FIGURE 3.

Ionizing radiation induces a wide variety of DNA damage. (A) IR causes dsDNA breaks that are repaired by HR (in S/G2 phase) or NHEJ (all phases of cell cycle). In HR, the RPA complex and BRC proteins form a scaffold complex with the sister chromatid and use it as a template to correct damage without error. NHEJ utilizes the KU70/80/DNA-PKc complex to quickly combine and ligate double-strand breaks. (B) IR-mediated radiolysis of water leads to ROS formation, which then creates base damage through oxidation. BER then repairs these lesions through the use of a type II DNA glycosylase (OGG1), AP endonuclease (APE1/APE2), PARP1, DNA polymerase, and ligase. This occurs through either short patch or long patch BER.