1C-13 Octamer and Sox elements are required for transcriptional cis-regulation of Nanog gene expression

The pluripotential cell-specific gene Nanog is a homeodomain-bearing transcription factor required for maintaining the un-differentiated state of stem cells. However, the molecular mechanisms that regulate Nanog gene expression are largely unknown. To address this important aspect, we determined the regulatory element by luciferase assays with deletion fragments of the 5'-flanking region. The adjacent Octamer and Sox elements were found to be essential for activating pluripotential state-specific gene expression. DNA sequences of the Octamer and Sox elements were identical among the mouse, human and monkey. These elements were sufficient for mediating proper expression of the GFP reporter gene even in human ES cells. Electrophoretic mobility shift analyses with F9 EC cell nuclear extracts revealed that OCT4 and SOX2 bound to the Octamer/Sox element. However, with R1 ES cell nuclear extracts, a complex between OCT4 and an undefined factor preferentially bound to the Octamer/Sox element. Thus Nanog transcription may be regu-lated through synergistic action with OCT4 and a novel pluripotential cell-specific Sox element-binding factor, which is prominent in ES cells.