Figure 3. Overexpression of USP3 abrogates the recruitment of repair factors BRCA1 and 53BP1. (A) HeLa cells were transiently transfected with either GFP-USP3 fusion or GFP control construct for 48 h, exposed to 10 J/m2 UV, and fixed 2 h later. Cells were then immunostained with BRCA1 antibody. Arrow marks a cell in which GFP-USP3 impairs the BRCA1 foci formation. Calibration bar is 10 μm. (B) The graph depicts a series of representative experiments in which at least 100 cells from three microscopic fields were scored. The error bars indicate the standard deviation. *Indicates P value 0.05 on Student t test. (C) HeLa cells treated as described in Figure 3A but immunostained with 53BP1 antibody. Arrow marks a cell in which GFP-USP3 impairs the 53BP1 foci formation. Calibration bar is 10 μm. (D) The graph depicts quantitative analysis of data in Figure 3C. *Indicates P value 0.05 on Student t test.