Messenger RNA Turnover in Mammalian Cells

项目总结/摘要 真核生物mRNA的降解在基因表达的调节中起重要作用， mRNA生物合成的质量控制。去腺苷酸化是哺乳动物mRNA的第一个主要步骤 降解，并且通常是mRNA衰变和翻译沉默的限速步骤，使其成为一种 两个过程的重要控制点。然而，去腺苷化的调节机制 仍然未知。哺乳动物去腺苷化在两个阶段中进行，这两个阶段连续地由 Pan 2-Pan 3和Ccr 4-Caf 1脱腺苷酶复合物。最近的研究发现，Pan 3和Tob，两个 多聚腺苷酸结合蛋白（PABP）相互作用蛋白，调节去腺苷酸化，提出了一种新的模式， 通过去腺苷化的变化进行基因调控，这有助于细胞重置其蛋白质生产谱。 最近的研究进一步强调了去腺苷化在基因表达调控中的重要性。 意见。首先，microRNAs（miRNAs）通过加速mRNA的降解， 去腺苷化作为基因沉默的主要途径，尽管潜在的机制和调控 仍然很不清楚。第二，在RNA中发现不可翻译的mRNA-蛋白质复合物（mRNP）， 加工体（P-体），新发现的与mRNA周转有关的细胞质结构域， 不可翻译的mRNP的存储和翻译抑制。死亡的一个主要后果- 失活是形成不可翻译的mRNP，我们已经证明，去腺苷化是P- 在哺乳动物细胞中的身体形成。去腺苷化诱导主要的mRNP重塑是合理的 它决定了mRNP如何与介导其亚细胞定位的机制相互作用， 翻译或衰变。本提案的具体目标侧重于解决以下关键问题： 问题：1）去腺苷化的调节机制是什么？ 去腺苷化的调控影响mRNA的命运; 2)哪些反式作用因子参与了 微RNA介导的去腺苷化和衰变以及微RNA介导的mRNA衰变是如何调节的？和 3)去腺苷化在mRNA-蛋白质或mRNP复合物中引发了什么样的变化，这些变化是如何发生的？ 改变会影响mRNP的命运吗拟议的研究将揭示基本原则， 控制哺乳动物的mRNA周转，并提供了几个关键的新的机制见解 与去腺苷化、mRNA衰变、翻译和mRNP之间的动态关系有关的问题 重塑

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.