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. Author manuscript; available in PMC: 2015 Jul 1.
Published in final edited form as: DNA Repair (Amst). 2014 Apr 18;19:169–175. doi: 10.1016/j.dnarep.2014.03.014

Figure 1. DSB repair pathway choices and their regulation.

Figure 1

The three major modalities of DSB repair (NHEJ, HDR and MMEJ/SSA) are depicted. NHEJ can process ligatable DNA ends but is inhibited by modified/damaged DNA ends. In contrast, MMEH or HDR, which both initiate by resection, can process both types of ends. Competition between NHEJ and HDR takes place directly on DNA ends between KU and MRN, as well as in the vicinity of the break between 53BP1 and BRCA1. HDR is not operating in G1 due to the absence of a sister chromatin as homologous template. NHEJ in S-phase is toxic. See text for details.