Kruppel-like factor 4 (KLF4) represses histidine decarboxylase gene expression through an upstream Sp1 site and downstream gastrin responsive elements
Kruppel-like factor 4 (KLF4) represses histidine decarboxylase gene expression through an upstream Sp1 site and downstream gastrin responsive elements
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DOI：
10.1074/jbc.m308278200
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发表时间：
2004-03-05
影响因子：
4.8
通讯作者：
Wang, TC
中科院分区：
文献类型：
--
作者：
Ai, WD;Liu, Y;Wang, TC
组氨酸脱羧酶（HDC）是一种催化组氨酸转化为组胺的酶，组胺是一种生物胺，在过敏反应、炎症、神经传递和胃酸分泌中起重要作用。之前，我们证明了胃泌素通过三个重叠的下游启动子元件激活胃癌（AGS-E）细胞系的HDC启动子活性。在目前的研究中，我们使用酵母单杂交策略来识别与这三个元素结合的核因子。在单杂交筛选的8个阳性基因中，我们鉴定出kruppel样因子4 (KLF4)（以前称为富含肠道的kruppel样因子（GKLF））是与HDC启动子中胃泌素响应元件结合的一个因子。电泳迁移率转移实验证实KLF4能够结合所有三种胃泌素响应元件。此外，瞬时共转染实验表明，过表达KLF4对HDC启动子活性具有剂量依赖性和特异性。通过KLF4小干扰RNA和KLF4过表达改变内源性HDC信使RNA，证实了KLF4对HDC转录的调控作用。我们进一步发现KLF4通过在上游GC盒与Sp1竞争抑制HDC启动子活性，并通过结合三个下游胃泌素响应元件独立抑制HDC启动子活性。综上所述，这些结果表明KLF4可以通过sp1依赖性和非依赖性机制抑制HDC基因的表达。
Histidine decarboxylase (HDC) is the enzyme that catalyzes the conversion of histidine to histamine, a bioamine that plays an important role in allergic responses, inflammation, neurotransmission, and gastric acid secretion. Previously, we demonstrated that gastrin activates HDC promoter activity in a gastric cancer (AGS-E) cell line through three overlapping downstream promoter elements. In the current study, we used the yeast one-hybrid strategy to identify nuclear factors that bind to these three elements. Among eight positives from the one-hybrid screen, we identified Kruppel-like factor 4 (KLF4) (previously known as gut-enriched Kruppel-like factor ( GKLF)) as one factor that binds to the gastrin responsive elements in the HDC promoter. Electrophoretic mobility shift assays confirmed that KLF4 is able to bind all three gastrin responsive elements. In addition, transient cotransfection experiments showed that overexpression of KLF4 dose dependently and specifically inhibited HDC promoter activity. Regulation of HDC transcription by KLF4 was confirmed by changes in the endogenous HDC messenger RNA by KLF4 small interfering RNA and KLF4 overexpression. We further showed that KLF4 inhibits HDC promoter activity by competing with Sp1 at the upstream GC box and also independently by binding the three downstream gastrin responsive elements. Taken together, these results indicate that KLF4 can act to repress HDC gene expression by Sp1-dependent and - independent mechanisms.