Correction of alkylation hypersensitivity of CHO-W27-1 cells by transfection with human DNA

Abstract

Chinese hamster cells of the mutant strain W27-1 which is hypersensitive to UV and monofunctional alkylating agents were transfected with human DNA ligated to the bacterial xanthine-guanine phosphoribosyltransferase (gpt) gene. Selection was performed for resistance to mycophenolic acid and finally for survival after treatment with high doses of methyl methanesulfonate. A gpt⁺ transfectant was generated (T38-2-7) which acquired resistance to methyl methanesulfonate and cross-resistance to N-methyl-N′ -nitro-N-nitrosoguanidine at levels comparable with the parental (wild-type) strain CHO-9. T38-2-7 cells were not more resistant, however, to UV, mitomycin C and N-hydroxyethyl-N-chloroethylnitrosourea than the mutant W27-1. The transfectant contains integrated human DNA and was shown to be deficient for the O⁶ methyltransferase. The results indicate that the transfected DNA specifically complemented the defect underlying alkylation hypersensitivity of W27-1 cells or that a gene was transfected which is generally inactive in CHO cells and which causes alkylation resistance.