Bugaut Anthony, Balasubramanian Shankar
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
Biochemistry. 2008 Jan 15;47(2):689-97. doi: 10.1021/bi701873c. Epub 2007 Dec 20.
G-Rich sequences found within biologically important regions of the genome have been shown to form intramolecular G-quadruplexes with varied loop lengths and sequences. Many of these quadruplexes will be distinguishable from each other on the basis of their thermodynamic stabilities and folded conformations. It has been proposed that loop lengths can strongly influence the topology and stability of intramolecular G-quadruplexes. Previous studies have been limited to the analysis of quadruplex sequences with particular loop sequences, making it difficult to make generalizations. Here, we describe an original study that aimed to elucidate the effect of loop length on the biophysical properties of G-quadruplexes in a sequence-independent context. We employed UV melting and circular dichroism spectroscopy to examine and compare the properties of 21 DNA quadruplex libraries, each comprising partially randomized loop sequences with lengths ranging from one to three nucleotides. Our work supports a number of general predictions that can be made solely on the basis of loop lengths. In particular, the results emphasize the strong influence of single-nucleotide loops on quadruplex properties. This study provides a predictive framework that may help identify or classify biologically relevant G-quadruplex-forming sequences.
在基因组的生物学重要区域发现的富含鸟嘌呤（G）的序列已被证明能形成具有不同环长度和序列的分子内G-四链体。这些四链体中的许多将根据其热力学稳定性和折叠构象彼此区分开来。有人提出，环长度可强烈影响分子内G-四链体的拓扑结构和稳定性。先前的研究仅限于对具有特定环序列的四链体序列进行分析，因此难以得出一般性结论。在此，我们描述了一项原创性研究，旨在阐明在不依赖序列的情况下环长度对G-四链体生物物理性质的影响。我们采用紫外熔解和圆二色光谱来检测和比较21个DNA四链体文库的性质，每个文库都包含长度从一到三个核苷酸的部分随机化环序列。我们的工作支持了一些仅基于环长度就能做出的一般性预测。特别是，结果强调了单核苷酸环对四链体性质的强烈影响。这项研究提供了一个预测框架，可能有助于识别或分类与生物学相关的G-四链体形成序列。
