High-resolution three-dimensional NMR structure of the KRAS proto-oncogene promoter reveals key features of a G-quadruplex involved in transcriptional regulation
High-resolution three-dimensional NMR structure of the KRAS proto-oncogene promoter reveals key features of a G-quadruplex involved in transcriptional regulation
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DOI：
10.1074/jbc.m117.781906
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发表时间：
2017-05-12
影响因子：
4.8
通讯作者：
Salgado, Gilmar F.
中科院分区：
文献类型：
--
作者：
Kerkour, Abdelaziz;Marquevielle, Julien;Salgado, Gilmar F.
富含鸟嘌呤的DNA和RNA序列中的非正则碱基配对可以产生G-四联体，它们的堆积导致G-四联体(G4)的形成。在人类基因组中，G4S可以与典型的双链DNA共存，并被认为可以抑制基因转录，因此对疾病相关基因启动子区域的G4S的研究受到了极大的关注。例如，人的KRAS原癌基因包含一个位于主要转录起始点上游的核酸酶敏感元件。KRAS核酸酶超敏元件(NHE)区域包含一个富含G的元件(22RT；5‘-AGGGCGGTGTGGGAATAGG-GAA-3’)，并包含一个与Myc相关的锌指结合位点，调节KRAS的转录。因此，NEH区域被提议作为控制KRAS转录的新药的靶点，这需要对NHE结构的详细了解。在这项研究中，我们报告了KRAS NHE中富G元素的高分辨率核磁共振结构。我们发现，富含G的元素形成了一个平行的结构，三个G-四元组由一个四核苷酸环连接，两个短的单核苷酸双链反转环连接。此外，在G8和G9之间还发现了胸腺嘧啶的膨胀。不同长度的环和G-四元组之间存在的凸起是潜在的结构元件，可以被小的化学配体靶向，进一步稳定结构，干扰或阻止转录调控因子，如Myc相关的锌指，访问它们在KRAS启动子上的结合部位。总之，我们的工作为开发能够抑制KRAS表达的抗癌药物提供了一条可能的新途径。
Non-canonical base pairing within guanine-rich DNA and RNAsequences can produce G-quartets, whose stacking leads to the formation of a G-quadruplex (G4). G4s can coexist with canonical duplex DNA in the human genome and have been suggested to suppress gene transcription, and much attention has therefore focused on studying G4s in promotor regions of disease-related genes. For example, the human KRAS proto-oncogene contains a nuclease-hypersensitive element located upstream of the major transcription start site. The KRAS nuclease-hypersensitive element (NHE) region contains a G-rich element (22RT; 5'-AGGGCGGTGTGGGAATAGG-GAA-3') and encompasses a Myc-associated zinc finger-binding site that regulates KRAS transcription. The NEH region therefore has been proposed as a target for new drugs that control KRAS transcription, which requires detailed knowledge of the NHE structure. In this study, we report a high-resolution NMR structure of the G-rich element within the KRAS NHE. We found that the G-rich element forms a parallel structure with three G-quartets connected by a four-nucleotide loop and two short one-nucleotide double-chain reversal loops. In addition, a thymine bulge is found between G8 and G9. The loops of different lengths and the presence of a bulge between the G-quartets are structural elements that potentially can be targeted by small chemical ligands that would further stabilize the structure and interfere or block transcriptional regulators such as Myc-associated zinc finger from accessing their binding sites on the KRAS promoter. In conclusion, our work suggests a possible new route for the development of anticancer agents that could suppress KRAS expression.