Human Telomere G-Quadruplexes with Five Repeats Accommodate 8-Oxo-7,8-dihydroguanine by Looping out the DNA Damage.
Human Telomere G-Quadruplexes with Five Repeats Accommodate 8-Oxo-7,8-dihydroguanine by Looping out the DNA Damage.
复制标题
DOI：
10.1021/acschembio.5b00844
复制
发表时间：
2016-02-19
影响因子：
4
通讯作者：
Burrows CJ
中科院分区：
文献类型：
--
作者：
An N;Fleming AM;Burrows CJ
炎症和氧化应激产生自由基，将DNA中的鸟嘌呤(G)氧化为8-氧-7,8-二氢鸟嘌呤（OG），该反应在富含G的端粒序列中表现突出。在端粒中，OG不能通过允许其浓度增加的修复途径有效地去除，令人惊讶的是，它对稳定性没有任何直接的负面影响。在此，OG在人类端粒序列（TTAGGG）n的5个重复序列中合成，位于代表氧化热点的5 ' -most，中间和3 ' -most G轨道的5 ' -G上。这些合成的低聚物以相应数量的K+/Na+折叠，形成杂化的g -四重折叠。采用圆二色性、热熔融、1H-NMR和α-溶血素纳米孔单分子谱分析了OG的结构影响。在这些结果的基础上，通过环出受损的G轨道，使其他四个轨道采用混合G四重体，OG在五重复序列中被很好地容纳。这些结果与之前对四重复端粒序列中OG的研究相反，这些研究发现OG高度不稳定并导致显著的折叠重新定向。当对人类端粒序列进行更广泛的观察并考虑额外的重复时，我们发现OG对结构的影响最小。这种重复序列的可塑性解决了OG浓度如何在端粒中增加而不会立即端粒不稳定或磨损。
Inflammation and oxidative stress generate free radicals that oxidize guanine (G) in DNA to 8-oxo-7,8-dihydroguanine (OG), and this reaction is prominent in the G-rich telomere sequence. In telomeres, OG is not efficiently removed by repair pathways allowing its concentration to build, surprisingly without any immediate negative consequences to stability. Herein, OG was synthesized in five repeats of the human-telomere sequence (TTAGGG)n, at the 5′-G of the 5′-most, middle, and 3′-most G tracks, representing hotspots for oxidation. These synthetic oligomers were folded in relevant amounts of K+/Na+ to adopt hybrid G-quadruplex folds. The structural impact of OG was assayed by circular dichroism, thermal melting, 1H-NMR, and single-molecule profiling by the α-hemolysin nanopore. On the basis of these results, OG was well accommodated in the five-repeat sequences by looping out the damaged G track to allow the other four tracks to adopt a hybrid G-quadruplex. These results run counter to previous studies with OG in four-repeat telomere sequences that found OG to be highly destabilizing and causing significant reorientation of the fold. When taking a wider view of the human telomere sequence and considering additional repeats, we found OG to cause minimal impact on the structure. The plasticity of this repeat sequence addresses how OG concentrations can increase in telomeres without immediate telomere instability or attrition.