A Tcf/Lef element within the enhancer region of the human NANOG gene plays a role in promoter activation

Abstract

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 beta-catenin stimulated human NANOG promoter activity, while shRNA-mediated knockdown of beta-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 Lefl and beta-catenin bind to the Tcf/Lef element in the enhancer region of the NANOG gene. Forced expression of GSK-31 inhibited basal, Lefl -induced, and beta-catenin-induced NANOG promoter activity, while treatment with the GSK-3 beta inhibitor SB216763 resulted in the accumulation of beta-catenin and NANOG protein. Furthermore, DvI-1-induced NANOG promoter activity was abrogated by the expression of beta-catenin shRNA. Stable overexpression of Dvl-1 caused beta-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. (C) 2011 Elsevier Inc. All rights reserved.