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 (By similarity). Acts together with PDP1 and MSI4/FVE to regulate the function of the PRC2 complex on FLC (PubMed:29314758). Interacts with AHL16 (PubMed:23394836). Interacts with LHP1, PDP2, PDP3 and PDP6 (PubMed:29314758). Component of the PRC2 (polycomb repressive complex 2) complex which regulates histone methylation on histone H3K27 (PubMed:29314758). The DWD box is required for interaction with DDB1A. Reduced H3K27me3 level but increased levels of histone H3 acetylation and H3K4me3 on FLC in the fve msi5 double mutant. Belongs to the WD repeat RBAP46/RBAP48/MSI1 family.