Cell growth control by cell and organelle size-dependent ribosome biogenesis

通过细胞和细胞器大小依赖性核糖体生物发生控制细胞生长

基本信息

批准号：
8355129
负责人：
Clifford P Brangwynne
金额：
$ 241.5万
依托单位：
PRINCETON UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-09-30 至 2017-06-30
项目状态：
已结题

项目摘要

DESCRIPTION (Provided by the applicant) Abstract: Biological processes ranging from embryonic development to carcinogenesis rely on the regulation or dysregulation of cell growth and size; despite this central biomedical importance, the mechanisms by which cells ""know"" to grow to a certain size remain poorly understood. With few exceptions, virtually all current thinking about cell size control is based on traditional paradigms that focus on signaling networks such as the TOR metabolic pathway, or the cell cycle pathway. However, we lack even a basic mechanistic understanding of the way in which cellular variables such as genomic content (ploidy) and ribosome biosynthetic activity exert their well-known effects on cell size, particularly in the context of cell size homeostasis i multicellular organisms. The fundamental gap in our understanding of this critical biological process underscores the urgent need for new ways of quantitatively looking at cell size control. We recently introduced the novel concept that non-membrane bound ribonucleoprotein (RNP) bodies, including the ribosome-producing nucleolus, are dynamic liquid phase micro-reactors for rapid RNA processing. Our previous studies with other disordered liquid-like bodies suggest that the size of nucleoli should scale with the size of cells. However, basic biophysical considerations suggest that nucleoli of different size will produce ribosomal subunits at different rates; large nucleoli in large cells may not be able to keep up with the ribosome requirements for steady cell growth, providing a biophysical mechanism for cell size feedback and growth control. To test this hypothesis, we will use novel imaging-based assays to measure the function of individual nucleoli of different size, utilizing a biochemically accessible Xenopus oocyte system. We will then examine the consequences of this size- dependent activity, dissecting the relationship between nucleolus size and activity, and cell size, within the multicellular worm C.elegans. Using 3D confocal imaging and custom image analysis algorithms, we will measure the effects of altered nucleolus size and biosynthetic activity on cell size, in both diploid and tetraploid worms. Finally, we will develop theoretical biophysical models for understanding these data based on the size dependence of the rate of ribosomal RNA processing within the dynamic liquid- like nucleolar material. Public Health Relevance: Biological processes ranging from embryonic development to cancer all rely on the regulation or dysregulation of cell growth and size. The nucleolus is a nuclear organelle that plays a well known role in cell growth control. This proposal seeks to identify the biophysical mechanism by which the nucleolus may provide cell size feedback for regulating cell growth, which will have important implications for understanding and controlling physiological and disease driven cell growth processes.

描述（由申请人提供）摘要：从胚胎发育到癌变的生物过程依赖于细胞生长和大小的调节或失调。尽管具有这一重要的生物医学重要性，但细胞“知道”生长到一定大小的机制仍然知之甚少。除了少数例外，几乎所有当前关于单元尺寸控制的想法都是基于传统范式侧重于信号网络，例如 TOR 代谢途径或细胞周期途径。然而，我们甚至缺乏对基因组含量（倍性）和核糖体生物合成活性等细胞变量对细胞大小产生众所周知的影响的方式的基本机制理解，特别是在多细胞生物的细胞大小稳态的背景下。我们对这一关键生物过程的理解存在根本差距，这凸显了迫切需要定量研究细胞大小控制的新方法。我们最近引入了一个新概念，即非膜结合核糖核蛋白 (RNP) 体，包括产生核糖体的核仁，是用于快速 RNA 处理的动态液相微反应器。我们之前对其他无序液体状物体的研究表明，核仁的大小应该与细胞的大小成比例。然而，基本的生物物理学考虑表明，不同大小的核仁会在不同的时间产生核糖体亚基。费率；大细胞中的大核仁可能无法满足细胞稳定生长的核糖体需求，从而为细胞大小反馈和生长控制提供了生物物理机制。为了检验这一假设，我们将使用新的基于成像的检测方法，利用生物化学上可访问的非洲爪蟾卵母细胞系统来测量不同大小的单个核仁的功能。然后，我们将检查这种大小依赖性活动的后果，剖析多细胞线虫中核仁大小和活动以及细胞大小之间的关系。使用 3D 共焦成像和定制图像分析算法，我们将测量二倍体和四倍体蠕虫中核仁大小和生物合成活性改变对细胞大小的影响。最后，我们将基于动态液体状核仁材料中核糖体 RNA 加工速率的大小依赖性，开发理论生物物理模型来理解这些数据。公共健康相关性：从胚胎发育到癌症的生物过程都依赖于细胞生长和大小的调节或失调。核仁是一种核细胞器，在细胞生长控制中发挥着众所周知的作用。该提案旨在确定核仁为调节细胞生长提供细胞大小反馈的生物物理机制，这对于理解和控制生理和疾病驱动的细胞生长过程具有重要意义。