Chromosome Research

, Volume 14, Issue 4, pp 363–375 | Cite as

From genetics to epigenetics: the tale of Polycomb group and trithorax group genes

  • Charlotte Grimaud
  • Nicolas Nègre
  • Giacomo CavalliEmail author


The Polycomb gene was discovered 60 years ago as a mutation inducing a particular homeotic phenotype. Subsequent work showed that Polycomb is a general repressor of homeotic genes. Other genes with similar function were identified and named Polycomb group (PcG) genes, while trithorax group (trxG) genes were shown to counteract PcG-mediated repression of homeotic genes. We now know that PcG and trxG proteins are conserved factors that regulate hundreds of different genomic loci. A sophisticated pathway is responsible for recruitment of these proteins at regulatory regions that were named PcG and trxG response elements (PRE and TRE). Once recruited to their targets, multimeric PcG and trxG protein complexes regulate transcription by modulating chromatin structure, in particular via deposition of specific post-translational histone modification marks and control of chromatin accessibility, as well as regulation of the three-dimensional nuclear organization of PRE and TRE. Here, we recapitulate the history of PcG and trxG gene discovery, we review the current evidence on their molecular function and, based on this evidence, we propose a revised classification of genes involved in PcG and trxG regulatory pathways.

Key words

chromatin Drosophila epigenetics Polycomb group trithorax group 


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Copyright information

© Springer 2006

Authors and Affiliations

  • Charlotte Grimaud
    • 1
  • Nicolas Nègre
    • 1
  • Giacomo Cavalli
    • 1
    Email author
  1. 1.Institute of Human Genetics, CNRSMontpellier Cedex 5France

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