NMR STRUCTURAL STUDIES OF THE IONIZING-RADIATION ADDUCT 7-HYDRO-8-OXODEOXYGUANOSINE (8-OXO-7H-DG) OPPOSITE DEOXYADENOSINE IN A DNA DUPLEX - 8-OXO-7H-DG(SYN).DA(ANTI) ALIGNMENT AT LESION SITE
NMR STRUCTURAL STUDIES OF THE IONIZING-RADIATION ADDUCT 7-HYDRO-8-OXODEOXYGUANOSINE (8-OXO-7H-DG) OPPOSITE DEOXYADENOSINE IN A DNA DUPLEX - 8-OXO-7H-DG(SYN).DA(ANTI) ALIGNMENT AT LESION SITE
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DOI：
10.1021/bi00219a034
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发表时间：
1991-02-05
期刊：
影响因子：
2.9
通讯作者：
PATEL, DJ
中科院分区：
文献类型：
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作者：
KOUCHAKDJIAN, M;BODEPUDI, V;PATEL, DJ
质子核磁共振研究报道了互补d（C1-C2-A3-C4-T5-A6-oxo-G7-T8-C9-A10-C11-C12）。d（G13-G14-T15-G16-A17-A18-T19-A20-G21-T22-G23-G-24）十二核苷双相（编号8-oxo-7H-dG）。dA 12-mer)，它含有位于中心位置的7-氢-8-氧-脱氧鸟苷（8-氧- 7h - dg）残基，这一基团通常存在于暴露于电离辐射或氧化自由基的DNA中。从核磁共振光谱可以推断，这部分存在作为两个互变异构体，或产生两个DNA构象，是在平衡和缓慢交换。本研究的重点是源于8-氧- 7h - dg的6,8-二氧互变异构体的平衡的主要组成部分。我们在8-oxo-7H-dG的8-oxo-7H-dG7的Watson-Crick和Hoogstgeen边指定了可交换的NH1， NH7和NH2-2碱基质子。dA - 12双聚体，利用分析水溶液中的一维和二维核Overhauser增强（NOE）数据。由8-oxo-7H-dG7的NH7质子与dA18的H-2和NH2-6质子产生的NOEs建立了8-oxo-7H-dG7（syn）。8-oxo-7H-dG中病变部位的dA18（抗）对准。溶液中的dA - 12双聚体。通过对8-oxo- 7h - dg的NOESY光谱分析，进一步表征了8-oxo- 7h - dg的这种定位，将8-oxo基团置于次要凹槽中。D2O溶液中的dA - 12双聚体。我们能够在d（A6-oxo-G7-T8）中相邻残基上的质子（可交换和不可交换）之间检测到一组链内和链间的NOEs。d（A17-A18-T19）三核苷酸片段围绕oxo-dG7（syn）堆叠的病变部位为中心。稳定的沃森-克里克dA6之间的dA（抗）对。dT19和dT8。A17碱基对与最小扰动的螺旋。因此，8-氧- 7h - dg的两条链。dA 12-mer双相在病变部位及其附近呈右手构象，未修饰的碱基呈抗糖苷扭转角，碱基堆叠成螺旋状。中心d（A6-oxo-G7-T8）的能量最小化构象。d（A17-A18-T19）片段要求8-oxo-7H-dG7（syn）。8-oxo-7H-dG7（syn）的NH7和O6分别与dA18（anti）的N1和NH2-6形成两个氢键，稳定了dA18（anti）的定位。8-oxo-7H-dG的Hoogsteen边形成的氢键与8-oxo-7H-dG的NH7质子（氢键）向下移动12.57 ppm和8-oxo-7H-dG（同步）的NH1质子（非氢键）向上移动10.54 ppm相一致。12聚双相。我们的结构研究表明，8-oxo-7H-dG（syn）。dA（抗）在螺旋内部形成一个稳定的对，为当读取发生在这个氧化核苷碱基上时观察到的与8-oxo-7H-dG相反的dA的结合提供了基础。
Proton NMR studies are reported on the complementary d(C1-C2-A3-C4-T5-A6-oxo-G7-T8-C9-A10-C11-C12).d(G13-G14-T15-G16-A17-A18-T19-A20-G21-T22-G23-G-24) dodecanucleotide duplex (designated 8-oxo-7H-dG.dA 12-mer), which contains a centrally located 7-hydro-8-oxodeoxyguanosine (8-oxo-7H-dG) residue, a group commonly found in DNA that has been exposed to ionizing radiation or oxidizing free radicals. From the NMR spectra it can be deduced that this moiety exists as tow tautomers, or gives rise to two DNA conformations, that are in equilibrium and that exchange slowly. The present study focuses on the major component of the equilibrium that originates in the 6,8-dioxo tautomer of 8-oxo-7H-dG. We have assigned the exchangeable NH1, NH7, and NH2-2 base protons located on the Watson-Crick and Hoogstgeen edges of 8-oxo-7H-dG7 in the 8-oxo-7H-dG.dA 12-mer duplex, using an analysis of one- and two-dimensional nuclear Overhauser enhancement (NOE) data in H2O solution. The observed NOEs derived from the NH7 proton of 8-oxo-7H-dG7 to the H-2 and NH2-6 protons of dA18 establish an 8-oxo-7H-dG7(syn).dA18(anti) alignment at the lesion site in the 8-oxo-7H-dG.dA 12-mer duplex in solution. This alignment, which places the 8-oxo group in the minor groove, was further characterized by an analysis of the NOESY spectrum of the 8-oxo-7H-dG.dA 12-mer duplex in D2O solution. We were able to detect a set of intra- and interstrand NOEs between protons (exchangeable and nonexchangeable) on adjacent residues in the d(A6-oxo-G7-T8).d(A17-A18-T19) trinucleotide segment centered about the lesion site that establishes stacking of the oxo-dG7(syn).dA(anti) pair between stable Watson-Crick dA6.dT19 and dT8.A17 base pairs with minimal perturbation of the helix. Thus, both strands of the 8-oxo-7H-dG.dA 12-mer duplex adopt right-handed conformations at and adjacent to the lesion site, the unmodified bases adopt anti glycosidic torsion angles, and the bases are stacked into the helix. The energy-minimized conformation of the central d(A6-oxo-G7-T8).d(A17-A18-T19) segment requires that the 8-oxo-7H-dG7(syn).dA18(anti) alignment be stabilized by two hydrogen bonds from NH7 and O6 of 8-oxo-7H-dG7(syn) to N1 and NH2-6 of dA18(anti), respectievly, at the lesion site. The proposed hydrogen-bond formation involving the Hoogsteen edge of 8-oxo-7H-dG is consistent with the 12.57 ppm downfield shift of the NH7 proton (hydrogen-bonded) and the 10.54 ppm upfield shift of the NH1 proton (not hydrogen-bonded) of 8-oxo-7H-dG(syn) in the 8-oxo-7H-dG.dA 12-mer duplex. Our structural studies demonstrate that 8-oxo-7H-dG(syn).dA(anti) forms a stable pair in the interior of the helix, providing a basis for the observed incorporation of dA opposite 8-oxo-7H-dG when readthrough occurs past this oxidized nucleoside base.