Acts as a transcriptional transactivator of TCEA1 elongation activity (By similarity). Acts as a transcriptional transactivator of ELL and ELL2 elongation activities. Potent inducer of apoptosis in prostatic and non-prostatic cell lines. Inhibits prostate tumor growth in vivo. Isoform 1 and isoform 2 interact with TCEA1 (By similarity). Component of the super elongation complex (SEC), at least composed of EAF1, EAF2, CDK9, MLLT3/AF9, AFF (AFF1 or AFF4), the P-TEFb complex and ELL (ELL, ELL2 or ELL3). Interacts with ELL and ELL2. Expressed in heart, brain, placenta, lung, skeletal muscle, kidney, pancreas, spleen, prostate, testis, small intestine, colon, adrenal, bone marrow, lymph node, spinal gland, stomach, thyroid, trachea, thymus, liver and leukocytes. By androgen. Belongs to the EAF family.