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Sanfaçon H. Re-examination of nepovirus polyprotein cleavage sites highlights the diverse specificities and evolutionary relationships of nepovirus 3C-like proteases. Arch Virol 2022; 167:2529-2543. [PMID: 36042138 PMCID: PMC9741568 DOI: 10.1007/s00705-022-05564-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 06/30/2022] [Indexed: 12/14/2022]
Abstract
Plant-infecting viruses of the genus Nepovirus (subfamily Comovirinae, family Secoviridae, order Picornavirales) are bipartite positive-strand RNA viruses with each genomic RNA encoding a single large polyprotein. The RNA1-encoded 3C-like protease cleaves the RNA1 polyprotein at five sites and the RNA2 polyprotein at two or three sites, depending on the nepovirus. The specificity of nepovirus 3C-like proteases is notoriously diverse, making the prediction of cleavage sites difficult. In this study, the position of nepovirus cleavage sites was systematically re-evaluated using alignments of the RNA1 and RNA2 polyproteins, phylogenetic relationships of the proteases, and sequence logos to examine specific preferences for the P6 to P1' positions of the cleavage sites. Based on these analyses, the positions of previously elusive cleavage sites, notably the 2a-MP cleavage sites of subgroup B nepoviruses, are now proposed. Distinct nepovirus protease clades were identified, each with different cleavage site specificities, mostly determined by the nature of the amino acid at the P1 and P1' positions of the cleavage sites, as well as the P2 and P4 positions. The results will assist the prediction of cleavage sites for new nepoviruses and help refine the taxonomy of nepoviruses. An improved understanding of the specificity of nepovirus 3C-like proteases can also be used to investigate the cleavage of plant proteins by nepovirus proteases and to understand their adaptation to a broad range of hosts.
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Affiliation(s)
- Hélène Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, 4200 Highway 97, V0H1Z0, Summerland, BC, Canada.
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Sanfaçon H. Modulation of disease severity by plant positive-strand RNA viruses: The complex interplay of multifunctional viral proteins, subviral RNAs and virus-associated RNAs with plant signaling pathways and defense responses. Adv Virus Res 2020; 107:87-131. [PMID: 32711736 DOI: 10.1016/bs.aivir.2020.04.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Plant viruses induce a range of symptoms of varying intensity, ranging from severe systemic necrosis to mild or asymptomatic infection. Several evolutionary constraints drive virus virulence, including the dependence of viruses on host factors to complete their infection cycle, the requirement to counteract or evade plant antiviral defense responses and the mode of virus transmission. Viruses have developed an array of strategies to modulate disease severity. Accumulating evidence has highlighted not only the multifunctional role that viral proteins play in disrupting or highjacking plant factors, hormone signaling pathways and intracellular organelles, but also the interaction networks between viral proteins, subviral RNAs and/or other viral-associated RNAs that regulate disease severity. This review focusses on positive-strand RNA viruses, which constitute the majority of characterized plant viruses. Using well-characterized viruses with different genome types as examples, recent advances are discussed as well as knowledge gaps and opportunities for further research.
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Affiliation(s)
- Hélène Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada.
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Mann KS, Sanfaçon H. Expanding Repertoire of Plant Positive-Strand RNA Virus Proteases. Viruses 2019; 11:v11010066. [PMID: 30650571 PMCID: PMC6357015 DOI: 10.3390/v11010066] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 01/11/2019] [Accepted: 01/12/2019] [Indexed: 12/13/2022] Open
Abstract
Many plant viruses express their proteins through a polyprotein strategy, requiring the acquisition of protease domains to regulate the release of functional mature proteins and/or intermediate polyproteins. Positive-strand RNA viruses constitute the vast majority of plant viruses and they are diverse in their genomic organization and protein expression strategies. Until recently, proteases encoded by positive-strand RNA viruses were described as belonging to two categories: (1) chymotrypsin-like cysteine and serine proteases and (2) papain-like cysteine protease. However, the functional characterization of plant virus cysteine and serine proteases has highlighted their diversity in terms of biological activities, cleavage site specificities, regulatory mechanisms, and three-dimensional structures. The recent discovery of a plant picorna-like virus glutamic protease with possible structural similarities with fungal and bacterial glutamic proteases also revealed new unexpected sources of protease domains. We discuss the variety of plant positive-strand RNA virus protease domains. We also highlight possible evolution scenarios of these viral proteases, including evidence for the exchange of protease domains amongst unrelated viruses.
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Affiliation(s)
- Krin S Mann
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC V0H 1Z0, Canada.
| | - Hélène Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC V0H 1Z0, Canada.
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Fuchs M, Schmitt-Keichinger C, Sanfaçon H. A Renaissance in Nepovirus Research Provides New Insights Into Their Molecular Interface With Hosts and Vectors. Adv Virus Res 2016; 97:61-105. [PMID: 28057260 DOI: 10.1016/bs.aivir.2016.08.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Nepoviruses supplied seminal landmarks to the historical trail of plant virology. Among the first agriculturally relevant viruses recognized in the late 1920s and among the first plant viruses officially classified in the early 1970s, nepoviruses also comprise the first species for which a soil-borne ectoparasitic nematode vector was identified. Early research on nepoviruses shed light on the genome structure and expression, biological properties of the two genomic RNAs, and mode of transmission. In recent years, research on nepoviruses enjoyed an extraordinary renaissance. This resurgence provided new insights into the molecular interface between viruses and their plant hosts, and between viruses and dagger nematode vectors to advance our understanding of some of the major steps of the infectious cycle. Here we examine these recent findings, highlight ongoing work, and offer some perspectives for future research.
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Affiliation(s)
- M Fuchs
- Section of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Science, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, United States.
| | - C Schmitt-Keichinger
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
| | - H Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, Canada
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Symptom recovery in virus-infected plants: Revisiting the role of RNA silencing mechanisms. Virology 2015; 479-480:167-79. [DOI: 10.1016/j.virol.2015.01.008] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 01/02/2015] [Accepted: 01/08/2015] [Indexed: 01/11/2023]
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6
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In vitro and in vivo evidence for differences in the protease activity of two arabis mosaic nepovirus isolates and their impact on the infectivity of chimeric cDNA clones. Virology 2013; 446:102-11. [DOI: 10.1016/j.virol.2013.07.040] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 07/11/2013] [Accepted: 07/31/2013] [Indexed: 11/19/2022]
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von Bargen S, Langer J, Robel J, Rumbou A, Büttner C. Complete nucleotide sequence of Cherry leaf roll virus (CLRV), a subgroup C nepovirus. Virus Res 2011; 163:678-83. [PMID: 22230314 DOI: 10.1016/j.virusres.2011.12.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 12/22/2011] [Accepted: 12/26/2011] [Indexed: 11/26/2022]
Abstract
The complete nucleotide sequence of both genomic (+)ss RNAs of a rhubarb isolate of Cherry leaf roll virus (CLRV) was determined. The larger RNA1 is 7918 nucleotides and the shorter RNA2 6360 nucleotides in size, each genome component comprising a single open reading frame (ORF). The RNA1-encoded polyprotein (P1) is 2112 amino acids long (235.6 kDa) containing domains characteristic for a proteinase-cofactor (PCo), nucleotide-binding helicase (Hel), genome-linked protein (VPg), proteinase (Pro), and an RNA-dependent RNA polymerase (Pol). The RNA2-encoded polyprotein (P2) has a molecular mass of 174.9 kDa (1589 aa) encoding the putative movement protein (MP) and the coat protein (CP) of CLRV. The genome region upstream of the MP has a coding capacity of 77 kDa, however processing of P2 by the putative virus-encoded proteinase and protein-function encoded by this region is unknown. Furthermore, it could be demonstrated that the 5'-termini including the N-terminal region (208 aa) of P1 and P2 of the rhubarb isolate of CLRV are nearly identical among the two genome segments. The taxonomic position of CLRV as member of the genus Nepovirus was confirmed by phylogenetic analyses employing the amino acid sequences of the conserved Pro-Pol region of RNA1, the complete P2, and the CP. However, clustering of Nepovirus-species according to allocated subgroups was inconsistent and depended on the compared genome fragment.
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Affiliation(s)
- Susanne von Bargen
- Humboldt-Universität zu Berlin, Department of Crop and Animal Sciences, Division Phytomedicine, Lentzeallee 55/57, D-14195 Berlin, Germany.
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Wetzel T, Chisholm J, Bassler A, Sanfaçon H. Characterization of proteinase cleavage sites in the N-terminal region of the RNA1-encoded polyprotein from Arabis mosaic virus (subgroup A nepovirus). Virology 2008; 375:159-69. [DOI: 10.1016/j.virol.2008.01.046] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 12/20/2007] [Accepted: 01/30/2008] [Indexed: 11/25/2022]
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Chisholm J, Zhang G, Wang A, Sanfaçon H. Peripheral association of a polyprotein precursor form of the RNA-dependent RNA polymerase of Tomato ringspot virus with the membrane-bound viral replication complex. Virology 2007; 368:133-44. [PMID: 17658576 DOI: 10.1016/j.virol.2007.06.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Revised: 06/13/2007] [Accepted: 06/29/2007] [Indexed: 11/23/2022]
Abstract
Replication of Tomato ringspot virus (ToRSV) occurs in association with endoplasmic reticulum (ER)-derived membranes. We have previously shown that the putative nucleotide triphosphate-binding protein (NTB) of ToRSV is an ER-targeted protein and that an intermediate polyprotein containing the domains for NTB and for the genome-linked viral protein (VPg) is associated with the replication complex. We now report the detection of a 95-kDa polyprotein that contains the domains for the RNA-dependent RNA polymerase (Pol), the proteinase (Pro) and the VPg. This polyprotein appears to be a truncated version of the full-length 111-kDa VPg-Pro-Pol polyprotein and was termed VPg-Pro-Pol'. A subpopulation of VPg-Pro-Pol' was peripherally associated with ER-derived membranes active in viral replication. However, the VPg, Pro and Pol domains did not target to membranes in the absence of viral infection. We propose a model in which VPg-Pro-Pol' is brought to the site of replication through interaction with a viral membrane protein.
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Affiliation(s)
- Joan Chisholm
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, P.O. Box 5000, 4200 Highway 97, Summerland, B.C., Canada V0H 1Z0
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Zhang G, Sanfaçon H. Characterization of membrane association domains within the Tomato ringspot nepovirus X2 protein, an endoplasmic reticulum-targeted polytopic membrane protein. J Virol 2006; 80:10847-57. [PMID: 16928745 PMCID: PMC1641798 DOI: 10.1128/jvi.00789-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 08/09/2006] [Indexed: 12/19/2022] Open
Abstract
Replication of nepoviruses (family Comoviridae) occurs in association with endoplasmic reticulum (ER)-derived membranes. We have previously shown that the putative nucleoside triphosphate-binding protein (NTB) of Tomato ringspot nepovirus is an integral membrane protein with two ER-targeting sequences and have suggested that it anchors the viral replication complex (VRC) to the membranes. A second highly hydrophobic protein domain (X2) is located immediately upstream of the NTB domain in the RNA1-encoded polyprotein. X2 shares conserved sequence motifs with the comovirus 32-kDa protein, an ER-targeted protein implicated in VRC assembly. In this study, we examined the ability of X2 to associate with intracellular membranes. The X2 protein was fused to the green fluorescent protein and expressed in Nicotiana benthamiana by agroinfiltration. Confocal microscopy and membrane flotation experiments suggested that X2 is targeted to ER membranes. Mutagenesis studies revealed that X2 contains multiple ER-targeting domains, including two C-terminal transmembrane helices and a less-well-defined domain further upstream. To investigate the topology of the protein in the membrane, in vitro glycosylation assays were conducted using X2 derivatives that contained N-glycosylation sites introduced at the N or C termini of the protein. The results led us to propose a topological model for X2 in which the protein traverses the membrane three times, with the N terminus oriented in the lumen and the C terminus exposed to the cytoplasmic face. Taken together, our results indicate that X2 is an ER-targeted polytopic membrane protein and raises the possibility that it acts as a second membrane anchor for the VRC.
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Affiliation(s)
- Guangzhi Zhang
- Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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van Aken D, Benckhuijsen WE, Drijfhout JW, Wassenaar AL, Gorbalenya AE, Snijder EJ. Expression, purification, and in vitro activity of an arterivirus main proteinase. Virus Res 2006; 120:97-106. [PMID: 16527369 PMCID: PMC7114227 DOI: 10.1016/j.virusres.2006.01.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2005] [Revised: 01/26/2006] [Accepted: 01/30/2006] [Indexed: 11/20/2022]
Abstract
To allow the biochemical and structural characterization of the chymotrypsin-like "main proteinase" (non-structural protein 4; nsp4) of the arterivirus prototype Equine Arteritis Virus (EAV), we developed protocols for the large-scale production of recombinant nsp4 in Escherichia coli. The nsp4 proteinase was expressed either fused to maltose binding protein or carrying a C-terminal hexahistidine tag. Following purification, the nsp4 moiety of MBP-nsp4 was successfully used for structural studies [Barrette-Ng, I.H., Ng, K.K.S., Mark, B.L., van Aken, D., Cherney, M.M., Garen, C, Kolodenko, Y., Gorbalenya, A.E., Snijder, E.J., James, M.N.G, 2002. Structure of arterivirus nsp4-the smallest chymotrypsin-like proteinase with an alpha/beta C-terminal extension and alternate conformations of the oxyanion hole. J. Biol. Chem. 277, 39960-39966]. Furthermore, both forms of the EAV proteinase were shown to be proteolytically active in two different trans-cleavage assays. Recombinant nsp4 cleaved the cognate nsp6/7- and nsp7/8 site in in vitro synthesized substrates. In a synthetic peptide-based activity assay, the potential of the recombinant proteinase to cleave peptides mimicking the P9-P7' residues of six nsp4 cleavage sites was investigated. The peptide representing the EAV nsp7/8 junction was used to optimize the reaction conditions (pH 7.5, 25mM NaCl, 30% glycerol at 30 degrees C), which resulted in a maximum turnover of 15% of this substrate in 4h, using a substrate to enzyme molar ratio of 24:1. The assays described in this study can be used for a more extensive biochemical characterization of the EAV main proteinase, including studies aiming to identify inhibitors of proteolytic activity.
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Affiliation(s)
- Danny van Aken
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - Willemien E. Benckhuijsen
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - Jan W. Drijfhout
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - Alfred L.M. Wassenaar
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - Alexander E. Gorbalenya
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, P.O. Box 9600, 2300 RC Leiden, The Netherlands
| | - Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, LUMC P4-26, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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Someya Y, Takeda N, Miyamura T. Characterization of the norovirus 3C-like protease. Virus Res 2005; 110:91-7. [PMID: 15845259 PMCID: PMC7114197 DOI: 10.1016/j.virusres.2005.02.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Revised: 02/08/2005] [Accepted: 02/08/2005] [Indexed: 11/17/2022]
Abstract
The recombinant 3C-like protease of Chiba virus, a Norovirus, expressed in Escherichia coli cells was purified and characterized as to effects of pH, temperature, salt contents, and SH reagents on its proteolytic activity. The optimal pH and temperature of the 3C-like protease for the proteolytic activity were 8.6 and 37 degrees C, respectively. Increased concentration (approximately 100 mM) of monovalent cations such as Na+ and K+ was inhibitory to the activity. Hg2+ and Zn2+ remarkably inhibited the protease activity, while Mg2+ and Ca2+ had no virtual effect. Several sulfhydryl reagents such as p-chloromercuribenzoic acid, methyl methanethiosulfonate, N-ethylmaleimide and N-phenylmaleimide also blocked the activity, confirming the previous result that cysteine residue(s) were responsible for the proteolysis.
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Affiliation(s)
| | | | - Tatsuo Miyamura
- Department of Virology II, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku, Tokyo 162-8640, Japan
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Wen R, Zhang SC, Michaud D, Sanfaçon H. Inhibitory effects of cystatins on proteolytic activities of the Plum pox potyvirus cysteine proteinases. Virus Res 2005; 105:175-82. [PMID: 15351491 DOI: 10.1016/j.virusres.2004.05.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2004] [Revised: 05/28/2004] [Accepted: 05/28/2004] [Indexed: 11/17/2022]
Abstract
In an effort to develop new antiviral strategies effective against potyviruses, several cystatins were evaluated for their ability to inhibit the cysteine proteinases of Plum pox potyvirus (PPV) using in vitro proteolytic assays. The following cystatins were purified as GST fusion proteins and shown to be active against papain:oryzacystatins I and II (OCI and OCII), corn cystatin II (CCII), human stefin A (HSA), the domain 8 of tomato multicystatin (TMC-8) and a large 24kDa tomato cystatin (LTCyst). These cystatins did not inhibit the activity of purified recombinant PPV NIa proteinase, a serine-like cysteine proteinases related to the 3C proteinases of picornaviruses and to chymotrypsin. The cystatins were shown to inhibit slightly the activity of the PPV HC-Pro proteinase with CCII being the best inhibitor. However a large excess of the cystatins was required to observe any inhibition. Based on these results and on the documented pleiotropic effects of cystatins on the metabolism of plants, we conclude that they are not the best candidates for antiviral strategies targeted to viral cysteine proteinases. The availability of soluble active recombinant PPV NIa proteinase will be instrumental for the selection of other proteinase inhibitors with increased affinity and specificity for this proteinase.
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Affiliation(s)
- Rui Wen
- Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, BC, Canada V0H 1Z0
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Léonard S, Chisholm J, Laliberté JF, Sanfaçon H. Interaction in vitro between the proteinase of Tomato ringspot virus (genus Nepovirus) and the eukaryotic translation initiation factor iso4E from Arabidopsis thaliana. J Gen Virol 2002; 83:2085-2089. [PMID: 12124472 DOI: 10.1099/0022-1317-83-8-2085] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Eukaryotic initiation factor eIF(iso)4E binds to the cap structure of mRNAs leading to assembly of the translation complex. This factor also interacts with the potyvirus VPg and this interaction has been correlated with virus infectivity. In this study, we show an interaction between eIF(iso)4E and the proteinase (Pro) of a nepovirus (Tomato ringspot virus; ToRSV) in vitro. The ToRSV VPg did not interact with eIF(iso)4E although its presence on the VPg-Pro precursor increased the binding affinity of Pro for the initiation factor. A major determinant of the interaction was mapped to the first 93 residues of Pro. Formation of the complex was inhibited by addition of m(7)GTP (a cap analogue), suggesting that Pro-containing molecules compete with cellular mRNAs for eIF(iso)4E binding. The possible implications of this interaction for translation and/or replication of the virus genome are discussed.
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Affiliation(s)
- Simon Léonard
- Centre de Microbiologie et Biotechnologie, INRS-Institut Armand-Frappier, 531 Boulevard des Prairies, Ville de Laval, Québec, CanadaH7V 1B71
| | - Joan Chisholm
- Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, BC, CanadaV0H 1Z02
| | - Jean-François Laliberté
- Centre de Microbiologie et Biotechnologie, INRS-Institut Armand-Frappier, 531 Boulevard des Prairies, Ville de Laval, Québec, CanadaH7V 1B71
| | - Hélène Sanfaçon
- Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, BC, CanadaV0H 1Z02
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