Ribosome Protein Heterogeneity: The basis of wide spread roles for specialized ribosomes in tuning global gene expression.

传统的核糖体观点认为，每个大小核糖体亚基都是由核糖体RNA和一组确定的核糖体蛋白组成的。现在，新出现的证据开始挑战这种静态的通用核糖体结构的观点，因为越来越明显的是，不同的核糖体可以在许多核心核糖体蛋白的组成上有所不同。最近发表的数据也揭示了核糖体的可变核糖体蛋白质组成的功能意义，因为有实例表明特定mRNA的翻译需要特定的核糖体蛋白质。例如，最近发表的工作描述了在发育过程中，含有Rp 138的核糖体是如何在特定细胞中翻译特定Hox基因所必需的。人们可以想象出许多场景，它们的核心核糖体蛋白含量不同的专门核糖体如何被调谐以在不同细胞类型和组织中进行最佳基因表达。初步数据：根据先前发表的数据，量化了不同小鼠组织之间的一些核糖体蛋白mRNA的巨大差异，我们定量比较了来自一些小鼠组织和细胞系的纯化核糖体的核糖体蛋白质组。我们的初步数据与mRNA表达数据一致，其中我们还量化了几种核糖体蛋白的高度可变丰度，而其他蛋白保持不变。为了进一步研究核糖体的变异性，我们的具体目标如下：目的1）定量核糖体变异：完成我们对从不同小鼠组织和细胞系中纯化的核糖体的核糖体蛋白质组差异的定量。目的2）核糖体变体的功能研究：在存在和不存在表现出可变核糖体占据的核糖体蛋白的情况下，鉴定在鼠3 T3细胞系中的多核糖体中活跃翻译的mRNA。目的3）翻译逃避的机制研究：研究这些mRNA在核糖体特异性选择性翻译下如何不被典型的5 '-帽依赖性翻译翻译而需要特定的核糖体蛋白进行翻译的分子基础。影响：通过选择性mRNA翻译证明核糖体在基因表达中的作用的广度将重新定义我们如何看待核糖体在蛋白质合成中的作用。核糖体在基因表达调控中发挥积极作用的鉴定可能是转录后基因调控中最大的被忽视的方面之一，并且有可能在发育和疾病中发挥许多调控作用。

The traditional view of the ribosome is where each large and small ribosomal subunit is composed of its ribosomal RNAs and a defined set of ribosomal proteins. Now emerging evidence is beginning to challenge this view of a static universal ribosome structure as it is becoming apparent that different ribosomes can vary in their make-up of many core ribosomal proteins. Recent published data is also revealing the functional implications of variable ribosomal protein composition of ribosomes as there are examples demonstrating the requirement for specific ribosomal proteins for the translation of specific mRNAs. For example, recently published work describes how ribosomes containing Rpl38 are required for the translation of specific Hox genes in specific cells during development. One can envision numerous scenarios how specialized ribosomes which vary in their core ribosomal protein content are tuned for optimal gene expression in different cell types and tissues. Preliminary Data: Following up on previously published data that quantified large differences for some ribosomal protein mRNAs between different murine tissues, we have quantitatively compared the ribosomal proteome of purified ribosomes from some murine tissues and cell lines. Our preliminary data is in agreement with the mRNA expression data where we have also quantified highly variable abundances for several ribosomal proteins while others remain constant. This variability of a subset of ribosomal proteins merits further investigations into the functional implications in gene expression.To further investigate ribosome variability we are pursuing the following Specific Aims:Aim 1) Quantifying Ribosomal Variations: Complete our quantification of the differences in the ribosomal proteome of ribosomes purified from different murine tissues and cell lines. Aim 2) Functional Investigations of Ribosomal Variants: Identify the mRNAs being actively translated in polysomes in the murine 3T3 cell line in the presence and absence of ribosomal proteins that exhibit variable ribosomal occupancy. Aim 3) Mechanistic Investigations of Translational Evasion: Investigate the molecular basis of how these mRNAs under ribosomal specific selective translation are not translated by canonical 5'-cap dependent translation and require specific ribosomal proteins for translation.Impact: The demonstration of the breadth of the role for ribosomes in gene expression by selective mRNA translation would redefine how we view the role of ribosomes in protein synthesis. The identification of ribosomes playing an active role in the regulation of gene expression may be one of the largest overlooked aspects of post transcriptional gene regulation and has the potential to function in numerous regulatory roles in both development and disease.