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. Author manuscript; available in PMC: 2016 Nov 28.
Published in final edited form as: Cell Rep. 2016 Nov 1;17(6):1646–1656. doi: 10.1016/j.celrep.2016.10.008

Figure 6. DDR Pathways at Natural Chromosome Ends versus Telomere-Internal DSB.

Figure 6

Schematic representation of the DDR pathways responding to DSBs inside the telomeric repeats and possible outcomes of HR and alt-NHEJ activities at these breaks. The same pathways are repressed at the natural ends of chromosomes. The telomere-internal FokI-induced DSB activate ATM kinase signaling and processed by 5′ end resection, resulting in one end that has a G-strand overhang and thus resembles the natural telomere terminus. This end can load POT1a/b and would therefore be protected from further resection. The other end has the C-rich telomeric strand exposed and hence is not protected from further resection. Annealing of the two ends will lead to alt-NHEJ. Because of lack of POT1 binding, the C-strand overhang becomes a substrate for Rad51-mediated strand-invasion into the sister telomere, initiating HR.