ASF1A

ASF1A (Anti-silencing function 1A) is a conserved eukaryotic histone chaperone encoded by the human ASF1A gene. It is one of two closely related paralogs in vertebrates (ASF1A and ASF1B) and has homologs in yeast and other organisms, reflecting a conserved role in chromatin biology.

ASF1A binds histone H3-H4 dimers and facilitates their deposition and removal during nucleosome assembly and disassembly. It acts in both replication-coupled and replication-independent chromatin assembly pathways by delivering H3-H4 to chromatin assembly factors such as CAF-1 and the HIRA complex. ASF1A also promotes histone post-translational modifications, including acetylation of H3 residues, by presenting histone substrates to acetyltransferases. Through these activities it contributes to DNA replication, transcriptional regulation, DNA repair, and chromatin restoration after damage.

Functionally, ASF1A is implicated in the DNA damage response and homologous recombination, and it participates in cell cycle progression, genome stability, and epigenetic maintenance. Structural studies indicate a conserved domain that mediates H3-H4 binding and interactions with partner proteins. ASF1A expression and activity have been linked to cellular proliferation and senescence, and dysregulation has been observed in various cancers, making it of interest in studies of tumor biology and chromatin-related therapies.