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. 2011 Feb 11;30(6):1079–1092. doi: 10.1038/emboj.2011.27

Figure 5.

Figure 5

CtIP siRNA allows repair to be switched from HR to NHEJ. (A) CtIP siRNA and BRCA2 siRNA causes a similar DSB repair defect in XLF-defective cells following IR. DSB repair was monitored by γH2AX foci enumeration after 2 Gy X-rays using the treatments and/or cells indicated. As in Figure 4, CtIP siRNA shows faster repair, whereas BRCA2 siRNA confers a repair defect in WT G2 cells. In contrast, CtIP or BRCA2 siRNA in XLF cells showed a similar DSB repair defect, demonstrating that DSB repair following CtIP siRNA occurs by NHEJ. (B, C) CtIP siRNA alleviates the BRCA2-dependent repair defect in A549 G2 cells after 2 Gy X-rays. The slightly higher γH2AX foci numbers following combined BRCA2 and CtIP siRNA than following CtIP siRNA alone at 8 h is probably a result of imperfect siRNA efficiency. (D) CtIP or BRCA2 siRNA inhibits IR-induced SCEs. Ku80 or BRCA2 siRNA but not CtIP siRNA causes increased deletion events. IR-induced SCEs in G2 phase were analysed following 2 Gy X-rays (left panel). Genomic deletions were examined in metaphase preparations following 2 Gy X-rays (right panel).