An attempt to transfer radiation resistance to an ataxia-telangiectasia cell line

Fibroblasts from ataxia-telangiectasia (AT) are hypersensitive to the lethal effects of ionizing radiation. Genomic DNA from normal human cells was transfected together with the selectable bacterial marker, gpt, on plasmid pSV2 into an SV40-transformed AT line, AT5BIVA. One radiation resistant clone (67) was recovered following repeated cycles of gamma-irradiation from a population of 90,000 clones. The normal level of radiation resistance has been maintained for at least 11 months in the absence of further selection by radiation. The resistant clone is not a contaminant as determined by isoenzyme analysis, carries one copy of the gpt gene, and its DNA synthesis is inhibited after radiation to an extent intermediate between that of AT and normal cells. It is not yet established whether clone 67 is a bona fide transformant or arose as a consequence of mutation of the parent AT line.