The Rb protein is crucial in controlling the cell cycle's transition from the G1 phase to the S phase, where DNA replication occurs. Rb exerts its function by binding to and inhibiting transcription factors such as E2F, preventing cell cycle progression. When Rb is phosphorylated by cyclin-CDK complexes, it releases E2F, allowing the cell cycle to proceed. Mutations or inactivation of Rb can lead to unregulated cell proliferation, contributing to cancer development.
