FIGURE 4.

Loss of RAP80 causes an increase in DSB resection in S/G₂ phase of the cell cycle. A, cells were irradiated with 10 grays and fixed after 3 h. Cells were stained for RPA and CENPF to demonstrate CENPF cell cycle specificity. B, cells stably expressing hairpins to luciferase or RAP80 were irradiated and stained for RPA and CENPF 30 min and 3 h later. Cells treated with RAP80 shRNA showed an increase in RPA focus formation in CENPF (S/G₂)-positive cells. Error bars, S.E. of three independent experiments. p values were calculated in comparison with control siRNA-treated cells. C, cells expressing the indicated shRNAs were irradiated and subsequently fixed at 30 min, 3 h, or 6 h after DNA damage. Cells were stained for RPA and CENPF. Cells containing RPA foci were scored for CENPF positivity. D, HCC1937 cells, expressing a truncated BRCA1 protein that does not interact with RAP80 or accumulate at DSBs, were treated with control or RAP80 siRNA and analyzed for RPA focus formation after ionizing radiation. Loss of RAP80 resulted in an increase in RPA focus formation in BRCA1-mutated cells. Error bars, S.E. from two independent experiments. p values were calculated in comparison with control siRNA-treated cells.