Abstract
The multifunctional nucleocapsid (N) protein in SARS-CoV-2 binds the ~30 kb viral RNA genome to aid its packaging into the 80-90 nm membrane-enveloped virion. The N protein is composed of N-terminal RNA-binding and C-terminal dimerization domains that are flanked by three intrinsically disordered regions. Here we demonstrate that the N protein's central disordered domain drives phase separation with RNA, and that phosphorylation of an adjacent serine/arginine rich region modulates the physical properties of the resulting condensates. In cells, N forms condensates that recruit the stress granule protein G3BP1, highlighting a potential role for N in G3BP1 sequestration and stress granule inhibition. The SARS-CoV-2 membrane (M) protein independently induces N protein phase separation, and three-component mixtures of N + M + RNA form condensates with mutually exclusive compartments containing N + M or N + RNA, including annular structures in which the M protein coats the outside of an N + RNA condensate. These findings support a model in which phase separation of the SARS-CoV-2 N protein contributes both to suppression of the G3BP1-dependent host immune response and to packaging genomic RNA during virion assembly.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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COVID-19 / genetics
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COVID-19 / metabolism
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COVID-19 / virology*
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Cell Membrane / virology
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Coronavirus Nucleocapsid Proteins / chemistry
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Coronavirus Nucleocapsid Proteins / genetics
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Coronavirus Nucleocapsid Proteins / metabolism*
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DNA Helicases / genetics
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DNA Helicases / metabolism
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Humans
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Phosphoproteins / chemistry
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Phosphoproteins / genetics
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Phosphoproteins / metabolism
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Poly-ADP-Ribose Binding Proteins / genetics
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Poly-ADP-Ribose Binding Proteins / metabolism
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Protein Binding
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Protein Domains
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RNA Helicases / genetics
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RNA Helicases / metabolism
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RNA Recognition Motif Proteins / genetics
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RNA Recognition Motif Proteins / metabolism
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RNA, Viral / genetics
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RNA, Viral / metabolism*
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SARS-CoV-2 / chemistry
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SARS-CoV-2 / genetics
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SARS-CoV-2 / metabolism*
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Viral Matrix Proteins / chemistry
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Viral Matrix Proteins / genetics
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Viral Matrix Proteins / metabolism*
Substances
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Coronavirus Nucleocapsid Proteins
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Phosphoproteins
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Poly-ADP-Ribose Binding Proteins
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RNA Recognition Motif Proteins
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RNA, Viral
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Viral Matrix Proteins
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membrane protein, SARS-CoV-2
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nucleocapsid phosphoprotein, SARS-CoV-2
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DNA Helicases
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G3BP1 protein, human
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RNA Helicases