Recruitment and activation of Chk1 Phosphorylation and activation of CHK2 by ATM PathwayStep4479 PathwayStep4473 PathwayStep4472 G2/M DNA damage checkpoint Reactome Database ID Release 4369473 Reactome, http://www.reactome.org ReactomeREACT_897 Throughout the cell cycle, the genome is constantly monitored for damage, resulting either from errors of replication, by-products of metabolism or through extrinsic sources such as ultra-violet or ionizing radiation. The different DNA damage checkpoints act to inhibit or maintain the inhibition of the relevant CDK that will control the next cell cycle transition. The G2 DNA damage checkpoint prevents mitotic entry solely through T14Y15 phosphorylation of Cdc2 (Cdk1). Failure of the G2 DNA damage checkpoint leads to catastrophic attempts to segregate unrepaired chromosomes. Chk1/Chk2(Cds1) mediated inactivation of Cyclin B:Cdk1 complex