Unraveling the mechanism by which Rps26-deficient ribosomes form to support the stress response

项目总结/摘要 最近，核糖体亚群的组成不同，缺乏单个核糖体蛋白（RP）， 或含有特定修饰的基因已经引起了人们的极大兴趣。在RP内容的情况下，多项研究 已经表明，细胞中存在缺乏特异性RPs的核糖体，包括Rps 26缺陷的核糖体。 虽然在大多数情况下，它们的生理相关性仍不清楚，但Karbstein实验室最近 证明缺乏Rps 26的核糖体在高盐和pH胁迫下特异性产生， 编码来自Hog 1和Rim 101途径的蛋白质的mRNA的优先翻译， 对这些压力的反应。这种mRNA特异性在含有Rps 26的和缺乏Rps 26的之间的变化， 核糖体源于Rps 26对Kozak序列-4位置的识别，从而支持 富含Rps 26的核糖体对翻译良好的mRNA的翻译， Hog 1和Rim 101途径中的特异性mRNA通过Rps 26缺陷核糖体在这些核糖体下形成， 压力 目前尚不清楚的是Rps 26缺陷型核糖体在高盐和高pH胁迫下如何形成。我 初步结果表明，Rps 26缺陷型核糖体是通过从预先存在的核糖体中释放Rps 26而产生的。 核糖体因此，我将进一步详细剖析导致Rps 26产生的机制- 缺陷的核糖体，探索Rps 26特异性伴侣Tsr 2在递送和提取 Rps 26从核糖体（Aim 1），并测试翻译后修饰调节这一途径（Aim 2）。 接下来，我将测试Rps 26是否被（重新）整合到Rps 26缺陷的核糖体中，以允许快速转换到Rps 26缺陷的核糖体中。 mRNA特异性而不需要重建新的核糖体，或者这些核糖体是否 已降级（Aim 3）。 总之，这些实验将阐明Rps 26缺陷核糖体在应激下如何形成。除了进一步 扩展了这种应激诱导产生特定核糖体群体的新范式，结果 也将对与Rps 26缺乏症有关的疾病的发展产生影响，如钻石- 布莱克凡氏贫血。因为所有病例中10-15%的病因仍然未知，并且与RP无关， 缺乏，可能导致RP释放的途径（如Rps 26）过度活化， 负责一个子集的情况下，类似于由Rps 26-伴侣蛋白缺乏引起的病例子集 TSR 2此外，在癌细胞中产生缺乏单个RP（包括Rps 26）的核糖体，其中 它们与不良结果有关。因此，这项工作也将有助于描述癌细胞如何调节肿瘤细胞的生长。 翻译机器颠覆翻译的目的。

Project Summary/Abstract Recently ribosome subpopulations that differ in their composition, lacking individual ribosomal proteins (RPs), or containing specific modifications have garnered a lot of interest. In the case of RP content, multiple studies have shown that ribosomes lacking specific RPs are present in cells, including ribosomes deficient in Rps26. While their physiological relevance remains unclear in most cases, the Karbstein lab has recently demonstrated that ribosomes lacking Rps26 are produced specifically under high salt and pH stress to enable the preferential translation of mRNAs encoding proteins from the Hog1 and Rim101 pathways that are required for the response to these stresses. This change in mRNA specificity between Rps26-containing and deficient ribosomes arises from the recognition of the -4 position of the Kozak sequence by Rps26, thereby supporting the translation of well-translated mRNAs by Rps26-containing ribosomes in rich medium, and the translation of specific mRNAs in the Hog1 and Rim101 pathways by Rps26-deficient ribosomes that are formed under these stresses. What remains unknown is how Rps26-deficient ribosomes form under high salt and high pH stress. My preliminary results suggest Rps26-deficient ribosomes are produced by release of Rps26 from pre-existing ribosomes. Therefore, I will further dissect in more detail the mechanism that leads to the production of Rps26- deficient ribosomes, exploring the role of the Rps26-specific chaperone Tsr2 in delivering to and extracting Rps26 from ribosomes (Aim1), and testing which posttranslational modifications regulate this pathway (Aim2). Next, I will test if Rps26 is (re-) incorporated into Rps26-deficient ribosomes, to allow for a rapid switch in mRNA-specificity without the costs of re-building new ribosomes, or whether instead these ribosomes are degraded (Aim3). Together, these experiments will clarify how Rps26-deficient ribosomes form under stress. In addition to further expanding on this novel paradigm of stress-induced production of a specific ribosome population, the results will also have implications for the development of diseases linked to Rps26-deficiency, such as Diamond- Blackfan anemia. Because the etiology of 10-15% of all cases remains unknown, and is not linked to RP- deficiency, it is possible that overactivation of pathways leading to the release of RPs such as Rps26 might be responsible for a subset of cases, similar to the subset of cases caused by deficiency of the Rps26-chaperone Tsr2. Furthermore, ribosomes lacking individual RPs, including Rps26, are produced in cancer cells, where they are associated with poor outcomes. Thus, this work will also help delineate how cancer cells modulate the translational machinery to subvert translation to its purposes.