Figure 6.
DNA replication and damage checkpoint regulation. Replication stress or blockage or DNA damage induces activation of a signal transduction pathway of many different proteins. The proteins are in different classes indicated as sensors, mediators, transducers, and effector targets. For example, if DNA replication is blocked, ssDNA coated by RPA sends a signal to activate Mec1 protein kinase. Mec1 binds to Mrc1, which amplifies the signal by binding to and activating Chk2 (Rad53) protein kinase. Chk2, in turn, inhibits Cdc45 helicase activation and loading of the replisome.