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  • Title: Kinetics of O6-methylguanine repair in human normal and ataxia telangiectasia cell lines and correlation of repair capacity with cellular sensitivity to methylating agents.
    Author: Shiloh Y, Becker Y.
    Journal: Cancer Res; 1981 Dec; 41(12 Pt 1):5114-20. PubMed ID: 7307010.
    Abstract:
    Human lymphoblastoid cell lines from normal individuals and from patients with ataxia telangiectasia were either proficient or deficient in their ability to repair the mutagenic DNA adduct O6-methylguanine that is induced by methylating carcinogens. There was no relationship between the capacity to repair O6-methylguanine and the ataxia telangiectasia phenotype. Time-course studies done following a short pulse (2 min) of alkylation with 0.5 microgram of N-[3H]methyl-N'-nitro-N-nitrosguanidine per ml revealed that the repair of O6-methylguanine in human lymphoblastoid lines proficient in this ability is a rapid process, which proceeds with a half-life of 10 to 15 min. Lymphoblastoid lines with deficient capacity to repair this DNA adduct were hypersensitive to the cytotoxic effect of the methylating carcinogens N-methyl-N'-nitro-N-nitrosoguanidine, N-methyl-N-nitrosourea, and methyl methanesulfonate, and this hypersensitivity was correlated with the relative amount of O6-methylguanine induced by each of the three chemicals. This was taken as an indication of the lethality of unrepaired O6-methylgluanine. The extent of DNA repair synthesis induced by the three carcinogens was the same in cell lines proficient and deficient in O6-methylguanine repair, indicating no major deficiency in an excision repair pathway in the hypersensitive cell lines.
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