Histone chaperone Asf1 is required for histone H3 lysine 56 acetylation, a modification associated with S phase in mitosis and meiosis.

Histone acetylation affects many nuclear processes including transcription, chromatin assembly, and DNA damage repair. Acetylation of histone H3 lysine 56 (H3 K56ac) in budding yeast occurs during mitotic S phase and persists during DNA damage repair. Here, we show that H3 K56ac is also present during premeiotic S phase and is conserved in fission yeast. Furthermore, the H3 K56ac modification is not observed in the absence of the histone chaperone Asf1. asf1delta and H3 K56R mutants exhibit similar sensitivity to DNA damaging agents. Mutational analysis of Asf1 demonstrates that DNA damage sensitivity correlates with (i) decreased levels of H3 K56ac and (ii) a region implicated in histone binding. In contrast, multiple asf1 mutants that are resistant to DNA damage display WT levels of K56ac. These data suggest that maintenance of H3 K56 acetylation is a primary contribution of Asf1 to genome stability in yeast.