FIG 1.

Lesion removal does not necessarily correlate with the onset of replication recovery following oxidative stress. (A) [³H]thymidine was added to cultures for 2 min at the indicated times following either UV irradiation or H₂O₂ treatment at time zero. The rate of DNA synthesis (³H/2 min) relative to the amount incorporated immediately prior to exposure are plotted for wild-type cells exposed to mock treatment (open symbols), 50 J/m² UV (filled symbols), or 10 mM H₂O₂ (filled symbols). Graphs represent an average from at least two independent experiments. Error bars represent one standard error of the mean. (B) Wild-type cultures were either UV irradiated at 50 J/m² or treated with 10 mM H₂O₂ for 5 min. The survival of wild-type cultures after UV irradiation or oxidative challenge is plotted. Bar graphs represent the averages from three independent experiments. Error bars represent one standard error of the mean. (C) Wild-type cultures were either UV irradiated at 50 J/m² (top panel) or treated with 10 mM H₂O₂ for 5 min (bottom panel) and allowed to recover, and then genomic DNA was purified at the indicated times. For UV-irradiated samples, DNA was either treated with T4 endonuclease V (T4 Endo V) or no T4 Endo V for 1 h at 37°C and then analyzed on alkali agarose gels. For H₂O₂-treated samples, DNA was either treated with Fpg or no glycosylase for 1 h at 37°C and then analyzed on alkali agarose gels. A representative gel is shown for each treatment. Arrows indicate lesion-free DNA. (D) The fraction of lesion-free, high-molecular-weight (HMW) DNA in T4 Endo V-treated (top graph) or Fpg-treated (bottom graph) samples is plotted for each time point relative to mock-treated samples. Graphs represent the averages from at least two independent experiments. Error bars represent one standard error of the mean. (E) Cells were either exposed to 10 mM H₂O₂ for 5 min (filled symbols) or mock treated (open symbols) at time zero and then allowed to recover. At the indicated times, [³H]thymidine was added to cultures for 2 min. The amount of DNA synthesis/2 min (³H) is plotted. The graph represents an average from at least two independent experiments. Error bars represent one standard error of the mean.