The study investigates the transcriptional regulation of the Nanog gene by Oct4 and Sox2, two key transcription factors essential for maintaining pluripotency in embryonic stem cells. The research identifies a conserved composite oct-sox cis-regulatory element in the Nanog promoter that is essential for pluripotent-specific expression. This element is highly conserved across eutherian mammals, suggesting a critical functional role in maintaining pluripotency. A reporter gene construct containing the Nanog promoter and enhanced green fluorescent protein (EGFP) recapitulates endogenous Nanog expression in embryonic stem cells and their derivatives. Mutagenesis and in vitro binding assays confirm that Oct4 and Sox2 interact with the Nanog promoter. Electrophoretic mobility shift assays show that the Oct4/Sox2 heterodimer binds more efficiently to the Nanog promoter than to the Fgf4 promoter. Chromatin immunoprecipitation experiments demonstrate that Oct4 and Sox2 bind to the Nanog promoter in both mouse and human embryonic stem cells. RNA interference experiments further support a genetic link between Oct4, Sox2, and the Nanog promoter. These findings highlight the role of the Sox2-Oct4 complex as a top regulatory element in the pluripotent genetic network. The study also shows that the Nanog promoter contains sufficient cis-regulatory information to recapitulate endogenous expression, and that the Oct and Sox elements are required for promoter activity. The results indicate that Oct4 and Sox2 bind to the Nanog promoter in vivo and regulate its activity. The study further demonstrates that Sox2 is essential for Nanog transcription in embryonic stem cells. The findings provide important insights into the molecular mechanisms underlying pluripotency and the regulatory network that maintains it.The study investigates the transcriptional regulation of the Nanog gene by Oct4 and Sox2, two key transcription factors essential for maintaining pluripotency in embryonic stem cells. The research identifies a conserved composite oct-sox cis-regulatory element in the Nanog promoter that is essential for pluripotent-specific expression. This element is highly conserved across eutherian mammals, suggesting a critical functional role in maintaining pluripotency. A reporter gene construct containing the Nanog promoter and enhanced green fluorescent protein (EGFP) recapitulates endogenous Nanog expression in embryonic stem cells and their derivatives. Mutagenesis and in vitro binding assays confirm that Oct4 and Sox2 interact with the Nanog promoter. Electrophoretic mobility shift assays show that the Oct4/Sox2 heterodimer binds more efficiently to the Nanog promoter than to the Fgf4 promoter. Chromatin immunoprecipitation experiments demonstrate that Oct4 and Sox2 bind to the Nanog promoter in both mouse and human embryonic stem cells. RNA interference experiments further support a genetic link between Oct4, Sox2, and the Nanog promoter. These findings highlight the role of the Sox2-Oct4 complex as a top regulatory element in the pluripotent genetic network. The study also shows that the Nanog promoter contains sufficient cis-regulatory information to recapitulate endogenous expression, and that the Oct and Sox elements are required for promoter activity. The results indicate that Oct4 and Sox2 bind to the Nanog promoter in vivo and regulate its activity. The study further demonstrates that Sox2 is essential for Nanog transcription in embryonic stem cells. The findings provide important insights into the molecular mechanisms underlying pluripotency and the regulatory network that maintains it.