m1A甲基转移酶TRMT6在肝癌中调控Wnt通路的分子机制研究

Emerging evidence indicates that epigenetics plays a vital role in mediating hepatocarcinogenesis. However, canonical epigenetics mainly focuses on DNA and histone level, and it is largely known how RNA participates in epigenetics. RNA methylation is a novel form of epigenetics. By highthrough-put screening, we found that m1A methyltransferase TRMT6 was highly expressed in liver cancer tissues and hepatoma cells, which was mediated by transcription factor MYC. Based on in vitro studies, we found that TRMT6 promoted liver cancer cell proliferation and migration. Subsequent studies found that TRMT6 can bind to LRP5 mRNA and mediate its m1A methylation. Silence of TRMT6 reduced the mRNA level of LRP5 and impaired the protein level and transcriptional activity of its downstream target β-catenin. Thus, we proposed that MYC/TRMT6/LRP5 axis was essential for the modulation of liver cancer cell growth. We plan to use cell and animal model, combined with clinical samples, to characterize the clinical importance of TRMT6. And we also plan to elucidate how MYC/TRMT6/LRP5 axis mediates liver cancer cell proliferation, which sheds light on developing novel therapeutic target for Hepatocellular carcinoma.

不断涌现的证据表明表观遗传学在肝癌发生过程中起着重要作用。然而传统表观遗传学多停留在DNA和组蛋白的层面，RNA层面所知甚少。RNA甲基化是表观遗传学的新形式。通过高通量的筛选，我们发现m1A甲基转移酶TRMT6在肝癌组织和肝癌细胞中显著高表达，而转录因子MYC会激活TRMT6的转录。细胞实验发现TRMT6促进肝癌细胞的增殖与爬行。随后实验发现TRMT6能结合LRP5 mRNA和介导其m1A修饰。沉默TRMT6后，LRP5 mRNA表达下调。作为LRP5下游靶蛋白，沉默TRMT6后，β-catenin蛋白表达及转录活性都出现下降。因此我们提出，MYC/TRMT6/LRP5信号轴在调控肝癌细胞生长中起着重要作用。本项目拟通过细胞及动物实验，结合临床样本，明确TRMT6在肝癌中的临床意义。同时阐述MYC/TRMT6/LRP5信号轴调控肝癌细胞生长的分子机制，为开发新分子药物靶点提供理论依据。

研究发现肝癌常常出现异常表观遗传学修饰，如DNA甲基化修饰、组蛋白乙酰化修饰等。以往表观遗传学研究过去多聚焦于DNA或者蛋白质，在RNA层面少见报道。RNA甲基化是表观遗传学的新形式。我们发现m1A甲基转移酶TRMT6在肝癌组织和肝癌细胞中显著高表达。细胞实验发现TRMT6促进肝癌细胞的增殖与爬行。随后实验发现TRMT6能结合LMO7 mRNA和介导其m1A修饰。沉默TRMT6后，LMO7 mRNA表达上调。LMO7可以促进STING泛素化修饰从而活化STING/TBK1/IRF3信号轴，最终刺激诱导I型干扰素的生成。沉默TRMT6后会活化STING/TBK1/IRF3信号轴，最终导致I型干扰素的生成，从而抑制肝癌细胞生长。本项目通过细胞及动物实验，结合临床样本，明确了TRMT6在肝癌中的临床意义。同时阐述TRMT6/LMO7/STING信号轴调控肝癌细胞生长的分子机制，为开发新分子药物靶点提供理论依据。