Institute, Tianjin Academy of Agricultural Sciences, Tianjin, People's Republic of China
| | - Lin Cao
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- College of Life Science, Nankai University, Tianjin, People's Republic of China
| | - Zihan Jia
- College of Life Science, Nankai University, Tianjin, People's Republic of China
- School of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin, People's Republic of China
| | - Luqing Shang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
| | - Cheng Yang
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
| | - Yu Guo
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
- Frontiers Science Center for Cell Responses, Nankai University, Tianjin, People's Republic of China
| | - Zihe Rao
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin, People's Republic of China
- Drug Discovery Center for Infectious Diseases, Nankai University, Tianjin, People's Republic of China
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin, People's Republic of China
- College of Life Science, Nankai University, Tianjin, People's Republic of China
- Frontiers Science Center for Cell Responses, Nankai University, Tianjin, People's Republic of China
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Determination of Critical Requirements for Classical Swine Fever Virus NS2-3-Independent Virion Formation. J Virol 2019; 93:JVI.00679-19. [PMID: 31292243 DOI: 10.1128/jvi.00679-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 06/27/2019] [Indexed: 01/07/2023] Open
Abstract
For members of the Flaviviridae, it is known that, besides the structural proteins, nonstructural (NS) proteins also play a critical role in virion formation. Pestiviruses, such as bovine viral diarrhea virus (BVDV), rely on uncleaved NS2-3 for virion formation, while its cleavage product, NS3, is selectively active in RNA replication. This dogma was recently challenged by the selection of gain-of-function mutations in NS2 and NS3 which allowed virion formation in the absence of uncleaved NS2-3 in BVDV type 1 (BVDV-1) variants encoding either a ubiquitin (Ubi) (NS2-Ubi-NS3) or an internal ribosome entry site (IRES) (NS2-IRES-NS3) between NS2 and NS3. To determine whether the ability to adapt to NS2-3-independent virion morphogenesis is conserved among pestiviruses, we studied the corresponding NS2 and NS3 mutations (2/T444-V and 3/M132-A) in classical swine fever virus (CSFV). We observed that these mutations were capable of restoring low-level NS2-3-independent virion formation only for CSFV NS2-Ubi-NS3. Interestingly, a second NS2 mutation (V439-D), identified by selection, was essential for high-titer virion production. Similar to previous findings for BVDV-1, these mutations in NS2 and NS3 allowed for low-titer virion production only in CSFV NS2-IRES-NS3. For efficient virion morphogenesis, additional exchanges in NS4A (A48-T) and NS5B (D280-G) were required, indicating that these proteins cooperate in NS2-3-independent virion formation. Interestingly, both NS5B mutations, selected independently for NS2-IRES-NS3 variants of BVDV-1 and CSFV, are located in the fingertip region of the viral RNA-dependent RNA polymerase, classifying this structural element as a novel determinant for pestiviral NS2-3-independent virion formation. Together, these findings will stimulate further mechanistic studies on the genome packaging of pestiviruses.IMPORTANCE For Flaviviridae members, the nonstructural proteins are essential for virion formation and thus exert a dual role in RNA replication and virion morphogenesis. However, it remains unclear how these proteins are functionalized for either process. In wild-type pestiviruses, the NS3/4A complex is selectively active in RNA replication, while NS2-3/4A is essential for virion formation. Mutations recently identified in BVDV-1 rendered NS3/4A capable of supporting NS2-3-independent virion morphogenesis. A comparison of NS3/4A complexes incapable/capable of supporting virion morphogenesis revealed that changes in NS3/NS4A surface interactions are decisive for the gain of function. However, so far, the role of the NS2 mutations as well as the accessory mutations additionally required in the NS2-IRES-NS3 virus variant has not been clarified. To unravel the course of genome packaging, the additional sets of mutations obtained for a second pestivirus species (CSFV) are of significant importance to develop mechanistic models for this complex process.
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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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Uncoupling of Protease trans-Cleavage and Helicase Activities in Pestivirus NS3. J Virol 2017; 91:JVI.01094-17. [PMID: 28835495 DOI: 10.1128/jvi.01094-17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 08/07/2017] [Indexed: 01/25/2023] Open
Abstract
The nonstructural protein NS3 from the Flaviviridae family is a multifunctional protein that contains an N-terminal protease and a C-terminal helicase, playing essential roles in viral polyprotein processing and genome replication. Here we report a full-length crystal structure of the classical swine fever virus (CSFV) NS3 in complex with its NS4A protease cofactor segment (PCS) at a 2.35-Å resolution. The structure reveals a previously unidentified ∼2,200-Å2 intramolecular protease-helicase interface comprising three clusters of interactions, representing a "closed" global conformation related to the NS3-NS4A cis-cleavage event. Although this conformation is incompatible with protease trans-cleavage, it appears to be functionally important and beneficial to the helicase activity, as the mutations designed to perturb this conformation impaired both the helicase activities in vitro and virus production in vivo Our work reveals important features of protease-helicase coordination in pestivirus NS3 and provides a key basis for how different conformational states may explicitly contribute to certain functions of this natural protease-helicase fusion protein.IMPORTANCE Many RNA viruses encode helicases to aid their RNA genome replication and transcription by unwinding structured RNA. Being naturally fused to a protease participating in viral polyprotein processing, the NS3 helicases encoded by the Flaviviridae family viruses are unique. Therefore, how these two enzyme modules coordinate in a single polypeptide is of particular interest. Here we report a previously unidentified conformation of pestivirus NS3 in complex with its NS4A protease cofactor segment (PCS). This conformational state is related to the protease cis-cleavage event and is optimal for the function of helicase. This work provides an important basis to understand how different enzymatic activities of NS3 may be achieved by the coordination between the protease and helicase through different conformational states.
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18
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Zhao C, Shen X, Wu R, Li L, Pan Z. Classical swine fever virus nonstructural protein p7 modulates infectious virus production. Sci Rep 2017; 7:12995. [PMID: 29021567 PMCID: PMC5636883 DOI: 10.1038/s41598-017-13352-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Accepted: 09/21/2017] [Indexed: 02/07/2023] Open
Abstract
The classical swine fever virus (CSFV) nonstructural protein p7 is crucial for virus production, yet precisely how the p7 modulates this process is unclear. In this study, we first identified the interactions of p7 with E2 and NS2. The key binding regions of both p7 and NS2 mapped to the first transmembrane (TM1) domain of two proteins. Three amino acid substitutions in the TM1 region of p7 (p7TDI18/19/20AAA, p7EVV21/22/23AAA and p7YFY25/26/30AAA) impaired infectious virus production and reduced the interaction of p7 with the NS2 protein. The E2p7 processing and mature p7, but not the E2p7 precursor, are essential for infectious virus production. Bicistronic mutants (pSM/E2/IRES) with single substitutions at residues 1 to 9 of p7 exhibited a significantly increased infectious CSFV titer compared to their counterparts in the context of pSM. Viral genomic RNA copies of the mutants exhibited similar levels compared with the wt CSFV. Our results demonstrated that CSFV p7 and its precursor E2p7 modulate viral protein interactions and infectious virus production without influencing viral RNA replication.
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Affiliation(s)
- Cheng Zhao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Xiaofang Shen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Rui Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Ling Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Zishu Pan
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
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Lei J, Hilgenfeld R. RNA-virus proteases counteracting host innate immunity. FEBS Lett 2017; 591:3190-3210. [PMID: 28850669 PMCID: PMC7163997 DOI: 10.1002/1873-3468.12827] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 08/21/2017] [Accepted: 08/22/2017] [Indexed: 01/20/2023]
Abstract
Virus invasion triggers host immune responses, in particular, innate immune responses. Pathogen‐associated molecular patterns of viruses (such as dsRNA, ssRNA, or viral proteins) released during virus replication are detected by the corresponding pattern‐recognition receptors of the host, and innate immune responses are induced. Through production of type‐I and type‐III interferons as well as various other cytokines, the host innate immune system forms the frontline to protect host cells and inhibit virus infection. Not surprisingly, viruses have evolved diverse strategies to counter this antiviral system. In this review, we discuss the multiple strategies used by proteases of positive‐sense single‐stranded RNA viruses of the families Picornaviridae, Coronaviridae, and Flaviviridae, when counteracting host innate immune responses.
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Affiliation(s)
- Jian Lei
- Institute of Biochemistry, Center for Structural and Cell Biology in Medicine, University of Lübeck, Germany
| | - Rolf Hilgenfeld
- Institute of Biochemistry, Center for Structural and Cell Biology in Medicine, University of Lübeck, Germany.,German Center for Infection Research (DZIF), Hamburg - Lübeck - Borstel - Riems Site, University of Lübeck, Germany
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Complex Virus-Host Interactions Involved in the Regulation of Classical Swine Fever Virus Replication: A Minireview. Viruses 2017; 9:v9070171. [PMID: 28678154 PMCID: PMC5537663 DOI: 10.3390/v9070171] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/15/2017] [Accepted: 06/27/2017] [Indexed: 02/06/2023] Open
Abstract
Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is one of the most devastating epizootic diseases of pigs in many countries. Viruses are small intracellular parasites and thus rely on the cellular factors for replication. Fundamental aspects of CSFV-host interactions have been well described, such as factors contributing to viral attachment, modulation of genomic replication and translation, antagonism of innate immunity, and inhibition of cell apoptosis. However, those host factors that participate in the viral entry, assembly, and release largely remain to be elucidated. In this review, we summarize recent progress in the virus-host interactions involved in the life cycle of CSFV and analyze the potential mechanisms of viral entry, assembly, and release. We conclude with future perspectives and highlight areas that require further understanding.
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