Figure 4.

Enhanced sensitivity of human cells transformed with mutant hRAD18 to various DNA-damaging agents. (A) Intracellular localization of wild-type and mutant hRad18. Plasmids containing hRAD18 cDNA were microinjected into the nuclei of mouse p53^−/− primary fibroblasts. The cells were cultured for 2 h. Localization of overexpressed hRad18 protein was visualized by the indirect immunostaining method by using polyclonal rabbit serum against hRad18. From left to right, wild-type hRad18, hRad18(C28F), hRad18(C28F) 1 h after UV irradiation (15 J/m²), and hRad18(C207F). (B) Sensitivity of Mori-SV-stable transformants with mutant hRAD18 cDNA to various DNA-damaging agents. Cells were irradiated with UV (Left), or treated with mitomycin C (Center) or methyl methanesulfonate (Right) for 1 h, and sensitivity was determined by the colony-formation assay. Mean values of triplicate dishes are shown with standard deviations. (C) Sensitivity of Saos2 stable transformants to different DNA-damaging agents. Saos2 antisense is a stable transformant with pcDNA3 containing hRAD18 cDNA in the opposite direction.