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 several complexes which regulate chromatin metabolism. These include the chromatin assembly factor 1 (CAF-1) complex, which is required for chromatin assembly following DNA replication and DNA repair; the nucleosome remodeling and deacetylase complex (the NuRD complex), which promotes transcriptional repression by histone deacetylation and nucleosome remodeling; the nucleosome remodeling factor (NURF) complex, which catalyzes ATP-dependent nucleosome sliding and facilitates transcription of chromatin; and the polycomb group (PcG) repressor complex ESC-E(Z), which promotes repression of homeotic genes during development. Also required for transcriptional repression of E2F target genes by E2f2 and Rbf or Rbf2. Probably binds directly to helix 1 of the histone fold of histone H4, a region that is not accessible when H4 is in chromatin. Self associates. Associates with chromatin. Component of the CAF-1 complex, composed of Caf1-55, Caf1-105 and Caf1-180. Within the CAF-1 complex, Caf1-180 interacts directly with both Caf1-55 and Caf1-105. Component of the NuRD complex, composed of at least Caf1-55, Mi-2, MTA1-like and HDAC1/Rpd3. Within the NuRD complex, Caf1-55 may interact directly with Mi-2, MTA1-like and HDAC1/Rpd3. The NuRD complex may also associate with the methyl-DNA binding protein MBD-like via Caf1-55 and Mi-2. Component of the NURF complex, composed of Caf1-55, E(bx), Nurf-38 and Iswi. Component of the Esc/E(z) complex, composed of Caf1-55, esc, E(z), Su(z)1, and possibly Pho1. The Esc/E(z) complex may also associate with Pcl and HDAC1/Rpd3 during early embryogenesis. Interacts with Rbf and Rbf2. Component of the DREAM complex at least composed of Myb, Caf1-55, mip40, mip120, mip130, E2f2, Dp, Rbf, Rbf2, lin-52, HDAC1/Rpd3 and l(3)mbt. Highest level during early embryogenesis and then decreases in larvae, pupae and adults. Belongs to the WD repeat RBAP46/RBAP48/MSI1 family.