Characterization of the murine Hox-2.3 promoter: involvement of the transcription factor USF (MLTF)

The murine homeoox-containing gene Hox-2.3 contains a basal promoter in a 210-bp region upstream of the transcription start site. In vitro studies of DNA-protein interactions in this region, and in a 1.3-kb upstream region which is known to play a role in tissue specific expression in vivo, led to the identification of DNA elements interacting with nuclear proteins from embryocarcinoma cells. Among the factors bindingto the basal promoter is the upstream stimulating factor (USF), also known as major late transcription factor (MLTF). A single point mutation in its binding site abolishes binding in vitro and leads to 50% reduction of the transcriptional activity as measured in reporter gene experiments, showing that it is an activator of Hox-2.3 expression.