Although there has been some indication that H3K79me2 and H3K79me3 may have similar binding profiles in mammalian cells18,35, most work has focused on the association of H3K79me2 with active gene bodies in MLL-r leukemia cells18,24,26,35, and it is unclear whether there is a distinction between the two methylation states. This evidence concerns the gene KMT2A and leukemia.