Regulation of the restriction point involves a complex interplay of various proteins and signaling pathways. One of the key regulators is the retinoblastoma protein (Rb), which, when phosphorylated by CDKs, releases the transcription factor E2F. This release allows for the transcription of genes necessary for S-phase entry. The p53 protein also plays a critical role by halting the cell cycle in response to DNA damage, thus preventing the passage through the restriction point.
