3-Aminobenzamide does not affect radiation-induced inhibition of DNA synthesis in human cells

3-Aminobenzamide (3AB), a potent inhibitor of poly(ADP-ribose) synthesis, does not affect the dose response for ionizing radiation-induced inhibition of DNA synthesis in human fibroblasts. If the radioresistant DNA synthesis observed in fibroblasts from patients with ataxia-telangiectasia (A-T) were due to reduced poly(ADP-ribose) synthesis after irradiation, as has been proposed, the response in normal cells incubated with 3AB would have been similar to that observed in A-T cells. Therefore, altered poly(ADP-ribose) synthesis in A-T cells is not solely responsible for their radioresistant DNA synthesis.