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Updated: Sep 4, 2025

Detection of SARS-CoV-2 Neutralizing Antibodies using High-Throughput Fluorescent Imaging of Pseudovirus Infection
Published on: June 5, 2021
Viral E protein neutralizes BET protein-mediated post-entry antagonism of SARS-CoV-2
Irene P Chen1, James E Longbotham2, Sarah McMahon1
1Gladstone Institutes, San Francisco, CA 94158, USA; Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Medicine, University of California, San Francisco, San Francisco, CA, USA; Quantitative Biosciences Institute COVID-19 Research Group (QCRG), University of California, San Francisco, San Francisco, CA 94158, USA.
Abstract:
Inhibitors of bromodomain and extraterminal domain (BET) proteins are possible anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) prophylactics as they downregulate angiotensin-converting enzyme 2 (ACE2). Here we show that BET proteins should not be inactivated therapeutically because they are critical antiviral factors at the post-entry level. Depletion of BRD3 or BRD4 in cells overexpressing ACE2 exacerbates SARS-CoV-2 infection; the same is observed when cells with endogenous ACE2 expression are treated with BET inhibitors during infection and not before. Viral replication and mortality are also enhanced in BET inhibitor-treated mice overexpressing ACE2. BET inactivation suppresses interferon production induced by SARS-CoV-2, a process phenocopied by the envelope (E) protein previously identified as a possible "histone mimetic." E protein, in an acetylated form, directly binds the second bromodomain of BRD4. Our data support a model where SARS-CoV-2 E protein evolved to antagonize interferon responses via BET protein inhibition; this neutralization should not be further enhanced with BET inhibitor treatment.
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