title: DNA polymerase function in repair synthesis in human fibroblasts.
abstract: We have analyzed DNA polymerase function in repair synthesis in human diploid fibroblasts. Previous studies from many laboratories have resulted in confusing and apparently contradictory findings; our studies suggest a unifying hypothesis and indicate that previous results may not actually be in conflict. Nongrowing (confluent) cells were damaged with N-methyl-N-nitrosourea (MNU), bleomycin, X-ray, UV radiation, or N-acetoxy-2-acetylaminofluorene (NA-AAF) over a wide range of doses, and repair synthesis was studied in the presence of one of three polymerase inhibitor, aphidicolin, dideoxythymidine triphosphate (ddTTP), or N-ethyl maleimide. We find that both polymerase alpha and a non-alpha polymerase, probably polymerase beta, are involved in repair synthesis. Furthermore, there is a dose dependence for polymerase function: at low doses of damage repair synthesis is mediated primarily by the non-alpha polymerase; as the amount of damage is increased, polymerase alpha participates to an increasing extent and at high levels of damage is responsible for approximately 50-80% of the repair synthesis. In a study in rapidly growing cells, repair synthesis following a high dose of UV was refractory to aphidicolin; these findings indicate that in growing and quiescent cells DNA polymerases may function differently in repair synthesis. All of the above results may be analyzed in terms of a simple model in which two repair synthesis systems, each involving one of the polymerases, compete to put repair patches into damaged DNA.
mesh_terms: D000099:Acetoxyacetylaminofluorene / Q000494:pharmacology; D016590:Aphidicolin; D001761:Bleomycin / Q000494:pharmacology; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D054306:Dideoxynucleotides; D004224:Diterpenes / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D008770:Methylnitrosourea / Q000494:pharmacology; D013942:Thymine Nucleotides / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D054306:Dideoxynucleotides; D004224:Diterpenes; D013942:Thymine Nucleotides; D001761:Bleomycin; D016590:Aphidicolin; D000099:Acetoxyacetylaminofluorene; D008770:Methylnitrosourea; D004259:DNA-Directed DNA Polymerase; C017216:2',3'-dideoxythymidine triphosphate; D005033:Ethylmaleimide