Unscheduled DNA synthesis in cultured ataxia telangiectasia fibroblast-like cells.

The capacity of cultured fibroblast-like cells from 5 ataxia telangiectasia (AT) patients to repair gamma-ray-induced damage formed in DNA under aerobic conditions was measured by unscheduled DNA synthesis (UDS). The AT cultures exhibited generally reduced UDS compared to the normal cultures for gamma-ray doses of 4--12 kR. Reduced UDS in the AT cultures was observed for repair-incubation periods at which UDS was not saturated (0.5 and 1 h), and for periods characterized by maximal amounts of UDS in both the normal and AT cultures (2 and 4 h). The results suggest a class of lesions repairable in the normal cells by UDS within 1 h may persist in the AT cells for 4 h or longer.