The C. elegans Polycomb gene SOP-2 encodes an RNA binding protein

Mol Cell. 2004 Jun 18;14(6):841-7. doi: 10.1016/j.molcel.2004.06.001.


Epigenetic silencing of Hox cluster genes by Polycomb group (PcG) proteins is thought to involve the formation of a stably inherited repressive chromatin structure. Here we show that the C. elegans-specific PcG protein SOP-2 directly binds to RNA through three nonoverlapping regions, each of which is essential for its localization to characteristic nuclear bodies and for its in vivo function in the repression of Hox genes. Functional studies indicate that the RNA involved in SOP-2 binding is distinct from either siRNA or microRNA. Remarkably, the vertebrate PcG protein Rae28, which is functionally and structurally related to SOP-2, also binds to RNA through an FCS finger domain. Substitution of the Rae28 FCS finger for the essential RNA binding region of SOP-2 partially restores localization to nuclear bodies. These observations suggest that direct binding to RNA is an evolutionarily conserved and potentially important property of PcG proteins.

Publication types

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

MeSH terms

  • Animals
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans Proteins / chemistry*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / physiology*
  • Gene Expression Regulation
  • Genes, Homeobox
  • RNA-Binding Proteins / chemistry*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Repressor Proteins / chemistry*
  • Repressor Proteins / genetics
  • Repressor Proteins / physiology*


  • Caenorhabditis elegans Proteins
  • RNA-Binding Proteins
  • Repressor Proteins
  • Sop-2 protein, C elegans