title: Repair of O6-alkylguanine lesions in DNA by chromatin enzymes.
abstract: Disappearance of 7-ethylguanine and O6-ethylguanine lesions from nuclear DNA is observed on incubation of isolated rat liver nuclei previously treated with ethylnitrosourea. Free 7-ethylguanine but no free O6-ethylguanine is released in the medium. Incubation of methylated or ethylated DNA with chromatin proteins leads to the disappearance of O6-methylguanine or O6-ethylguanine from DNA; the methyl group or the ethyl group is transferred to proteins where it is accepted by cystein residues. Repair of O6-methylguanine and repair of O6-ethylguanine lesions in DNA consume a common reactant which is likely the acceptor protein. The repair does not seem however to be a simple bimolecular reaction between the O6-alkylguanine and the cystein of the acceptor protein.
mesh_terms: D000478:Alkylation; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000187:drug effects / Q000201:enzymology*; D045647:DNA Glycosylases; D004260:DNA Repair; D005038:Ethylnitrosourea / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives*; D008099:Liver / Q000378:metabolism; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D009607:Nitrosourea Compounds / Q000494:pharmacology*; D051381:Rats
chemical_list: D002843:Chromatin; D009607:Nitrosourea Compounds; D006147:Guanine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D005038:Ethylnitrosourea