Immunological detection of O6-methylguanine in alkylated DNA

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Abstract
Antibodies to O6-methyldeoxyguanosine were produced in rabbits and utilized in a radioimmunoassay to detect this nucleoside at picomole levels. The specificity of the antibodies was demonstrated by the use of nucleoside analogs as inhibitors in the radioimmunoassay. The antibodies cross-reacted with O6-methylguanosine, O6-methylguanine and O6-ethylguanosine. There was 104-106 times less sensitivity to inhibition by deoxyadenosine, deoxyguanosine and guanosine than by O6-methyldeoxyguanosine. The radioimmunoassay also detected O6-methylguanine in DNA alkylated by agents known to produce O6-methylguanine, such as N''-methyl-N-nitrosourea. DNA alkylated with dimethyl sulfate, which does not produce O6-methylguanine, cross-reacted with the antibodies to a limited extent. Such an assay system for modified nucleic acid components would be useful in following the production, persistence and repair of these lesions in a variety of cells and tissues treated with a broad spectrum of carcinogens and suspected carcinogens.