RB Family Tumor Suppressor Activity May Not Relate to Active Silencing of E2F Target Genes

The retinoblastoma protein pRB and its two homologs p130 and p107 form the family of pocket proteins and play a major role in cell-cycle regulation and suppression of human and mouse tumorigenesis. Pocket proteins regulate the activity of E2F transcription factors during G1–S transition. Two mechanisms have been described: (i) pocket protein binding blocks the transactivation domain of activator E2Fs, inhibiting E2F-dependent transcription and...