Figure 5.

Updated models. (a) The core MSL complex is targeted to MREs in CESs in part by the DNA-binding activity of CLAMP, which provides a molecular link between the complex and DNA in a sequence-specific manner. Selection of CESs also strongly favours an active chromatin context, with pre-existing enrichment of the histone marks H3K36me3 and H4K16Ac and the chromosomal kinase Jil-1 that can be observed even in female cells (thus, not due to the presence of the MSL complex itself). (b) Insulators contribute to the long-range interactions between PREs. In this way, PcG complexes may be brought to distal sites of activity. As yet unresolved, however, is the identity of factors that are critical for initial targeting of the PcG complexes. Certainly, Pho plays a major role, but other, unidentified factors also clearly take part.