Acts as a component of chromatin assembly factor 1 (CAF-1), which assembles histone octamers onto replicating DNA in vitro. It performs the first step of the nucleosome assembly process, bringing newly synthesized histones H3 and H4 to replicating DNA; histones H2A/H2B can bind to this chromatin precursor subsequent to DNA replication to complete the histone octamer. p50 and p60 form complexes with newly synthesized histones H3 and acetylated H4 in cell extracts (By similarity). Component of chromatin assembly factor 1 (CAF-1), which is composed of MSI1/p50, CAC2/p60 and CAC1/p90 (Probable). Interacts with RTT106 (PubMed:19683497). Present with 2130 molecules/cell in log phase SD medium. Belongs to the WD repeat HIR1 family.