Structural Basis of Poxvirus Transcription: Vaccinia RNA Polymerase Complexes

Cell. 2019 Dec 12;179(7):1537-1550.e19. doi: 10.1016/j.cell.2019.11.024.


Poxviruses encode a multisubunit DNA-dependent RNA polymerase (vRNAP) that carries out viral gene expression in the host cytoplasm. We report cryo-EM structures of core and complete vRNAP enzymes from Vaccinia virus at 2.8 Å resolution. The vRNAP core enzyme resembles eukaryotic RNA polymerase II (Pol II) but also reveals many virus-specific features, including the transcription factor Rap94. The complete enzyme additionally contains the transcription factor VETF, the mRNA processing factors VTF/CE and NPH-I, the viral core protein E11, and host tRNAGln. This complex can carry out the entire early transcription cycle. The structures show that Rap94 partially resembles the Pol II initiation factor TFIIB, that the vRNAP subunit Rpo30 resembles the Pol II elongation factor TFIIS, and that NPH-I resembles chromatin remodeling enzymes. Together with the accompanying paper (Hillen et al., 2019), these results provide the basis for unraveling the mechanisms of poxvirus transcription and RNA processing.

Keywords: DNA-dependent RNA polymerase; RNA polymerase; cryo electron microscopy; cryo-EM; cryo-EM reconstruction; poxviridae; single particle; structure; transcription; vaccinia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy
  • DNA-Directed RNA Polymerases / chemistry*
  • Multienzyme Complexes / chemistry
  • Multienzyme Complexes / ultrastructure
  • Single Molecule Imaging
  • Transcription Factors / chemistry*
  • Vaccinia virus / genetics
  • Vaccinia virus / metabolism
  • Vaccinia virus / ultrastructure*
  • Viral Proteins / chemistry*


  • Multienzyme Complexes
  • RAP94 protein, Vaccinia virus
  • Transcription Factors
  • Viral Proteins
  • early transcription factor protein, Vaccinia virus
  • DNA-Directed RNA Polymerases