Kinney W R, McNamara R K, Valcourt E, Routtenberg A
Cresap Neuroscience Laboratory, Northwestern University, Evanston, IL 60208, USA.
Brain Res Mol Brain Res. 1996 May;38(1):25-36. doi: 10.1016/0169-328x(95)00287-3.
The presence in hippocampus of a basic helix-loop-helix (bHLH) family of transcription factors (TFs) specifically binding in an electrophoretic mobility shift assay (EMSA) to the E-box recognition element was established by selective blockade of binding both by cold competition and by an antibody to MyoD1, an E-box TF. Protein source was from a micro-dissected preparation enriched in hippocampal granule cells. Specific E-box binding of hippocampal transcription factors was significantly reduced in kainate acid (KA) treated animals. This was observed at 24 and 72 h, but not before (3, 6 h) or after (96 h). This is the first report to our knowledge to study functional regulation of E-box binding protein in adult hippocampus. To determine the generality of this E-box regulatory event, we studied four other situations, in addition to kainate treatment, where axonal growth is known or has been suggested to increase: NGF treatment of PC12 cells, unilateral hilar lesions, long-term potentiation after 1 h, and postnatal rat hippocampal development. In all four cases, decreased E-box binding was observed. The recent link of F1/GAP-43 mRNA induction in hippocampal granule cells by KA to growth of their axons, the mossy fibers in the adult rat, suggests a potential role for the F1/GAP-43 5' flanking promoter region in regulating neurite outgrowth. Since in all cases decreased E-box binding preceded increased F1/GAP-43 mRNA expression, it is suggested that E-box binding to the F1/GAP-43 promoter in hippocampal granule cells could negatively regulate F1/GAP-43 gene expression. Indeed, analysis of recognition elements on the F1/GAP-43 gene revealed an arrangement, previously described in other genes, of multiple adjacent E-box elements. E-box binding of bHLH transcription factors is likely to occur on several different genes in addition to F1/GAP-43. It is, therefore, attractive to think that E-box binding is regulated by in vivo activation of the adult brain and that this gene regulatory event participates in the orchestration of molecular and cellular responses underlying axonal growth.
通过冷竞争和针对E-box转录因子MyoD1的抗体选择性阻断结合，确定了在海马体中存在一个碱性螺旋-环-螺旋（bHLH）转录因子（TFs）家族，其在电泳迁移率变动分析（EMSA）中特异性结合E-box识别元件。蛋白质来源是来自富含海马颗粒细胞的显微切割制剂。在海藻酸（KA）处理的动物中，海马转录因子的特异性E-box结合显著降低。在24小时和72小时观察到这种情况，但在之前（3、6小时）或之后（96小时）未观察到。据我们所知，这是第一项研究成年海马体中E-box结合蛋白功能调节的报告。为了确定这种E-box调节事件的普遍性，除了海藻酸处理外，我们还研究了其他四种已知或已被认为轴突生长会增加的情况：用神经生长因子（NGF）处理PC12细胞、单侧海马门损伤、1小时后的长时程增强以及新生大鼠海马体发育。在所有这四种情况下，均观察到E-box结合减少。最近发现KA诱导成年大鼠海马颗粒细胞中F1/GAP-43 mRNA表达与它们的轴突（苔藓纤维）生长有关，这表明F1/GAP-43 5'侧翼启动子区域在调节神经突生长中可能发挥作用。由于在所有情况下，E-box结合减少都先于F1/GAP-43 mRNA表达增加，因此表明海马颗粒细胞中E-box与F1/GAP-43启动子的结合可能对F1/GAP-43基因表达起负调节作用。实际上，对F1/GAP-43基因上识别元件的分析揭示了一种先前在其他基因中描述过的多个相邻E-box元件的排列。除了F1/GAP-43外，bHLH转录因子的E-box结合可能还会发生在其他几个不同的基因上。因此，有吸引力的一种想法是，E-box结合受成年大脑的体内激活调节，并且这种基因调节事件参与了轴突生长背后分子和细胞反应的协调。
