Regulation of Eukaryotic Protein Synthesis Initiation

描述（由申请人提供）：本项目的长期目标是 了解真核mRNA募集过程中发生的步骤， 核糖体以及它们是如何被调控的这个过程决定了 蛋白质合成的总速率以及mRNA翻译的谱。 四个具体目标主要涉及两个相互作用的启动因素 这一过程的核心是：eIF 4 E，一种结合 mRNA的含7-甲基鸟苷帽，和eIF 4G，连接 所有已知参与mRNA募集的起始因子。的 线虫C.秀丽线虫为研究这种 作为蛋白质合成起始的复杂生化过程。令人惊讶的是， 它表达五种eIF 4 E同种型，称为IFE蛋白，它们具有不同的 封端结合性质。在具体目标1中，我们将尝试推断出 通过研究它们与m7 G-和m3的生物化学相互作用， 含“2”7 G的帽类似物和寡核苷酸与mRNA以及与其他 蛋白质，在后一种情况下利用MALDI-TOF质谱。在特定 目的2，我们将确定人eIF 4 E磷酸化对蛋白质的影响， 合成速率eIF 4G结合eIF 4 E和poly（A）结合蛋白， 两个C是mRNA募集的作用效应物，但许多eIF 4G和 在哺乳动物细胞中观察到eIF 4G mRNA。在具体目标3中，我们 确定这些eIF 4G亚型的结构、功能和起源， 表征已知起始因子与它们的结合。具体目标 4、我们将确定eIF 4G亚型在体内的功能，特别是在 强调eIF 4G切割在picomavirus-induced 宿主关闭蛋白质合成。因为eIF 4 E和eIF 4 E的过度表达， eIF 4G导致细胞的恶性转化，并且由于天然存在 肿瘤中eIF 4 E的水平大大升高，这些研究具有相关性 到癌症它们也与由小核糖核酸病毒引起的疾病有关， 如脊髓灰质炎病毒（小儿麻痹症），鼻病毒（普通感冒）和柯萨奇病毒（心脏 失败）。

DESCRIPTION (provided by applicant): The long-term goals of this project are to understand the steps that occur during the recruitment of eukaryotic mRNA to the ribosome and how they are regulated. This process determines both the overall rate of protein synthesis and also the spectrum of mRNAs translated. The four Specific Aims principally concern two interacting initiation factors that are central to this process: eIF4E, the protein that binds the 7-methylguanosine-containing cap of mRNA, and eIF4G, the protein that links together all initiation factors known to be involved in mRNA recruitment. The nematode C. elegans provides unparalleled advantages for studying such a complex biochemical process as initiation of protein synthesis. Surprisingly, it expresses five eIF4E isoforms, termed IFE proteins, which have differing cap-binding properties. In Specific Aim 1, we wi2ll attempt to infer their biological roles by studying their biochemical interactions with m7G- and m3 '2'7G-containing cap analogues and oligonucleotides, with mRNAs, and with other proteins, utilizing MALDI-TOF mass spectrometry in the latter case. In Specific Aim 2, we will determine the effect of human eIF4E phosphorylation on protein synthesis rate. eIF4G binds to both eIF4E and the poly(A)-binding protein, the two C is-acting effectors for mRNA recruitment, yet many isoforms of eIF4G and eIF4G mRNA are observed in mammalian cells. In Specific Aim 3, we will determine the structure, function, and origin of these eIF4G isoforms and characterize the binding of known initiation factors to them. In Specific Aim 4, we will determine the function of eIF4G isoforms in vivo, with special emphasis on the relative importance of eIF4G cleavage in picomavirus-induced host shut-off of protein synthesis. Because overexpression of both eIF4E and eIF4G causes malignant transformation of cells, and because naturally occurring tumors contain greatly elevated levels of eIF4E, these studies have relevance to cancer. They also have relevance for diseases caused by picornaviruses such as poliovirus (polio), rhinovirus (the common cold) and Coxsackievirus (heart failure).