Mechanisms of microRNA turnover in Arabidopsis

 描述（由申请人提供）：微小RNA（miRNAs）是基因表达的序列特异性调节因子，影响各种真核生物中几乎所有的生物过程。miRNA水平或活性的缺陷与许多疾病相关。生物合成和降解都有助于体内miRNA的稳态水平。miRNA生物发生的基本分子框架已经阐明。相反，尽管在纤毛虫、藻类、植物和动物模型中的研究已经暗示存在降解miRNA和相关小RNA的保守过程，例如小干扰RNA（siRNA）和piwi相互作用RNA（piRNA），但降解小RNA的酶在大多数生物体中尚未被鉴定。因此，miRNA降解的基本框架有待进一步研究。本项目的目标是建立这样一个框架。 该项目利用了PI实验室使用拟南芥模型在miRNA降解领域的最新进展。PI的实验室鉴定了负责真核生物中两种保守的miRNA降解过程的酶，即3'截短和3'尿苷化（向miRNA添加短的富含U的尾部）。拟议的研究采用遗传学，基因组学和生物化学方法的组合来检查这些酶的活性，相互依赖性和协同作用，旨在建立miRNA降解的一般框架。PI的实验室还收集了初步证据，表明内源性靶模拟RNA参与了miRNA的周转。该项目将研究目标模拟RNA和一般miRNA降解机制之间的相互作用如何导致特定miRNA的周转。 通过阐明miRNA降解的原理，该项目将产生深远的影响。越来越多的证据表明，在不同的真核生物中的miRNA降解的保守的分子机制，提出的研究使用拟南芥模型，其中两个保守的miRNA降解过程首次被描述，并负责这些过程的酶首次被确定，将建立一个一般的框架的miRNA降解，可能适用于其他真核生物，包括人类。这些知识将丰富我们对miRNA影响的各种生物学过程的理解，并增强我们控制miRNA丰度以治疗疾病的能力。miRNA降解的分子框架也可能适用于siRNA或piRNA，它们正在成为赋予植物和动物表观遗传记忆的试剂，从而进一步扩大了这项工作的影响。

 DESCRIPTION (provided by applicant): microRNAs (miRNAs) are sequence-specific regulators of gene expression that impact almost all biological processes in diverse eukaryotes. Defects in miRNA levels or activities are associated with numerous diseases. Both biogenesis and degradation contribute to the steady-state levels of miRNAs in vivo. The basic molecular framework underlying miRNA biogenesis has been elucidated. In contrast, although studies in ciliate, algal, plant, and animal models have implicated the existence of conserved processes that degrade miRNAs and related small RNAs, such as small interfering RNAs (siRNAs) and piwi-interacting RNAs (piRNAs), the enzymes that degrade small RNAs have yet to be identified in most organisms. As such, a basic framework of miRNA degradation awaits further studies. The goal of this project is to establish such a framework. The project capitalizes on recent advances in the area of miRNA degradation made in the PI's laboratory using the Arabidopsis model. The PI's lab identified the enzymes responsible for two conserved miRNA degradation processes in eukaryotes, 3' truncation and 3' uridylation (addition of a short, U-rich tail to miRNAs). The proposed research employs a combination of genetics, genomics, and biochemical approaches to examine the activities, interdependence and concerted actions of these enzymes with the goal of establishing a general framework of miRNA degradation. The PI's lab has also gathered preliminary evidence that implicates endogenous target mimic RNAs in miRNA turnover. The project will examine how the interplay between target mimic RNAs and the general miRNA degradation machinery results in the turnover of specific miRNAs. By elucidating principles governing miRNA degradation, the project will generate far-reaching impacts. As mounting evidence points to conserved molecular mechanisms underlying miRNA degradation in diverse eukaryotes, the proposed studies using the Arabidopsis model, from which two conserved miRNA degradation processes were first described and the enzymes responsible for these processes were first identified, will establish a general framework of miRNA degradation that is likely applicable to other eukaryotes including humans. The knowledge will enrich our understanding of various biological processes that are influenced by miRNAs and enhance our ability to control miRNA abundance to treat diseases. The molecular framework of miRNA degradation is also likely applicable to siRNAs or piRNAs, which are emerging as agents that confer epigenetic memory in plants and animals, thus further broadening the impacts of the work.