Licensed to elongate: a molecular mechanism for MLL-based leukaemogenesis

This article discusses the possible function of the super elongation complex (SEC) and the DOT1 H3K79 methyltransferase complex (DotCom) in leukaemia that is induced by translocation of mixed lineage leukaemia ( MLL ). The RNA polymerase II (Pol II) elongation factor (ELL) was the first translocation partner of mixed lineage leukaemia (MLL) for which a biochemical function was determined. It was therefore proposed that the regulation of the elongation stage of transcription could be fundamental to MLL-based leukaemogenesis. Recent studies have identified ELL complexed with several of the translocation partners of MLL in a transcriptional super elongation complex (SEC). These studies provide evidence for the importance of the regulation of Pol II elongation in disease pathogenesis and suggest that MLL chimaeras function by licensing Pol II transcription elongation without the appropriate checkpoints.