Core histone-binding subunit that may target chromatin remodeling factors, histone acetyltransferases and histone deacetylases to their histone substrates in a manner that is regulated by nucleosomal DNA. Component of several complexes which regulate chromatin metabolism. These include the type B histone acetyltransferase (HAT) complex, which is required for chromatin assembly following DNA replication; the core histone deacetylase (HDAC) complex, which promotes histone deacetylation and consequent transcriptional repression; the nucleosome remodeling and histone deacetylase complex (the NuRD complex), which promotes transcriptional repression by histone deacetylation and nucleosome remodeling; and the PRC2/EED-EZH2 complex, which promotes repression of homeotic genes during development; and the NURF (nucleosome remodeling factor) complex (By similarity). Binds directly to helix 1 of the histone fold of histone H4, a region that is not accessible when H4 is in chromatin. Subunit of the type B histone acetyltransferase (HAT) complex, composed of RBBP7 and HAT1. Subunit of the core histone deacetylase (HDAC) complex, which is composed of HDAC1, HDAC2, RBBP4 and RBBP7. The core HDAC complex associates with SIN3A, ARID4B/SAP180, SAP18, SAP30, SAP130, SUDS3/SAP45 and possibly ARID4A/RBP1 and ING1 to form the SIN3 HDAC complex. The core HDAC complex may also associate with MTA2, MBD3, CHD3 and CHD4 to form the nucleosome remodeling and histone deacetylase complex (the NuRD complex). The NuRD complex may also interact with MBD3L1 and MBD3L2. Interacts with MTA1. Subunit of the PRC2/EED-EZH2 complex, which is composed of at least EED, EZH2, RBBP4, RBBP7 and SUZ12. The PRC2/EED-EZH2 complex may also associate with HDAC1. Component of the NURF-1 ISWI chromatin remodeling complex (also called the nucleosome-remodeling factor (NURF) complex) at least composed of SMARCA1; BPTF; RBBP4 and RBBP7 (By similarity). Within the complex interacts with SMARCA1 (By similarity). Interacts with the viral protein-binding domain of the retinoblastoma protein (RB1). Interacts with CREBBP, and this interaction may be enhanced by the binding of phosphorylated CREB1 to CREBBP. Interacts with CENPA. Interacts with BRCA1, HDAC7 and SUV39H1 (By similarity). Interacts with PWWP2B (By similarity). Belongs to the WD repeat RBAP46/RBAP48/MSI1 family.