CtIP regulates resection from Top2 adducts. (A) Control (ΔMock) and CtIP-depleted extracts were supplemented with sperm nuclei (5,000/µl) and incubated with 0.05 U/µl PflMI or 100 µM etoposide (Etop.). Chromatin was purified at the indicated times and processed for Western blot with Top2, CtIP, RPA70, Ku70, and H3 (loading control) antibodies. NS, no sperm control. (B) Plot of RPA binding as shown in A for control and CtIP-depleted extracts treated with PflMI or etoposide. Shown are mean RPA intensities. Error bars represent SD; n = 3. (C) Chromatin-bound RPA70 was monitored in control (ΔMock) and CtIP-depleted extracts treated with etoposide or ICRF-193. a.u., arbitrary units.