FIGURE 1.

Ataxia telangiectasia and Rad3‐related (ATR) signaling network in the DNA damage response (DDR). ATR kinase plays a critical role in regulating DDR, particularly during DNA replication. ATR activates the cell cycle checkpoint pathway that halts the cell cycle in response to DNA damage or replication stress (RS). ATR regulates DNA replication by inhibiting the replicative helicase, preventing further origin firing. When a replication fork stalls, ATR phosphorylates some proteins that are involved in stabilizing the fork, preventing its collapse, promoting repair, and restarting forks to promote RS tolerance mechanisms. ATR also functions in mitosis to ensure chromosome segregation. These functions are controlled by the indicated representative factors directly or indirectly regulated by ATR or Chk1. By coordinating these processes, ATR helps to maintain genomic integrity.