Histone chaperone that facilitates histone deposition and histone exchange and removal during nucleosome assembly and disassembly (PubMed:11897662, PubMed:14718166, PubMed:15664198, PubMed:16151251, PubMed:21454524, PubMed:26527279). Cooperates with chromatin assembly factor 1 (CAF-1) to promote replication-dependent chromatin assembly (PubMed:11897662, PubMed:14718166, PubMed:15664198, PubMed:16151251). Also involved in the nuclear import of the histone H3-H4 dimer together with importin-4 (IPO4): specifically recognizes and binds newly synthesized histones with the monomethylation of H3 'Lys-9' (H3K9me1) and diacetylation at 'Lys-5' and 'Lys-12' of H4 (H4K5K12ac) marks in the cytosol (PubMed:20953179, PubMed:21454524, PubMed:26527279). Does not participate in replication-independent nucleosome deposition which is mediated by ASF1A and HIRA (PubMed:11897662, PubMed:14718166, PubMed:15664198, PubMed:16151251). Required for gonad development (PubMed:12842904). Interacts with histone H3 (including both histone H3.1 and H3.3) and histone H4 (PubMed:12842904, PubMed:14718166, PubMed:15664198, PubMed:16537536). Interacts with the CHAF1A, CHAF1B and RBBP4 subunits of the CAF-1 complex (PubMed:11897662, PubMed:14718166, PubMed:16537536, PubMed:16980972). Interacts with HAT1, NASP and TAF1 (PubMed:12842904). Interacts with CDAN1 (PubMed:22407294). Found in a cytosolic complex with IPO4 and histones H3 and H4 (PubMed:20953179. PubMed:21454524, PubMed:22407294). Interacts with CREBBP (PubMed:24616510). Highly expressed in testis and at lower levels in colon, small intestine and thymus. Phosphorylated by TLK1 and TLK2. Belongs to the ASF1 family.