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Vol. 305 no. 5689 pp. 1437-1441
DOI: 10.1126/science.1102513
  • Research Article

Argonaute2 Is the Catalytic Engine of Mammalian RNAi

  1. Gregory J. Hannon1,
  1. 1 Cold Spring Harbor Laboratory, Watson School of Biological Sciences, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
  2. 2 Program in Genetics, Stony Brook University, Stony Brook, NY 11794, USA.
  3. 3 Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
  1. To whom correspondence should be addressed. E-mail: hannon{at}
  • * These authors contributed equally to this work.


Gene silencing through RNA interference (RNAi) is carried out by RISC, the RNA-induced silencing complex. RISC contains two signature components, small interfering RNAs (siRNAs) and Argonaute family proteins. Here, we show that the multiple Argonaute proteins present in mammals are both biologically and biochemically distinct, with a single mammalian family member, Argonaute2, being responsible for messenger RNA cleavage activity. This protein is essential for mouse development, and cells lacking Argonaute2 are unable to mount an experimental response to siRNAs. Mutations within a cryptic ribonuclease H domain within Argonaute2, as identified by comparison with the structure of an archeal Argonaute protein, inactivate RISC. Thus, our evidence supports a model in which Argonaute contributes “Slicer” activity to RISC, providing the catalytic engine for RNAi.

    • Received for publication 8 July 2004.
    • Accepted for publication 19 July 2004.