Characterization of a microRNA regulated F-box protein in Arabidopsis development

描述（由申请人提供）：MicroRNA （miR）调控和蛋白质破坏是细胞网络时空调控的两个共同主题。这些转录后机制微调了细胞内蛋白质的作用，并在真核生物的多种过程中发挥重要作用，包括致癌信号传导、细胞周期调节、昼夜节律、病原体反应和细胞规范。miR和泛素-蛋白酶体机制在真核生物中都是高度保守的，它们在植物中的研究比其他模式系统有一些明显的优势。例如，植物miRs靶向独特的、易于识别的mrna，最大限度地减少了间接影响的可能性。这与后生动物系统形成对比，后者的miR目标预测仍然很困难。植物也有大量的F-box蛋白，这些分子控制着蛋白质降解的主要途径。这种扩展可能有助于增加细胞类型和这些蛋白质的过程专业化。由于F-box蛋白的特异性尚不清楚，在模式植物拟南芥中的研究提供了一个独特的机会来研究准确的底物靶向是如何发生的。本研究的重点是拟南芥ULO （UNUSUAL LATERAL ORGANS）蛋白的功能和调控，ULO是一个包含F-box蛋白的Kelch结构域，转录后受两个miRs （miR394a/b）调控。具体而言，本项目旨在(1)确定ULO特异性蛋白质降解复合物（es）的组成，(2)检查ULO的转录和转录后控制，以及(3)确定ULO对器官发生的贡献。这些目标将通过生物化学、蛋白质组学、遗传学和显微镜学来实现。ULO提供了一个独特的机会来研究深度保守的miR-和蛋白酶体介导的多细胞生物调节机制之间的相互作用。

DESCRIPTION (provided by applicant): MicroRNA (miR) regulation and protein destruction are two common themes in spatiotemporal regulation of cellular networks. These post-transcriptional mechanisms fine tune protein action within cells and play important roles in diverse processes among eukaryotes including oncogenic signaling, cell cycle regulation, circadian rhythms, pathogen response and cell specification. Both the miR and ubiquitin- proteasome machineries are highly conserved between eukaryotes, and their study in plants has some marked advantages over other model systems. For instance, plant miRs target unique, easily identifiable mRNAs, minimizing the possibility of indirect effects. This is in contrast to metozoan systems where miR target prediction is still difficult. Plants also have a greatly expanded number of F-box proteins, molecules controlling a major route of protein degradation. This expansion may have contributed to increased cell type and process specialization for these proteins. As the specificity of F-box proteins is not well understood, studies in the model plant Arabidopsis provide a unique opportunity to examine how accurate substrate targeting occurs. This proposal is focused on the function and regulation of the Arabidopsis ULO (UNUSUAL LATERAL ORGANS) protein, a Kelch domain containing F-box protein that is post-transcriptionally regulated by two miRs (miR394a/b). Specifically, this project aims to (1) determine the composition of ULO-specific protein degradation complex(es), (2) examine the transcriptional and post-transcriptional control of ULO, and (3) determine the contribution of ULO to organogenesis. These goals will be accomplished by employing biochemistry, proteomics, genetics, and microscropy. ULO provides a unique opportunity to study the interplay between the deeply conserved miR- and proteasome-mediated regulatory mechanisms in a genetically tractable, multicellular organism. PUBLIC HEALTH RELEVANCE: This research is focused on plant development and utilizes Arabidopsis thaliana (mouse-ear cress), which is a key model organism and a close relative of numerous crop species such as canola, broccoli and papaya. The goal is to determine the role of a protein, UNUSUAL LATERAL ORGANS (ULO), in organ patterning during embryo, leaf and flower formation. ULO-related proteins are found in many organisms, including humans, and this large family of proteins can play important roles in many aspect of human disease, including cancer and diabetes.