Regulation of Mammalian mRNA Decay

GM067005资助父母助学金摘要： MRNA稳定性的控制是转录后调控的关键决定因素 真核基因的表达。即使是信使核糖核酸稳定性的微小变化也可能 深远的后果，并可能表现为临床表型，如 异常表达的原癌基因可能导致恶性肿瘤的能力。 真核mRNAs通常被认为具有一个N7甲基鸟苷(M7G)帽 在其5美分端，以促进其稳定性和翻译。然而，我们最近 证明哺乳动物的mRNAs也可以携带5‘端的烟酰胺腺嘌呤 二核苷酸(NAD)帽与m7G帽不同，它促进mRNA衰退，提供 信使核糖核酸末端加工的新范式及核苷酸的作用 信使核糖核酸周转中的代谢产物。我们现在证明，NAD的氧化还原状态也可以 以游离NAD为辅因子调控3‘RNA衰变增强RNA衰变 潜在地提供了与细胞能量学的联系。此外，黄素腺嘌呤 二磷酸(FAD)也可以作为带有Nudt16和Nudt16的哺乳动物RNA的5‘帽 DXO水解酶作为蛋白质发挥作用，可以去除FAD帽(DeFADding) 体外培养。在整个提案中，我们将在这些新发现的基础上，在三个具体范围内 目标。第一个将讨论游离NAD在控制3‘端RNA中的功能作用 体外腐烂，描述其促进腐烂的分子机制。 第二个将推断由于NAD水平改变而导致的信使核糖核酸衰退的变化 并评估应激条件在调节RNA中的调节作用 通过控制NAD水平而腐烂。在最后一个目标中，我们将时尚帽设置为一个 替代RNA帽，识别FAD上限的RNA并破译FAD帽和 细胞中的脱脂酶。总的来说，拟议的研究将提供洞察力 一种迄今未知的基本转录后调控机制 将为潜在的控制基因表达的新途径提供框架。 正常状态和疾病状态。

Summary of the funded parental grant GM067005: The control of mRNA stability is a critical determinant in the post-transcriptional regulation of eukaryotic gene expression. Even minor alterations in mRNA stability can have profound consequences and may manifest as clinical phenotypes as illustrated by the ability of aberrantly expressed proto-oncogenes that can give rise to malignancies. Eukaryotic mRNAs are generally thought to possess an N7 methyl guanosine (m7G) cap at their 5¢ end to promote their stability and translation. However, our recent demonstration that mammalian mRNAs can also carry a 5´-end nicotinamide adenine dinucleotide (NAD) cap that in contrast to the m7G cap promotes mRNA decay, provides a new paradigm for mRNA 5´ end processing and the contribution of nucleotide metabolites in mRNA turnover. We now demonstrate that the redox state of NAD can also modulate 3´ RNA decay with free NAD functioning as a cofactor to enhance RNA decay and potentially providing a link to cellular energetics. Moreover, flavin adenine diphosphate (FAD) can also serve as a 5´ cap on mammalian RNAs with Nudt16 and DXO hydrolases functioning as proteins that can remove the FAD cap (deFADding) in vitro. We will build on these novel findings throughout this proposal within three specific aims. The first will address the functional role of free NAD on the control of 3´ end RNA decay in vitro and delineate the molecular mechanism involved in its stimulation of decay. The second will deduce changes in mRNA decay as a consequence of altered NAD levels in cells and assess the regulatory role imparted by stress conditions in modulating RNA decay through the control of NAD levels. In the last aim, we establish FAD cap as an alternative RNA cap, identify FAD-capped RNAs and decipher the role of FAD caps and the deFADding enzymes in cells. Collectively, the proposed studies will provide insight into a heretofore unknown fundamental post-transcriptional regulatory mechanism and will provide the framework for potential novel avenues to control gene expression in normal and disease states.