Figure 1.

ATM activation and downstream signaling in response to DSB. DSB induces a rapid activation of the ATM dimer and the MRN complex, which in turn induces the autophosphorylation and monomerization of ATM protein. ATM becomes fully active and phosphorylates a large subset of downstream proteins including γH2AX which serves as a scaffold for the recruitment of repair proteins, MDC1, BP53, and BRCA1 involved in DNA repair, CHK2 involved in cell cycle arrest and p53 involved apoptosis induction. CHK2 also phosphorylates P53 to promote cell-cycle arrest or apoptosis.