The GAP-43 gene is a direct downstream target of the basic helix-loop-helix transcription factors
The GAP-43 gene is a direct downstream target of the basic helix-loop-helix transcription factors
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DOI：
10.1074/jbc.271.36.22035
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发表时间：
1996-09-06
影响因子：
4.8
通讯作者：
Zuber, MX
中科院分区：
文献类型：
--
作者：
Chiaramello, A;Neuman, T;Zuber, MX
GAP-43启动子区包含七个E-box（E1至E7），它们组织成两个簇，远端簇（E3至E7）和近端簇（E1和E2）。GAP-43启动子区的删除分析和定点诱变表明，只有最近端的E1 E-box显着调节GAP-43启动子活性。该 E-box 在侧翼序列、核心序列 (CAGTTG) 和位置方面在大鼠和人 GAP-43 启动子序列之间是保守的。我们发现神经元 N18 细胞中存在的内源性 E-box 结合蛋白识别 E1 E-box 并激活 GAP-43 启动子。 GAP-43启动子的转录活性不仅受到负调节因子Id2蛋白的抑制，而且还受到两种A类碱性螺旋-环-螺旋蛋白E12和ME1a的抑制。体外分析表明 ME1a 和 E12 均以同型二聚体形式与 E1 E-box 结合。通过 Northern 分析，我们建立了各种神经元细胞系以及 ME1a 过表达 PC12 细胞中 E12 和 ME1a mRNA 以及 GAP-43 mRNA 水平之间的负相关性。因此，我们鉴定了位于 GAP-43 启动子区域的顺式作用元件 E1 E-box，它根据占据该位点的 E-box 结合蛋白正向或负向调节 GAP-43 基因的表达。总之，这些数据表明基本螺旋-环-螺旋转录因子调节 GAP-43 基因的表达，并且 A 类 ME1a 和 E12 蛋白充当 GAP-43 表达的下调因子。
The GAP-43 promoter region contains seven E-boxes (E1 to E7) that are organized in two clusters, a distal cluster (E3 to E7) and a proximal cluster (E1 and E2), Deletion analysis and site-directed mutagenesis of the GAP-43 promoter region showed that only the most proximal E1 E-box significantly modulates GAP-43 promoter activity. This E-box is conserved between the rat and human GAP-43 promoter sequences in terms of flanking sequence, core sequence (CAGTTG), and position. We found that endogenous E-box-binding proteins present in neuronal N18 cells recognize the E1 E-box and activate the GAP-43 promoter. The transcriptional activity of the GAP-43 promoter was repressed not only by the negative regulator Id2 protein, but also by two class A basic helix-loop-helix proteins, E12 and ME1a. In vitro analyses showed that both ME1a and E12 bind to the E1 E-box as homodimers. By Northern analyses, we established an inverse correlation between the level of E12 and ME1a mRNAs and GAP-43 mRNA in various neuronal cell lines as well as in ME1a-overexpressing PC12 cells. Therefore, we have identified a cis-acting element, the E1 E-box, located in the GAP-43 promoter region that modulates either positively or negatively the expression of the GAP-43 gene depending on which E-box-binding proteins occupy this site. Together, these data indicate that basic helix-loop-helix transcription factors regulate the expression of the GAP-43 gene and that the class A ME1a and E12 proteins act as down-regulators of GAP-43 expression.