Roles of R2D2, a cytoplasmic D2 body component, in the endogenous siRNA pathway in Drosophila

Mol Cell. 2013 Feb 21;49(4):680-91. doi: 10.1016/j.molcel.2012.12.024. Epub 2013 Jan 31.


Endogenous small interfering RNAs (endo-siRNAs) in Drosophila are processed by Dicer-2 (Dcr-2) and loaded onto Ago2 by the Dcr-2/R2D2 heterodimer. In r2d2 mutants, the level of endo-siRNAs is unchanged, but endo-siRNAs are misloaded onto Ago1. However, the mechanism underlying the control of endo-siRNA sorting by R2D2 remains unknown. Here, we show that R2D2 controls endo-siRNA sorting by localizing Dcr-2, and presumably endo-siRNA duplexes, to cytoplasmic foci, D2 bodies. Ago2, but not Ago1, localized to D2 bodies. dsRNA-binding-deficient mutant, but not wild-type, R2D2 failed to localize D2 bodies and caused endo-siRNA misdirection to Ago1 in R2D2-depleted cells. However, R2D2 was dispensable for sorting miRNAs and exogenous siRNAs onto Ago1 and Ago2, respectively, in vivo. Endo- and exo-siRNA guide selection also occurred R2D2 independently. The functions of R2D2 are required to avoid endo-siRNA misdirection to Ago1, because Ago1 is capable of loading incompletely complementary miRNA duplexes and endo-siRNA duplexes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Argonaute Proteins / metabolism
  • Cell Line
  • Cytoplasmic Granules / metabolism*
  • Drosophila Proteins / chemistry
  • Drosophila Proteins / metabolism
  • Drosophila Proteins / physiology*
  • Drosophila melanogaster / cytology
  • Drosophila melanogaster / genetics*
  • Female
  • Oocytes / metabolism
  • Protein Interaction Domains and Motifs
  • Protein Transport
  • RNA Helicases / chemistry
  • RNA Helicases / metabolism
  • RNA Interference*
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism*
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / metabolism
  • RNA-Binding Proteins / physiology*
  • Ribonuclease III / chemistry
  • Ribonuclease III / metabolism


  • AGO2 protein, Drosophila
  • Argonaute Proteins
  • Drosophila Proteins
  • R2D2 protein, Drosophila
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • DCR-2 protein, Drosophila
  • Ribonuclease III
  • RNA Helicases