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. 2016 Sep 19;7:12889. doi: 10.1038/ncomms12889

Figure 4. CtIP 5′-flap endonuclease activity shows epistasis with MRE11 3′–5′ exonuclease activity in counteracting Ku binding to seDSBs.

Figure 4

(a) Schematic of CtIP domains with the position of N289 and H290 residues. (b) Immunoblotting of extracts from U2OS T-REx cells stably transfected with control or siRNA-resistant wild-type (WT) or NAHA HA-CtIP-expressing plasmids, and transfected with the indicated siRNA. (c) Quantification of Ku focus number in replicating cells transfected as in b and treated with CPT. (d) Immunoblotting of extracts from U2OS T-REx cells stably transfected with control or siRNA-resistant WT HA-CtIP and HA-MRE11 or NAHA HA-CtIP and H63N HA-MRE11, and transfected with the indicated siRNAs. (e) Quantification of Ku foci in U2OS T-REx stably transfected with control or the specified siRNA-resistant constructs and transfected with the indicated siRNAs. Error bars are s.d. Significant differences between specified pairs of conditions, as judged by t-test, are highlighted by stars (*P<0.05; **P<0.01; ***P<0.0005; ****P<0.0001). NS, non-significant difference.