EGO-1, a putative RNA-dependent RNA polymerase, is required for heterochromatin assembly on unpaired dna during C. elegans meiosis

Curr Biol. 2005 Nov 8;15(21):1972-8. doi: 10.1016/j.cub.2005.09.049.


During meiosis in C. elegans, unpaired chromosomes and chromosomal regions accumulate high levels of histone H3 lysine 9 dimethylation (H3K9me2), a modification associated with facultative heterochromatin assembly and the resulting transcriptional silencing. Meiotic silencing of unpaired DNA may be a widely conserved genome defense mechanism. The mechanisms of meiotic silencing remain unclear, although both transcriptional and posttranscriptional processes are implicated. Cellular RNA-dependent RNA polymerases (RdRPs) function in development and RNA-mediated silencing in many species and in heterochromatin assembly in S. pombe. There are four C. elegans RdRPs, including two with known germline functions. EGO-1 is required for fertility and robust germline RNAi. RRF-3 acts genetically to repress RNAi and is required for normal meiosis and spermatogenesis at elevated temperatures (S. L'Hernault, personal communication). Among C. elegans RdRPs, we find that only EGO-1 is required for H3K9me2 enrichment on unpaired chromosomal regions during meiosis. This H3K9me2 enrichment does not require Dicer or Drosha nuclease or any of several other proteins required for RNAi. ego-1 interacts genetically with him-17, another regulator of chromatin and meiosis, to promote germline development. We conclude that EGO-1 is an essential component of meiotic silencing in C. elegans.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Caenorhabditis elegans / enzymology*
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Caenorhabditis elegans Proteins / physiology
  • Cell Cycle Proteins / metabolism
  • DNA / metabolism*
  • Fluorescent Antibody Technique, Indirect
  • Gene Silencing / physiology*
  • Heterochromatin / enzymology
  • Heterochromatin / physiology*
  • Histone Methyltransferases
  • Histone-Lysine N-Methyltransferase / metabolism
  • Meiosis / genetics
  • Meiosis / physiology*
  • Methylation
  • Models, Molecular
  • Mutation / genetics
  • Protein Methyltransferases
  • RNA-Dependent RNA Polymerase / genetics
  • RNA-Dependent RNA Polymerase / metabolism*
  • RNA-Dependent RNA Polymerase / physiology


  • Caenorhabditis elegans Proteins
  • Cell Cycle Proteins
  • HIM-17 protein, C elegans
  • Heterochromatin
  • DNA
  • Histone Methyltransferases
  • Protein Methyltransferases
  • Histone-Lysine N-Methyltransferase
  • EGO-1 protein, C elegans
  • RNA-Dependent RNA Polymerase