Transcription in Archaea

Using the sequences of all the known transcription-associated proteins from Bacteria and Eucarya (a total of 4,147), we have identified their homologo us counterparts in the four complete archaeal genomes. Through extensive se quence comparisons, me establish the presence of 280 predicted transcriptio n factors or transcription associated proteins in the four archaeal genomes , of which 168 have homologs only in Bacteria, 51 have homologs only in Euc arya, and the remaining 61 have homologs in both phylogenetic domains. Alth ough bacterial and eukaryotic transcription have very few factors in common , each exclusively shares a significantly greater number with the Archaea, especially the Bacteria. This last fact contrasts with the obvious close re lationship between the archaeal and eukaryotic transcription mechanisms per se, and in particular, basic transcription initiation. We interpret these results to mean that the archaeal transcription system has retained more an cestral characteristics than have the transcription mechanisms in either of the other two domains.