Figure 4.

Increased cellular iron content correlates with lowered 25S and 18S rRNA stability during oxidative stress. A, whole-cell lysates prepared from equal cell numbers of the indicated yeast strains were analyzed by ICP-MS for levels of iron. Three replicates of each sample from independent isolates were analyzed. ***, P < 0.001; *, P < 0.05 (two-tailed two-sample unequal variance t test). B, indicated yeast cultures were grown overnight in YPDA at 30 °C, diluted with fresh medium to A₆₀₀ of ∼0.3, grown for an additional 4 h, and treated with 50 μm menadione for 2 h (+) or left untreated (−). RNA was isolated and analyzed by Northern hybridization with the indicated probes. A representative blot from three independent experimental repeats is shown. C, quantification of rRNAs stability in the experiment shown in B. K_RS determined as described in Fig. 3D for menadione-treated samples was normalized by the corresponding values in untreated samples for each strain **, P < 0.01; *, P < 0.05, (two-tailed two-sample unequal variance t test).