Figure 2.
Rad18 mutants are defective in DNA repair. (A) The indicated strains were grown to midlogarithmic phase and then irradiated with 450 Gy of ionizing radiation. Samples were taken at the indicated times (hours) and processed for pulse field gel electrophoresis. Unirradiated controls (U) were included and used as standards for the positions of the three chromosomes. (B) Wild-type cells (▪ and □) and rad18-X (● and ○) were synchronized by cdc25-22 block and release and then irradiated with 50 J/m2 UV-C (closed symbols) or mock irradiated (open symbols). Cultures were incubated at 25°C, and ethanol-fixed samples were taken at theindicated times for DAPI staining. The percentages of cells that had passed mitosis were assessed from each sample by fluorescence microscopy. (C) The indicated strains in the background of cdc25-22 were arrested in late G2 by incubation at 36°C for 3 h. Cells were then irradiated with 100 J/m2 UV-C (closed symbols) or mock irradiated (open symbols; time = 0) and were maintained at 36°C for 2 h after irradiation and then shifted to 25°C. Samples were assayed by DAPI staining, and normal mitoses (▪ and □) and aberrant mitoses (● and ○) as a percentage of total cells were counted from three samples of 100–150 cells per time point. Data represent the mean of these samples; SE ≤ 5%.