School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, PR China.
Biochem Biophys Res Commun. 2010 Nov 26;402(4):614-8. doi: 10.1016/j.bbrc.2010.10.065. Epub 2010 Oct 29.
Mg(2+) is one of the most important cations in cells, affecting the structures and functions of the proteins and nucleic acids. It should be noted that Mg(2+) is indispensable in DNA transcription, where G-quadruplex is believed to be actively involved. Therefore, it is important to investigate the influence of Mg(2+) on G-quadruplex. Here we studied the effect of Mg(2+) on G-quadruplex DNA with CD, FRET, EMSA, and PCR-stop assay. We found that various G-quadruplexes could be differentiated through simultaneous addition of both K(+) and Mg(2+), which could be used for selective identification of G-quadruplexes in promoter oncogene but not in telomere. Mg(2+) at physiological relevant concentration not only greatly enhanced the thermostability of oncogene G-quadruplexes but also efficiently protected them from unfolding by their complementary strands, which revealed the great impact of Mg(2+) on the equilibrium between promoter G-quadruplex and duplex DNA. The PCR-stop assay further confirmed that Mg(2+) could affect gene transcription by stabilizing promoter G-quadruplex. The above studies were carried out for various G-quadruplexes of varying sequences in promoter oncogenes and telomeric region. Our results suggest that Mg(2+) may be a key regulator for G-quadruplexes of oncogene promoter, which can subsequently affect the expression of related genes.
镁（Mg2+）是细胞中最重要的阳离子之一，影响蛋白质和核酸的结构和功能。值得注意的是，Mg2+在 DNA 转录中是不可或缺的，人们认为 G-四链体在其中积极参与。因此，研究 Mg2+对 G-四链体的影响非常重要。在这里，我们使用 CD、FRET、EMSA 和 PCR-停止测定法研究了 Mg2+对 G-四链体 DNA 的影响。我们发现，通过同时添加 K+和 Mg2+，可以区分各种 G-四链体，这可用于选择性识别启动子致癌基因中的 G-四链体，而不是端粒中的 G-四链体。生理相关浓度的 Mg2+不仅极大地增强了致癌基因 G-四链体的热稳定性，而且有效地保护它们免受互补链的展开，这揭示了 Mg2+对启动子 G-四链体和双链 DNA 之间平衡的巨大影响。PCR-停止测定法进一步证实，Mg2+可以通过稳定启动子 G-四链体来影响基因转录。上述研究是针对启动子致癌基因和端粒区中不同序列的各种 G-四链体进行的。我们的研究结果表明，Mg2+可能是致癌基因启动子 G-四链体的关键调节剂，随后可能会影响相关基因的表达。
