Gut-enriched Kruppel-like factor represses ornithine decarboxylase gene expression and functions as checkpoint regulator in colonic cancer cells
Gut-enriched Kruppel-like factor represses ornithine decarboxylase gene expression and functions as checkpoint regulator in colonic cancer cells
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DOI：
10.1074/jbc.m204816200
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发表时间：
2002-11-29
影响因子：
4.8
通讯作者：
Tseng, CC
中科院分区：
文献类型：
--
作者：
Chen, ZY;Shie, JL;Tseng, CC
富含肠道的kruppel样因子（GKLF, KLF4）是一种上皮特异性转录因子，在胃肠道中表达并介导结肠上皮的生长停滞。其生长抑制作用的分子机制尚未完全阐明。在本研究中，我们发现干扰素γ治疗诱导GKLF mRNA和蛋白表达与结肠癌HT-29细胞中鸟氨酸脱羧酶（ODC）基因表达和酶活性的降低有关。在HT-29细胞中，过表达GKLF可显著降低ODC mRNA和蛋白水平以及酶活性，导致生长停滞，表明ODC可能是GYCLF的下游靶点。GKLF mRNA和蛋白浓度在细胞周期的G(1)/S边界处最高，ODC mRNA和蛋白水平在此边界处最低，并且GKLF的过表达导致细胞在G(1)/S期停滞。报告基因转染研究和电泳迁移率凝胶转移试验表明，GYCLF抑制ODC启动子活性，这些作用似乎是通过与启动子近端GC盒的相互作用介导的。使用报告基因构建和染色质免疫沉淀法的转染研究也表明，GKLF通过干扰Sp1与ODC启动子的结合来抑制ODC基因的转激活。这些结果表明GKLF可能作为G(1)/S检查点调节剂，通过下调ODC基因的表达来发挥其抑制生长的作用。此外，GKLF是ODC基因的转录抑制因子，这些作用是通过与启动子上富含gc的区域相互作用介导的。
Gut-enriched Kruppel-like factor (GKLF, KLF4) is an epithelial-specific transcription factor that expresses in the gastrointestinal tract and mediates growth arrest of colonic epithelium. The molecular mechanisms governing its growth inhibitory effect have not been fully elucidated. In the present study, we showed that induction of GKLF mRNA and protein expression by interferon-gamma treatment was associated with reduction of ornithine decarboxylase (ODC) gene expression and enzyme activity in colon cancer HT-29 cells. Overexpression of GKLF in HT-29 cells significantly reduced ODC mRNA and protein levels as well as enzyme activity and resulted in growth arrest, indicating that ODC might be a downstream target of GYCLF. This conclusion was further supported by data showing that GKLF mRNA and protein concentrations were the highest at the G(1)/S boundary of the cell cycle, where ODC mRNA and protein levels were the lowest and that overexpression of GKLF resulted in cell arrested at the G, phase. Reporter gene transfection studies and electrophoretic mobility gel shift assays demonstrated that GYCLF repressed ODC promoter activity and that these effects appeared to be mediated through interaction with a GC box in the proximal portion of the promoter. Transfection studies using reporter constructs and chromatin immunoprecipitation assays also demonstrated that GKLF inhibited transactivation of the ODC gene by interfering with the binding of Sp1 to the ODC promoter. These results indicate that GKLF may function as a G(1)/S checkpoint regulator and exert its growth arrest effect through down-regulation of ODC gene expression. Furthermore, GKLF is a transcriptional repressor of the ODC gene, and these effects are mediated by interaction with the GC-rich region on the promoter.