HOXA9 and leukemia: The acetyltransferase Tip60 is required for embryonic and adult hematopoietic stem cell (HSC) maintenance and mixed lineage leukemia (MLL) fusion-driven leukemia.55,56 In both cases, Tip60 functions are associated with H2A.Z acetylation on key effector genes such as HOXA9 in leukemia.