Mutagenic effect and mutation spectrum induced by 3H decay in the 8th position of DNA purine bases in Saccharomyces cerevisiae

Lethal and mutagenic effects and the mutation spectrum induced by 3H decay in the 8th position of adenine and guanine in yeast DNA have been studied. For haploid cells labelled with 8-3H]deoxyadenosinemonophosphate (8-3H-A) and 8-3H]deoxyguanosinemonophosphate (8-3H-G), the lethal efficiencies were determined as (3.0 +/- 0.8) X 10(-3) decay-1 and (3.8 +/- 0.6) X 10(-3) decay-1, respectively, and the mutagenic efficiencies as (5.7 +/- 1.1) X 10(-8) decay-1 and (8.7 +/- 1.4) X 10(-8) decay-1, respectively. The lethal effect of 8-3H]purines may be explained as being due to internal beta-irradiation. In contrast, the local effect of 3H-transmutation was twice as mutagenic as beta-irradiation when the induction of forward gene mutations was examined. Within the spectrum of mutations induced by 8-3H-G, a preference for GC----AT transitions was observed.