Histone chaperone that facilitates histone deposition and histone exchange and removal during nucleosome assembly and disassembly (By similarity). Not critical for histone deposition during nucleosome assembly (PubMed:17576589). Interacts with histone H3 (including both histone H3.1 and H3.3) and histone H4 (By similarity). Interacts with hira and p60 (PubMed:17576589). Belongs to the ASF1 family.