Cell Cycle G2-M Checkpoint

The cell cycle G2-M checkpoint is a critical regulatory mechanism in eukaryotic cells that ensures the integrity of the genome before a cell enters mitosis (M phase). This checkpoint occurs at the transition between the G2 phase (the second gap phase) and M phase, serving as a quality control system to prevent cells with damaged or incompletely replicated DNA from proceeding into mitosis. The primary function is to detect DNA damage or incomplete DNA replication after S phase and halt cell cycle progression until these issues are resolved. If errors or damage are detected, signaling pathways activate repair mechanisms. If repair is unsuccessful, apoptosis may be triggered to prevent propagation of defective genetic material. Key components include Cyclin B-CDK1 complex, Wee1 and Myt1 kinases, Cdc25 phosphatase, ATM/ATR kinases, Chk1/Chk2 kinases, and p53 tumor suppressor protein. Loss of integrity in this pathway leads to genomic instability and cancer predisposition.