Department of Biomedical Science and Technology, Research Center for Transcription Control, Konkuk University, Seoul 143-701, Republic of Korea.
Biochem Biophys Res Commun. 2011 Jul 8;410(3):637-42. doi: 10.1016/j.bbrc.2011.06.044. Epub 2011 Jun 13.
NANOG is a homeodomain-containing transcription factor that is essential for the maintenance of pluripotency and self-renewal in embryonic stem cells. However, the molecular mechanisms underlying the regulation of NANOG expression in human cells remain largely unknown. Here, we investigated the role of Tcf/Lef response elements located in the enhancer of the human NANOG gene. We found that forced expression of Lef1 or β-catenin stimulated human NANOG promoter activity, while shRNA-mediated knockdown of β-catenin reduced Lef1-induced NANOG promoter activation. Deletion or mutation of the Tcf/Lef element within the enhancer region of the human NANOG gene completely abrogated Lef1-induced NANOG promoter activity. The results of a chromatin immunoprecipitation assay demonstrated that Lef1 and β-catenin bind to the Tcf/Lef element in the enhancer region of the NANOG gene. Forced expression of GSK-3β inhibited basal, Lef1-induced, and β-catenin-induced NANOG promoter activity, while treatment with the GSK-3β inhibitor SB216763 resulted in the accumulation of β-catenin and NANOG protein. Furthermore, Dvl-1-induced NANOG promoter activity was abrogated by the expression of β-catenin shRNA. Stable overexpression of Dvl-1 caused β-catenin and NANOG to accumulate. These results indicate that the Tcf/Lef response element in the enhancer region of the human NANOG gene is able to stimulate NANOG gene transcription.
NANOG 是一种含有同源结构域的转录因子，对于维持胚胎干细胞的多能性和自我更新至关重要。然而，人细胞中 NANOG 表达调控的分子机制在很大程度上仍然未知。在这里，我们研究了位于人 NANOG 基因增强子中的 Tcf/Lef 反应元件的作用。我们发现 Lef1 或 β-catenin 的强制表达刺激了人 NANOG 启动子活性，而 shRNA 介导的 β-catenin 敲低降低了 Lef1 诱导的 NANOG 启动子激活。人 NANOG 基因增强子区域内 Tcf/Lef 元件的缺失或突变完全消除了 Lef1 诱导的 NANOG 启动子活性。染色质免疫沉淀检测的结果表明 Lef1 和 β-catenin 结合到 NANOG 基因增强子区域内的 Tcf/Lef 元件上。GSK-3β 的强制表达抑制了基础、Lef1 诱导和 β-catenin 诱导的 NANOG 启动子活性，而 GSK-3β 抑制剂 SB216763 的处理导致了 β-catenin 和 NANOG 蛋白的积累。此外，Dvl-1 诱导的 NANOG 启动子活性被 β-catenin shRNA 的表达所抑制。Dvl-1 的稳定过表达导致 β-catenin 和 NANOG 的积累。这些结果表明，人 NANOG 基因增强子区域内的 Tcf/Lef 反应元件能够刺激 NANOG 基因转录。
