Enigmatic origin of the poxvirus membrane from the endoplasmic reticulum shown by 3D imaging of vaccinia virus assembly mutants

Andrea S. Weisberg, Liliana Maruri-Avidal, Himani Bisht, Bryan T. Hansen, Cindi L. Schwartz, Elizabeth R. Fischer, Xiangzhi Meng, Yan Xiang, Bernard Moss

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


The long-standing inability to visualize connections between poxvirus membranes and cellular organelles has led to uncertainty regarding the origin of the viral membrane. Indeed, there has been speculation that viral membranes form de novo in cytoplasmic factories. Another possibility, that the connections are too shortlived to be captured by microscopy during a normal infection, motivated us to identify and characterize virus mutants that are arrested in assembly. Five conserved vaccinia virus proteins, referred to as Viral Membrane Assembly Proteins (VMAPs), that are necessary for formation of immature virions were found. Transmission electron microscopy studies of two VMAP deletion mutants had suggested retention of connections between viral membranes and the endoplasmic reticulum (ER). We now analyzed cells infected with each of the five VMAP deletion mutants by electron tomography, which is necessary to validate membrane continuity, in addition to conventional transmission electron microscopy. In all cases, connections between the ER and viral membranes were demonstrated by 3D reconstructions, supporting a role for the VMAPs in creating and/or stabilizing membrane scissions. Furthermore, coexpression of the viral reticulon-like transmembrane protein A17 and the capsid-like scaffold protein D13 was sufficient to form similar ER-associated viral structures in the absence of other major virion proteins. Determination of the mechanism of ER disruption during a normal VACV infection and the likely participation of both viral and cell proteins in this process may provide important insights into membrane dynamics.

Original languageEnglish (US)
Pages (from-to)E11001-E11009
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number51
StatePublished - Dec 19 2017


  • Endoplasmic reticulum breakage
  • Endoplasmic reticulum dynamics
  • Membrane disruption
  • Membrane dynamics
  • Poxvirus assembly

ASJC Scopus subject areas

  • General


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