AFF4 directly binds to the P‐TEFb subunit cyclin T1, and to the other SEC subunits including one of the ELL proteins ELL or ELL2, to eleven‐nineteen leukemia (ENL) or ALL1‐fused gene from chromosome 9 (AF9), and to one of the ELL‐associated factor proteins EAF1 or EAF2 [6, 7, 8, 9, 10, 12, 13]. Here, ELL is linked to leukemia.