RNA m6A甲基转移酶METTL3和METTL14促进鼻咽癌进展及机制

Epigenetic alterations immensely contributed to human carcinogenesis. Recent studies have shown that RNA methylation, especially the N6-methyladenosine (m6A) on eukaryotic mRNA, is very important to the regulation of mRNA stability, splicing, and translation. Our data suggest that METTL3 and METTL14, major RNA N6-adenosine methyltransferase, were significantly up-regulated in human nasopharyngeal carcinoma (NPC) cell lines and tissues. Functionally, we proved that knockdown of endogenic METTL3 or METTL14 drastically reduced cell proliferation, colony formation, migration and sphere formation of NPC cells in vitro. In mechanism study, we found that METTL3 or METTL14 has a special interaction and colocalization with polycomb group protein BMI1 in cell nuclear. The m6A sequence data showed that the mRNA of BMI1 had m6A modification in NPC cells, knock down of endogenic METTL3 induced low expression of BMI1. Thus we propose RNA N6-methyladenosine methyltransferases METTL3 and METTL14 promote nasopharyngeal carcinoma progression by N6-methyladenosine modification which required BMI1 interaction. This project is set out to apply m6A-seq, plus in vitro and in vivo models alone with clinical specimen, in order to further understand the molecular mechanisms of METTL3 and METTL14 in contributingthe to progression of nasopharyngeal carcinoma. The accomplishment of this project could provide a new molecular target for the prevention and treatment of nasopharyngeal carcinoma.

表观遗传改变在肿瘤发生发展过程中起着非常重要的作用，最近研究表明RNA甲基化，尤其是N6甲基腺嘌呤（m6A）甲基化，对于mRNA的稳定性、剪接和翻译都起着关键的调节作用。我们发现m6A甲基转移酶METTL3和METTL14在鼻咽癌细胞株和组织中高表达；在鼻咽癌细胞中敲低内源性M3或者M14，明显抑制细胞增殖、克隆形成、侵袭转移和球囊形成等肿瘤干细胞特性。机制研究发现M3和M14与多梳蛋白BMI1存在特异的相互作用；测序结果显示BMI1 mRNA存在m6A甲基化修饰，敲低内源性METTL3导致BMI1表达下调。据此，我们提出科学假说：甲基转移酶M3和M14通过稳定BMI1的表达，同时与BMI1相互作用介导细胞内特异基因的m6A修饰从而促进鼻咽癌进展。本项目将在预实验基础上结合体内外模型深入研究METTL3和METTL14在鼻咽癌进展中的生物学功能和分子机制，有望为鼻咽癌的防治提供新的分子靶标

EBV是鼻咽癌最重要的生物学致病因素，对于鼻咽癌等病毒感染相关肿瘤的发生发展具有重要的生物学意义，阐明EB病毒感染宿主细胞的机制及影响因素对于鼻咽癌的防治具有重要意义。表观遗传改变在肿瘤发生发展过程中起着非常重要的作用，最近研究表明RNA甲基化，尤其是N6甲基腺嘌呤(m6A)甲基化，对于mRNA的稳定性、剪接和翻译都起着关键的调节作用。已有研究表明，病毒相关基因产物会影响宿主基因的表观遗传修饰，导致宿主基因表达及关键信号通路活性发生改变，进而促进肿瘤发生发展。在本研究中，我们的研究结果阐明EBV感染鼻咽上皮细胞后宿主细胞的m6A修饰改变以及宿主基因表达的情况，确认病毒感染对宿主基因修饰和表达的影响。EBV裂解感染基因BZLF1抑制m6A甲基化转移酶METTL3的启动子活性从而下调METTL3表达，METTL3和识别蛋白YTHDF2加速宿主基因KLF4的mRNA降解，METTL3表达下调导致宿主基因KLF4的表达，进而促进EBV感染。因此，我们的结果表明存在通过细胞 mRNA m6A 水平在EBV和宿主分子之间形成的正反馈回路，并且该反馈回路进一步促进EBV病毒感染。该机制包含控制病毒传染病的多个潜在目标，对全面了解病毒与宿主细胞之间的互作提供新的视角，对于控制EBV感染和肿瘤防治提供了科学依据。