Mechanisms of Post-Transcriptional Control of Neuronal mRNAs

描述（由申请人提供）：除了转录，转录后机制，如RNA加工，mRNA稳定性和局部翻译对控制许多神经系统特异性基因的表达也很重要。对于大量的神经元基因，其表达水平受mRNA稳定性变化的控制。这些过程是由rna结合蛋白和mrna中赋予不稳定性的序列之间的特定相互作用调节的。神经元中最具特征的转录后调控基因之一是GAP-43。在我们之前的资助下所做的工作表明，GAP-43基因的表达受到mRNA稳定性的选择性变化的调节，这一过程取决于mRNA 3‘非翻译区（3’UTR）中高度保守的调控元件与神经元特异性rna结合蛋白HuD的相互作用。HuD不仅能够稳定培养发育神经元中GAP-43 mRNA的表达，而且在转基因小鼠中过表达该蛋白会增加海马和新皮层中GAP-43基因的表达。我们最近发现，促不稳定rna结合蛋白KSRP也与GAP-43 mRNA结合，这表明该蛋白可能是成熟齿状颗粒细胞中观察到的GAP-43 mRNA快速降解的原因。基于我们的初步研究，我们提出GAP-43和其他转录后调控的神经元基因的稳定性是由促稳定因子如HuD和促降解因子如KSRP的相互作用控制的。为了验证这一假设，我们计划在以下两个具体目标下进行研究：目的1。探讨HuD和KSRP调控神经元mrna稳定性的机制。目标2。明确HuD和KSRP在发育和成体可塑性过程中神经元基因表达的转录后调控中的功能。虽然目标集中在GAP-43上，但我们的研究将包括HuD的其他靶点，如neuroserpin和tau。之所以选择这些mrna，是因为它们是轴突定位的，受发育调控，在损伤反应中上调，因此可能受到类似机制的控制。提出的研究将表征GAP-43和其他转录后调控的神经元mrna的控制机制。鉴于这些蛋白在神经系统发育、突触可塑性和神经再生中的作用，阐明控制其mrna的调控机制具有广泛的潜在应用，从神经发育障碍的治疗到脑外伤和脊髓损伤的恢复。

DESCRIPTION (provided by applicant): Besides transcription, post-transcriptional mechanisms such as RNA processing, mRNA stability and local translation are also important for controlling the expression of many nervous system-specific genes. For a large number of neuronal genes, expression levels are controlled by changes in mRNA stability. These processes are regulated by specific interactions between RNA-binding proteins and instability-conferring sequences in the mRNAs. One of the best characterized post-transcriptionally regulated genes in neurons is that for GAP-43. Work done under our previous grants demonstrated that GAP-43 gene expression is regulated by selective changes in the stability of its mRNA and that this process depends on the interaction of a highly conserved regulatory element in the 3'untranslated region (3'UTR) of the mRNA with the neuronal-specific RNA-binding protein HuD. Not only is HuD capable of stabilizing GAP-43 mRNA in developing neurons in culture, but also overexpression of this protein in transgenic mice increases GAP-43 gene expression in the hippocampus and neocortex. We have recently found that the pro-destabilizing RNA-binding protein KSRP also binds to the GAP-43 mRNA, suggesting that this protein may be responsible for the fast degradation of the GAP-43 mRNA observed in mature dentate granule cells. Based upon our preliminary studies, we propose that the stability of GAP-43 and other post- transcriptionally-regulated neuronal genes is controlled by the interplay of pro-stabilization factors such as HuD and pro-degradation factors such as KSRP. To test this hypothesis, we plan to perform the studies under the following two specific aims: Aim 1. To explore the mechanism by which HuD and KSRP control the stability of neuronal mRNAs. Aim 2. To define the function of HuD and KSRP in the post-transcriptional control of neuronal gene expression in vivo during developmental and adult plasticity. Although the aims are focused on GAP-43, our studies will include other targets of HuD such as neuroserpin and tau. These mRNAs were chosen because they are axonally-localized, developmentally- regulated, up-regulated in response to injury and thus, likely to be controlled by similar mechanisms. The proposed studies will characterize the mechanisms of control of GAP-43 and other post- transcriptionally-regulated neuronal mRNAs. Given the role of these proteins in nervous system development, synaptic plasticity, and nerve regeneration, the elucidation of regulatory mechanisms controlling their mRNAs has a broad range of potential applications, from the treatment of neurodevelopmental disorders to the recovery from brain trauma and spinal cord injury.