Acts at E2F-responsive promoters as coregulator to integrate signals provided by PHD- and/or bromodomain-containing transcription factors. Stimulates E2F1/TFDP1 transcriptional activity. Renders the activity of cyclin D1/CDK4 resistant to the inhibitory effects of CDKN2A/p16INK4A. Interacts with the PHD-bromodomain of TIF1, TRIM28/TIF1B and p300/CBP. Interacts with E2F1 and TFDP1; modulates transactivation activity of TFDP1/E2F complexes. Also interacts with CDK4. Transcript levels remain constant in all phases of the cell cycle. In contrast, protein levels accumulate at the G1/S phase boundary and decrease progressively through S phase until G2/M phase is reached. Polyubiquitinated, which promotes proteasomal degradation.