In MLLr leukemias, the N-terminal of the COMPASS family H3K4 methyltransferase MLL1 (KMT2A) is fused with the C-terminal of any one of many fusion partners, including subunits of the DOT1L complex (DOTCOM) and the super elongation complex (SEC) (45, 46). The gene discussed is KMT2A; the disease is leukemia.