Fig. 1.

Schematic diagram of DNA damage response. External and internal stresses induce DNA lesions. The damaged DNA may activate the DNA damage response signaling pathway, where DNA damage checkpoints play a central role in arresting the cell cycle and mediating the DNA repair process. The unsuccessful repairing of DNA lesions may cause apoptosis, cell death or cancer. Homologous recombination (HR); Non-homologous end joining (NHEJ); Base excision repair (BER); Nucleotide excision repair (NER); Postreplication repair (PRR); Mismatch repair (MMR).