title: Differences in replicon behavior between X-irradiation-sensitive L5178Y mouse lymphoma cells and A-T fibroblasts using DNA fiber autoradiography.
abstract: Replicon behavior in radiosensitive Ataxia telangiectasia (A-T) fibroblasts and mouse lymphoma L5178Y (LS) cells was studied by DNA fiber autoradiography. LS cells, irradiated at 13 Gy, showed a similar reduction in rate of DNA chain growth and initiation of replicons as did resistant (LR) cells. A progressive increase in the intensity of [3H]TdR labeling of many replicons was observed after irradiation in the LS cells, but not in LR cells. This indicated a reduced or absent endogenous dTTP supply after irradiation in the LS cells, implicating a defect in nucleoside precursor production. Irradiated normal human and A-T cells did not show this effect. After 2 Gy, the frequency of initiation of replicons into synthesis was temporarily reduced in the normal human but not in the A-T cells. After 20 Gy, the rate of DNA chain growth was preferentially reduced in the normal human cells, but an increase was observed in the A-T cells. This increased rate could be explained in terms of a normal supply of complexes involved in chain elongation being distributed over a reduced number of initiated replicon clusters in the A-T cells.
mesh_terms: D000818:Animals; D001260:Ataxia Telangiectasia / Q000378:metabolism*; D001345:Autoradiography; D002460:Cell Line; D004247:DNA / Q000032:analysis / Q000378:metabolism / Q000528:radiation effects*; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D007940:Leukemia L5178 / Q000378:metabolism*; D007942:Leukemia, Experimental / Q000378:metabolism*; D051379:Mice; D012093:Replicon / Q000528:radiation effects*; D013997:Time Factors; D014965:X-Rays
chemical_list: D004247:DNA