Ataxia-telangiectasia cells are not uniformly deficient in poly(ADP-ribose) synthesis following X-irradiation.

The synthesis of poly(adenosine diphosphoribose) [poly(ADR-R)] follows the DNA strand breakage produced by a number of physical and chemical agents, including X-radiation, and may be important for repair of several types of DNA damage. The reduction or abolition of its synthesis following X-irradiation might explain the enhanced sensitivity of ataxia-telangiectasia (A-T) cells to X-ray. We have examined 8 lines of human fibroblasts (including 4 A-T lines) for stimulation of the synthesis of poly(ADP-R) by X-irradiation. Similar amounts of X-ray-stimulated synthesis of poly(ADP-R) were detected in 4 lines of A-T fibroblasts, and in fibroblasts from a xeroderma pigmentosum (XP) patient, a Fanconi's anemia (FA) patient and 2 normal patients. 6 lines of human lymphoblastoid lines were also examined for X-ray-stimulated poly(ADP-R) synthesis. 4 A-T lines displayed an unusually high synthesis of poly(ADP-R) in unirradiated cells compared with 2 normal lines. Despite this complication, some but not all, of the A-T lymphoblastoid lines did synthesize poly(ADP-R) following X-irradiation similarly to the normal lines. Thus, deficient poly(ADP-R) synthesis following X-irradiation is not likely to explain the enhanced sensitivity of all A-T cells to this DNA-breaking agent.