Histone acetyltransferase type B catalytic subunit; Catalytic component of the histone acetylase B (HAT-B) complex. Acetylates 'Lys-12' of histone H4 which is required for telomeric silencing. Has intrinsic substrate specificity that modifies lysine in recognition sequence GXGKXG. Involved in DNA double-strand break repair (By similarity) (378 aa)