Histone chaperone that facilitates histone deposition and histone exchange and removal during nucleosome assembly and disassembly. Cooperates with chromatin assembly factor 1 (CAF-1) to promote replication-dependent chromatin assembly. Does not participate in replication-independent nucleosome deposition which is mediated by ASF1A and HIRA. Required for spermatogenesis. Interacts with histone H3 (including both histone H3.1 and H3.3) and histone H4. Interacts with the CHAF1A, CHAF1B and RBBP4 subunits of the CAF-1 complex. Interacts with HAT1, NASP, TAF1, TLK1 and TLK2. Highly expressed in testis and at lower levels in colon, small intestine and thymus. Belongs to the ASF1 family. Note: This description may include information from UniProtKB.