Core histone-binding subunit that may target chromatin assembly factors, chromatin remodeling factors and histone deacetylases to their histone substrates in a manner that is regulated by nucleosomal DNA. Component of the DREAM complex (By similarity). Binds directly to histone H4, probably via helix 1 of the histone fold, a region that is not accessible when histone H4 is in chromatin (PubMed:11112423). Interacts with CHAF1A, HDAC1, HDAC2, HDAC3 and HIRA (PubMed:10347232, PubMed:15527972, PubMed:17065558). May also interact with HAT1 (PubMed:11112423, PubMed:11160883). Belongs to the WD repeat RBAP46/RBAP48/MSI1 family.