RNA interference is mediated by 21- and 22-nucleotide RNAs

Genes Dev. 2001 Jan 15;15(2):188-200. doi: 10.1101/gad.862301.


Double-stranded RNA (dsRNA) induces sequence-specific posttranscriptional gene silencing in many organisms by a process known as RNA interference (RNAi). Using a Drosophila in vitro system, we demonstrate that 21- and 22-nt RNA fragments are the sequence-specific mediators of RNAi. The short interfering RNAs (siRNAs) are generated by an RNase III-like processing reaction from long dsRNA. Chemically synthesized siRNA duplexes with overhanging 3' ends mediate efficient target RNA cleavage in the lysate, and the cleavage site is located near the center of the region spanned by the guiding siRNA. Furthermore, we provide evidence that the direction of dsRNA processing determines whether sense or antisense target RNA can be cleaved by the siRNA-protein complex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Binding Sites / genetics
  • DNA Primers / genetics
  • Drosophila / genetics
  • Drosophila / metabolism
  • Endoribonucleases / metabolism
  • Gene Silencing
  • In Vitro Techniques
  • Models, Biological
  • Molecular Sequence Data
  • RNA / genetics*
  • RNA / metabolism*
  • RNA Processing, Post-Transcriptional
  • RNA, Antisense / genetics
  • RNA, Antisense / metabolism
  • RNA, Double-Stranded / genetics
  • RNA, Double-Stranded / metabolism
  • Ribonuclease III


  • DNA Primers
  • RNA, Antisense
  • RNA, Double-Stranded
  • RNA
  • Endoribonucleases
  • Ribonuclease III