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<p>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. This heterodimeric factor comprises an atypical TBP/TFIIB pair forming a stable ring structure inert towards DNA in the absence of viral RNA polymerase. Promoter recognition instead requires concerted VITF-3 and viral RNA polymerase binding, as shown by cryo-EM analysis of the intermediate pre-initiation complex. During the formation of this complex, viral RNA polymerase facilitates ring opening and loading of VITF-3 onto the promoter, anchoring the polymerase at the transcription start site. Our findings suggest viral RNA polymerase could act as a clamp loader for VITF-3 and identify VITF-3 as an unusual TBP/TFIIB pair.</p>

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Cooperative clamp-mediated promoter recognition by poxviral RNA polymerase and its TBP/TFIIB-like partner

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月18日

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  • Stefan Jungwirth,
  • Julia Bartuli,
  • Stephanie Lamer,
  • Andreas Schlosser,
  • Clemens Grimm,
  • Utz Fischer

摘要

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. This heterodimeric factor comprises an atypical TBP/TFIIB pair forming a stable ring structure inert towards DNA in the absence of viral RNA polymerase. Promoter recognition instead requires concerted VITF-3 and viral RNA polymerase binding, as shown by cryo-EM analysis of the intermediate pre-initiation complex. During the formation of this complex, viral RNA polymerase facilitates ring opening and loading of VITF-3 onto the promoter, anchoring the polymerase at the transcription start site. Our findings suggest viral RNA polymerase could act as a clamp loader for VITF-3 and identify VITF-3 as an unusual TBP/TFIIB pair.