The intronless and TATA-less human TAFII55 gene contains a functional initiator and a downstream promoter element

Human TAF(II)55 (hTAF(II)55) 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(II)55 gene and dissected the regulatory elements and the core promoter responsible for hTAF(II)55 gene expression. Surprisingly, the hTAF(II)55 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(II)55 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.