Oxidative stress and genomic instability. (A and B) Overexpression of SOD1 or SOD2 extends life span and reduces genomic stability associated with gis1Δ mutants. *, P < 0.05; **, P < 0.01; compared with gis1Δ, two-tailed t test at the indicated time points (n = 4). (C) mRNA levels of REV1 in wild-type (WT; DBY746), gis1Δ, and gis1Δ cells overexpressing either SOD1 or SOD2. mRNA extracted from 3-d-old cells was subjected to quantitative real-time PCR analysis. **, P < 0.01; mutant versus WT (n = 12, ANOVA test, Tukey's test). Error bars indicate ±SEM.