Piwi and piRNAs act upstream of an endogenous siRNA pathway to suppress Tc3 transposon mobility in the Caenorhabditis elegans germline

Mol Cell. 2008 Jul 11;31(1):79-90. doi: 10.1016/j.molcel.2008.06.003. Epub 2008 Jun 19.


The Piwi proteins of the Argonaute superfamily are required for normal germline development in Drosophila, zebrafish, and mice and associate with 24-30 nucleotide RNAs termed piRNAs. We identify a class of 21 nucleotide RNAs, previously named 21U-RNAs, as the piRNAs of C. elegans. Piwi and piRNA expression is restricted to the male and female germline and independent of many proteins in other small-RNA pathways, including DCR-1. We show that Piwi is specifically required to silence Tc3, but not other Tc/mariner DNA transposons. Tc3 excision rates in the germline are increased at least 100-fold in piwi mutants as compared to wild-type. We find no evidence for a Ping-Pong model for piRNA amplification in C. elegans. Instead, we demonstrate that Piwi acts upstream of an endogenous siRNA pathway in Tc3 silencing. These data might suggest a link between piRNA and siRNA function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Argonaute Proteins
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / metabolism*
  • DNA Transposable Elements / genetics*
  • Drosophila Proteins
  • Female
  • Gene Silencing
  • Genes, Helminth
  • Germ Cells / growth & development
  • Germ Cells / metabolism*
  • Male
  • Proteins / genetics
  • Proteins / metabolism*
  • RNA, Helminth / metabolism
  • RNA, Small Interfering / metabolism*
  • RNA-Induced Silencing Complex
  • Transposases / metabolism


  • Argonaute Proteins
  • Caenorhabditis elegans Proteins
  • DNA Transposable Elements
  • Drosophila Proteins
  • PRG-1 protein, C elegans
  • PRG-2 protein, C elegans
  • Proteins
  • RNA, Helminth
  • RNA, Small Interfering
  • RNA-Induced Silencing Complex
  • piwi protein, Drosophila
  • Transposases