eIF2B (eukaryotic initiation factor 2B): regulation of its activity and expression, and its roles in translation initiation

蛋白质的产生是所有活细胞的一个关键过程，使它们能够利用DNA中基因中的遗传信息。大多数基因包含制造蛋白质的信息，蛋白质是细胞的组成部分，几乎执行细胞的所有功能。为了制造特定基因编码的蛋白质，DNA中的字母首先被复制到另一个类似的分子上，即mRNA，这一过程被称为转录。mRNA分子随后被称为核糖体的分子机器“读取”，以产生蛋白质，这一过程被称为翻译。细胞内表达的蛋白质决定了它的性质，例如，它将如何发挥作用并对其环境作出反应。蛋白质合成的过程消耗了细胞很大一部分能量和营养，因此必须严格控制。此外，这一过程可以通过允许机器优先“读取”某些mRNA分子来改变，从而有利于不同蛋白质的产生，从而使细胞能够快速响应由可用营养物质或能量减少引起的压力环境。当细胞经历生长和分裂阶段，即细胞周期时，这种机制也可以控制不同蛋白质的表达。控制蛋白质合成的一个关键部分涉及称为“起始因子”的蛋白质，这是本研究的重点。这些起始因子控制mRNA分子与核糖体的附着，对蛋白质合成的开始至关重要。它们也是多种情况下调控的关键点，因为它们控制着招募哪些mRNA分子，甚至精确地从哪里开始读取它们的代码。这项研究的主要焦点是一个被称为eIF2B的因子，它由5个独立的蛋白质“亚基”组成。我们还将研究在蛋白质合成过程中与eIF2B共同作用的两个蛋白eIF2和ABC50。申请人的实验室在研究所有这些蛋白质方面有多年的经验。破坏eIF2B的正常功能可导致疾病。编码eIF2B的5个亚基的基因中的轻微拼写错误会导致一种通常很严重的脑部疾病，被称为“白质消失”。它也对胰岛素有反应，因此在I型（胰岛素依赖型）糖尿病中被错误调节。这意味着eIF2B的正常功能是维持健康细胞所必需的。此外，eIF2B、eIF2和ABC50限制了细胞产生药物或疾病诊断蛋白的能力，这些蛋白具有很大的商业价值。我们的目标是研究eIF2B的四个主要方面：1。如何控制，根据申请人实验室或其他实验室的新发现，更多地了解如何在细胞中不同条件下控制这一重要蛋白质；2 .细胞如何控制这种蛋白质的含量，以及这与控制eIF2和ABC50的含量有何关系：这很重要，因为所有这些蛋白质含量的变化将影响蛋白质的合成速度和控制蛋白质生产的方式；eIF2B（和ABC50）的数量或细胞活性的变化如何影响特定蛋白质的产生。这一点很重要，因为如上所述，蛋白质合成的变化对细胞中存在的不同蛋白质的数量有重大影响，从而影响细胞的功能和“健康”；它的结构，使用最先进的技术来研究它的五个亚基的排列方式，以及它们如何与它的伴侣蛋白eIF2相互作用。

The production of proteins is a key process in all living cells, allowing them to use the genetic information held in the genes in their DNA. Most genes contain the information for making proteins, which are the cellular components that carry out almost all the functions of the cell. To make the protein coded for by a given gene, the letters in the DNA are first copied to a second similar molecule, known as mRNA, in a process called transcription. This mRNA molecule is then 'read' by molecular machines called ribosomes in order to produce the protein, a process known as translation. The proteins expressed within a cell determine its properties, e.g., how it will function and respond to its environment. The process of protein synthesis consumes a large proportion of a cell's energy and nutrients, and so it must be very tightly controlled. Furthermore, this process can be altered to favour the production of different proteins by allowing the machinery to preferentially 'read' certain mRNA molecules, which therefore allows the cell to respond quickly to a stressful environment caused, for example, by a reduction in available nutrients or energy. This kind of mechanism can also control the expression of different proteins as a cell goes through its stages of growth and division, the cell cycle. A key part of the control of protein synthesis involves proteins termed 'initiation factors', which are the focus of this research. These initiation factors control the attachment of the mRNA molecules to ribosomes and are vital to allow protein synthesis to start. They are also a key point of regulation under a wide variety of conditions because they control which mRNA molecules to recruit and even exactly where to start reading their code. The main focus of this research is a factor termed eIF2B, which is composed of 5 separate protein 'subunits'. We will also study two proteins that work with eIF2B in the process of protein synthesis, eIF2 and ABC50. The applicant's laboratory has many years' experience in investigating all these proteins.Disruption of the normal function of eIF2B can lead to disease. Slight spelling mistakes in the genes that encode the 5 subunits of eIF2B lead to an often-serious brain disease, known as 'vanishing white matter'. It also responds to insulin, and so is mis-regulated in type I (insulin-dependent) diabetes. This implies that the proper functioning of eIF2B is necessary to maintain a healthy cell. Furthermore, eIF2B, eIF2 and ABC50 limit the capacity of cells to make proteins that are used as drugs or in disease diagnosis, and which are of great commercial value.We aim to study four main aspects of eIF2B:1. How it is controlled, based on new discoveries made by the applicant's laboratory or others, to learn more about how this important protein can be controlled under different conditions in the cell;2. How cells can control how much of this protein they contain, and how this is related to the control of the amounts of eIF2 and ABC50: this is important as changes in the amounts of all these proteins will affect both how fast proteins can be made and how protein production is controlled;3. How changes in the amounts or the cellular activity of eIF2B (and ABC50) affect the production of specific proteins. This is important since, as described above, changes in protein synthesis have a major affect on how much of different proteins are present in cells, and thus on the function and 'health' of the cell;4. Its structure, using state-of-the-art techniques to investigate the way in which its five subunits are arranged and how they interact with its partner protein, eIF2.