title: Endonucleolytic activity for gamma-irradiated DNA in normal and ataxia telangiectasia fibroblast cell extracts.
abstract: The increased sensitivity of ataxia telangiectasia cells towards ionizing radiation may be related to their inability to incise DNA near sites of radiation-induced base damages. When compared to 3 unaffected controls, crude extracts from 5 lines of fibroblast cells derived from ataxia telangiectasia patients were capable of incising gamma-irradiated DNA to the same extent as normal cells as determined in a nicking assay, using the circular replicative form of phiX174. However, the types of alterations introduced into DNA by gamma-irradiation could be distinguished from sites of base loss due to depurination or depyrimidination and from sites of base modification by OsO4. The specific endonuclease involved was demonstrated to be distinct from the apurinic endonuclease by its rate of temperature inactivation.
mesh_terms: D001260:Ataxia Telangiectasia / Q000201:enzymology / Q000235:genetics*; D002460:Cell Line; D002474:Cell-Free System; D004260:DNA Repair / Q000528:radiation effects*; D004261:DNA Replication / Q000528:radiation effects*; D004720:Endonucleases / Q000378:metabolism*; D005720:Gamma Rays; D006801:Humans
chemical_list: D004720:Endonucleases