MLL-AF4, along with other MLL-FPs, is thought to drive leukemia by binding at the promoters of key oncogenes and upregulating their expression by the recruitment of a complex of elongation-associated factors, including the RNA Polymerase (RNAP) II-Associated Factor complex (PAF1C), Eleven Nineteen Leukemia (ENL, also known as MLLT1), AF9, DOT1L, AFF4 and P-TEFb37–39. The gene discussed is AFF1; the disease is leukemia.