Mechanism and regulation of nuclear RNA export

摘要 核信使核糖核酸输出是真核生物基因表达程序的一个基本组成部分，是 与上游(转录和核RNA监测)和下游(翻译和 细胞质RNA衰变)事件。在我的团队中，我们研究命运(核出口)的机制 确定和调节了mRNA-蛋白质复合体(MRNP)的相对衰变。目前实验室内的研究 重点了解mRNP的RNA结合蛋白(RBP)成分如何指导核RNA加工 和出口，包括与核孔复合体(NPC)的相互作用。我的团队最近的努力导致了 发现转录因子Dbp5和类SR蛋白NPL3在tRNA输出中的新功能 在减数分裂剪接调控网络中。此外，我们已经确定了突变诱导的改变在 促进限制性商业惯例在mRNA和非编码(NC)RNA之间分布不平衡的聚腺苷酸化 核RNA加工过程和损失的动态平衡。这些事件的核心是mRNP，它 关于mRNP架构的变化，包括特定RBP的收益或损失，如何指导仍不明确 不同的转录本命运，包括信使核糖核酸的输出。因此，我们在未来五年的目标集中在 对mRNP生物学的定量询问，包括功能、调节和结构。追求这一目标 及时地考虑到新积累的限制性商业惯例对mRNA和ncRNA生物学都至关重要的知识， 可用于应用这些问题的技术，以及了解疾病状态是如何在 保守的RBP组分内的突变或其被病毒调节的背景。信使核糖核酸的一个关键因子 Export是Dbp5(在人类中为DDX19)，是一种高度保守的死盒蛋白(DBP)，介导定向mRNP 通过RNA-蛋白质相互作用的调节，通过NPC进行输出。Dbp5由NPC组件Gle1激活- InsP6，除了Gle1在mRNA中的已知作用外，我们还发现tRNA输出也需要InsP6 出口。为了弥合RNA出口领域的主要知识差距，必须解决的问题包括：(1) 如何调节mRNP的组成以实现通过npC的定向运输？(2)mRNP和ncRNA 输出途径是集成的还是不同的？(3)是否通过共享限制性商业惯例协调RNA的处理和输出 在mRNPs和ncRNPs之间？通过解决这些问题，我们希望提供一个分子框架 这描述了DBP5和其他限制性商业惯例如何参与、修改和指导核RNA处理和出口。这些 数据对于了解通过NPC的RNP流量以匹配蜂窝需求以及如何改变是必不可少的 这一突变过程会导致疾病。此外，这些成果将有助于理解和 在死盒蛋白、RNA运输和基因表达领域的方法学，从而从根本上 对RNA生物学的研究做出了贡献。

ABSTRACT Nuclear mRNA export is a fundamental component of the gene expression program in eukaryotes and is intimately linked to upstream (transcription and nuclear RNA surveillance) and downstream (translation and cytoplasmic RNA decay) events. Within my group, we study the mechanisms by which the fate (nuclear export vs. decay) of an mRNA-protein complex (mRNP) is determined and regulated. Current studies within the lab focus on understanding how RNA-binding protein (RBP) constituents of an mRNP direct nuclear RNA processing and export, including interactions with the nuclear pore complex (NPC). Recent efforts in my group have led to the discovery of a novel function for the mRNA export factor Dbp5 in tRNA export and the SR-like protein Npl3 in the meiotic splicing regulatory network. In addition, we have characterized mutation-induced alterations in polyadenylation that promote imbalances in the distribution of RBPs between mRNA and non-coding (nc)RNA processes and the loss of nuclear RNA processing homeostasis. At the core of these events is the mRNP, which remains ill-defined in terms of how changes in mRNP architecture, including gain or loss of specific RBPs, directs distinct transcript fates, including mRNA export. Consequently, our goals over the next five years focus on a quantitative interrogation of mRNP biology, encompassing function, regulation, and structure. Pursuing this goal is timely given the newly amassed knowledge of RBPs central to both mRNA and ncRNA biology, the technologies available to apply these questions, and the need to understand how disease states arise in the context of mutations within conserved RBP components or their modulation by viruses. A critical factor in mRNA export is Dbp5 (DDX19 in humans), a highly conserved DEAD-box protein (DBP) that mediates directional mRNP export through NPCs via modulation of RNA-protein interactions. Dbp5 is activated by the NPC component Gle1- InsP6, which we have also shown to be required for tRNA export, in addition to the known role of Gle1 in mRNA export. Questions that must be addressed to close major knowledge gaps in the RNA export field include: (1) How is mRNP composition regulated to achieve directional transport through NPCs? (2) Are mRNA and ncRNA export pathways integrated or distinct? (3) Is there coordination of RNA processing and export via shared RBPs between mRNPs and ncRNPs? By addressing these questions, we expect to provide a molecular framework that describes how Dbp5 and other RBPs engage, modify, and direct nuclear RNA processing and export. These data are essential to understanding the flux of RNPs through NPCs to match cellular demand and how altering this process by mutation leads to disease. In addition, these results will contribute to the understanding and methodology within the DEAD-box protein, RNA transport, and gene expression fields, thereby fundamentally contributing to the study of RNA biology.