Structure of adduct X, the last unknown of the six major DNA adducts of mitomycin C formed in EMT6 mouse mammary tumor cells.
Treatment of EMT6 mouse mammary tumor cells with mitomycin C (MC) results in the formation of six major MC-DNA adducts. We identified the last unknown of these ("adduct X") as a guanine N(2) adduct of 2, 7-diaminomitosene (2,7-DAM), in which the mitosene is linked at its C-10 position to guanine N(2). The assigned structure is based on UV and mass spectra of adduct X isolated directly from the cells, as well as on its difference UV, second-derivative UV, and circular dichroism spectra, synthesis from [8-(3)H]deoxyguanosine, and observation of its heat stability. These tests were carried out using 17 microg of synthetic material altogether. The mechanism of formation of adduct X involves reductive metabolism of MC to 2,7-DAM, which undergoes a second round of reductive activation to alkylate DNA, yielding adduct X and another 2,7-DAM-guanine adduct (adduct Y), which is linked at guanine N7 to the mitosene. Adduct Y has been described previously. Adduct X is formed preferentially at GpC, while adduct Y favors the GpG sequence. In contrast to MC-DNA adducts, the 2,7-DAM-DNA adducts are not cytotoxic.
Palom
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Department of Chemistry, Hunter College, City University of New York, New York, New York 10021, USA.
Belcourt
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Musser
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Sartorelli
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Rockwell
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Tomasz
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D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000378:metabolism / Q000494:pharmacology*; D018736:DNA Adducts / Q000096:biosynthesis / Q000737:chemistry; D004249:DNA Damage / Q000187:drug effects; D004273:DNA, Neoplasm / Q000737:chemistry / Q000187:drug effects; D005260:Female; D015674:Mammary Neoplasms, Animal; D013058:Mass Spectrometry; D051379:Mice; D016685:Mitomycin / Q000378:metabolism / Q000494:pharmacology*; D015394:Molecular Structure; D014407:Tumor Cells, Cultured
D000903:Antibiotics, Antineoplastic; D003432:Cross-Linking Reagents; D018736:DNA Adducts; D004273:DNA, Neoplasm; D016685:Mitomycin