人端粒DNA和其他很多富鸟嘌呤（G）序列能形成一类称作鸟嘌呤－四重折叠（G-quadruplex）的DNA四重折叠高级结构。这种结构与很多生物学过程、治疗癌症以及分子机器有关。折叠平衡常数Kf是衡量G－四重折叠形成能力的定量描述。生理条件下的G－四重折叠结构不是独立存在，而是伴有旁侧结构或与蛋白结合。然而现有的Kf测定方法只能用于核心序列。动物所谭铮研究组建立了一个测定Kf的等温差异杂交方法，不仅能用于核心序列，同时适用于伴有旁侧结构或结合蛋白存在的情况这一方法将为了解生理条件下G－四重折叠形成提供一个有用的工具。
该项研究得到了国家科技部和国家自然科学基金的资助。（生物谷Bioon.com）
生物谷推荐原文出处：
Anal. Chem., 2010, 82 (22), pp 9469–9475 DOI: 10.1021/ac102168m
Folding Equilibrium Constants of Telomere G-Quadruplexes in Free State or Associated with Proteins Determined by Isothermal Differential Hybridization
Quan Wang, Li Ma, Yu-hua Hao, and Zheng Tan*
Guanine rich (G-rich) nucleic acids form G-quadruplex structures that are implicated in many biological processes, pharmaceutical applications, and molecular machinery. The folding equilibrium constant (KF) of the G-quadruplex not only determines its stability and competition against duplex formation in genomic DNA but also defines its recognition by proteins and drugs and technical specifications. The KF is most conveniently derived from thermal melting analysis that has so far yielded extremely diversified results for the human telomere G-quadruplex. Melting analysis cannot be used for nucleic acids associated with proteins, thus has difficulty to study how protein association affects the folding equilibrium of G-quadruplex structure. In this work, we established an isothermal differential hybridization (IDH) method that is able to determine the KF of G-quadruplex, either alone or associated with proteins. Using this method, we studied the folding equilibrium of the core sequence G3(T2AG3)3 from vertebrate telomere in K+ and Na+ solutions and how it is affected by proteins associated at its adjacent regions. Our results show that the KF obtained for the free G-quadruplex is within 1 order of magnitude of most of those obtained by melting analysis and protein binding beside a G-quadruplex can dramatically destabilize the G-quadruplex.
