The murine Htf9-a/RanBP1 and Htf9-c genes are divergently transcribed from a shared TATA-less promoter. Transcription of both genes is initiated on complementary DNA strands and is controlled by cell cycle-dependent mechanisms, The bidirectional promoter harbors a genomic footprint flanking the major transcription start site of both genes, Transient promoter assays showed that the footprinted element is important for transcription of both genes. Protein-binding experiments and antibody assays indicated that members of the retinoid X receptor family interact with the double-stranded site, In addition, distinct factors interact with single DNA strands of the element, Double-stranded binding factors were highly expressed in liver cells, in which neither gene is transcribed, while single-stranded binding proteins were abundant in cycling cells, in which transcription of both genes is efficient, In vivo S1 analysis of the promoter depicted an S1-sensitive organization in cells in which transcription of both genes is active; SI sensitivity was not detected in conditions of transcriptional repression, Thus, the same element is a target for either retinoid X receptor factors, or for single-stranded binding proteins, and form distinct complexes in different cellular conditions depending on the DNA conformation in the binding site.
