RB1(redirected from p105-Rb)
RB1A gene on chromosome 13q14.2 that encodes a tumour suppressor protein which is a key regulator of entry into cell division, promoting G0-G1 transition following phosphorylation by CDK3/cyclin-C. RB1 represses transcription of E2F1 target genes. Underphosphorylated,
active forms of RB1 interact with E2F1 and repress its transcription activity, leading to cell cycle arrest. With calcium influx, RB1 is dephosphorylated by calcineurin, leading to release of the repressor complex.
Defects in RB1 cause childhood retinoblastoma, some forms of osteogenic sarcoma and increased susceptibility to bladder cancer.