microRNA 后转录水平调控机制的研究

MicroRNAs (miRNAs) are small endogenous non-coding RNAs that regulate gene expression by repressing translation and/or promoting degradation of their target mRNAs. Aberrant dysregulation of mature miRNAs is commonly observed in many human cancers and can have a causative function in tumorigenesis. Although the efficiency of Drosha-mediated process is crucial for determining miRNA abundance, the mechanisms for dynamic and specific regulation of miRNA biogenesis in Drosha microprocessor are poorly understood. A better understanding of miRNA regulation is required to determine how aberrant miRNA activity mechanistically contributes to tumorigenesis and to predict therapeutic target miRNAs. While core components (Drosha and DGCR8) in the microprocessor have no binding specificity for primary miRNAs (pri-miRNAs), increasing evidence has shown that regulatory RNA-binding proteins may confer the specificity for recruiting and processing premature pri-miRNAs. In our recent study, we identified a RNA-binding protein, DEAD-box RNA helicase 1 (DDX1) as a key regulatory component in the Drosha complex, which promotes the processing of a subset of miRNAs. Interestingly, a majority of the DDX1-dependent miRNAs is induced after DNA damage and this induction is facilitated by the ATM-mediated phosphorylation of DDX1. Inhibiting DDX1 promotes ovarian tumor progression in a syngeneic ovarian tumor mouse model. These findings suggest that DDX1 may be a key modulator in miRNA maturation and ovarian tumor suppression. Based on our previous observation, we hypothesize that Drosha-associated DDX1 (1) specifically bind and regulate miRNA processing, (2) transmit cellular stress signals to miRNA biogenesis to maintain cellular homeostasis, and (3) dysregulation of DDX proteins lead to cancer.

MicroRNA（miRNA）是一类内源性的小分子非编码RNA，通过抑制翻译和降解靶mRNA来调控基因的表达。MiRNA的异常表达常出现在人类各种疾病中包括癌症。MiRNA后转录水平的调节是其生物生成的重要调控。由于Drosha缺乏结合miRNA的特异性，miRNA生物生成的动态调节机制知之甚少。我们发现一种新的RNA结合蛋白DDX1，能特异结合一些miRNA（包括miR-200家族）并促进它们的加工合成。ATM在DNA损伤后诱导DDX1磷酸化并上调依赖DDX1的miRNA水平。抑制DDX1能促进卵巢肿瘤在体内的发展。因此，我们假设Drosha相关蛋白DDX1（1）能特异地结合并调节miRNA加工合成；（2）传递细胞应激信号到miRNA生物生成以维持细胞内稳态；（3）DDX1蛋白的失调能导致癌症。该课题将为miRNA在癌症发展中异常表达的分子机制提供理论和实验依据。

MicroRNA（miRNA）是一类小分子非编码RNA，对mRNA的动态合成、代谢和翻译进行着精细的调控。其失调与肿瘤的生长，转移，侵袭，耐药和患者预后严重相关。我们前期通过大量的基础证明了miRNA在肿瘤生长转移过程中的加工合成主要是依赖于一些RNA结合蛋白，这些RNA结合蛋白能够特异的结合miRNA环路或者茎部结构，促进它们的加工合成。本课题在此概念之下探讨了RNA结合蛋白DDX1调控miRNA加工合成的分子机制，深入剖析了DDX1对其依赖的miR-200s家族成员的作用机理，阐明了DDX1在DNA损伤条件下活性的调控机制。并在卵巢癌小鼠模型上验证了DDX1介导miRNA加工生成的体内作用，为阐明卵巢癌转移机制提供了理论基础和实验依据。同时发现了一个新的RNA结合蛋白RALY在肿瘤中促进miRNA加工合成的机制，RALY能够通过m6A调控开关促进特定miRNA的加工合成，对肿瘤细胞的有氧糖酵解途径有潜在的作用，为进一步探讨RNA结合蛋白介导miRNA参与肿瘤发生发展的分子机制提供重要的基础。