In vitro DNA repair synthesis assay. Repair mediated by the extract prepared from the repair-proficient HeLa cell line was monitored using unmodified pBR322 plasmid and pUC19 plasmid, unmodified or modified at rb = 0.03 with cisplatin, 1 or 2. A. Results of a typical experiment. Top panel, autoradiogram of the gel showing the incorporation of [α-32P]dCTP; bottom panel, a photograph of the EtBr stained gel. Lanes: cisplatin, unmodified pBR322 plus pUC19 modified with cisplatin; 1, unmodified pBR322 plus pUC19 modified with 1, 2, unmodified pBR322 plus pUC19 modified with 2. (B) Incorporation of [α-32P]dCTP into unmodified or platinated pUC19 plasmid. For all quantifications representing the mean values of three separate experiments, incorporation of radioactive material is corrected for the relative DNA content in each band. The radioactivity associated with incorporation of [α-32P]dCTP into DNA modified with cisplatin was arbitrarily set to 100%. Values shown in the graph are the means (±SEM) of three separate experiments, each conducted in quadruplicate.