The archaeal TFIIE[alpha] homologue facilitates transcription initiation by enhancing TATA-box recognition

Transcription from many archaeal promoters can be reconstituted in vitrousing recombinant TATA-box binding protein (TBP) and transcription factor B (TFB)--homologues of eukaryal TBP and TFIIB--together with purified RNA polymerase (RNAP). However, all archaeal genomes sequenced to date reveal the presence of TFE, a homologue of the [alpha]-subunit of the eukaryal general transcription factor, TFIIE. We show that, while TFE is not absolutely required for transcription in the reconstituted in vitrosystem, it nonetheless plays a stimulatory role on some promoters and under certain conditions. Mutagenesis of the TATA box or reduction of TBP concentration in transcription reactions sensitizes a promoter to TFE addition. Conversely, saturating reactions with TBP de-sensitizes promoters to TFE. These results suggest that TFE facilitates or stabilizes interactions between TBP and the TATA box.