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Abstract
Transcription initiation of archaeal RNA polymerase (RNAP) and eukaryotic RNAPII is assisted by conserved basal transcription factors. The eukaryotic transcription factor TFIIE consists of α and β subunits. Here we have identified and characterised the function of the TFIIEβ homologue in archaea that on the primary sequence level is related to the RNAPIII subunit hRPC39. Both archaeal TFEβ and hRPC39 harbour a cubane 4Fe-4S cluster, which is crucial for heterodimerization of TFEα/β and its engagement with the RNAP clamp. TFEα/β stabilises the preinitiation complex, enhances DNA melting, and stimulates abortive and productive transcription. These activities are strictly dependent on the β subunit and the promoter sequence. Our results suggest that archaeal TFEα/β is likely to represent the evolutionary ancestor of TFIIE-like factors in extant eukaryotes.
Highlights
The conserved core of the archaeal and eukaryotic transcription machineries encompasses a highly complex multisubunit RNA polymerase (RNAP) as well as evolutionary conserved transcription factors that govern its activities through the transcription cycle
While we found no evidence that the RNAP, TBP or TFB1 copurified with Sso0944, TFEα co-eluted with Sso0944, indicating that TFEα and Sso0944 are associated in vivo (Figure 1B)
On the sequence level TFEβ is homologous to the eukaryotic RNAPIII subunit hRPC39 and we show that both S. solfataricus (Sso) TFEβ and human hRPC39 harbour a cubane FeS cluster at their C-termini
Summary
The conserved core of the archaeal and eukaryotic transcription machineries encompasses a highly complex multisubunit RNAP as well as evolutionary conserved transcription factors that govern its activities through the transcription cycle. TBP and TFB facilitate promoter recognition and the recruitment of RNAP (Werner and Grohmann, 2011). In archaea as well as eukaryotes a third factor TFE (TFIIE) enhances the step in initiation, the transition of the closed to the open complex (Holstege et al, 1995, 1996; Werner and Weinzierl, 2005). Similar to TFIIE, TFEα facilitates open complex formation by directly interacting with the non-template DNA strand (NTS), and via an allosteric mechanism that is likely to involve structural changes in the RNAP clamp and stalk (Grohmann et al, 2011). While in archaea the closed-to-open complex transition occurs spontaneously (Werner and Weinzierl, 2002), on most eukaryotic RNAPII promoters it is dependent on the translocase activity of Blombach et al eLife 2015;4:e08378.
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