Stabilization of the G-quadruplex at the VEGF IRES represses cap-independent translation
Stabilization of the G-quadruplex at the VEGF IRES represses cap-independent translation
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DOI：
10.1080/15476286.2015.1017236
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发表时间：
2015-03-01
期刊：
影响因子：
4.1
通讯作者：
Millevoi, Stefania
中科院分区：
文献类型：
--
作者：
Cammas, Anne;Dubrac, Alexandre;Millevoi, Stefania
翻译的激活有助于恶性转化，是癌症治疗的一个新兴靶点。RNAG-四链结构是帽依赖的mRNA翻译的一般抑制物，最近被证明是癌蛋白翻译激活的靶点。然而，相反，人血管内皮生长因子A(VEGF)5‘非编码区的G-四链被证明是IRES介导的翻译所必需的。由于血管内皮生长因子在肿瘤血管生成中起关键作用，也是抗肿瘤治疗的主要靶点，我们研究了血管内皮生长因子G-四联体的结构/功能关系，并确定了它是否具有治疗潜力。我们发现，在应激条件下，血管内皮生长因子IRES中的G-四链对于帽非依赖性的功能和激活是必不可少的。然而，通过增加G-伸展长度或用NRAS取代G-伸展长度来稳定VEGFG-四链会导致强烈抑制IRES介导的VEGF四聚体的翻译。我们还证明了G-四链配体在体外稳定了血管内皮生长因子G-四链并抑制了帽非依赖性翻译。重要的是，在高度选择性稳定的G-四链配体存在的情况下，与多聚体相关的人血管内皮生长因子mRNA的数量减少，导致血管内皮生长因子蛋白表达减少。总之，我们的结果揭示了功能沉默的G-四链结构的存在，这些结构容易转化为帽非依赖的mRNA翻译的有效抑制物。这些发现对G-四链靶向化合物的体内应用和抗血管生成治疗具有重要意义。
The activation of translation contributes to malignant transformation and is an emerging target for cancer therapies. RNA G-quadruplex structures are general inhibitors of cap-dependent mRNA translation and were recently shown to be targeted for oncoprotein translational activation. In contrast however, the G-quadruplex within the 5'UTR of the human vascular endothelial growth factor A (VEGF) has been shown to be essential for IRES-mediated translation. Since VEGF has a pivotal role in tumor angiogenesis and is a major target of anti-tumoral therapies, we investigated the structure/function relationship of the VEGF G-quadruplex and defined whether it could have a therapeutic potential. We found that the G-quadruplex within the VEGF IRES is dispensable for cap-independent function and activation in stress conditions. However, stabilization of the VEGF G-quadruplex by increasing the G-stretches length or by replacing it with the one of NRAS results in strong inhibition of IRES-mediated translation of VEGF. We also demonstrate that G-quadruplex ligands stabilize the VEGF G-quadruplex and inhibit cap-independent translation in vitro. Importantly, the amount of human VEGF mRNA associated with polysomes decreases in the presence of a highly selective stabilizing G-quadruplex ligand, resulting in reduced VEGF protein expression. Together, our results uncover the existence of functionally silent G-quadruplex structures that are susceptible to conversion into efficient repressors of cap-independent mRNA translation. These findings have implications for the in vivo applications of G-quadruplex-targeting compounds and for anti-angiogenic therapies.