Regulation of Mammalian mRNA Decapping

描述(申请人提供)：在真核基因表达的转录后调控中，信使核糖核酸稳定性的控制是一个关键的决定因素。即使是mRNA稳定性的微小变化也可能产生深远的后果，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所表明的那样。尽管信使核糖核酸的稳定性在控制基因表达方面很重要，但直到最近，才在鉴定和表征控制信使核糖核酸周转及其最终生理结果的成分方面取得了进展。我们一直致力于研究与mRNA衰变有关的核酸酶，特别是mRNA5‘端解链和解链的细胞生物学意义。我们现在已经确定了多种已证实的和可能的解帽结合酶，它们似乎调节着选定的一组mRNAs和通路。在这项提案中，我们将进一步阐述信使核糖核酸解离酶在细胞生物学和功能上的作用。我们已经证明了Dcp2解封酶选择性地调节参与先天性免疫的mRNAs的解封，并将继续探讨其在Aim1的先天性免疫反应中的作用。我们已经鉴定出以哺乳动物DXO蛋白为代表的一类新的解帽蛋白，它具有不同寻常的内在双重解帽和核酸外切酶活性。我们已经证明了DXO在核前mRNA5‘端质量控制机制中优先作用于不完全封顶的前mRNAs，现在有证据表明，它也作为一种“规范的”解离酶发挥作用，不成比例地调节参与细胞骨架结构和细胞迁移的mRNAs的子集。我们将探讨DXO在AIM2中的mRNA解离和细胞迁移中的作用。在Aim3中，我们将继续努力识别更多的mRNA解离酶，并破译我们最近在体外证明的六个新的Nudex家族蛋白的功能作用，它们是Nudt2、Nudt3、Nudt12、NUDT15、Nudt17和Nudt19。我们首先将重点放在进化上保守的Nudt3蛋白上，初步数据表明它是细胞中真正的脱氧核糖核酸酶。总而言之，这项工作将为涉及基因表达的基本转录后调控机制和病理条件下治疗干预的创新方法框架提供新的见解。

DESCRIPTION (provided by applicant): 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. Despite the importance of mRNA stability in the control of gene expression, progress has only recently been made in the identification and characterization of the components that control mRNA turnover and their ultimate physiological consequence. We have focused our efforts on the study of nucleases involved in mRNA decay, in particular, mRNA 5'end decapping and the cell biological significance of decapping. We have now identified multiple confirmed and putative decapping enzymes, which appear to modulate a select subset of mRNAs and pathways. In this proposal we will expand on the cell biological and functional role of mRNA decapping enzymes. We have shown the Dcp2 decapping enzyme selectively modulates the decapping of mRNAs involved in innate immunity and will pursue its role in the innate immune response in Aim1. We have identified a novel class of decapping proteins represented by the mammalian DXO protein, which possesses an unusual intrinsic dual decapping and exonuclease activities. We have already shown DXO preferentially functions on incompletely capped pre-mRNAs in a nuclear pre-mRNA 5'end quality control mechanism, and now have evidence it also functions as a "canonical" decapping enzyme disproportionally modulating a subset of mRNAs involved in cytoskeletal architecture and cell migration. We will pursue the role of DXO in mRNA decapping and cell migration in Aim2. In Aim3, we will build on our ongoing efforts to identify additional mRNA decapping enzymes and decipher the functional role of six new Nudix family proteins we recently demonstrated contain decapping activity in vitro, Nudt2, Nudt3, Nudt12, Nudt15, Nudt17 and Nudt19. We will initially focus on the evolutionarily conserved Nudt3 protein where preliminary data indicates it is a bona fide decapping enzyme in cells. Collectively, this work will provide novel insights into a fundamental post-transcriptional regulatory mechanism involved in gene expression and a framework for innovative approaches for therapeutic intervention in pathological conditions.