Eukaryotic Ribosome Assembly

项目摘要 核糖体负责快速而准确地生产细胞中各种形式的所有蛋白质 地球上的生命。这些分子机器进行忠实翻译的能力取决于它们的复杂性 允许与配体进行动态相互作用的结构。真核细胞中成熟的核糖体由 两个部分，大的60S亚基合成细胞中的所有蛋白质，小的40S亚基 对信使核糖核酸进行解码。真核细胞核糖体的生产涉及200多个辅助因子，其中 协调核糖体RNA的复杂加工和折叠以及核糖体蛋白的组装。 考虑到核糖体结构和功能的复杂性及其在破译我们的基因中的关键作用 对于细胞来说，确保它们的正确组装是一项必要但艰巨的任务。最近，相当可观 人们的兴趣主要集中在核糖体生物发生途径的质量控制机制上。这项建议 集中在核糖体组装中的两个不同的主题；(1)评估结构和 新组装的60S亚基的功能完整性和(2)从90年代初前核糖体的过渡 40年代以前的前身的前身。 关于结构和功能完整性的评估，本提案涉及三个相关问题 问题：I.如何评估新产生的亚基的功能？有缺陷的亚基的命运是什么？三. 向有缺陷的核糖体发放许可证的后果是什么？在人类中，这些过程中的缺陷会导致 各种疾病，包括T细胞急性淋巴细胞性白血病和Shwachman-Diamond综合征。 小核糖体亚基的组装涉及90年代的逐步共转录组装 颗粒是一种大的蛋白质-RNA复合体，固定在U3-snoRNA上。然而，U3的存在是相互的 与小亚基RNA的最终折叠结构不相容，一旦转录 RNA已经完成，90年代的粒子已经完全组装。从90年代到40岁之前的转变很糟糕 明白了。我们认为，U3被RNA解旋酶Dhr1置换是驱动 90年代到40年代之前的粒子的过渡。我们将确定Dhr1的活性是如何调节到 确保U3及时发布。

Project Summary Ribosomes are responsible for the rapid and accurate production of all proteins in cells in all forms of life on earth. The ability of these molecular machines to carry out faithful translation depends on their complex structure that allows dynamic interaction with ligands. The mature ribosome in eukaryotic cells is composed of two parts, the large 60S subunit that synthesizes all the proteins in a cell and the small 40S subunit that decodes mRNA. The production of a eukaryotic ribosome involves over 200 accessory factors which orchestrate the intricate processing and folding of the ribosomal RNA and assembly of the ribosomal proteins. Considering the complexity of ribosome structure and function and its critical role in decoding our genetic information, ensuring their correct assembly is a necessary but daunting task for cells. Lately, considerable interest has been focused on mechanisms of quality control in the ribosome biogenesis pathway. This proposal focuses on two distinct topics within ribosome assembly; (1) the mechanisms for assessing the structural and functional integrity of the newly assembled 60S subunit and (2) the transition from the early 90S pre-ribosomal precursor to the pre-40S precursor. With respect to assessment of structural and functional integrity, this proposal addresses three related questions: I. How are newly minted subunits assessed for function? II. What is the fate of defective subunits? III. What is the consequence of licensing defective ribosomes? In humans, defects in these processes lead to various diseases, including T-cell acute lymphoblastic leukemia and Shwachman-Diamond syndrome. Assembly of the small ribosomal subunit involves stepwise cotranscriptional assembly of the 90S particle, a large protein-RNA complex, scaffolded on U3-snoRNA. However, the presence of U3 is mutually incompatible with the final folded structure of small subunit RNA and must be removed once transcription of the RNA is complete and the 90S particle has fully assembled. The transition from the 90S to pre-40S is poorly understood. We propose that the displacement of U3 by the RNA helicase Dhr1 is a primary event that drives the transition of the 90S into the pre-40S particle. We will determine how the activity of Dhr1 is regulated to ensure the timely release of U3.