Dose-dependent increase in repair of 1-beta-D-arabinofuranosylcytosine-detectable DNA lesions in UV-treated xeroderma pigmentosum (group A) fibroblasts.
The extent of DNA-excision repair was determined in human fibroblast strains from clinically normal and xeroderma pigmentosum complementation group A (XP-A) donors after irradiation with 254-nm ultraviolet (UV) light. Repair was monitored by the use of 1-beta-D-arabinofuranosylcytosine (araC), a potent inhibitor of DNA synthesis, and alkaline sucrose velocity sedimentation to quantitate DNA single-strand breaks. In this approach, the number of araC-accumulated breaks in post-UV incubated cultures becomes a measure of the efficiency of a particular strain to perform long-patch excision repair. The maximal rate of removal of araC-detectable DNA lesions equalled approximately 1.8 sites/10(8) dalton/h in the normal strains (GM38, GM43), while it was more than 10-fold lower in both XP-A strains (XP4LO, XP12BE) examined. In normal fibroblasts the number of lesions removed during the first 4 h after irradiation saturated at approximately 10 J/m2. In contrast, the residual amount of repair in the excision-deficient cells increased as a linear function of UV fluence over a range 5-120 J/m2. Thus we conclude that the repair of araC-detectable UV photoproducts in XP group A fibroblasts is limited by availability of damaged regions in the genome to repair complexes.
Mirzayans
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R
Molecular Genetics and Carcinogenesis Laboratory, Cross Cancer Institute, Edmonton, Alb., Canada.
Paterson
M C
MC
D002499:Centrifugation, Density Gradient; D003561:Cytarabine / Q000494:pharmacology; D004247:DNA / Q000187:drug effects; D004260:DNA Repair / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D066298:In Vitro Techniques; D013997:Time Factors; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000235:genetics*
D003561:Cytarabine; D004247:DNA