Similarity between a ubiquitous promoter element in an ancient eukaryote and mammalian initiator elements.

To identify regulatory elements that play a role in transcription initiation in ancient eukaryotes, we have analyzed the upstream regions of protein-coding genes from Trichomonas vaginalis, one of the most ancient eukaryotes studied to date. Characterization of seven protein-coding genes from this protist invariably revealed the presence of a highly conserved DNA sequence motif immediately upstream of the coding region. This 13-nt motif was shown to surround and contain precise sites for transcription initiation. No typical TATA boxes, positioned at 25-30 nt upstream of the transcription start sites of these genes, were found. The start-site regions from all seven T. vaginalis genes impart strong specific initiation of transcription in a mammalian in vitro transcription assay. This consensus promoter element in an ancient eukaryote is similar, both structurally and functionally, to initiator elements found in promoters of higher eukaryotes.