Functional dissection of Polycomb repressive complex 1 reveals the importance of a charged domain.

Silencing of homeotic genes requires the Polycomb repressive complex 1 (PRC1) family of protein complexes, which are composed of Polycomb-group (PcG) proteins and frequently include other subunits. We discuss here two aspects of PRC1 that might contribute to this activity. Inhibiting the action of remodeling factors via chromatin compaction is believed to be one mechanism by which PRC1 represses genes. We show that PRC1s from fly and mouse have conserved this activity as complexes. Additionally, we provide evidence that a different subunit in the mouse complex retains the conserved repression activity and that activity appears to be mediated by charge interactions. We show that Zeste interacts specifically with the Ph subunit of PRC1 and discuss the possibility of these factors contributing to spreading of PRC1 complexes. Our results suggest that one aspect of PRC1 repression is likely to be mediated by charge-charge interactions.