The MES-2/MES-3/MES-6 complex and regulation of histone H3 methylation in C. elegans

Curr Biol. 2004 Sep 21;14(18):1639-43. doi: 10.1016/j.cub.2004.08.062.


The C. elegans proteins MES-2 and MES-6, orthologs of the Polycomb group (PcG) chromatin repressors E(Z) and ESC, exist in a complex with their novel partner MES-3. The MES system participates in silencing the X chromosomes in the hermaphrodite germline. Loss of maternal MES function leads to germline degeneration and sterility. We report here that the MES complex is responsible for di- and trimethylation of histone H3 Lys27 (H3-K27) in the adult germline and in early embryos and that MES-dependent H3-K27 marks are concentrated on the X's. Another H3-K27 HMT functions in adult somatic cells, oocytes, and the PGCs of embryos. In PGCs, the MES complex may specifically convert dimethyl to trimethyl H3-K27. The HMT activity of the MES complex appears to be dependent on the SET domain of MES-2. MES-2 thus joins its orthologs Drosophila E(Z) and human EZH2 among SET domain proteins known to function as HMTs (reviewed in ). Methylation of histones is important for long-term epigenetic regulation of chromatin and plays a key role in diverse processes such as X inactivation and oncogenesis. Our results contribute to understanding the composition and roles of E(Z)/MES-2 complexes across species.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blotting, Western
  • Caenorhabditis elegans / embryology
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / metabolism*
  • Dosage Compensation, Genetic
  • Fluorescent Antibody Technique
  • Histone Methyltransferases
  • Histone-Lysine N-Methyltransferase / metabolism
  • Histones / metabolism*
  • Immunoprecipitation
  • Methylation
  • Nuclear Proteins / metabolism*
  • Polycomb-Group Proteins
  • Protein Methyltransferases
  • Protein Structure, Tertiary


  • Caenorhabditis elegans Proteins
  • Histones
  • Mes-3 protein, C elegans
  • Nuclear Proteins
  • Polycomb-Group Proteins
  • mes-2 protein, C elegans
  • mes-6 protein, C elegans
  • Histone Methyltransferases
  • Protein Methyltransferases
  • Histone-Lysine N-Methyltransferase