Basal and regulated transcription in Archaea

The basal transcription machinery of Archaea is fundamentally related to th e eucaryal RNA polymerase (RNAP) II apparatus. In addition to a 12-subunit RNAP, Archaea possess two general transcription factors, the activities of which are required for accurate and efficient in vitro transcription, These factors, TBP and TFB, are homologues of the eucaryal TATA-box binding prot ein and TFIIB respectively. Archaea also possess TFE, a homologue of the eu caryal RNAP II general transcription factor TFIIE. Although not absolutely required for transcription in vitro, TFE nonetheless plays a stimulatory ro le under conditions where promoter recognition by TBP is sub-optimal. The b asal transcription apparatus of Archaea is closely related to that of Eucar ya but archaeal transcriptional regulators resemble those of bacteria. The mode of action of two such regulators has been characterized to determine h ow these 'bacterial-like' regulators impinge on the 'eucaryal-like' basal m achinery.