cell cycle control system

CDKs

are regulated by cyclins, which bind to and activate them.

retinoblastoma protein

The (Rb) is a key cell cycle regulator that helps control the progression from G1 to the S phase.

Rb

is phosphorylated by cyclin- dependent kinases (CDKs) during the G1 phase, which releases E2F transcription factors that activate the expression of genes required for DNA synthesis.

E2F transcription factors

are released from the retinoblastoma protein (Rb) when Rb is phosphorylated by cyclin- dependent kinases.

early G1 phase

In the , Rb is hypophosphorylated and acts as a transcriptional repressor, inhibiting the expression of E2F- regulated genes.

Cyclins

bind to and activate CDKs, which then phosphorylate specific target proteins, leading to changes in their activity and function.

E2F transcription factors

are proteins that regulate the expression of genes required for DNA synthesis and are activated during the cell cycles G1 to S phase transition.