Figure 7.

XPF–ERCC1-dependent γH2AX enhancement by ABT-888 in non-replicating cells. U2OS cells were transfected with XPF siRNAs or control siRNAs (Neg siRNA). Two days later, the cells were labeled with EdU and treated with CPT (1 µM) for 30 min in the absence or presence of ABT-888 (0.5 µM). Cells were fixed and stained for immunofluorescence assays. (A) Representative confocal microscopy images (red signal: EdU; green signal: γH2AX; blue signal: DAPI to stain nuclei); bar = 8 µm. (B) Quantitation of γH2AX signals in individual cells (represented as scattered dots) from one representative experiment; Mean values ± SEM are shown as red lines. Numbers above each cluster indicate the number of cells counted. Standard t-tests were used for statistical analyses of the data from the representative experiment, **P < 0.01; NS, no significant difference. (C) XPF-dependent effect of ABT-888 in non-replicating (EdU negative) cells. Percentages of γH2AX-positive cells were scored based on drug treatment and XPF knockdown. The number of γH2AX positive cells and total number of cells scored in each group are indicated above each bar.