Enzymatic repair of O-alkylated thymidine residues in DNA: involvement of a O4-methylthymine-DNA methyltransferase and a O2-methylthymine DNA glycosylase.
Alkylation of poly(dT) by N-[methyl-3H] (N-nitrosomethylurea) and subsequent annealing with poly(dA) yield a substrate containing O2 and O4-methylthymidine, 3-methylthymidine and phosphotriesters. In an in vitro assay using this substrate, cell extracts from Escherichia coli catalyse i) the transfer of the O4-methyl present in O4 methylthymidine to a protein which becomes alkylated; ii) the release of O2-methylthymine by a glycosylase activity. The two DNA repair activities described above appear to be involved in the adaptive response.
D000478:Alkylation; D002850:Chromatography, Gel; D004260:DNA Repair; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D008780:Methyltransferases / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D011067:Poly dA-dT / Q000378:metabolism; D013379:Substrate Specificity
D004269:DNA, Bacterial; D011067:Poly dA-dT; D008780:Methyltransferases; C040998:O(4)-methylthymine-DNA methyltransferase; D009699:N-Glycosyl Hydrolases; C040999:O(2)-methylthymine-DNA glycosidase