Polycomb bodies are concentrations of Polycomb Group proteins detectable in the nucleus at various intensities. The largest or most intense have been shown to contain genomic clusters of Polycomb Group targets such as the Hox gene clusters. Since, in general, the number of Polycomb bodies visible is an order of magnitude smaller than the known number of Polycomb target genes in the genome, they are often thought to involve the association of multiple genomic regions that are distant from one another in the genome. This chapter reviews the evidence for Polycomb bodies, their formation and their genomic content. While different lines of evidence indicate that genomically remote Polycomb target genes can associate, often enhancing the repressive effect, other evidence indicates that this is not usually a stable interaction, varies from one tissue to another, and is strongly dependent on the presence of insulator protein binding sites near Polycomb targets. The effects of transcriptional derepression and of post-transcriptional modifications of Polycomb proteins or of insulator proteins as factors modulating the association lf remote Polycomb target sites are also discussed.
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)