TCGA data indicate that in multiple types of cancer MLL3/4 (lysine methyltransferase 2C/D, or mixed-lineage leukemia 3/4) complex and p300/CBP (E1A binding protein p300/ CREB binding protein) histone acetyltransferase are frequently mutated, which are key enzymes for H3K4me1 and H3K27ac, respectively18. The gene discussed is KMT2C; the disease is leukemia.