MLL rearrangements lead to loss of the methyltransferase activity of MLL and the C-terminal portion of the translocation partner (most frequently AF9, AF4 and ENL in AML) recruits the fusion protein to complexes associated with transcriptional elongation (reviewed in Deshpande et al., 2012 [14]). Here, MLLT3 is linked to acute myeloid leukemia.