DOT1L and leukemia: Both 1° AML-3 and 1° MPAL-1 carry a KMT2A–AF9 fusion protein, whereas KOPN-8 carries a KMT2A–ENL fusion, suggesting that the AF9 fusion partner recruits particularly high levels of DOT1L to oncoprotein target loci while other leukemias can be variable for DOT1L recruitment.