In bacteria and eukaryotes, proteins TFIIB and sigma factor are involved in the initiation of transcription, where they facilitate preinitiation complex formation and specific RNA Polymerase-DNA binding. The archaeal counterpart to these two proteins is TFB, which was first identified in the species Pyrococcus woesei in 1992. Since then, research has found that archaeal species must contain at least one copy of TFB to function, although some species may have multiple isoforms in their genome.