ABSENCE OF UV-INDUCED NONHOMOLOGOUS RECOMBINATION IN REPAIR-DEFICIENTCHO CELL-LINES TRANSFECTED WITH ERCC GENES

The nucleotide excision repair pathway removes a broad spectrum of DNA lesions, including W-induced damage. To ascertain whether the repair of the latter has a causative role in the enhancement of non-homologou s recombination, Chinese hamster CHO cell lines proficient and deficie nt in the ability to repair W-induced damage were transfected with a p lasmid containing the bacterial neo(R) gene, Following W-treatment an enhancement of non-homologous recombination above the spontaneous leve l was observed in repair-proficient cells, whereas no increase was obs erved in repair-deficient cell lines, Hence, the latter were transfect ed with the corresponding excision repair cross complementing human ge nes and the resulting repair-proficient transfectants were tested for UV-induced non-homologous recombination, In both untreated and UV-trea ted transfectants, the frequencies of the event were not significantly different. Cumulatively, the results suggest that non-homologous reco mbination induced by UV-irradiation is not restored by the correction of the excision repair defect.