Menin is found in a subset of COMPASS-like (complex of proteins associated with Set1) mixed lineage leukemia (MLL) complexes that trimethylate histone H3 at lysine 4 (H3K4), specifically in MLL1/MLL2-containing complexes that trimethylate H3K4 [4], [5]. This evidence concerns the gene KMT2A and leukemia.