Evidence that covalent complex formation between BCNU-treated oligonucleotides and E. coli alkyltransferases requires the O6- alkylguanine function

Abstract

Chloroethylnitrosoureas (CENUs) are thought to induce cytotoxic DNA interstrand cross-links via an initial reaction at O6-position of guanine, yielding a rearranged intermediate, O6,N1-ethanoguanine. Repair of these adducts by mammalian and bacterial DNA alkyltransferases blocks the formation of cross-links. Human alkyltransferase can form a covalent complex with DNA containing BCNU-induced cross-link precursors, but the nature of the DNA-protein linkage remains unknown. Using E. coli alkyltransferases expressed by the ada and ogt genes, we now demonstrate that both enzymes can form such complexes with CENU-treated DNA. We attribute this reaction to the O6-alkylguanine repair function, because an N-terminal fragment of the ada protein, which has only alkylphosphotriester repair activity, failed to form a similar complex. This result is consistent with the idea that complex formation requires an alkyltransferase reaction with a guanine adduct, such as O6,N1-ethanoguanine. It tends to exclude the possibility that such reactions simply involve alkylation of the enzyme by reactive DNA adducts such as chloroethylphosphate or chloroethylguanine.

DOI: 10.1093/nar/18.13.3961

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@article{Gonzaga1990EvidenceTC, title={Evidence that covalent complex formation between BCNU-treated oligonucleotides and E. coli alkyltransferases requires the O6- alkylguanine function}, author={P. E. Gonzaga and L. Harris and G. P. Margison and T. P. Brent}, journal={Nucleic acids research}, year={1990}, volume={18 13}, pages={3961-6} }