Histone H2A monoubiquitination and Polycomb repression

Abstract

Polycomb group (PcG) proteins were originally identified as negative regulators of HOX genes in Drosophila but have since emerged as a widely used transcriptional repression system that controls a variety of developmental processes in animals and plants. PcG proteins exist in multi-protein complexes that comprise specific chromatin-modifying enzymatic activities. Genome-wide binding studies in Drosophila and in mammalian cells revealed that these complexes co-localize at a large set of genes encoding developmental regulators. Recent analyses in Drosophila have begun to explore how the different chromatin-modifying activities of PcG protein complexes contribute to the repression of individual target genes. These studies suggest that monoubiquitination of histone H2A (H2Aub) by the PcG protein Sce is only essential for repression of a subset of PcG target genes but is not required for the Polycomb-mediated repression of other targets. Calypso/dBap1, a major deubiquitinase for H2Aub is also critically needed...