Dis3L2和hnRNP U协同调控肿瘤细胞pre-mRNA选择性剪接的机制研究

Recently, Dis3L2 has been identified as a type of RNA binding protein, which can specifically recognize and degrade mRNA or non-coding RNA in the cytoplasm by utilizing its 3'-5' exoribonuclease activity. However, by now, little is known about the function of Dis3L2 during tumorigenesis and tumor development. In our preliminarily experiments, we found that Dis3L2 is highly expressed in human liver tumor tissues and promotes tumor cell proliferation, indicating that Dis3L2 is a potential carcinogenic gene. In addition, we have validated the interaction between Dis3L2 and hnRNP U, a splicing-associated factor, as well as their colocalization in the cell nucleus. Therefore, we postulate that Dis3L2 may regulate alternative splicing of pre-mRNA by interaction with hnRNP U in tumor cells and affect biological behavior of tumor. We will further explore which of and how pre-mRNAs’ alternative splicing are cooperatively regulated by Dis3L2 and hnRNP U. Furthermore, we will investigate whether specific splicing products would be produced by regulation of Dis3L2 and hnRNP U, regulate tumor signal transduction and affect tumorigenesis and tumor development. In conclusion, we will try to explore a new mechanism on regulation of alternative splicing in tumor, which hopefully will add biomedical significance to this project.

DIS3L2是最近发现的一种RNA结合蛋白，能利用其核酸外切酶活性在细胞质中对mRNA和非编码RNA进行选择性识别和降解，然而Dis3L2在肿瘤发生发展中的作用仍有待于探索。我们前期研究发现Dis3L2在肝癌组织中高表达并促进肝癌细胞的增殖，提示其为一种可能的促癌基因。我们还发现dis3L2能与hnRNP U这种剪接相关蛋白相结合，且在细胞核内具有共定位。于是我们推测Dis3L2可能通过与hnRNP U的相互作用调控肿瘤细胞中pre-mRNA的选择性剪接，从而影响肿瘤的生物学行为。我们将进一步鉴定它们协同调控了哪些pre-mRNA的选择性剪接，并对其调控的分子机理进行解析。我们还将探讨Dis3L2是否通过与hnRNP U协同调控产生特异性的剪接产物，从而调节肿瘤的信号传导并最终影响肿瘤的发生发展。本项目的研究将丰富我们对肿瘤中选择性剪接调控机制的认识，研究结果具有潜在而重要的生物医学意义。

Dis3L2作为一种3’-5’外切核酸酶能降解细胞内异常的RNA。然而，它在肿瘤发生发展中的功能仍远未明晰。本项目中，我们发现Dis3L2在肝癌组织中异常高表达，且促进肝癌的进展。进一步的功能研究发现，Dis3L2参与调节hnRNP U介导的pre-mRNA可变剪接：Dis3L2通过它的CSD结构域与hnRNP U相互作用，将其募集到pre-Rac1 mRNA，从而增强其剪接过程中exon 3b的保留，但不依赖于其3’-5’外切核酸酶活性。产生的Rac1b能作为一种促癌剪接变体、促进肝癌的发生。体内体外实验均证明，Rac1b介导Dis3L2对肝癌发生发展的促进作用。总之，我们的研究揭示了Dis3L2通过参与调控hnRNP U介导的可变剪接，以一种的全新的方式促进肝癌的发展进程。

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