The archaeal TFIIE alpha homologue facilitates transcription initiation byenhancing TATA-box recognition

Transcription from many archaeal promoters can be reconstituted in vitro us ing recombinant TATA-box binding protein (TBP) and transcription factor B ( TFB)-homologues of eukaryal TBP and TFIIB-together with purified RNA polyme rase (RNAP). However, all archaeal genomes sequenced to date reveal the pre sence of TFE, a homologue of the a-subunit of the eukaryal general transcri ption factor, TFIIE. We show that, while TFE is not absolutely required for transcription in the reconstituted in vitro system, it nonetheless plays a stimulatory role on some promoters and under certain conditions. Mutagenes is of the TATA box or reduction of TBP concentration in transcription react ions sensitizes a promoter to TFE addition. Conversely, saturating reaction s with TBP de-sensitizes promoters to TFE. These results suggest that TFE f acilitates or stabilizes interactions between TBP and the TATA box.