FACTOR REQUIREMENTS FOR TRANSCRIPTION IN THE ARCHAEON SULFOLOBUS-SHIBATAE

Archaea (archaebacteria) constitute a domain of life that is distinct from Bacteria (eubacteria) and Eucarya (eukaryotes), Although archaeal cells share many morphological features with eubacteria, their transc riptional apparatus is more akin to eukaryotic RNA polymerases I, II a nd III than it is to eubacterial transcription systems, Thus, in addit ion to possessing a 10 subunit RNA polymerase and a homologue of the T ATA-binding protein (TBP), Archaea possess a polypeptide termed TFB th at is homologous to eukaryotic TFIIB, Here, we investigate the factor requirements for transcription of several promoters of the archaeon Su lfolobus shibatae and its associated virus SSV. Through in vitro trans cription and immunodepletion, we demonstrate that S. shibatae TBP, TFB and RNA polymerase are not complexed tightly with one another and tha t each is required for efficient transcription of all promoters tested , Furthermore, full transcription is restored by supplementing respect ive depleted extracts with recombinant TBP or TFB, indicating that TBP -associated factors or TFB-associated factors are not required, Indeed , gel-filtration suggests that Sulfolobus TBP and TFB are not associat ed stably with other proteins, Finally, all promoters analysed are tra nscribed accurately and efficiently in an in vitro system comprising r ecombinant TBP and TFB, together with essentially homogeneous preparat ion of RNA polymerase, Transcription in Archaea is therefore fundament ally homologous to that in eukaryotes, although factor requirements ap pear to be much less complex.