Post-transcriptional gene regulation in Alzheimer's Disease

哺乳动物细胞通过改变基因表达模式来响应生理和病理信号。转录后过程(RNA剪接和成熟，以及mRNA的运输、稳定和翻译)越来越被认为是控制基因表达的关键。两项研究正在RNA调节科进行，以调查阿尔茨海默病(AD)的转录后基因控制。通过这些研究，我们试图阐明在AD发病机制中，mRNA序列、RNA结合蛋白和microRNAs在调节关键基因产物表达方面的作用。 第一组研究旨在研究淀粉样前体蛋白(APP)表达的转录后调控。APP是一种细胞表面蛋白，其切割可导致与AD相关的小胞外肽(Aβ或淀粉样β蛋白)的产生。淀粉样变细胞过度表达APP mRNA，进而促进有毒Abeta肽的产生，导致它们在AD患者的大脑中积累和沉积。鉴于早期的报道称，APP的表达受到改变的mRNA稳定性和蛋白质生物合成的关键调控，我们正在寻求系统地鉴定与APP mRNA相关的RNA结合蛋白和microRNAs，并影响它们的半衰期和翻译。使用一些体外和体内的方法，我们已经开始评估APP mRNA与已知的识别AU丰富转录本的RNA结合蛋白的相关性，包括Hur、AUF1、TTP、TIA-1、TIAR、KSRP、FMRP、NF-90、hnRNP A1和BRF1。我们已经鉴定出两种RNA结合蛋白，它们通过与APP mRNA的编码区结合来调节APP的翻译，并调节其亚细胞定位。最近提交了一份描述我们调查结果的报告以供发表。另一种与APP mRNA相互作用的RBP(RBP HUD)最近被发现受microRNA miR-375调控(Abdelmohsen等人，Mol.牢房。比奥尔。2010)。 其次，我们计划研究多态非编码序列对AD易感基因转录后调控的影响。晚发性AD的发病机制尚不清楚，但连锁研究已将关键的晚发性AD易感基因定位于12号染色体上的一个区域。该染色体区域的两个基因被推测参与AD的发病：氧化型低密度脂蛋白受体1(OLR1)和转录因子LBP-1c/CP2/LSF。鉴于这两个基因具有3UTR多态，我们正在调查这些具有多态未翻译序列的等位基因是否受到不同转录后调控。 与I.I.Kruan博士合作，我们研究了AD发病机制的一个特征，即神经元对大分子损伤的反应能力受损。最近的一份报告描述了周期蛋白C是激活有丝分裂后神经元中非同源末端加入DNA修复所必需的(Tomashevski等人，Cell Death Diff)。2010)。

Mammalian cells respond to physiological and pathological cues by implementing changes in gene expression patterns. Post-transcriptional processes (RNA splicing and maturation, as well as mRNA transport, stability and translation) are increasingly recognized as being critically responsible for controlling gene expression. Two studies are underway in the RNA Regulation Section to investigate post-transcriptional gene control in Alzheimers Disease (AD). Through these studies, we seek to elucidate the contribution of mRNA sequences, RNA-binding proteins, and microRNAs towards regulating the expression of critical gene products in AD pathogenesis. The first set of studies is aimed at investigating the post-transcriptional regulation of amyloid precursor protein (APP) expression. APP is a cell-surface protein whose cleavage can lead to the generation of small extracellular peptides (Abeta or amyloid-beta peptides) which are involved in AD. Amyloidogenic cells overexpress APP mRNA, which in turn enhances the production of toxic Abeta peptides leading to their accumulation and deposit in the brains of patients with AD. Given earlier reports that APP expression is critically regulated by altered mRNA stability and protein biosynthesis, we are seeking to systematically identify the RNA-binding proteins and microRNAs that associate with the APP mRNA and influence their half-life and translation. Using a number of in vitro and in vivo approaches, we have began to assess the association of APP mRNA with known RNA-binding proteins that recognize AU-rich transcripts, including HuR, AUF1, TTP, TIA-1, TIAR, KSRP, FMRP, NF-90, hnRNP A1, and BRF1. We have identified two RNA-binding proteins that regulate the translation of APP by binding to the coding region of APP mRNA and modulate its subcellular localization. A report describing our findings was recently submitted for publication. Another RBP that interacts with the APP mRNA (the RBP HuD) was recently identified as being regulated by microRNA miR-375 (Abdelmohsen et al., Mol. Cell. Biol. 2010). Second, we plan to investigate the influence of polymorphic noncoding sequences on the post-transcriptional regulation of AD susceptibility genes. The pathogenesis of late-onset AD is not well understood, but linkage studies have mapped critical late-onset AD susceptibility genes to a region in chromosome 12. Two genes in this chromosomal region have been postulated to participate in AD: oxidized LDL-receptor 1 (OLR1) and transcription factor LBP-1c/CP2/LSF. Given that these two genes bear 3UTR polymorphisms, we are investigating if such alleles with polymorphic untranslated sequences are subject to differential post-transcriptional regulation. In collaboration with Dr. I.I. Kruman, we investigated a feature of AD pathogenesis, the impaired ability of neurons to respond to macromolecular damage. A recent report describes that cyclin C is necessary for activation of nonhomologous end joining DNA repair in postmitotic neurons (Tomashevski et al., Cell Death Diff. 2010).