Julia Bartuli

Abstract The recruitment of RNA polymerase to gene promoters is a critical step in gene expression. For RNA polymerase II, this process is initiated by TBP and TFIIB, with homologs of these TBP/TFIIB pairs found in all known multi-subunit RNA polymerase systems. Here, we describe a mode of promoter recognition by the poxviral intermediate transcription factor 3, VITF-3.

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Highlights • Structures of Vaccinia RNA polymerase during transcription and cap formation • Capping enzyme contains mobile modules that bind to the polymerase and transcript • Comparison with complete vRNAP suggests large rearrangements during initiation • The Vaccinia-specific Rap94 resembles TFIIB and is displaced by nucleic acids Summary Poxviruses use virus-encoded multisubunit RNA polymerases (vRNAPs) and RNA-processing factors to generate m 7G-capped mRNAs in the host cytoplasm.