The Intronless and TATA-less Human TAF_II55 Gene Contains a Functional Initiator and a Downstream Promoter Element

Human TAF_II55 (hTAF_II55) is a component of the multisubunit general transcription factor TFIID and has been shown to mediate the functions of many transcriptional activators via direct protein-protein interactions. To uncover the regulatory properties of the general transcription machinery, we have isolated the hTAF_II55 gene and dissected the regulatory elements and the core promoter responsible for hTAF_II55 gene expression. Surprisingly, the hTAF_II55 gene has a single uninterrupted open reading frame and is the only intronless general transcription factor identified so far. Its expression is driven by a TATA-less promoter that contains a functional initiator and a downstream promoter element, as illustrated by both transfection assays and mutational analyses. Moreover, this core promoter can mediate the activity of a transcriptional activator that is artificially recruited to the promoter in a heterologous context. Interestingly, in the promoter-proximal region there are multiple Sp1-binding sites juxtaposed to a single AP2-binding site, indicating that Sp1 and AP2 may regulate the core promoter activity of the hTAF_II55 gene. These findings indicate that a combinatorial regulation of a general transcription factor-encoding gene can be conferred by both ubiquitous and cell type-specific transcriptional regulators.