The Control of Gene Expression by Eukaryotic Ribonucleases

描述（由申请人提供）：RNA分子的降解提供了控制特定基因表达的有力手段。真核细胞中的主要RNA降解途径之一是无义介导的mRNA降解途径，其降解含有过早翻译终止密码子（PTC）的RNA。虽然该途径在消除含PTC的RNA中的功能已得到充分证实，但该途径在内源性转录物的表达调控和质量控制中的影响仍不清楚。该项目将重点研究NMD在特定基因调控途径中的三个主要功能。首先，我们将研究NMD如何与其他降解系统合作降解未剪接的前体mRNA，以及将这些未剪接的RNA定向到不同降解途径的机制。这种功能非常关键，因为未剪接的前mRNA的积累将导致产生具有有害或显性负特性的蛋白质。此外，我们将调查如何NMD可以调节生产的选择性剪接或调节转录本。这将包括使用RNA-Seq方法对在包括PTC在内的可变剪接位点剪接的转录本进行基因组研究，并了解这些可变剪接事件如何调节以应对环境变化。我们还发现了一个意想不到的功能的NMD RNA解旋酶Upf 1 p在控制转录特异性剪接或减数分裂过程中表达，我们将调查Upf 1 p在这个过程中的具体作用。最后，我们发现NMD降解了位于亚端粒区域内的许多基因的5 '延伸形式，并且我们已经证明这些延伸形式介导了真正启动子处的转录抑制。我们将研究这些RNA介导这些抑制功能的机制以及NMD在这种新的调控系统中的作用。总体而言，拟议的研究应说明NMD在基因表达调控中的RNA降解的主要影响，并揭示由这种独特的RNA质量控制途径控制的基因调控的新范式。 公共卫生相关性：导致遗传疾病的突变通常导致过早的翻译终止密码子，这反过来又通过无义介导的衰变介导这些基因编码的mRNA的快速降解。遗传性疾病也可由剪接信号的突变引起，其降低剪接效率或激活隐蔽剪接位点。我们对未剪接和错误剪接的RNA的周转的研究将揭示RNA降解控制大量遗传疾病背景下突变基因表达的机制。

DESCRIPTION (provided by applicant): Degradation of RNA molecules provides a powerful means to control the expression of specific genes. One of the major RNA degradation pathways in eukaryotic cells is the Nonsense-Mediated mRNA decay pathway, which degrades RNA containing premature translation termination codons (PTCs). While the functions of this pathway in eliminating PTC-containing RNAs are well documented, the impact of this pathway in the regulation of expression and the quality control of endogenous transcripts is still unclear. The proposed project will focus on three major functions for NMD in specific gene regulation pathways. First, we will study how NMD can cooperate with other degradation systems to degrade unspliced pre-mRNAs, and the mechanisms that are involved to direct these unspliced RNAs to the different degradation routes. This function is highly critical since accumulation of unspliced pre-mRNAs would result in the production of proteins with deleterious or dominant-negative properties. In addition we will investigate how NMD can regulate the production of alternatively spliced or regulated transcripts. This will include the genomic investigation of transcripts that are spliced at alternative splice sites that include PTCs using RNA-Seq approaches, and understanding how these alternative splicing events are regulated to respond to environmental changes. We have also found an unexpected function for the NMD RNA helicase Upf1p in the control of transcripts specifically spliced or expressed during meiosis and we will investigate the specific role of Upf1p in this process. Finally we found that NMD degrades 5'-extended forms of many genes located within subtelomeric regions, and we have demonstrated that these extended forms mediate the repression of transcription at the bona fide promoters. We will investigate the mechanisms by which these RNAs mediate these repressive functions and the role of NMD in this novel regulatory system. Overall the proposed studies should illustrate the major impact of RNA degradation by NMD in the regulation of gene expression and reveal novel paradigms of gene regulation controlled by this unique RNA quality control pathway. PUBLIC HEALTH RELEVANCE: Mutations that cause genetic diseases often result in premature translation termination codons, which in turn mediate the rapid degradation of mRNAs encoded by these genes by Nonsense Mediated Decay. Genetic Diseases can also result from mutations in splicing signals, which reduce the splicing efficiency or activate cryptic splice sites. Our studies of the turnover of unspliced and mis-spliced RNAs will shed light on the mechanisms by which RNA degradation controls the expression of genes mutated in the context of a large number of genetic diseases.