Archaeal RNA polymerase subunits F and P are bona fide homologs of eukaryotic RPB4 and RPB12

The archaeal and eukaryotic evolutionary domains diverged from each other s imilar to2 billion years ago, but many of the core components of their tran scriptional and translational machineries still display a readily recogniza ble degree of similarity in their primary structures. The F and P subunits present in archaeal RNA polymerases were only recently identified in a puri fied archaeal RNA polymerase preparation and, on the basis of localized seq uence homologies, tentatively identified as archaeal versions of the eukary otic RPB4 and RPB12 RNA polymerase subunits, respectively. We prepared reco mbinant versions of the F and P subunits from Methanococcus jannaschii and used them in in vitro and in vivo protein interaction assays to demonstrate that they interact with other archaeal subunits in a manner predicted from their eukaryotic counterparts. The overall structural conservation of the M.jannaschii F subunit, although not readily recognizable on the primary am ino acid sequence level, is sufficiently high to allow the formation of an archaeal-human F-RPB7 hybrid complex.