Size selective recognition of siRNA by an RNA silencing suppressor

Cell. 2003 Dec 26;115(7):799-811. doi: 10.1016/s0092-8674(03)00984-x.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence / genetics
  • Binding Sites / genetics
  • Crystallography, X-Ray
  • Dianthus / virology
  • Dimerization
  • Gene Expression Regulation, Plant / genetics
  • Models, Molecular
  • Molecular Sequence Data
  • Molecular Structure
  • Molecular Weight
  • Mutation / genetics
  • RNA Interference / physiology*
  • RNA, Small Interfering / genetics*
  • Tombusviridae / genetics*
  • Tryptophan / genetics
  • Viral Proteins / chemistry
  • Viral Proteins / genetics*


  • RNA, Small Interfering
  • Viral Proteins
  • Tryptophan

Associated data

  • PDB/1RPU