NSun2对血管衰老过程中衰老相关基因的多靶标调控作用

Apart from the 5’cap, methylation is found at the 5’ untranslated region, 3’ untranslated region, and coding region of mRNA. However, the functional impact of methylation at positions other than the 5’cap remains unclear. In previous studies, we have found that: 1) tRNA methytransferase NSun2 functions as a common regulator for p16, ICAM-1, p66Shc, and p27 by methylating the mRNAs of above genes; 2) NSun2 could also enhances the expression of p53 by methylating p53 mRNA; 3) In the process of oxidative stress induced senescence of HUVEC cells, NSun2, p16, p53, ICAM-1, p66Shc, and p27 were greatly induced; knockdown of NSun2 antagonized the effect of oxidative stress in inducing the expression of above genes; 4) In the aorta tissue of ApoE-deficient mice under high fat diet, the protein levels of NSun2, p16, p53, ICAM-1, p66Shc, and p27 remarkably increased. Based on above findings, we set out to investigate the mechanism underlying the regulation of p53 by NSun2-mediated methylation, and address the impact of NSun2-p16, NSun2-p53, NSun2-p66Shc, NSun2-ICAM-1, and NSun2-p27 regulatory processes in the process of endothelial and vascular aging. Our study will elucidate the mechanisms underlying the gene regulation during vascular aging, and provides experimental evidence for the treatment and prevention of aging-related vascular diseases.

除帽子结构外，mRNA其它区域也存在甲基化现象，但其生物学意义不明。我室前期研究发现：1）tRNA甲基转移酶NSun2作为共同调控因子甲基化衰老相关基因p16、p66Shc、ICAM-1、及p27 mRNA并调控其表达； 2）NSun2也甲基化p53 mRNA并促进其表达；3）氧化应激诱导HUVEC细胞NSun2、p16、p27、 p66Shc、ICAM-1、及p53的表达；沉默NSun2可拮抗氧化应激对上述基因的诱导; 4）高脂饮食诱导ApoE-/-小鼠动脉组织NSun2、p16、p27、ICAM1、p66Shc及p53表达。本课题将在此基础上进一步探讨NSun2催化p53 mRNA甲基化并调控其表达的机制，探讨NSun2对衰老相关基因的调控在血管衰老过程中的意义，筛选并鉴定NSun2作用的新靶标。上述研究将从新角度解析血管衰老的分子机制，为干预血管衰老相关病理过程提供实验依据。

相关基因表达紊乱是老年心血管疾病的基础，探讨这些基因的调控的机制对诠释老年心血管疾病的发生发展机理并从根本上防治这些疾病都具有十分重要的现实意义。甲基化是RNA的普遍修饰方式，但其在衰老、特别是血管衰老过程中的意义亟待探讨。 .在本项目资助下，本课题对NSun2催化的衰老相关基因 mRNA甲基化，甲基化的基因调控作用与机制，甲基化在衰老、特别是血管衰老过程中的意义做了系统、深入的探讨，取得以下进展：1）NSun2甲基化CDK1 mRNA 3’翻译区 (3’UTR)，促进CDK1翻译，进而促进细胞生长；2) NSun2可甲基化microRNA miR-125b的初始转录本、前体以及成熟体, 抑制miR-125b的加工与功能，从而抑制氧化应激下miR-125b的基因沉默功能； 3）NSun2甲基化p27KIP1 mRNA 5’UTR，在翻译水平抑制p27表达, 进而抑制复制性细胞衰老过程; 4) NSun2催化SHC、p53以及p16 mRNA甲基化，促进应激诱导的血管内皮细胞（HUVEC）早衰过程中p66SHC、p52SHC、p46SHC、p53以及p16表达，进而促进应激诱导的血管内皮细胞（HUVEC）早衰 ；5) NSun2 甲基化内皮细胞粘附分子ICAM-1 mRNA, 促进后者翻译并因此促进同型半胱氨酸诱导的血管炎症; 6) NSUN2催化的m5C甲基化与METTL3/METTL14催化的m6A甲基化以相互促进的方式甲基化p21 mRNA 3’UTR, 协同促进p21翻译，进而调控氧化应激诱导的细胞衰老过程中p21的表达。这些研究结果在近期相继总结为7篇SCI论文 （见项目成果总结）。.上述研究表明，NSun2介导的RNA甲基化至少可以作为关键调控节点，在血管衰老及其相关病理过程 (血管炎症、动脉粥样硬化等）中发挥着极其重要的调节作用。这些发现有望为血管衰老及其相关疾病的诊疗提供新的关键靶点，也将为相关领域的同类研究提供新的思路。