title: Structural influence of C8-phenoxy-guanine in the NarI recognition DNA sequence.
abstract: Phenoxyl radicals can covalently attach to the C8 site of 2'-deoxyguanosine (dG) to generate oxygen-linked biaryl ether C8-dG adducts. To assess the structural impact of an O-linked C8-dG adduct in duplex DNA, C8-phenoxy-G ((PhO)G) and C8-4-fluorophenoxy-G ((4FPhO)G) were incorporated into the G(3) position of the 12-mer NarI recognition sequence (5'-CTCGGCXCCATC, where X = G, (PhO)G, or (4FPhO)G) using solid-phase DNA synthesis with O-linked C8-dG phosphoramidites. The modified strands were hybridized to six different complementary strands that include regular base pairing to C [NarI'(C)], mismatches with G, A, T [NarI'(N)], and an abasic site [NarI'(THF)], and a 10-mer sequence to model a -2 deletion duplex [NarI'(-2)]. All duplex structures were characterized using UV-vis thermal melting temperature analysis, and in each instance, the O-linked C8-phenoxy-G adducts were found to destabilize the duplex relative to the unmodified controls. The most stable duplex structures match the O-linked C8-dG adduct against C and a G mismatch, which are comparable in terms of stability. These duplexes were further characterized using circular dichroism, dynamic (19)F nuclear magnetic resonance experiments, and molecular dynamics simulations. On the basis of these findings, (PhO)dG adopts the B conformation opposite C, with the phenoxy moiety residing in the solvent-exposed major groove. However, opposite the G mismatch, (PhO)dG adopts a "W-type" wedge conformation with the phenoxy group residing in the minor groove. These studies predict that the O-linked C8-dG lesion (PhO)G will have a weak mutagenic effect, as determined for the corresponding single-ringed nitrogen-linked C8-dG adduct derived from aniline.
authors.affiliation: Departments of Chemistry and Toxicology, University of Guelph , Guelph, Ontario, Canada N1G 2W1.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kuska
authors.forename: Aaron A
authors.initials: AA
authors.lastname: Witham
authors.forename: Michael
authors.initials: M
authors.lastname: Sproviero
authors.forename: Richard A
authors.initials: RA
authors.lastname: Manderville
authors.forename: Mohadeseh
authors.initials: M
authors.lastname: Majdi Yazdi
authors.forename: Purshotam
authors.initials: P
authors.lastname: Sharma
authors.forename: Stacey D
authors.initials: SD
authors.lastname: Wetmore
mesh_terms: D000595:Amino Acid Sequence; D020137:Base Pair Mismatch; D004247:DNA / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D004262:DNA Restriction Enzymes / Q000378:metabolism*; D003849:Deoxyguanosine / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D010636:Phenols; C042329:phenoxy radical; D004247:DNA; D004262:DNA Restriction Enzymes; D003849:Deoxyguanosine