Departments of Chemistry and Toxicology, University of Guelph , Guelph, Ontario, Canada N1G 2W1.
Chem Res Toxicol. 2013 Sep 16;26(9):1397-408. doi: 10.1021/tx400252g. Epub 2013 Aug 28.
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.
苯氧自由基可以共价结合到 2'-脱氧鸟苷 (dG) 的 C8 位，生成氧连接的联芳醚 C8-dG 加合物。为了评估双链 DNA 中 O 连接的 C8-dG 加合物的结构影响，将 C8-苯氧-G((PhO)G)和 C8-4-氟苯氧-G((4FPhO)G) 通过固相 DNA 合成掺入到 12 -mer NarI 识别序列 (5'-CTCGGCXCCATC，其中 X = G、(PhO)G 或 (4FPhO)G) 的 G(3)位置，其中 X = G、(PhO)G 或 (4FPhO)G)，使用 O 连接的 C8-dG 亚磷酰胺。修饰的链与六个不同的互补链杂交，包括与 C 的规则碱基配对[NarI'(C)]、与 G、A、T 的错配[NarI'(N)]和无碱基位点[NarI'(THF)]，以及一个 10 个碱基序列来模拟-2 缺失双链[NarI'(-2)]。使用紫外可见热融温度分析对所有双链结构进行了表征，在每种情况下，都发现 O 连接的 C8-苯氧-G 加合物使双链相对于未修饰的对照物不稳定。最稳定的双链结构与未修饰的对照物相比，与 C 和 G 错配的 O 连接的 C8-dG 加合物具有可比性。这些双链结构进一步使用圆二色性、动态(19)F 核磁共振实验和分子动力学模拟进行了表征。基于这些发现，(PhO)dG 与 C 形成 B 构象，苯氧基部分位于溶剂暴露的大沟中。然而，与 G 错配相反，(PhO)dG 采用“W 型”楔形构象，苯氧基位于小沟中。这些研究预测，O 连接的 C8-dG 损伤(PhO)G 将具有弱致突变效应，这与苯胺衍生的相应单环氮连接的 C8-dG 加合物相同。
