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Updated: May 21, 2025

Visualization of SARS-CoV-2 using Immuno RNA-Fluorescence In Situ Hybridization
Published on: December 23, 2020
SARS-CoV-2 ORF3a drives dynamic dense body formation for optimal viral infectivity
Stella Hartmann1,2, Lisa Radochonski1,2, Chengjin Ye3
1Department of Microbiology, University of Chicago, Chicago, IL, USA.
Abstract:
SARS-CoV-2 hijacks multiple organelles for virion assembly, of which the mechanisms have not been fully understood. Here, we identified a SARS-CoV-2-driven membrane structure named the 3a dense body (3DB). 3DBs are unusual electron-dense and dynamic structures driven by the accessory protein ORF3a via remodeling a specific subset of the trans-Golgi network (TGN) and early endosomal membrane. 3DB formation is conserved in related bat and pangolin coronaviruses but was lost during the evolution to SARS-CoV. During SARS-CoV-2 infection, 3DB recruits the viral structural proteins spike (S) and membrane (M) and undergoes dynamic fusion/fission to maintain the optimal unprocessed-to-processed ratio of S on assembled virions. Disruption of 3DB formation resulted in virions assembled with an abnormal S processing rate, leading to a dramatic reduction in viral entry efficiency. Our study uncovers the crucial role of 3DB in maintaining maximal SARS-CoV-2 infectivity and highlights its potential as a target for COVID-19 prophylactics and therapeutics.
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