Fig. 3

UV-exposed cells experience reduced DNA damage levels in response to subsequent UV exposure. Immunoblotting was done to assess UV-induced CPD formation and repair kinetics. Suspended yeast cells were UV exposed, as described in Fig. 1, and following indicated incubation periods, DNA was isolated from culture aliquots. Equal amounts of DNA were slot blotted and probed with anti-thymine dimer antibodies. Images were then evaluated by densitometry. Assays were done a minimum of three times, with mean ± 1 SE reported for each condition (*p < 0.01). A. UV repair kinetics. Log-phase cultures were initially exposed to UV at 50 J/m² (+ UV), or mock exposed (−UV), followed by a 4 h incubation, and then a secondary UV exposure at 50 J/m². Samples were collected at the indicated timepoints for DNA isolation and analysis. −UV and + UV images shown are from the same blot using identical exposure conditions. B. Densitometry analysis of the experiments presented in A, reported as the percentage of remaining CPD levels relative to the amount of CPDs present immediately after the second exposure. C. CPD levels acquired in pre-exposed (+ UV) and unexposed controls (−UV) during secondary UV exposures. Cultures were initially exposed to 50 J/m², followed by a 4 h incubation, and then a secondary exposure at varying dosages (0–200 J/m²). Samples were collected immediately after the second exposure for DNA isolation and analysis. −UV and + UV images shown are from the same blot using identical exposure conditions. D. Densitometry analysis of the experiments presented in C, reported as CPD levels relative to the amount of CPDs present in the −UV/50 J/m² samples