title: Evidence that O6-alkylguanine-DNA alkyltransferase becomes covalently bound to DNA containing 1,3-bis(2-chloroethyl)-1-nitrosourea-induced precursors of interstrand cross-links.
abstract: The reaction of partially purified human O6-alkylguanine-DNA alkyltransferase with 1,3-bis(2-chloroethyl)-1-nitrosourea-treated DNA resulted in formation of a DNA-protein covalent complex. Complex formation required active alkyltransferase and brief treatment of DNA with the drug. DNA lost its capacity to form the complex once drug-induced DNA interstrand cross-links were completely formed. These results are consistent with a model in which the transferase catalyzes cleavage at O6-guanine and transfer of the alkyl moiety in a putative O6, N1-ethanoguanine intermediate of cross-link formation. DNA-protein complex formation presumably results when the transferase accepts the N1-ethanoguanine-DNA structure, analogous to its acceptance of simple alkyl groups.
mesh_terms: D002330:Carmustine / Q000494:pharmacology*; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism*; D019853:O(6)-Methylguanine-DNA Methyltransferase
chemical_list: D003432:Cross-Linking Reagents; D004247:DNA; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D002330:Carmustine