Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
PLoS One. 2012;7(2):e31201. doi: 10.1371/journal.pone.0031201. Epub 2012 Feb 21.
It has been reported that binding of STAT3 protein to the 5'-flanking region of the relaxin gene may result in downregulation of the relaxin expression. There is a Guanine(G)-rich segment located in about 3.8 Kb upstream of the relaxin gene and very close to the STAT3's binding site. In our study, NMR spectroscopy revealed the formation of G-quadruplex by this G-rich strand, and the result was confirmed by ESI mass spectrometry and CD spectroscopy. The theoretical structure of RLX G-quadruplex was constructed and refined by molecular modeling. When this relaxin G-quadruplex was stabilized by berberine(ΔTm = 10°C), a natural alkaloid from a Chinese herb, the gene expression could be up-regulated in a dose-dependent manner which was proved by luciferase assay. This result is different from the general G-quadruplex function that inhibiting the telomere replication or down-regulating many oncogenes expression. Therefore, our study reported a novel G-quadruplex in the relaxin gene and complemented the regulation mechanism about gene expression by G-quadruplexes.
据报道，STAT3 蛋白与松弛素基因 5'-侧翼区的结合可能导致松弛素表达的下调。在松弛素基因上游约 3.8kb 处有一个富含鸟嘌呤（G）的片段，非常靠近 STAT3 的结合位点。在我们的研究中，NMR 光谱显示该富含 G 的链形成了 G-四链体，ESI 质谱和 CD 光谱的结果证实了这一点。通过分子建模构建并优化了 RLX G-四链体的理论结构。当这种松弛素 G-四链体被小檗碱（ΔTm=10°C）稳定时，一种来自中国草药的天然生物碱，可以以剂量依赖的方式上调基因表达，这一点通过荧光素酶检测得到了证实。这一结果与 G-四链体抑制端粒复制或下调许多致癌基因表达的一般功能不同。因此，我们的研究报道了松弛素基因中的一种新型 G-四链体，并补充了 G-四链体对基因表达的调控机制。
