Non-canonical Promoter Recognition in Poxviral Transcription by a TBP/TFIIB-like ring complex
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ABSTRACT: The recruitment of RNA polymerase (RNAP) to gene promoters is a critical step in gene expression. For RNAP II, this process is initiated by the TATA-box binding protein (TBP) and transcription factor IIB (TFIIB), with homologs of these TBP/TFIIB pairs found in all known multi-subunit RNAP systems. Here we describe a previously unknown mode of promoter recognition by the poxviral intermediate transcription factor 3 (VITF-3). This heterodimeric factor comprises an atypical TBP/TFIIB pair forming a stable ring structure inert towards DNA in the absence of viral RNAP (vRNAP). Promoter recognition instead requires concerted VITF-3 and vRNAP binding, as revealed by cryo-EM analysis of the intermediate pre-initiation complex (iPIC). During iPIC formation, vRNAP facilitates ring opening and loading of VITF-3 onto the promoter, anchoring the polymerase at the transcription start site. Our findings propose vRNAP as a clamp loader for VITF-3 and reveal a thus far unknown transcription initiation mechanism.
INSTRUMENT(S):
ORGANISM(S): Homo Sapiens (human) Vaccinia Virus
SUBMITTER:
Stefan Jungwirth
LAB HEAD: Utz Fischer
PROVIDER: PXD065561 | Pride | 2025-12-17
REPOSITORIES: Pride
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