Translational Control by the Fragile X Mental Retardation Protein

 描述(由申请人提供) 脆性X综合征是一种疾病，困扰着大约10万美国人和全球约300万人，导致患者智力残疾、童年癫痫和自闭症行为。这种疾病是由脆性X智力低下1基因(FMR1)的转录沉默引起的。FMR1基因编码一种RNA结合蛋白，即脆性X智力低下蛋白(FMRP)，它在大脑中高度表达，对大脑的正常发育至关重要。哺乳动物有两个常染色体平行的FMRP，分别被命名为脆性X相关蛋白1和2(FXR1和FXR2)。FXR1是肌肉发生所必需的，而FXR1的表达改变会导致面肩肩周肌营养不良，这是最常见的肌肉营养不良形式。FXR2的失活不会导致人类患病；然而，FMRP和FXR2的缺失会导致小鼠和果蝇患上更严重的FXS。因此，FMRP和FXR2似乎在大脑中具有重叠的功能，而FXR1对肌肉发育更关键。FMRP、FXR1和FXR2参与了几种mRNAs的翻译调控。然而，这些蛋白质调节这些mRNAs表达的确切机制尚不清楚。这项研究的目的是了解FMRP、FXR1和FXR2调节蛋白质合成的分子机制。我们有强有力的初步结果表明，FMRP可以直接与80S核糖体结合，调节蛋白质的合成。在具体目标1中，我们将剖析 果蝇FMRP的翻译调控机制在具体目标2中，我们将重点研究人类FMRP、FXR1和FXR2的翻译调控机制。对于这两个特定目标，我们将使用我们实验室开发的强大的体外翻译系统和定量生物物理方法，以及使用人类细胞系和转基因果蝇进行的体内研究。这些功能分析与所提出的高分辨率冷冻电子显微镜相结合，将极大地促进我们对FMRP、FXR1和FXR2调节蛋白质合成的分子机制的理解。这些研究的结果将为确定治疗脆性X的潜在药物靶点提供有用的见解 综合征和面肩肩关节肌营养不良症。

 DESCRIPTION (provided by applicant) Fragile X syndrome is a disease that afflicts about 100,000 Americans and about 3 million people worldwide, resulting in intellectual disability, childhood seizures, and autistic behavior i the patients. The disease is caused by the transcriptional silencing of the fragile X mental retardation 1 gene (FMR1). FMR1 gene codes for a RNA-binding protein, the fragile X mental retardation protein (FMRP), which is highly expressed in the brain and is essential for the normal development of the brain. Mammals have two autosomal paralogs of FMRP designated as fragile X related 1 and 2 (FXR1 and FXR2) proteins. FXR1 is essential for myogenesis and the altered expression of FXR1 causes facioscapulohumeral muscular dystrophy, the most prevalent form of muscular dystrophy. Inactivation of FXR2 does not cause a disease in humans; however, loss of both FMRP and FXR2 results in a more severe form of FXS in mice and Drosophila. Thus, FMRP and FXR2 appear to have overlapping functions in the brain, whereas FXR1 is more critical for muscle development. FMRP, FXR1 and FXR2 have been implicated in regulating the translation of several mRNAs. However, the precise mechanism by which these proteins regulate the expression of these mRNAs is unknown. The goal of the proposed study is to understand the molecular mechanism underlying the regulation of protein synthesis by FMRP, FXR1 and FXR2. We have strong initial results showing that FMRP can bind directly to the 80S ribosome to regulate protein synthesis. In Specific Aim 1, we will dissect the mechanism of translational control by Drosophila FMRP. In Specific Aim 2, we will focus on the mechanism of translational control by human FMRP, FXR1 and FXR2. For both specific aims, we will use a robust in vitro translation system and quantitative biophysical methods that have been developed in our laboratory, and in vivo studies, using human cell lines and transgenic Drosophila. These functional analyses, in conjunction with the proposed high-resolution cryo-electron microscopy, will significantly advance our understanding of the molecular mechanism used by FMRP, FXR1 and FXR2 to regulate protein synthesis. Results of these studies will provide useful insights in identifying potential drug targets to treat fragile X syndrome and facioscapulohumeral muscular dystrophy.