CHROMATIN-SILENCING MECHANISMS IN DROSOPHILA MAINTAIN PATTERNS OF GENE-EXPRESSION

The Polycomb-Group proteins form chromatin complexes that can silence gene expression over large distances. The formation of these complexes at homeotic genes depends on early developmental events but the repre ssed state is then maintained through many cell divisions. In vivo, co mplexes formed at one genomic site can interact with those at other si tes, suggesting that they, like heterochromatin complexes, affect the folding of chromatin and the organization of chromosomes in the nucleu s.