Transcription factor. Inhibits cell proliferation by activating either CDKN1A/p21 transcription or RB1 transcription. ; [Isoform 1]: Binds CDKN1A promoter and activates its transcription; this activity is further potentiated in the presence of EP300 (synergistic) and ZBTB17/Miz-1 (additive). ; [Isoform 3]: Activates RB1 transcription most probably by antagonizing ZBTB17 repression of RB1. Does not bind directly RB1 promoter.
