Disruptor of telomeric silencing 1-like (DOT1L) catalyses the methylation of histone H3 at lysine 79 and has been implicated in leukaemia.72 In up to 10% of acute leukaemia cases the mixed lineage leukaemia (MLL) protein is fused to a partner protein such as AF9. The gene discussed is KMT2A; the disease is leukemia.