title: Size selective recognition of siRNA by an RNA silencing suppressor.
abstract: RNA silencing in plants likely exists as a defense mechanism against molecular parasites such as RNA viruses, retrotransposons, and transgenes. As a result, many plant viruses have adapted mechanisms to evade and suppress gene silencing. Tombusviruses express a 19 kDa protein (p19), which has been shown to suppress RNA silencing in vivo and bind silencing-generated and synthetic small interfering RNAs (siRNAs) in vitro. Here we report the 2.5 A crystal structure of p19 from the Carnation Italian ringspot virus (CIRV) bound to a 21 nt siRNA and demonstrate in biochemical and in vivo assays that CIRV p19 protein acts as a molecular caliper to specifically select siRNAs based on the length of the duplex region of the RNA.
authors.affiliation: Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Vargason
authors.forename: György
authors.initials: G
authors.lastname: Szittya
authors.forename: József
authors.initials: J
authors.lastname: Burgyán
authors.forename: Traci M Tanka
authors.initials: TM
authors.lastname: Hall
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D018360:Crystallography, X-Ray; D029749:Dianthus / Q000821:virology; D019281:Dimerization; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D034622:RNA Interference / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics*; D019183:Tombusviridae / Q000235:genetics*; D014364:Tryptophan / Q000235:genetics; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics*
chemical_list: D034741:RNA, Small Interfering; D014764:Viral Proteins; D014364:Tryptophan