Information regarding transcriptional regulation in Archaea has begun to em
erge from in vivo genetic studies. Evidence to date suggests a varied reper
toire of regulatory mechanisms in Archaea that invokes both bacterial and e
ukaryal paradigms, as well as some novel features. Overall simplicity of me
chanisms may reflect the prokaryotic lifestyle. Sequencing projects suggest
the existence of certain classes of regulators, but experimental verificat
ion is needed.