Transcriptional activation of the Hepatocyte Growth Factor receptor (c-met) gene by its ligand (Hepatocyte Growth Factor) is mediated through AP-1
Transcriptional activation of the Hepatocyte Growth Factor receptor (c-met) gene by its ligand (Hepatocyte Growth Factor) is mediated through AP-1
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DOI：
10.1038/sj.onc.1203404
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发表时间：
2000-02-24
期刊：
影响因子：
8
通讯作者：
Zarnegar, R
中科院分区：
文献类型：
--
作者：
Seol, DW;Chen, QY;Zarnegar, R
肝细胞生长因子 (HGF) 通过结合和激活跨膜蛋白酪氨酸激酶受体（称为 c-Met）发挥其生物学作用。我们实验室之前的研究表明，c-met基因表达是由其自身配体（HGF）诱导的，然而，该过程中涉及的分子机制尚不清楚。本研究就是为了解决这个问题而进行的。将各种 c-met-CAT 启动子构建体转染到小鼠肝细胞癌细胞系 Hepa 1-6 中，并结合电泳迁移率变动分析 (EMSA)，将响应元件鉴定为 c-mct 核心启动子区域内位置 -158 至 -152 的活化蛋白 1 (AP-1) 结合位点 (TGAGTCA)。 c-met AP-1 元件与 AP-1 蛋白特异性结合，经 supershift 测定验证。 EMSA 研究和启动子区域的突变分析还表明，转录因子 Sp 家族的成员（Sp-1 和 Sp-3）与与 AP-1 位点相邻的 c-met Sp-1 元件（位于位置 -124）结合。我们发现 Sp 结合抑制了 AP-1 与其 c-met 启动子区域同源位点的结合。用HGF刺激Hepa 1-6细胞导致AP-1结合活性快速且显着的增强以及AP-1蛋白水平的总体增加。 AP-1 表达载体（c-Fos 加 c-Jun）与 c-met 启动子构建体的共转染导致 c-met 启动子活性的刺激。我们发现AP-1对c-met启动子的反式激活可以被AP-I抑制剂姜黄素阻断，此外，我们发现加入姜黄素可以抑制HGF对内源c-met基因的诱导，结果表明HGF诱导的c-met基因转录至少部分是由于AP-1途径的激活。
Hepatocyte Growth Factor (HGF) exerts its biological effects via binding and activating a transmembrane protein tyrosine kinase receptor known as c-Met. Previous studies from our laboratory demonstrated that c-met gene expression is inducible by its own ligand (HGF), However, the molecular mechanism(s) involved in this process are unknown. The present study,vas carried out to address this question. Transfection of various c-met-CAT promoter constructs into the mouse hepatocellular carcinoma cell line Hepa 1-6 in combination with electrophoretic mobility shift assays (EMSA) identified the responsive element as an activated protein-1 (AP-1) binding site (TGAGTCA) within the c-mct core promoter region at position -158 to -152. The c-met AP-I element binds specifically to AP-I protein as, verified by supershift assays. EMSA studies and mutational analyses of the promoter region also revealed that the members of the Sp family of transcription factors (Sp-1 and Sp-3) bind to the c-met Sp-1 element (located at position -124) which is adjacent to the AP-1 site. We show that Sp binding dampens binding of AP-1 to its cognate site in the c-met promoter region. Stimulation of Hepa 1-6 cells with HGF resulted in a rapid and dramatic enhancement of the AP-1 binding activity as well as an overall increase in the le,el of AP-I protein. Cotransfection of AP-1 expression vectors (c-Fos plus c-Jun) with c-met promoter constructs resulted in stimulation of c-met promoter activity. We found that transactivation of the c-met promoter by AP-1 can be blocked by Curcumin, an inhibitor of AP-I, Moreover, we found that the induction of the endogenous c-met gene by HGF is inhibited by the addition of Curcumin, The results demonstrate that the HGF-induced transcription of the c-met gene by HGF is, at least in part, due to activation of the AP-1 pathway.