MITOSENE-DNA ADDUCTS - CHARACTERIZATION OF 2 MAJOR DNA MONOADDUCTS FORMED BY 1,10-BIS(ACETOXY)-7-METHOXYMITOSENE UPON REDUCTIVE ACTIVATION

Citation
M. Maliepaard et al., MITOSENE-DNA ADDUCTS - CHARACTERIZATION OF 2 MAJOR DNA MONOADDUCTS FORMED BY 1,10-BIS(ACETOXY)-7-METHOXYMITOSENE UPON REDUCTIVE ACTIVATION, Biochemistry, 36(30), 1997, pp. 9211-9220
Citations number
65
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
Journal title
ISSN journal
0006-2960
Volume
36
Issue
30
Year of publication
1997
Pages
9211 - 9220
Database
ISI
SICI code
0006-2960(1997)36:30<9211:MA-CO2>2.0.ZU;2-8
Abstract
Reductive activation of racemic 1,10-bis(acetoxy)-7-methoxymitosene WV 15 in the presence of DNA, followed by enzymatic digestion and HPLC an alysis, revealed the formation of various DNA adducts. Reduction is a necessary event for adduct formation to occur. This reductive activati on was performed under hypoxic conditions in various ways: (1) chemica lly, using a 2-fold excess of sodium dithionite (Na2S2O4), (2) enzymat ically using NADH-cytochrome c reductase, (3) electrochemically on a m ercury pool working electrode, and (4) catalytically, using a H-2/PtO2 system: Five different mitosene - DNA adducts were detected. These ad ducts were also present when poly(dG-dC) was used instead of DNA, but were absent with poly(dA-dT). All were shown to be adducts of guanine. Reduction of 1, 10-dihydroxymitosene WV14 in the presence of DNA did not result in detectable adduct formation, demonstrating the importanc e of good leaving groups for efficient adduct formation by these mitos enes. Finally, two of the adducts were isolated and their structures e lucidated, using mass spectrometry, H-1 NMR and circular dichroism (CD ). The structures were assigned as the diastereoisomers N-2-(1 ''-n-hy droxymitosen-10 ''-yl), 2'-deoxyguanosine (n = alpha or beta). These t ype of adducts, in which the mitosene C-10 is covalently bonded to the N-2 of a guanosylic group, are different from the well-known mitomyci n C 2'-deoxyguanosine monoadducts, that is linked via the mitomycin C C-l position, demonstrating that the order of reactivity of the C-l an d C-10 in these mitosenes is reversed, as compared to mitomycin C. The 7-methoxy substituent of WV15 is a likely factor causing this switch. Evidence is presented that the 7-substituent of mitosenes also influe nces their DNA alkylation site. Adducts 4 and 5 represent the first is olated and structurally characterized covalent adducts of DNA and a sy nthetic mitosene.