YTHDF2正向调控OCT4 mRNA 5'-UTR端的m6A修饰并促进肝癌进展的分子机制研究

OCT4 is an important pluripotency factor, which promote hepatocellular carcinoma progression. RNA m6A methylation is shown to play a critical role in regulating gene expression. We demonstrated mRNA m6A methylation within 3’-UTR region regulated mRNA stability in cancer cells. However, recent studies indicated mRNA m6A methylation within 5’-UTR region promoted protein translation, which was dependent on an m6A reader, YTHDF2. In further experiment, we established YTHDF2 knockout liver cancer cells and found that decreased stem cell phenotype was seen in YTHDF2 knockout liver cancer cells, as well as decreased OCT4 protein level instead of OCT4 mRNA level. We hypothesize YTHDF2 positively induced OCT4 mRNA m6A methylation within 5’-UTR region, which enhances OCT4 protein translation and leads to hepatocellular carcinoma progression. In the current project, we will explore the role of YTHDF2-OCT4 pathway in hepatocellular carcinoma progression by knocking out and overexpressing YTHDF2-OCT4 pathway, respectively. And we will also explore the molecular mechanism by which YTHDF2 regulate OCT4 mRNA m6A methylation within 5’-UTR region. This project will clarify the molecular mechanism by which YTHDF2 promote hepatocellular carcinoma progression and will offer new therapeutic target for treating hepatocellular carcinoma.

OCT4是促进肝癌进展的多能干性因子。RNA m6A修饰具有调控基因表达的重要作用。我们在前期研究中证实肿瘤细胞中mRNA 3’-UTR 的m6A能调控mRNA的稳定性。最新研究表明mRNA 5'-UTR的m6A能促进蛋白的翻译，这一过程依赖于m6A识别蛋白YTHDF2的活性。我们进一步发现YTHDF2基因敲除肝癌细胞的干性减弱，且OCT4蛋白水平降低，但mRNA水平不变，提示YTHDF2可能在转录后水平调控OCT4的表达。由此我们推测YTHDF2能通过调控OCT4 mRNA 5'-UTR端的m6A修饰，增强OCT4蛋白的翻译并促进肝癌的进展。本课题中，我们拟通过基因敲除和过表达YTHDF2-OCT4通路的方法证实其在肝癌进展中的作用，并探讨YTHDF2调控OCT4 mRNA 5'-UTR端m6A修饰的分子机制。本课题将阐明YTHDF2促进肝癌进展的分子机制，为肝癌的治疗提供新靶点。

OCT4是调控肝癌干细胞自我更新的重要靶点。m6A修饰在RNA中的不同功能与其修饰的位点相关。在本研究中，我们发现：YTHDF2基因敲除肝癌细胞的干性减弱，且OCT4蛋白水平降低，但mRNA水平不变，证实YTHDF2可能在转录后水平调控OCT4的表达。此外，在分子机制上，我们证实YTHDF2能通过调控OCT4 mRNA 5'-UTR端的m6A修饰，增强OCT4蛋白的翻译并促进肝癌干细胞的自我更新。最后，我们在动物实验和人肝癌组织标本上证实YTHDF2-OCT4通过促进肝癌干细胞的表型和肝癌在肺部的转移。本研究为肝癌的治疗提供了新靶点。