FIGURE 6.

DNA2, WRN, and BLM act in the same pathway of DSB end resection. A, frequency of camptothecin-induced RPA foci in nuclei of U2OS cells depleted of the indicated proteins. Cells were transfected with appropriate siRNAs and, 48 h later, treated with 1 μm camptothecin for 1 h. Cells were then detergent-extracted and fixed with formaldehyde. RPA and γ-H2AX (a marker of DNA damage) were visualized by indirect immunofluorescence. DAPI was used to stain nuclei. The average number of RPA foci per γ-H2AX-positive cell was determined for each sample using an Olympus Scan̂R screening station. The data points are mean ± S.D. (n = 3). B, Western blot analysis of extracts from U2OS cells transfected with indicated siRNAs. Blots were probed with the antibodies indicated on the right.