TRANSLATIONAL REGULATION OF CARDIAC PROTEIN SYNTHESIS

描述(由申请人提供)： 本项目研究了翻译在负荷诱导的心肌肥厚过程中加速总蛋白合成的作用。肥厚的另一个方面是相对较少的基因表达的质变，这是调节心脏生长和重塑所必需的。这一更新将集中在成年心肌细胞如何优先合成特定蛋白质，以响应增加的负荷，特别是在肥大生长期间发挥调节能力的蛋白质。单个mRNA必须相互竞争才能与核糖体结合，才能启动翻译。单个mRNA分子与核糖体结合的能力由5‘-非翻译区(5’-UTR)二级结构数量等内在特征和翻译起始因子活性等外在因素决定。大多数mRNAs被认为在翻译方面是第二强的，因为它们具有最小的二级结构和/或因为它们具有有利于核糖体结合的特征。一些人 例如编码肌动蛋白和肌球蛋白等肌节蛋白的mRNAs。相比之下， 转录因子、生长因子和细胞信号分子等调节蛋白来自于mRNAs，这些mRNAs在各自的5‘-UTRs中往往具有大量的二级结构。这些mRNAs在翻译方面被认为是“弱的”。在稳定状态下，由于核糖体优先与较强的mRNAs结合，弱的mRNAs的表达通常较低。为了使心肌细胞生长，我们假设相对于强的mRNAs，弱的mRNAs的翻译效率必须有选择地提高。因此，这一提议将检验一种假设，即负荷的增加会触发较弱的mRNAs的优先翻译，其中许多mRNAs编码心肌细胞生长所需的蛋白质。其具体目标是：1)通过测量具有弱(I类)mRNA5‘-UTR特征的候选mRNAs的效率来确定优先翻译的mRNAs；2)通过产生含有来自弱(I类和II类)和强(III类)mRNAs的5’-UTR的腺病毒报告载体，研究5‘-UTR中的结构元件如何优先调节翻译效率；3)通过测量eIF-4E和信使核糖核蛋白颗粒(MRNP)之间的相互作用，检查5’-UTR中的结构元件与参与调节翻译效率的特定蛋白质之间的联系。这项提议的意义在于，它将审查 如何通过解决成年心肌细胞如何通过转录以外的方式调节基因表达 优先翻译一组精选的蛋白质，这些蛋白质是生长过程中不可或缺的。

DESCRIPTION (provided by applicant): This project has addressed the role of translation in accelerating the rate of total protein synthesis during load-induced cardiac hypertrophy. Another aspect of hypertrophy is qualitative changes in the expression of a relatively small number of genes, which are required for regulating cardiac growth and remodeling. This renewal will focus on how select proteins are preferentially synthesized in the adult cardiocyte in response to increased load, specifically proteins which function in a regulatory capacity during hypertrophic growth. Individual mRNAs must compete with each other for binding to ribosomes in order to initiate translation. The capability of an individual mRNA molecule to bind ribosomes is determined by intrinsic features such as the amount of secondary structure in the 5'-untranslated region (5'-UTR), and by extrinsic factors such as the activity of translation initiation factors. The majority of mRNAs are considered to be iestrongld with respect to translation because they have minimal secondary structure and/or because they possess features favorable for ribosome binding. Some examples are mRNAs encoding for sarcomeric proteins such as actin and myosin. In contrast, regulatory proteins such as transcription factors, growth factors and cell signalling molecules are derived from mRNAs that tend to have an extensive amount of secondary structure in their respective 5'-UTRs. These mRNAs are considered to be "weak" with respect to translation. The expression of weak mRNAs is normally low at steady state because ribosomes bind preferentially to the stronger mRNAs. For cardiocyte growth to occur, we posit that translational efficiency of weak mRNAs must be selectively improved relative to strong mRNAs. Therefore, this proposal will test the hypothesis that an increase in load triggers the preferential translation of weaker mRNAs, many of which encode for proteins required for cardiocyte growth. The specific aims are: 1) to identify mRNAs that are preferentially translated in response to changes in load by measuring the efficiency of candidate mRNAs which have features in the 5'-UTR characteristic of weak (Class I) mRNAs; 2) to examine how structural elements in the 5'-UTR preferentially regulate translational efficiency by generating adenoviral reporter constructs containing 5'-UTRs derived from weak (Class I and Class II) and strong (Class III) mRNAs; 3) to examine the link between structural elements in the 5'-UTR and specific proteins involved in regulating translational efficiency by measuring interactions between eIF-4E and messenger ribonucleoprotein particles (mRNPs). The significance of this proposal is that will examine how gene expression is regulated beyond transcription by addressing how the adult cardiocyte preferentially translates a select set of proteins, which are integral to the growth process.