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，以及细胞如何调节这些过程以应对环境线索。这个过程被称为“蛋白质合成”，发生在相对较大和复杂的称为核糖体的分子机器内，核糖体解码从称为信使RNA（mRNA）的中间分子内的基因组传递的指令。每个人类细胞都含有超过一百万个核糖体。核糖体对mRNA的解码是通过“助手”的协同作用实现的：蛋白质合成因子和转运RNA（tRNA）。它们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。当生物体必须对不断变化的环境做出反应时，在正确的时间制造正确的蛋白质至关重要，特别是那些含有毒素或其他有害物质的环境。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都至关重要。直到最近，人们还认为核糖体只是平等地翻译所有的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。翻译控制还允许响应于不同信号非常快速地产生蛋白质水平的变化。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，氧化损伤诱导剂引起蛋白质合成的广泛抑制，但特别允许mRNA的一个子集的翻译，包括克服所施加的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活跃的翻译还不清楚，但我们以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，这些蛋白存在量较低，可以调节核糖体活性。以这种方式，核糖体相互作用蛋白可以产生专门的核糖体，例如被指示翻译特定mRNA的核糖体。我们已经确定了一个家庭的这些蛋白质的研究在这个建议。这些蛋白质被称为La相关蛋白或LARP。正如它们的名字所暗示的那样，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，含有称为La基序或LaM的保守RNA结合结构域。我们正在研究的LARP也结合活性核糖体。我们将研究两个LARP，我们的初步研究表明，功能，以提供不同的翻译结果。一种是蛋白质合成的潜在激活剂，其允许靶向mRNA响应于氧化应激而逃避翻译抑制。在这项提案中，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，这项建议主要是一项基础科学建议。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。对蛋白质合成机制的进一步了解将有助于设计用于制造先进产品和药物的优化商业蛋白质表达或发酵系统。

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.