School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore.
J Am Chem Soc. 2011 Aug 3;133(30):11462-5. doi: 10.1021/ja204197d. Epub 2011 Jul 11.
Structural studies of human telomeric repeats represent an active field of research with potential applications toward the development of specific telomeric quadruplex-targeting drugs for anticancer treatment. To date, high-definition structures were limited to DNA sequences containing up to four GGGTTA repeats. Here we investigate the formation of G-quadruplexes in sequences spanning five to seven human telomeric repeats using NMR, UV, and CD spectroscopy. A (3+1) G-quadruplex with a long propeller loop was isolated from a five-repeat sequence utilizing a guanine-to-inosine substitution. A simple approach of selective site-specific labeling of guanine residues was devised to rigorously determine the folding topology of the oligonucleotide. The same scaffold could be extrapolated to six- and seven-repeat sequences. Our results suggest that long human telomeric sequences consisting of five or more GGGTTA repeats could adopt (3+1) G-quadruplex structures harboring one or more repeat(s) within a single loop. We report on the formation of a Watson-Crick duplex within the long propeller loop upon addition of the complementary strand, demonstrating that the long loop could serve as a new recognition motif.
人类端粒重复序列的结构研究是一个活跃的研究领域，有可能开发出针对癌症治疗的特定端粒四链体靶向药物。迄今为止，高清晰度结构仅限于包含多达四个 GGGTTA 重复的 DNA 序列。在这里，我们使用 NMR、UV 和 CD 光谱研究了跨越五个到七个人类端粒重复序列的 G-四链体的形成。通过鸟嘌呤到肌苷的取代，从五重复序列中分离出具有长推进器环的（3+1）G-四链体。设计了一种简单的选择性碱基特异性标记鸟嘌呤残基的方法，以严格确定寡核苷酸的折叠拓扑结构。相同的支架可以外推到六重复和七重复序列。我们的结果表明，由五个或更多 GGGTTA 重复组成的长人类端粒序列可以采用（3+1）G-四链体结构，在单个环内包含一个或多个重复。我们报告了在添加互补链时长推进器环内形成的沃森-克里克双链体，证明长环可以作为新的识别基序。
