5'UTR RNA Regulons in ribosome-mediated control of embryonic development

 描述(由申请人提供)：基因在空间和时间上的表达控制在使细胞“知道”它们在发育中的胚胎中的位置以及成为什么方面发挥着重要作用，这一过程通常被称为细胞指定。几十年的研究已经证明，在转录和转录后水平上，对基因表达的控制有多个层次的调控，这些调控协调了这一过程。相反，基因表达的翻译调控在实验上受到的关注较少。最值得注意的是，流行的教条是，在蛋白质生产水平上，核糖体--尽管是一个极其复杂的分子机器--在翻译mRNA方面具有结构性功能，而不是调节功能。我们的发现出人意料地揭示了胚胎发育和组织模式的基本方面是由核糖体的高度调节功能控制的。重要的是，我们已经证明，含有独特的蛋白质组成或活性的“专门的核糖体”对哺乳动物基因组如何被解码成蛋白质具有极大的特异性。我们最近的研究也开始阐明编码在mRNA模板中的表达信息如何通过核糖体赋予基因调控潜力来指导胚胎发育。特别是，我们的研究发现了嵌入关键发育调控因子5‘UTRs中的新的RNA调节子，例如同源盒(Homeobox，HOX)基因的整个子集，它们指导基因产物如何在时间和空间上翻译，以形成哺乳动物的身体规划。这些发现改变了我们对基因调控的理解，并打开了一个新的理解门户，进入嵌入在脊椎动物5‘UTRs中的额外一层调节层，这对控制细胞规格、组织模式和胚胎发育至关重要。在这项提案中，我们将采用高度多学科的方法来表征这一新的调控代码，用于关键发育转录本的翻译控制，为转录后调控奠定基础。在Aim1中，我们将描述一种在时间和空间上控制Hox基因表达所需的新的转录后电路。特别是，我们将采用多方面的遗传学方法来揭示新的5‘UTRRNA调节子，包括多个HOX基因5’UTRs中的IRES样元件和Tie元件，对它们在体内表达和脊椎动物胚胎模式的关键方面所起的功能作用。在AIM2中，我们将描述Tie元件，这是一种新发现的RNA调节元件，具有显著的功能专门化哺乳动物基因组翻译的潜力。在Aim3中，我们将更广泛地定义RNA结合蛋白对IRES介导的关键脊椎动物发育调控因子的翻译控制的影响。总而言之，这些研究将打开一个新的门户，了解由脊椎动物5‘UTRs中嵌入的独特RNA元件促进的“语法规则”，这有助于扩大指导有机体发育的发育基因表达程序。

 DESCRIPTION (provided by applicant): Control of gene expression in space and time plays an important role in enabling cells to "know" where they are in the developing embryo and what to become, a process often referred to as cellular specification. Decades of research have demonstrated numerous layers of regulation in control of gene expression, at both the transcriptional and post-transcriptional level, which coordinate this process. Translational contro of gene expression has, on the contrary, received less experimental attention. Most notably, the prevailing dogma is that at the level of protein production, the ribosome -although an immensely complex molecular machine- possesses a constitutive rather than regulatory function in translating mRNAs. Our findings unexpectedly reveal that fundamental aspects of embryonic development and tissue patterning are instead controlled by a highly regulatory function of the ribosome. Importantly, we have shown that "specialized ribosomes" harboring a unique protein composition or activity confer tremendous specificity to how the mammalian genome is decoded into proteins. Our recent studies have also begun to elucidate how expression information encoded within the mRNA template confers gene regulatory potential by the ribosome to guide embryonic development. In particular, our research has identified novel RNA regulons embedded within the 5'UTRs of key developmental regulators, such as entire subsets of Homeobox (Hox) genes, which direct how gene products are translated in time and space to pattern the mammalian body plan. These findings transform our understanding of gene regulation and open a new portal of understanding into an additional layer of regulation embedded within vertebrate 5'UTRs vital to control of cell specification, tissue patterning, and embryonic development. In this proposal we will undertake a highly multidisciplinary approach to characterize this novel regulatory code for translational control of key developmental transcripts that primes them for post- transcriptional regulation. In Aim1 we will characterize a novel post-transcriptional circuitry required for control of Hox gene expression in time and space. In particular, we will undertake a multi-faceted genetic approach to uncover the functional roles of novel 5'UTR RNA Regulons including IRES-like and TIE elements in multiple Hox genes 5'UTRs towards key aspects of their expression in vivo and patterning of the vertebrate embryo. In Aim2 we will characterize the TIE element, a newly identified RNA regulatory element with remarkable potential to functionally specialize the translation of the mammalian genome. In Aim3 we will more broadly define the impact of RNA binding proteins on IRES-mediated translational control of key vertebrate developmental regulators. Together, these studies will open a new portal of understanding into the "grammatical rules" facilitated by unique RNA elements embedded within vertebrate 5'UTRs, which serves to expand developmental gene expression programs guiding organismal development.