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. acetyl-CoA + L-lysyl-[protein] = CoA + H(+) + N(6)-acetyl-L-lysyl-[protein] Component of the HAT-B complex composed of at least hat1 and hat2. The HAT-B complex binds to histone H4 tail (By similarity). Belongs to the HAT1 family.