The impact and regulation of eIF4A-multimerisation in establishing translational programmes

基因是构建生物体的蓝图，并定义其生物学特性。它们由保存在细胞核中的DNA组成。在基因表达的过程中，为了创造基因编码的东西，DNA被复制并以新的形式作为RNA。RNA中的信息被称为核糖体的分子机器读取，核糖体将这些信息翻译并转化为称为蛋白质的氨基酸序列。细胞内蛋白质的集合称为蛋白质组。RNA和蛋白质组是细胞内执行功能的主要颗粒。改变细胞内的RNA使蛋白质组发生动态变化，从而改变细胞功能和命运。基因组被协调调节，并结合在一起形成一个细胞活动程序，决定哪些RNA在特定时间产生哪些蛋白质。不幸的是，由于调节这些基因表达的基因突变，这些机制可能是错误的。这种失调可能导致细胞程序在错误的时间激活，产生导致致命疾病的RNA和蛋白质。一个毁灭性的例子是癌症，当RNA导致与细胞分裂相关的蛋白质的不受控制的产生时，大多数决定哪些RNA被选择翻译成蛋白质的细胞过程通过调节翻译起始复合物eIF4F的功能来进行。在它的心脏运作一种叫做eIF4A1的蛋白质。这种蛋白质是将RNA装载到核糖体上并启动蛋白质翻译所必需的。eIF4A1活性通过与许多其他蛋白质（称为辅因子）相互作用而改变。此外，RNA本身可以包含可能改变eIF4A1所需功能的元件。研究人员已经收集了关于eIF4A1活性如何被其辅因子改变的信息，并开始了解eIF4A1的失调具有致命的后果。然而，我们仍然不知道为什么以及如何建立这种失调。为了阐明这一点，我们首先需要知道eIF 4A1的功能如何受到其辅因子和RNA靶点的控制，这些辅因子和RNA靶点共同决定了核糖体选择哪些RNA进行翻译。本研究的目的是确定eIF4A1调控的模式和机制。人们一直认为eIF4A1作为单个分子是有活性的，但我们最近的工作表明，eIF4A1形成蛋白质复合物，这些复合物由一个或三个拷贝组装而成。我们还收集了证据，证明这些复合物具有不同的活性，RNA影响这些不同状态之间的分布。这创造了RNA如何决定eIF4A1活性的假设。因此，本研究将特别关注RNA本身对eIF4A1活性的影响。为了实现这一目标，我们需要了解哪些RNA招募哪些eIF4A1复合物，并准确定义RNA靶点所需的eIF4A1活性。为此，我们将分离出与不同eIF4A1复合物特异性结合的RNA。然后，我们将使用计算工具来找出这些RNA与其他RNA的区别。为了了解多eIF4A1复合物如何在RNA上发挥功能，我们将使用最先进的显微镜确定复合物的3D结构。这将确定复合物是如何形成的，并使我们能够产生不能形成这些复合物的修饰的eIF4A1。我们将使用修饰的复合物来剖析它们的活性，并重建RNA如何在无细胞环境中翻译成蛋白质的关键步骤，以了解它们的功能。这些发现将共同确定eIF4A1，RNA和最终决定蛋白质翻译的辅因子之间的关系。有了这个，我们将贡献基础知识，以增加我们对eIF4A1的调节和失调以及这如何影响细胞功能的理解。进一步地，它可以允许设计将影响特定eIF4A1活性的特定药物。

Genes are the blueprints for building an organism and define its biological properties. They are made of DNA that is kept in the nucleus of the cell. In the process of gene expression, to create what is encoded by a gene, DNA is copied and made in a new form as RNA. The information within RNAs is read by molecular machines, called ribosomes, that translate and convert this information into amino acid sequences named proteins. The collection of proteins within a cell is termed the proteome. RNA and the proteome are the main particles to carry out functions within cells. Altering the RNAs within a cell enables dynamic changes to the proteome and, hence, changes cell function and fate. Groups of genes are co-ordinately regulated and are combined to form a programme of cell activity that dictate which RNAs produce which proteins at specific times. Unfortunately, these mechanisms can be faulty due to mutations in genes that regulate the expression of these genes. Such dysregulation can lead to activation of cellular programmes at the wrong time producing RNA and proteins that cause fatal illnesses. A devastating example is cancer, when RNAs lead to uncontrolled production of proteins related to cell division.Most cellular processes that dictate which RNAs are selected for translation into protein operate by adjusting the function of the translation initiation complex eIF4F. At its hearts operates a protein called eIF4A1. This protein is essential for loading RNAs onto ribosomes and starting protein translation. eIF4A1 activity is changed by interacting with many other proteins, called cofactors. In addition, RNAs themselves can contain elements that may change which function of eIF4A1 is needed. Researchers have gathered information on how eIF4A1 activity is changed by its cofactors and are starting to understand that dysregulation of eIF4A1 has fatal outcomes. However, we still do not know why and how this dysregulation is established. To shed light on this, we first need to know how eIF4A1 function is controlled by its cofactors and RNA targets which together dictate which of these RNAs are selected for translation by the ribosome. This research proposal aims to identify these patterns and mechanisms of eIF4A1 regulation.It has been believed that eIF4A1 is active as a single molecule but our recent work revealed that eIF4A1 forms protein complexes that are assembled from one or three copies of it. We also gathered evidence that these complexes have different activities and that RNA affects the distribution between these different states. This creates the hypothesis of how RNA might dictate eIF4A1 activity. Thus, this research will focus particularly on the power of RNA itself to direct activity of eIF4A1.To achieve this goal, we need to understand which RNAs recruit which eIF4A1 complex and exactly define the eIF4A1 activity required by the RNA targets. To do this, we will isolate the RNAs that are specifically bound by different eIF4A1 complexes. We will then use computational tools to find out what discriminates these RNAs from others. To understand how the multi-eIF4A1 complexes perform their function on RNA we will determine the 3D structure of the complexes using state-of-the-art microscopes. This will identify how the complexes form and enable us to generate modified eIF4A1 that cannot form these complexes. We will use the modified complexes to dissect their activities and reconstitute key steps of how RNAs are translated into protein in a cell-free environment to understand their function. Together these findings will identify a relationship between eIF4A1, RNAs and cofactors that ultimately dictate protein translation. With this, we will contribute fundamental knowledge to increase our understanding of the regulation and dysregulation of eIF4A1 and how this affects cell function. In the further it may allow specific drugs to be designed that will affect specific eIF4A1 activities.