How Do External Signals Influence the Restriction Point?
External signals, such as growth factors and mitogens, play a crucial role in the regulation of the restriction point. These signals activate signaling pathways (like the PI3K/AKT pathway) that promote the expression and activation of cyclins and CDKs, facilitating the transition through the restriction point. Conversely, anti-proliferative signals can enhance the activity of CKIs, maintaining cells in the G1 phase or pushing them into quiescence.
