Messenger RNA Turnover in Mammalian Cells

项目摘要/摘要 真核细胞中mRNAs的降解在基因表达调控中起着至关重要的作用 在信使核糖核酸生物合成的质量控制中。去腺化是哺乳动物信使核糖核酸的第一步 降解，通常是mRNA衰退和翻译沉默的限速步骤，使其成为 这两个过程都是重要的控制点。然而，调节死烯基化的机制 仍然不为人所知。哺乳动物的去烯基化分两个阶段进行，由 PAN_2-PAN_3和CCR_4-CAF_1去烯基酶复合体。最近的研究发现，Pan3和Tob，两个 多聚(A)结合蛋白(PABP)相互作用的蛋白质，调节去烯化提示了一种新的模式 通过死烯基化的变化进行基因调控，这有助于细胞重置其蛋白质生产图谱。 最近的研究进一步强调了死烯基化在基因表达调控中的重要性。 观察。首先，microRNAs(MiRNAs)通过加速其信使核糖核酸靶标的快速衰退 死烯基化是基因沉默的主要途径，尽管潜在的机制和调控 在很大程度上仍不清楚。其次，在RNA中发现了不可翻译的mRNA-蛋白质复合体(MRNPs) 加工小体(P小体)，新发现的与mRNA周转有关的细胞质结构域， 存储不可翻译的mRNP，以及翻译抑制。死亡的一个主要后果是- 翻译是形成不可翻译的mRNPs，我们已经证明P-脱烯基化是必需的。 哺乳动物细胞中的身体形成。死烯基化可能导致主要的mRNP重塑。 这决定了mRNPs如何与调节其亚细胞定位的机制相互作用， 翻译，或腐烂。这项提案的具体目标侧重于解决以下关键问题 问题：1)死烯基化的调节机制是什么？ 2)哪些反式作用因子参与其中？ MiRNA介导的死烯基化和衰变以及miRNA介导的mRNA衰变是如何调节的？ 3)在mrna-蛋白质或mrnp复合体中，死烯基化引发了什么变化？这些变化是如何发生的？ 变化会影响mRNP的命运吗？拟议的研究将揭示以下基本原则 管理哺乳动物的mRNA周转，并对几个关键的关键机制提供关键的新见解 去烯基化、mRNA衰变、翻译与mRNP的动态关系问题 改建。

PROJECT SUMMARY/ABSTRACT Degradation of eukaryotic mRNAs plays an essential role in modulation of gene expression and in quality control of mRNA biogenesis. Deadenylation is the first major step in mammalian mRNA degradation and is often a rate-limiting step for mRNA decay and translational silencing, making it an important control point for both processes. Yet, the mechanisms by which deadenylation is regulated remain unknown. Mammalian deadenylation proceeds in two phases mediated consecutively by the Pan2-Pan3 and the Ccr4-Caf1 deadenylase complexes. Recent findings that Pan3 and Tob, two poly(A)-binding protein (PABP)-interacting proteins, modulate deadenylation suggest a new mode of gene regulation via changes in deadenylation, which helps cells reset their protein production profile. The importance of deadenylation in regulation of gene expression is further emphasized by recent observations. First, microRNAs (miRNAs) mediate rapid decay of their mRNA targets by accelerating deadenylation as a major route to gene silencing, though the underlying mechanisms and regulation remain largely unclear. Second, non-translatable mRNA-protein complexes (mRNPs) are found in RNA processing bodies (P-bodies), newly discovered cytoplasmic domains implicated in mRNA turnover, storage of non-translatable mRNPs, and translation repression. One major consequence of deadeny- lation is formation of non-translatable mRNPs, and we have shown that deadenylation is required for P- body formation in mammalian cells. It is plausible that deadenylation induces major mRNP remodeling that determines how mRNPs interact with the machinery mediating their subcellular localization, translation, or decay. The specific aims of this proposal focus on addressing the following key questions: 1) What are the mechanisms by which deadenylation is regulated and how does the regulation of deadenylation affect the fate of mRNA?; 2) What trans-acting factors are involved in miRNA-mediated deadenylation and decay and how is miRNA-mediated mRNA decay regulated?; and 3) What changes does deadenylation trigger in mRNA-protein or mRNP complexes and how do these changes influence an mRNP's fate? The proposed studies will reveal fundamental principles that govern mammalian mRNA turnover and provide crucial new mechanistic insights into several key issues related to the dynamic relationship between deadenylation, mRNA decay, translation and mRNP remodeling.