Fig. 1

MLL mechanism of transformation. Wild-type (WT) MLL targets important transcriptional regulators of the hematopoietic system. Normal homeotic gene expression depends on the tightly regulated pause and release of RNA Polymerase II (RNA Pol II) on these MLL target genes. Many leukemia associated MLL fusion proteins such as MLL-AF4 recruit the super elongation complex (SEC). This recruitment leads to the premature release of paused RNA Pol II and activation of transcriptional elongation, leading to the aberrant gene expression of MLL target genes that drive leukemogenesis