腺苷酸甲基化修饰引起RNA降解的分子机制研究

The methylation at N6 position of adenosine (m6A) is the most abundant RNA modification within protein-coding and long noncoding RNAs across many eukaryotic species that ranging from yeast to mammals. However, the functions of m6A modification still remain elusive. Until very recently, the discoveries of m6A methyltransferases and demethylases in mammalian cells for the first time reveal RNA methylation to be a dynamic and reversible process, highlighting its importance in basic biological functions. Indeed, the level of m6A modification is tightly regulated in mammals; and recent studies reveal that m6A modification is involved in a variety of critical biological processes, including embryonic stem cell self-renewal and differentiation, spermatogenesis, and control of brain function and circadian rhythms. Mechanistically, the YTH domain family proteins are known readers of m6A, the binding of which results in reduced abundance of m6A-containing RNAs. However, how these YTH domain family proteins lead to fast degradation of m6A-containing RNAs is poorly understood. In this study, we will take advantage of a well-established RNA decay monitor system to address this issue. We plan to elucidate which degradation pathway m6A-containing RNAs take, and to identify the effector proteins that are responsible for the shorter lifetime of m6A-containing RNAs and understand their relationship with the m6A reader proteins.

腺苷酸N6位的甲基化（N6-methyladenosine，m6A）是真核生物信使RNA和长非编码RNA内部最常见的修饰，也是迄今唯一被证明受到相应修饰酶和去修饰酶动态调控的RNA修饰。动物细胞中RNA的m6A修饰在时空上受到精密调控，参与调控了包括生殖、神经、生物节律等多个系统的功能，并对干细胞的干性维持和分化能力至关重要，是细胞内基因表达调控的重要方式之一。近期研究发现YTHDF家族蛋白可以识别和结合RNA的m6A修饰，并导致所在RNA的加速降解，但其中的分子机制尚属未知。本项目计划运用瞬时诱导的RNA表达系统，研究哺乳动物细胞中m6A修饰介导的RNA降解途径，鉴定引发RNA降解的关键核酸酶，探索相关效应蛋白和核酸酶的细胞定位及其对功能的影响，从而解答m6A修饰如何调控RNA代谢这一RNA修饰领域的重要问题，为深入理解m6A修饰的生物学功能和应用提供理论基础。

腺苷酸N6位的甲基化（N6-methyladenosine，m6A）是真核生物信使RNA和长非编码RNA内部最常见的修饰，也是迄今唯一被证明受到相应修饰酶和去修饰酶动态调控的RNA修饰。动物细胞中RNA的m6A修饰在时空上受到精密调控，参与调控了包括生殖、神经、生物节律等多个系统的功能，并对干细胞的干性维持和分化能力至关重要，是细胞内基因表达调控的重要方式之一。近期研究发现YTHDF家族蛋白可以识别和结合RNA的m6A修饰，并导致所在RNA的加速降解，但其中的分子机制尚属未知。本项目以哺乳动物细胞为研究对象，运用一种瞬时诱导表达的RNA降解监控系统，发现了RNA的m6A修饰可加速所在RNA的脱尾过程进而促进其降解这一重要分子机制，鉴定到参与该过程的关键核酸酶为CCR4-NOT复合体。具体而言，m6A的结合蛋白YTHDF2通过与CCR4-NOT复合体中的CNOT1亚基发生直接相互作用而招募该脱尾酶复合体，并通过CCR4-NOT复合体中具有催化活性的CAF1和CCR4亚基而加速m6A RNA的脱尾和降解。这项研究为解答m6A修饰如何介导所在RNA降解这一重要分子机制问题提供了扎实的证据，并为深入理解m6A修饰的生物学功能提供了理论基础。

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