Structure of an oligodeoxynucleotide containing a butadiene oxide-derived N1 beta-hydroxyalkyl deoxyinosine adduct in the human N-ras codon 61 sequence.
The solution structure of the N1-(1-hydroxy-3-buten-2(S)-yl)-2'-deoxyinosine adduct arising from the alkylation of adenine N1 by butadiene epoxide (BDO), followed by deamination to deoxyinosine, was determined, in the oligodeoxynucleotide d(CGGACXAGAAG).d(CTTCTCGTCCG). This oligodeoxynucleotide contained the BDO adduct at the second position of codon 61 of the human N-ras protooncogene, and was named the ras61 S-N1-BDO-(61,2) adduct. (1)H NMR revealed a weak C(5) H1' to X(6) H8 NOE, followed by an intense X(6) H8 to X(6) H1' NOE. Simultaneously, the X(6) H8 to X(6) H3' NOE was weak. The resonance arising from the T(17) imino proton was not observed. (1)H NOEs between the butadiene moiety and the DNA positioned the adduct in the major groove. Structural refinement based upon a total of 364 NOE-derived distance restraints yielded a structure in which the modified deoxyinosine was in the high syn conformation about the glycosyl bond, and T(17), the complementary nucleotide, was stacked into the helix, but not hydrogen bonded with the adducted inosine. The refined structure provided a plausible hypothesis as to why this N1 deoxyinosine adduct strongly coded for the incorporation of dCTP during trans lesion DNA replication, both in Escherichia coli [Rodriguez, D. A., Kowalczyk, A., Ward, J. B. J., Harris, C. M., Harris, T. M., and Lloyd, R. S. (2001) Environ. Mol. Mutagen. 38, 292-296], and in mammalian cells [Kanuri, M., Nechev, L. N., Tamura, P. J., Harris, C. M., Harris, T. M., and Lloyd, R. S. (2002) Chem. Res. Toxicol. 15, 1572-1580]. Rotation of the N1 deoxyinosine adduct into the high syn conformation may facilitate incorporation of dCTP via Hoogsteen-type templating with deoxyinosine, thus generating A-to-G mutations.
Scholdberg
Tandace A
TA
Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, USA.
Merritt
W Keither
WK
Dean
Stephen M
SM
Kowalcyzk
Agnieska
A
Harris
Constance M
CM
Harris
Thomas M
TM
Rizzo
Carmelo J
CJ
Lloyd
R Stephen
RS
Stone
Michael P
MP
D000477:Alkylating Agents / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D002070:Butadienes / Q000737:chemistry* / Q000378:metabolism; D003062:Codon / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D018736:DNA Adducts / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004852:Epoxy Compounds / Q000737:chemistry* / Q000378:metabolism; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D007288:Inosine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011522:Protons; D013816:Thermodynamics
D000477:Alkylating Agents; D002070:Butadienes; D003062:Codon; D018736:DNA Adducts; D004852:Epoxy Compounds; D009838:Oligodeoxyribonucleotides; D011522:Protons; C024370:3,4-epoxy-1-butene; D007288:Inosine; C012271:deoxyinosine; C031763:1,3-butadiene