Genetic & Molecular Studies of Nematode mRNA Degradation

描述(申请人提供)：真核生物mRNAs的稳定丰度由其合成和降解的相对速率决定。虽然我们对转录调控的分子机制知道很多，但相比之下，我们对mRNA降解的了解还很粗略。信使核糖核酸的稳定性是构成基因和调控基因表达的重要控制点。我们将研究线虫mRNA腐烂所需的基因。含有提前终止密码子的信使RNA比它们的野生型信使RNA降解得更快，这种现象被称为“无意义介导的信使核糖核酸衰退”(NMD)或“信使核糖核酸监测”。NMD存在于所有被测试的真核生物中，其作用对人类遗传病有重大影响。大约三分之一的遗传性疾病是由废话或移码突变引起的。NMD通过影响突变mRNA的丰度来改变许多疾病的表型。疾病的严重程度通常反映了突变的mRNA对NMD的敏感性。影响线虫八个基因(SMG-1至SMG-8)中任何一个的功能丧失突变可消除NMD。我们将利用这些突变体研究NMD的遗传和分子特性。我们的工作分为两大类：(1)研究NMD的分子机制；(2)研究NMD在野生动物中的生物学功能。我们的工作旨在回答两个普遍的问题：SMG蛋白与什么相互作用，以及它们如何调节mRNA的降解？野生型动物的哪些mRNAs被NMD降解？我们的方法结合了对SMG基因及其编码蛋白的遗传、分子和生化研究。我们的长期目标是了解mRNA周转的分子机制和NMD的生物学作用。我们的实验通过识别NMD所需的蛋白质，通过描述它们在体内的活动，以及通过研究NMD在正常生长和发育中的作用，为这些目标做出了贡献。

DESCRIPTION (provided by applicant): The steady-state abundance of eukaryotic mRNAs is dictated by the relative rates of their synthesis and degradation. While we know a great deal about molecular mechanisms of transcriptional control, our understanding of mRNA degradation is sketchy by comparison. mRNA stability is an important control point for both constitutive and regulated gene expression. We will investigate C. elegans genes required for mRNA decay. Messenger RNAs that contain premature stop codons are degraded more rapidly than their wild-type counterparts, a phenomenon termed "nonsense-mediated mRNA decay" (NMD) or "mRNA surveillance". NMD occurs in all eukaryotes tested, and its action has a substantial impact on human genetic disease. Approximately one third of inherited diseases are due to nonsense or frameshift mutations. NMD modifies many disease phenotypes by affecting abundance of the mutant mRNA. Disease severity often reflects sensitivity of the mutant mRNA to NMD. Loss-of-function mutations affecting any of eight C. elegans genes (smg-1 through smg-8) eliminate NMD. We will study genetic and molecular properties of NMD using these mutants. Our work falls into two broad categories: (1) investigating the molecular mechanisms of NMD; and (2) investigating the biological function of NMD in wild-type animals. Our work is designed to answer two general questions: With what do the SMG proteins interact and how do they regulate mRNA degradation? What mRNAs of wild-type animals are degraded by NMD? Our methods combine genetic, molecular, and biochemical investigations of smg genes and their encoded proteins. Our long-range goals are to understand the molecular mechanisms of mRNA turnover and the biological roles of NMD. Our experiments contribute to these goals by identifying proteins that are required for NMD, by describing their activities in vivo, and by investigating the role of NMD during normal growth and development.