What is the Role of the Rb Protein in the Restriction Point?
The Rb protein is a pivotal regulator of the restriction point. In its hypophosphorylated form, Rb binds to E2F transcription factors, preventing them from activating genes required for S phase entry. Upon phosphorylation by CDK-cyclin complexes, Rb releases E2F, allowing the cell to progress to the S phase. Mutations in the Rb gene or its upstream regulators can lead to loss of this control, contributing to tumorigenesis.
