Mechanism of IRES-Mediated Translation Initiation

描述(由申请人提供)：大多数信使RNA(MRNAs)由帽依赖的启动机制翻译。然而，大约5%到10%的mRNAs使用另一种启动蛋白质合成的机制，利用内部核糖体进入位点(IRES)来招募核糖体来传递信息。IRES存在于编码与细胞生长、增殖、凋亡、缺氧和血管生成有关的蛋白质的mRNAs中。由于许多参与肿瘤发生的细胞mRNAs含有IRESS，我们预计IRES介导的翻译是开发广泛适用于多种癌症的抗癌治疗的良好靶点。由于机制尚不清楚，我们对IRESS如何招募核糖体感兴趣。一些研究表明，蟋蟀麻痹病毒(CRPV)的基因间隔区IRES(IGR-IRES)和细胞IRESS具有相同的结合核糖体的机制，表明IGR-IRES是一个很好的IRES模型。由于酵母和哺乳动物细胞之间的翻译是高度保守的，我们在酵母中开发了一个遗传系统来回答以下问题：1)哪些IGR-IRES结构或序列对IRES功能重要？2)IGR-IRES介导的翻译需要哪些核糖体成分？3)这些接触如何促进核糖体结合？4)rRNA修饰对IRES活性有什么贡献？5)这些发现如何应用于哺乳动物细胞中的IRESS？这个系统为我们提供了遗传学、生物化学，并将允许我们以在哺乳动物细胞中不可能实现的方式来操纵翻译机器的组成部分。我们选择使用一种创新的遗传学方法来理解IRES介导的翻译，因为尽管多个实验室多年来的努力，但细胞IRESS的启动机制一直难以捉摸。 与公共卫生相关：一些病毒和细胞mRNAs利用另一种翻译启动机制，利用高度结构化的内部核糖体进入位点(IRES)在内部招募核糖体到消息中。IRES介导的细胞mRNAs翻译参与调控癌症、细胞死亡、细胞生长和血管生成，以及病毒RNA的翻译。我们正在使用酵母遗传学来理解IRES介导的翻译启动的机制。

DESCRIPTION (provided by applicant): The majority of messenger RNAs (mRNAs) are translated by a cap-dependent mechanism of initiation. However, about 5% to 10% of mRNAs use an alternative mechanism of initiating protein synthesis, utilizing an internal ribosome entry site (IRES) to recruit the ribosomes to the message. IRESs are found in mRNAs that encode proteins involved in cell growth, proliferation, apoptosis, hypoxia, and angiogenesis. Because many cellular mRNAs that are involved in tumorigenesis contain IRESs, we anticipate that IRES-mediated translation is a good target for the development of anti-cancer therapies that will be broadly applicable to several types of cancer. Since the mechanism is not understood we are interested in how IRESs recruit ribosomes. Several studies have suggested that the cricket paralysis virus (CrPV) intergenic region IRES (IGR-IRES) and cellular IRESs share some mechanisms for binding ribosomes suggesting that the IGR-IRES is a good model IRES. Because translation is highly conserved between yeast and mammalian cells we have developed a genetic system in yeast to answer the following questions: 1) Which IGR-IRES structures or sequences are important for IRES function? 2) What components of the ribosome are required for IGR-IRES mediated translation? 3) How do these contacts facilitate ribosome binding? 4) What is the contribution of rRNA modifications for IRES activity? 5) How do these findings apply to cellular IRESs in mammalian cells? This system provides us with genetics, biochemistry, and will allow us to manipulate components of the translational machinery in ways that are not possible in mammalian cells. We chose to use an innovative genetic approach to understand IRES-mediated translation because the mechanism of initiation by cellular IRESs has been elusive despite many years of effort by multiple laboratories. PUBLIC HEALTH RELEVANCE: Some viral and cellular mRNAs utilize an alternative mechanism of translation initiation that recruits ribosomes internally to the message using a highly structured internal ribosome entry site (IRES). IRES-mediated translation of cellular mRNAs is involved in regulating cancer, cell death, cell growth, and angiogenesis, as well as translation of viral RNAs. We are using yeast genetics to understand the mechanism of IRES-mediated translation initiation.