ASF1B

ASF1B, or anti-silencing function 1B, is a histone chaperone in animals that assists in the supply and deposition of histones H3 and H4 onto DNA. It is a paralog of ASF1A and participates in the organization of chromatin during DNA replication and repair. By delivering histones to sites of newly synthesized DNA, ASF1B helps ensure proper nucleosome assembly and maintenance of chromatin integrity.

In human cells, ASF1B contributes to replication-dependent chromatin assembly and plays a role in the DNA damage response. It functions in coordination with chromatin assembly factors such as CAF-1 to deposit H3/H4 onto replicated DNA, aiding in the restoration of chromatin structure after replication stress or DNA damage. The protein is primarily localized to the nucleus and is enriched in actively dividing cells.

Expression of ASF1B is associated with cellular proliferation. It is typically elevated in proliferative tissues and in various cancers, where high levels have been correlated with enhanced cell growth and poorer prognosis in some studies. Experimental reduction of ASF1B can impair S-phase progression, reduce cell proliferation, and increase sensitivity to replication stress, underscoring its role in supporting DNA replication and genome stability.

As a histone chaperone with a central role in nucleosome assembly, ASF1B participates in fundamental chromatin biology and is of interest in studies of cell cycle control, development, and oncology. Its activity is commonly examined in relation to ASF1A and the broader network of chromatin assembly factors.