Fig. 1. Normal rates of DNA single-strand break repair in ARH3-defective cells.

a ARH3 and XRCC1 protein levels in the indicated U2OS (left) and patient-derived fibroblasts (right) were measured by western blotting. b XRCC1 chromatin binding measured by indirect immunofluorescence in detergent pre-extracted control and patient fibroblasts before, immediately after 10 min treatment with 150 μM H₂O₂ on ice, and after 60 min release in H₂O₂-free medium. Representative ScanR images (right) and quantification using ScanR software (left) are shown. Statistical analysis (two-tailed t-test) is indicated (ns not significant). c Similar experiment to (b); wild-type and ARH3^−/− U2OS cells were treated for 10 min or not with 2 mM H₂O₂ on ice, followed by a repair period of 40 min or 120 min in H₂O₂-free medium. Data are as in panel b and both are the mean ± SEM of three biologically independent experiments. Statistical analysis (two-way analysis of variance) is indicated. The samples are not significantly different (ns). d DNA strand breakage quantified by alkaline comet assays in the indicated control and patient fibroblasts before, immediately after treatment with 50 μM H₂O₂ on ice, and after the indicated repair periods in H₂O₂-free medium. e Similar experiment to d; wild-type, ARH3^−/−, and XRCC1^−/− U2OS cells were treated with 100 μM H₂O₂ followed by a repair period of 15, 30, and 60 min in H₂O₂-free medium. f Alkaline comet tail moments in wild-type, ARH3^−/− and XRCC1^−/− U2OS cells before and after 20 min treatment with indicated doses of MMS. g Alkaline comet tail moments in wild-type, ARH3^−/− and XRCC1^−/− U2OS cells before and after 45 min treatment with 10 μM CPT. Data for d, e, f, and g are comet tail moments of 300 cells examined over three independent experiments (100 cells each), horizontal bars show the average. The only significantly different sample in each dataset is XRCC1^−/− U2OS (two-way analysis of variance). Representative pictures are shown in Supplementary Fig. 2.