http://repub.eur.nl/res/aut/15810/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/13882/ 2005-08-01T00:00:00Z Polycomb response elements (PREs) are cis-acting DNA elements that mediate epigenetic gene silencing by Polycomb group (PcG) proteins. Here, we report that Pleiohomeotic (PHO) and a multiprotein Polycomb core complex (PCC) bind highly cooperatively to PREs. We identified a conserved sequence motif, named PCC-binding element (PBE), which is required for PcG silencing in vivo. PHO sites and PBEs function as an integrated DNA platform for the synergistic assembly of a repressive PHO/PCC complex. We termed this nucleoprotein complex silenceosome to reflect that the molecular principles underpinning its assemblage are surprisingly similar to those that make an enhanceosome.