人端粒DNA和其他很多富鳥嘌呤（G）序列能形成一類稱作鳥嘌呤－四重折疊（G-quadruplex）的DNA四重折疊高級結構,。這種結構與很多生物學過程、治療癌癥以及分子機器有關,。折疊平衡常數(shù)Kf是衡量G－四重折疊形成能力的定量描述,。生理條件下的G－四重折疊結構不是獨立存在，而是伴有旁側結構或與蛋白結合,。然而現(xiàn)有的Kf測定方法只能用于核心序列,。動物所譚錚研究組建立了一個測定Kf的等溫差異雜交方法，不僅能用于核心序列,，同時適用于伴有旁側結構或結合蛋白存在的情況這一方法將為了解生理條件下G－四重折疊形成提供一個有用的工具,。
該項研究得到了國家科技部和國家自然科學基金的資助。（生物谷Bioon.com）
生物谷推薦原文出處：
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.
