Translesion Synthesis Polymerases in the Prevention and Promotion of Carcinogenesis
Figure 2
Frequency of 6-thioguanine-resistant () clones as a function of survival after UV irradiation. Cells were plated on three 150-mm-diameter dishes at a density of to determine mutant frequency or at cloning density to determine survival. After attachment, plates were irradiated with UV fluences to yield 20%–40% survival. The actual survival in the mutagenesis experiments was determined by refeeding the survival plates at one week and staining with crystal violet after two weeks. Percent survival for each UV fluence was corrected for replating and plotted on the x-axis. The corresponding mutant frequency at each survival is plotted on the -axis. Each point represents the mean of three independent dishes at the indicated survival, . Mutant frequency at the Hprt locus is defined as the number of clones per million clonable cells. Each data point represents independent experiments in which surviving cells were selected after UV irradiation and an 8- to 9-day expression period. The data have been corrected for cloning efficiency on the day of selection, and the spontaneous background mutant frequency () has been subtracted. The arrows indicate the reduction in mutant frequency when Polι is disrupted in the -deficient background (larger arrow) and in the Pol η-proficient background (smaller arrow). Reproduced with permission from Dumstorf et al. [60].
