Characterization of a hybrid hamster-human cell line complemented for the ataxia telangiectasia DNA repair defects

The fibroblast cell line AT5BIVA, from ataxia telangiectasia complementation group D, was transfected with a neo gene providing G418 resistance for subsequent selections. The G418 resistant cell line was fused with gamma-irradiated Chinese hamster ovary cells and a radioresistant hybrid, atxbc, was isolated following an X-ray selection procedure. All the cellular defects characteristic of ataxia telangiectasia were corrected to some degree; atxbc cells: (i) were confirmed to be resistant to X-rays; (ii) had regained control over DNA synthesis after DNA damage, and (iii) could overcome the radiation-induced block in the G2 phase of the cell cycle. Repetitive element polymerase chain reaction amplification of integrated hamster DNA from primers to middle repetitive elements confirmed the presence of hamster-specific sequences, suggesting that the phenotype of the cells had been corrected by integration of a normal hamster gene rather than by a reversion event.