Specialised ribosomes facilitating cellular responses to oxidative stress

我们研究细胞如何控制营养物质（或食物）转化为生命所需的新蛋白质，以及细胞如何根据环境线索调节这些过程。这个过程被称为“蛋白质合成”，发生在相对较大和复杂的核糖体分子机器中，核糖体解码来自基因组的指令，这些指令传递在称为信使rna （mrna）的中间分子中。每个人体细胞含有超过一百万个核糖体。核糖体的mRNA解码是通过“助手”的协同作用实现的：蛋白质合成因子和转移rna （tRNAs）。它们协调一致地将必需的氨基酸与指令结合在一起，以确保在正确的时间制造正确的蛋白质。当生物体必须应对不断变化的环境，特别是那些含有毒素或其他有害物质的环境时，在正确的时间制造正确的蛋白质是至关重要的。细胞如何感知变化并控制它们的反应对生物学的许多领域至关重要。直到最近，人们才认为核糖体只是平等地翻译所有mRNA， mRNA水平是基因表达的一个很好的代表。然而，对细胞中mRNA和蛋白质水平的越来越精确的测量表明，mRNA和蛋白质水平之间可能存在很大的差异。翻译控制是用来描述这些差异的主要贡献者的术语。翻译控制还允许蛋白质水平的变化，以非常迅速地产生响应不同的信号。我们在这里研究的一种压力是细胞对氧化损伤诱导剂的反应，氧化损伤诱导剂导致蛋白质合成的广泛抑制，但特别允许mrna子集的翻译，包括克服压力所需的抗氧化酶。目前，mrna如何克服一般应激诱导的蛋白质合成抑制并保持积极翻译尚不清楚，但我们之前的工作提供了强有力的线索，这是我们建议的重点。核糖体与许多辅助蛋白相互作用，这些辅助蛋白含量较低，可以调节核糖体的活性。通过这种方式，核糖体相互作用的蛋白质可以产生专门的核糖体，例如，指示核糖体翻译特定的mrna。我们已经确定了这些蛋白的一个家族用于本提案的研究。这些蛋白质被称为La相关蛋白或LARPs。顾名思义，它们与一种名为La的蛋白质有关，这种蛋白质是在自身免疫性疾病的研究中发现的。La和LARP蛋白是RNA结合蛋白，含有一个保守的RNA结合域，称为La基序或LaM。我们正在研究的LARPs也结合活性核糖体。我们将研究两种larp，我们的初步研究表明它们的功能会产生不同的翻译结果。一种是蛋白质合成的潜在激活剂，它允许靶向mrna在氧化应激反应中逃避翻译抑制。在本提案中，我们希望揭示它如何与核糖体和mrna相互作用，以及这些相互作用如何导致靶蛋白合成增强及其在氧化应激期间的持续翻译。因此，这个建议主要是一个基础科学建议。然而，这项工作的结果也可能对生产特定蛋白质作为药物治疗或商业产品的公司感兴趣。提高对蛋白质合成机制的理解将有助于设计优化的商业蛋白质表达或发酵系统，用于制造先进的产品和药物。

We study how cells control the conversion of nutrients (or food) into the new proteins that are required for life and how cells moderate these processes in response to environmental cues. Termed 'protein synthesis' this process occurs within relatively large and complex molecular machines called ribosomes that decode instructions relayed from the genome within intermediary molecules called messenger RNAs (mRNAs). Human cells each contain over a million ribosomes. mRNA decoding by ribosomes is made possible by the concerted action of 'helpers': protein synthesis factors and transfer RNAs (tRNAs). In concert they bring the necessary amino acids together with the instructions to ensure the correct proteins are made at the right time. Making the right proteins at the right time is critical when organisms have to respond to changing environments, especially those containing toxins or other harmful agents. How cells sense the changes and control their responses is critical to many areas of biology. Until relatively recently it was assumed that ribosomes simply translated all mRNAs equally and that mRNA levels were a good proxy for the expression of genes. However increasingly accurate measurements of mRNA and protein levels in cells show that there can be a wide discrepancy between mRNA and protein levels. Translational control is the term used to describe a major contributor to these differences. Translational controls also allow changes in protein levels to be generated very rapidly in response to different signals. One stress we are studying here is the cellular responses to oxidative damage inducing agents which causes widespread repression of protein synthesis, but specifically allows translation of a subset of mRNAs, including antioxidant enzymes needed to overcome the stress imposed. At present how mRNAs overcome the general stress induced repression of protein synthesis and remain actively translated is not clear, but our previous work has provided strong clues and this is the focus of our proposal.Ribosomes interact with many accessory proteins, which are present in lower amounts and can moderate ribosome activity. In this way ribosome interacting proteins may act to generate specialised ribosomes, for example ribosomes instructed to translate particular mRNAs. We have identified one family of these proteins for study in this proposal. These proteins are called La Related proteins or LARPs. As their name suggests, they are related to a protein called La, which was identified in the study of autoimmune disease. La and LARP proteins are RNA binding proteins that contain a conserved RNA binding domain called the La motif or LaM. The LARPs we are studying also bind active ribosomes. We will study two LARPs that our preliminary studies suggest function to give different translation outcomes. One is a potential activator of protein synthesis that allows targeted mRNAs to escape translational repression in response to oxidative stress. In this proposal we wish to uncover how it interacts with both ribosomes and mRNAs and how these interactions lead to enhanced protein synthesis of targets and their continued translation during oxidative stress. As such this proposal is primarily a basic science proposal. However the outcomes of the work may also be of interest to companies that produce specific proteins as drug therapeutics or commercial products. Improved understanding of protein synthesis mechanisms will assist in the design of optimized commercial protein expression or fermentation systems that are used to make advanced products and medicines.