Contents 1 Structure 2 Function 3 Evolution 4 History 5 References


Structure[edit] The structure of the tomato bushy stunt virus p19 protein bound to double-stranded RNA. The two p19 monomers are shown in blue and green; the RNA backbone is shown in orange. The alpha helices at the top and bottom interact with the ends of the RNA, ensuring that only RNA of the correct length is bound. This has been described as a "molecular caliper".[6] From PDB: 1R9F​.[1] The p19 protein received its name from its size, being approximately 19 kilodaltons. It forms a functional homodimer. The crystal structures are available of p19 proteins from the tomato bushy stunt virus[1] and Carnation Italian ringspot virus;[2] the protein consists of a novel protein fold and exemplifies a previously unknown mechanism for binding RNA, using a binding surface formed by a beta sheet and flanked by alpha helices to interact with double-stranded RNAs of around 21 nucleotides in length in a non-sequence-specific manner.[1][2][7]


Function[edit] The p19 protein binds to double-stranded RNAs that function as short interfering RNA (siRNA) and is specialized for the 21-nucleotide product of the enzyme DCL4 (a member of a family of plant enzymes with homology to Dicer).[7] By binding to siRNA, p19 sequesters these species and prevents them from interacting with the RNA-induced silencing complex (RISC), a protein complex that mediates the antiviral RNA silencing mechanism in the cell. The p19 protein is also capable of binding to microRNA molecules that are endogenous to the host cell, as well as the siRNAs that are ultimately derived from the virus's own genome. Notably, an exception to this pattern is p19's inefficiency in interacting with the microRNA miR-168, a regulatory non-coding RNA that represses expression of argonaute-1 (AGO1). The AGO1 protein is required for RNA silencing, thus selectively sparing its repressor from p19's general sequestration of miRNA has the effect of reducing cellular AGO1 levels and is an additional mechanism by which p19 inhibits silencing.[5][8] The two mechanisms are independent of one another and can be selectively abrogated by mutations.[9]


Evolution[edit] The gene encoding the p19 protein is an example of an overprinted gene, a genomic arrangement common in viruses in which multiple genes are encoded by the same portion of the genome read in alternate reading frames.[10][11] The open reading frame ORF4, which encodes p19, is completely contained within the open reading frame of another gene, which is designated ORF3 and encodes the movement protein p22. Both genes, and their relative positions, are conserved within the tombusvirus family.[4][11] P19 is thought to have originated de novo in this lineage.[11][12] Sequestration of dsRNA is a common viral counter-defense strategy against RNA silencing, evolved in a form of evolutionary arms race between virus and host.[5] The p19 protein is not unique in this role; in an example of convergent evolution, this strategy appears to have evolved at least three times in distinct viral lineages using proteins with distinct structures and physical means of binding RNA.[3][13][14]


History[edit] The tomato bushy stunt virus, which is the type species of the tombusvirus family, is a long-standing model system for the study of plant viruses. The open reading frame encoding p19 was originally discovered in the late 1980s when the virus's genome was sequenced; it was subsequently demonstrated that the predicted protein was indeed expressed from the gene, although its role in promoting virulence and infectivity was initially underappreciated. Following the elucidation of its role as a suppressor of RNA silencing, p19 has also been used as a tool in molecular biology research on RNA silencing, RNA interference, and related processes.[4][6]


References[edit] ^ a b c d e Ye, Keqiong; Malinina, Lucy; Patel, Dinshaw J. (3 December 2003). "Recognition of small interfering RNA by a viral suppressor of RNA silencing". Nature. 426 (6968): 874–878. Bibcode:2003Natur.426..874Y. doi:10.1038/nature02213. PMC 4694583 . PMID 14661029.  ^ a b c Vargason, Jeffrey M; Szittya, György; Burgyán, József; Hall, Traci M.Tanaka (December 2003). "Size Selective Recognition of siRNA by an RNA Silencing Suppressor". Cell. 115 (7): 799–811. doi:10.1016/S0092-8674(03)00984-X. PMID 14697199.  ^ a b Lakatos, Lóránt; Szittya, György; Silhavy, Dániel; Burgyán, József (19 February 2004). "Molecular mechanism of RNA silencing suppression mediated by p19 protein of tombusviruses". The EMBO Journal. 23 (4): 876–884. doi:10.1038/sj.emboj.7600096. PMC 381004 . PMID 14976549.  ^ a b c Scholthof, Herman B. (6 March 2006). "The Tombusvirus-encoded P19: from irrelevance to elegance". Nature Reviews Microbiology. 4 (5): 405–411. doi:10.1038/nrmicro1395. PMID 16518419.  ^ a b c Pumplin, Nathan; Voinnet, Olivier (16 October 2013). "RNA silencing suppression by plant pathogens: defence, counter-defence and counter-counter-defence". Nature Reviews Microbiology. 11 (11): 745–760. doi:10.1038/nrmicro3120. PMID 24129510.  ^ a b Danielson, Dana C.; Pezacki, John Paul (17 April 2013). "Studying the RNA silencing pathway with the p19 protein". FEBS Letters. 587 (8): 1198–1205. doi:10.1016/j.febslet.2013.01.036. PMID 23376479.  ^ a b Ding, Shou-Wei; Voinnet, Olivier (August 2007). "Antiviral Immunity Directed by Small RNAs". Cell. 130 (3): 413–426. doi:10.1016/j.cell.2007.07.039. PMC 2703654 . PMID 17693253.  ^ Várallyay, Éva; Válóczi, Anna; Ágyi, Ákos; Burgyán, József; Havelda, Zoltán (7 September 2010). "Plant virus-mediated induction of miR168 is associated with repression of ARGONAUTE1 accumulation". The EMBO Journal. 29 (20): 3507–3519. doi:10.1038/emboj.2010.215. PMC 2964164 . PMID 20823831.  ^ Varallyay, E.; Olah, E.; Havelda, Z. (22 September 2013). "Independent parallel functions of p19 plant viral suppressor of RNA silencing required for effective suppressor activity". Nucleic Acids Research. 42 (1): 599–608. doi:10.1093/nar/gkt846. PMC 3874164 . PMID 24062160.  ^ Scholthof, Herman B.; Scholthof, Karen-Beth G.; Kikkert, Marjolein; Jackson, A.O. (November 1995). "Tomato Bushy Stunt Virus Spread Is Regulated by Two Nested Genes That Function in Cell-to-Cell Movement and Host-Dependent Systemic Invasion". Virology. 213 (2): 425–438. doi:10.1006/viro.1995.0015. PMID 7491767.  ^ a b c Rancurel, C.; Khosravi, M.; Dunker, A. K.; Romero, P. R.; Karlin, D. (29 July 2009). "Overlapping Genes Produce Proteins with Unusual Sequence Properties and Offer Insight into De Novo Protein Creation". Journal of Virology. 83 (20): 10719–10736. doi:10.1128/JVI.00595-09. PMC 2753099 .  ^ Sabath, N.; Wagner, A.; Karlin, D. (19 July 2012). "Evolution of Viral Proteins Originated De Novo by Overprinting". Molecular Biology and Evolution. 29 (12): 3767–3780. doi:10.1093/molbev/mss179. PMC 3494269 . PMID 22821011.  ^ Lakatos, Lóránt; Csorba, Tibor; Pantaleo, Vitantonio; Chapman, Elisabeth J; Carrington, James C; Liu, Yu-Ping; Dolja, Valerian V; Calvino, Lourdes Fernández; López-Moya, Juan José; Burgyán, József (25 May 2006). "Small RNA binding is a common strategy to suppress RNA silencing by several viral suppressors". The EMBO Journal. 25 (12): 2768–2780. doi:10.1038/sj.emboj.7601164. PMC 1500863 . PMID 16724105.  ^ Voinnet, Olivier (10 February 2005). "Induction and suppression of RNA silencing: insights from viral infections". Nature Reviews Genetics. 6 (3): 206–220. doi:10.1038/nrg1555. PMID 15703763.  Retrieved from "https://en.wikipedia.org/w/index.php?title=RNA_silencing_suppressor_p19&oldid=776674277" Categories: Viral proteinsHidden categories: Use dmy dates from April 2017


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Protein DimerN-terminusC-terminusProtein Data BankPfamInterProPfamProtein Data BankPDBsumProteinGeneGenomeTombusvirusVirusPositive-sense Single-stranded RNA VirusPlant CellRNA SilencingNucleotideDouble-stranded RNASmall Interfering RNAVirulence FactorEvolutionary Arms RacePathogenEnlargeTomato Bushy Stunt VirusCaliperProtein Data BankKilodaltonHomodimerProtein CrystallographyTomato Bushy Stunt VirusCarnation Italian Ringspot VirusProtein FoldRNABeta SheetAlpha HelicesNucleotideShort Interfering RNADicerRNA-induced Silencing ComplexProtein ComplexRNA SilencingMicroRNANon-coding RNARepressor (genetics)ArgonauteMutationOverprinted GeneReading FrameOpen Reading FrameEvolutionary Arms RaceConvergent EvolutionTomato Bushy Stunt VirusType SpeciesTombusvirusModel OrganismPlant VirusMolecular BiologyRNA InterferenceBibcodeDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed IdentifierDigital Object IdentifierPubMed CentralDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed CentralPubMed IdentifierDigital Object IdentifierPubMed IdentifierHelp:CategoryCategory:Viral ProteinsCategory:Use Dmy Dates From April 2017Discussion About Edits From This IP Address [n]A List Of Edits Made From This IP Address [y]View The Content Page [c]Discussion About The Content Page [t]Edit This Page [e]Visit The Main Page [z]Guides To Browsing WikipediaFeatured Content – The Best Of WikipediaFind Background Information On Current EventsLoad A Random Article [x]Guidance On How To Use And Edit WikipediaFind Out About WikipediaAbout The Project, What You Can Do, Where To Find ThingsA List Of Recent Changes In The Wiki [r]List Of All English Wikipedia Pages Containing Links To This Page [j]Recent Changes In Pages Linked From This Page [k]Upload Files [u]A List Of All Special Pages [q]Wikipedia:AboutWikipedia:General Disclaimer



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