title: Detection of DNA single-strand breaks during the repair of UV damage in xeroderma pigmentosum cells.
abstract: In this investigation, xeroderma pigmentosum (XP) fibroblasts, XP12BE, were uv-irradiated and then incubated with cytosine arabinoside and hydroxyurea for 4 hr to inhibit the polymerase step of DNA excision repair. By alkaline elution, DNA single-strand breaks (SSB) were detected in XP cells with this regimen with an efficiency of 0.1-0.2 SSB per 10(9) daltons of DNA per J m-2. There was an approximately linear relation between the SSB frequency and uv dose over a range of 0.2 to 25 J m-2. This effect was approximately two orders of magnitude greater in excision-proficient normal human fibroblasts than in XP cells. These results support the conclusion that a low residual level of DNA excision repair occurs in XP group A cells and that the SSB generated during this repair can be accumulated with this polymerase inhibitor.
mesh_terms: D002478:Cells, Cultured; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000032:analysis / Q000528:radiation effects*; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors; D011740:Pyrimidine Dimers; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000378:metabolism*
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D011740:Pyrimidine Dimers; D003561:Cytarabine; D004247:DNA; D004259:DNA-Directed DNA Polymerase; D006918:Hydroxyurea