Mechanobiology Institute, National University of Singapore , 117411, Singapore.
J Am Chem Soc. 2015 Feb 25;137(7):2424-7. doi: 10.1021/ja511680u. Epub 2015 Feb 13.
A DNA G-quadruplex (G4) formed at the oncogene c-MYC promoter region functions as a gene silencer. Due to its high stability at physiological K(+) concentrations, its thermodynamics and kinetic properties have not been characterized in physiological solution conditions. In this work, we investigated the unfolding and folding transitions of single c-MYC G4 and several of its truncated or point mutants at 100 mM KCl concentration under mechanical force. We found that the wild type could fold into multiple species, and the major specie has a slow unfolding rate of (1.4 ± 1.0) × 10(-6) s(-1). The force-dependent thermodynamics and kinetic properties of the major specie were obtained by studying a truncated mutant, Myc2345, that contains the G-tracts 2, 3, 4, and 5. As the c-MYC G4 is a prototype of many other intermolecular parallel-stranded G4's, our results provide important insights into the stability of a broad class of promoter G4's which also play a role in transcription regulation and are potential anticancer targets.
位于癌基因 c-MYC 启动子区域的 DNA G-四链体（G4）作为一种基因沉默子发挥作用。由于其在生理 K（+）浓度下具有很高的稳定性，因此其热力学和动力学特性尚未在生理溶液条件下得到表征。在这项工作中，我们在 100 mM KCl 浓度下，在机械力的作用下，研究了单个 c-MYC G4 及其几个截断或点突变体的展开和折叠转变。我们发现野生型可以折叠成多种物种，主要物种的展开速率较慢，为（1.4 ± 1.0）×10（-6）s（-1）。通过研究包含 G-片段 2、3、4 和 5 的截断突变体 Myc2345，获得了主要物种的力依赖性热力学和动力学特性。由于 c-MYC G4 是许多其他分子间平行链 G4 的原型，因此我们的结果为广泛的启动子 G4 稳定性提供了重要的见解，这些 G4 也在转录调控中发挥作用，并且是潜在的抗癌靶标。
