Figure 4. USP3 is involved in regulating DDR to IR. (A) HeLa cells were transiently transfected with expressing constructs of either GFP-USP3 fusion or GFP control for 48 h, subjected to IR at a dose of 4 Gy, and fixed 2 h later. The cells were immunostained with BRCA1 antibody. Arrow marks a cell in which GFP-USP3 impairs the BRCA1 foci formation. (B) HeLa cells were transfected, exposed to IR and processed for immunofluorescent staining with 53BP1 antibody similarly to that described for Figure 4A.