Cell
Volume 181, Issue 5, 28 May 2020, Pages 1046-1061.e6
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Article
Structural and Proteomic Characterization of the Initiation of Giant Virus Infection

https://doi.org/10.1016/j.cell.2020.04.032Get rights and content
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Highlights

  • Giant virus infection intermediates characterized by cryo-EM, cryo-ET, and SEM

  • Proteomics reveal proteins released from capsids during infection

  • Low pH treatment releases proteins present in the viral seed

  • Low pH and high temperature fully open the stargate and release the genome

Summary

Since their discovery, giant viruses have expanded our understanding of the principles of virology. Due to their gargantuan size and complexity, little is known about the life cycles of these viruses. To answer outstanding questions regarding giant virus infection mechanisms, we set out to determine biomolecular conditions that promote giant virus genome release. We generated four infection intermediates in Samba virus (Mimivirus genus, lineage A) as visualized by cryoelectron microscopy (cryo-EM), cryoelectron tomography (cryo-ET), and scanning electron microscopy (SEM). Each of these four intermediates reflects similar morphology to a stage that occurs in vivo. We show that these genome release stages are conserved in other mimiviruses. Finally, we identified proteins that are released from Samba and newly discovered Tupanvirus through differential mass spectrometry. Our work revealed the molecular forces that trigger infection are conserved among disparate giant viruses. This study is also the first to identify specific proteins released during the initial stages of giant virus infection.

Keywords

stargate
proteomics
electron microscopy
virus stability
icosahedral symmetry
nucleocapsid
bubblegram imaging
cryoelectron microscopy
mass spectrometry

Cited by (0)

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Present address: Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA

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