Complementation of the DNA-repair defect in a CHO mutant by human DNA that lacks highly abundant repetitive sequences.
Recently, two human DNA-repair genes have been cloned which complement the defects in complementation groups 1 and 2 of the CHO mutants which are sensitive to ultraviolet light and deficient in the incision step of excision repair. Here we report human gene transfer-mediated complementation of a group 4 CHO mutant sensitive to ultraviolet light and mitomycin C (MMC). The transfectants generated by transfecting human DNA into the repair-deficient cell line demonstrate the repair-proficient phenotype, as they have wild-type levels of resistance to UV light and MMC and are competent in performing the incision step of excision repair in response to UV irradiation. 3 of the 8 transfectants isolated display no detectable human repetitive sequences, while the other 5 contain varying amounts of human repetitive DNA. As the evidence suggests that all of the transfectants are repair-proficient as a result of the uptake of human DNA, we conclude that the human gene that complements the repair defect in group 4 CHO mutants contains no highly abundant human repetitive sequences. This imposes the necessity of developing cloning strategies involving the identification of sequences that flank the gene.
D000818:Animals; D006224:Cricetinae; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair; D005816:Genetic Complementation Test; D006801:Humans; D016685:Mitomycin; D008937:Mitomycins / Q000494:pharmacology; D012091:Repetitive Sequences, Nucleic Acid; D014162:Transfection; D014466:Ultraviolet Rays
D008937:Mitomycins; D016685:Mitomycin; D004247:DNA