Histone chaperone that facilitates histone deposition and histone exchange and removal during nucleosome assembly and disassembly (PubMed:10591219, PubMed:12381660, PubMed:14561777, PubMed:16151251, PubMed:16396992). Cooperates with chromatin assembly factor 1 (CAF-1) to promote replication-dependent chromatin assembly (PubMed:11533245). Plays a role in the formation of silent heterochromatin (PubMed:12381660, PubMed:28320872). Component of the replication coupling assembly factor (RCAF), composed of asf1, histone H3 and histone H4 (PubMed:10591219). Interacts with the Caf1-105 subunit of the CAF-1 complex (PubMed:11533245). Interacts with brm, mor and tlk (PubMed:12381660, PubMed:14561777). Interacts with Daxx (PubMed:28320872). Localizes to multiple sites on polytene chromosomes including transcriptionally active developmental puffs, the chromocenter and the histone gene cluster (PubMed:12381660). Localizes to active foci of DNA replication throughout S-phase and is lost from stalled replication forks (PubMed:16396992). Not detected on condensed chromatin during mitosis (PubMed:16396992). Highly expressed in embryos and at lower levels in larvae, pupae and adults. Phosphorylated on undefined residues by tlk. Belongs to the ASF1 family.