Ribosomal Genes of Yeast and Their Regulation

描述(申请人提供)：分子机器，如核糖体或核孔，对于细胞的顺利运作至关重要。这项提议涉及两个问题，这两个问题对任何分子机器的构建都很重要，但对核糖体来说尤其尖锐：(A)如何提供适量的每个组成分子，以及(B)如何对最终产品进行质量控制，并处理那些不符合标准的复合体。对于酿酒酵母来说，核糖体的构建消耗了其经济的很大一部分；有效的核糖体合成对其适合性至关重要。对于哺乳动物生物来说，核糖体的结构被作为细胞健康的一种衡量标准而受到密切监测；核糖体合成异常会导致细胞周期停滞或细胞死亡，并已与几种疾病状态有关。我们已经确定了一个由四种蛋白质组成的复合体，它似乎是连接核糖体RNA和核糖体蛋白合成的关键因素。我们正在提议进行实验，以证实这种联系，并试图确定这种联系的生化和生理基础。我们已经开发出一种系统，其中存在各种类型的异常前核糖体的主要和慢性的、但不是致命的积累。我们将在遗传和生化实验中使用这个系统，以发现识别和降解这种异常的前核糖体背后的基因和生化。初步数据表明，泛素-蛋白酶体系统的几个不同成员以及TraMP-exosome复合体的一些成员参与了这一相当不寻常的集合。这些实验的成功将为细胞如何在分子机器组件的生产中保持平衡提供新的见解，以及细胞如何处理异常核糖体，至少对自己构成风险。

DESCRIPTION (provided by applicant): Molecular machines, such as the ribosome or the nuclear pore, are of critical importance for the smooth functioning of the cell. This proposal deals with two issues that are important for the construction of ANY molecular machine, but are particularly acute for the ribosome: (A) How to supply the right amount of each of the constituent molecules, and (B) How to exert quality control over the final product and dispose of those complexes that do not meet standards. For S. cerevisiae construction of the ribosome consumes a major portion of its economy; effective ribosome synthesis is critical for its fitness. For mammalian organisms the construction of the ribosome is closely monitored as a measure of the cell's health; aberrant ribosome synthesis leads to cell cycle arrest or cell death, and has been implicated in several disease states. We have identified a complex of four proteins that appears to be a key factor in coupling the synthesis of ribosomal RNA and ribosomal proteins. We are proposing experiments to confirm this connection and to try to identify the biochemical and physiological basis for this coupling. We have developed a system in which there is a major and chronic, but not lethal, accumulation of aberrant pre-ribosomes of various types. We will use this system in both genetic and biochemical experiments to discover the genes and the biochemistry behind the identification and degradation of such aberrant pre-ribosomes. Preliminary data suggests the involvement of a rather unusual set of several distinct members of the ubiquitin-proteasome system, as well as some members of the TRAMP-exosome complex. The success of these experiments will provide new insight into how a cell can maintain BALANCE in the production of the components of a molecular machine, as well as how the cell can dispose of aberrant ribosomes at least risk to itself.