Maturation of the Large Ribosomal Subunit in Yeast

描述(由申请人提供)： 摘要：核糖体负责快速而准确地产生地球上所有生命形式的细胞中的所有数千种不同的蛋白质。这些分子机器做到这一点的能力取决于一种既稳定又灵活的复杂结构，使其能够以动态的方式与配体相互作用。成熟的核糖体具有与多种配体的结合位点，包括起始因子、延伸因子、终止因子、tRNAs和mRNA，它必须在多种稳定构象之间棘轮运动，以极快的速度将tRNA移入和移出。一个功能齐全的真核核糖体的准确组装涉及200多个辅助组装因子，在许多情况下，这些辅助组装因子的功能尚不清楚。然而，最近的兴奋主要集中在这些蛋白质中的一些在细胞质的生物发生过程的后期发生的质量控制检查点上的作用。我们最近提出，60S亚基经历了细胞质“试驾”，在这个过程中，新组装的核糖体被结构上模拟翻译因子的生物发生因子测试其功能。本提案试图了解60S成熟的机制，重点放在这一途径的最后几步，Tif6和Nmd3的释放，我们认为这包括对大亚基的主要质量控制检查。这项建议旨在了解评估大核糖体亚单位功能和结构完整性的质量控制机制。这一建议建立在我们从上一个资助期获得的最新结果的基础上，该结果表明，新组装的亚基在真正的翻译之前经历了一次使用翻译因子的分子模拟的“试驾”。在与Jan Cools博士(比利时VIB)的合作下，我们最近还发现，这种质量控制检查中的缺陷与约8%的儿童急性T细胞白血病样本有关。这一步骤中的缺陷还与Shwachman-Diamond综合征有关，这是一种遗传性疾病，表现为骨髓衰竭、胰腺功能障碍和易患癌症等。这些结果突显了了解这一质量控制步骤的机制对于其作为新药治疗的潜在靶点的重要性。

DESCRIPTION (provided by applicant): Summary: Ribosomes are responsible for the rapid and accurate production of all the thousands of different proteins in cells in all forms of life on earth. The ability of these molecuar machines to do this depends upon a complex structure that is both stable and flexible, allowing it to interact with ligands in a dynamic fashion. The mature ribosome has binding sites for multiple ligands, including initiation factors, elongation factors, termination factors, tRNAs and mRNA, and it must ratchet between multiple stable conformations, moving tRNAs in and out at enormous rates. The accurate assembly of a fully functional eukaryotic ribosome involves over 200 accessory assembly factors, whose function, in many cases, is still unknown. However much recent excitement has focused on the role of some of these proteins in quality control checkpoints that occur late in the biogenesis process in the cytoplasm. We have recently proposed that the 60S subunit undergoes a cytoplasmic "test drive" in which newly assembled ribosomes are tested for function by biogenesis factors that structurally mimic translation factors. This proposal seeks to understand the mechanism of 60S maturation, focusing on the last steps of this pathway, the release of Tif6 and Nmd3, which, we believe, comprise the primary quality control checks on the large subunit. This proposal is directed at understanding quality control mechanisms that assess the functional and structural integrity of the large ribosomal subunit. This proposal builds on our recent results from the previous funding period suggesting that the newly assembled subunit undergoes a "test drive" that uses molecular mimics of translation factors prior to bona fide translation. In collaboration with Dr Jan Cools (VIB, Belgium) we have also recently shown that a defect in this quality control check is associated with ~8% of pediatric acute T-cell leukemia samples. Defects in this step are also associated with Shwachman-Diamond syndrome, an inherited disease that manifests in bone marrow failure, pancreatic dysfunction and predisposition to cancers among other conditions. These results highlight the importance of understanding the mechanism of this quality control step for its potential target for new drug therapies.