Mechanisms of Post-Transcriptional Control of Neuronal mRNAs

除了转录外，转录后机制，如RNA加工、mRNA稳定性和 局部翻译对于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，表达水平由mRNA稳定性的变化控制。 这些过程受到RNA结合蛋白和不稳定性之间的特定相互作用的调节， 赋予mRNA序列。转录后调节基因是最具特征的基因之一， 是GAP-43。在我们以前的赠款下所做的工作表明，GAP-43基因 表达受其mRNA稳定性的选择性变化调节，并且这一过程依赖于 在3 '非翻译区（3' UTR）的高度保守的调控元件的相互作用， mRNA与神经元特异性RNA结合蛋白HuD。HUD不仅能够稳定GAP-43 mRNA在培养的发育神经元中，而且在转基因小鼠中这种蛋白质的过表达 增加海马和新皮质中GAP-43基因的表达。我们最近发现， 促去稳定化RNA结合蛋白KSRP也与差距-43 mRNA结合，表明该蛋白 可能是导致成熟齿状回中差距-43 mRNA快速降解的原因 细胞根据我们的初步研究，我们建议GAP-43和其他后处理的稳定性， 转录调节的神经元基因受促稳定因子的相互作用控制 如HuD和促降解因子如KSRP。为了验证这一假设，我们计划进行 这些研究有以下两个具体目标： 目标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在神经元基因转录后调控中的作用 在发育和成年可塑性期间的体内表达。 虽然目标集中在GAP-43上，但我们的研究将包括HUD的其他目标，例如 neuroserpin和tau。选择这些mRNA是因为它们是轴突定位的，在发育过程中- 调节，响应于损伤而上调，因此可能由类似的机制控制。 拟议的研究将描述GAP-43和其他后- 转录调节的神经元mRNA。鉴于这些蛋白质在神经系统中的作用， 发育，突触可塑性和神经再生，阐明调控机制 控制它们的mRNA具有广泛的潜在应用，从治疗 神经发育障碍对脑创伤和脊髓损伤的恢复的影响。

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, upregulated 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.