Histone arginine demethylase JMJD6 is linked to stress granule assembly through demethylation of the stress granule–nucleating protein G3BP1

AbstractThe 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.

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SUMOylated Senataxin functions in genome stability, RNA degradation, and stress granule disassembly, and is linked with inherited ataxia and motor neuron disease

Molecular Genetics & Genomic Medicine ◽

10.1002/mgg3.1745 ◽

2021 ◽

Author(s):

Craig L. Bennett ◽

Albert R. La Spada

Keyword(s):

Motor Neuron ◽

Motor Neuron Disease ◽

Genome Stability ◽

Rna Degradation ◽

Stress Granule

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Transcriptome-Wide Comparison of Stress Granules and P-Bodies Reveals that Translation Plays a Major Role in RNA Partitioning

Molecular and Cellular Biology ◽

10.1128/mcb.00313-19 ◽

2019 ◽

Vol 39 (24) ◽

Cited By ~ 14

Author(s):

Tyler Matheny ◽

Bhalchandra S. Rao ◽

Roy Parker

Keyword(s):

Stress Granules ◽

Stress Granule ◽

Dominant Factor ◽

Differential Centrifugation ◽

P Bodies ◽

Translation Repression ◽

First Approximation ◽

Rnp Granules ◽

Interpretation Of Results

ABSTRACT The eukaryotic cytosol contains multiple RNP granules, including P-bodies and stress granules. Three different methods have been used to describe the transcriptome of stress granules or P-bodies, but how these methods compare and how RNA partitioning occurs between P-bodies and stress granules have not been addressed. Here, we compare the analysis of the stress granule transcriptome based on differential centrifugation with and without subsequent stress granule immunopurification. We find that while differential centrifugation alone gives a first approximation of the stress granule transcriptome, this methodology contains nonspecific transcripts that play a confounding role in the interpretation of results. We also immunopurify and compare the RNAs in stress granules and P-bodies under arsenite stress and compare those results to those for the P-body transcriptome described under nonstress conditions. We find that the P-body transcriptome is dominated by poorly translated mRNAs under nonstress conditions, but during arsenite stress, when translation is globally repressed, the P-body transcriptome is very similar to the stress granule transcriptome. This suggests that translation is a dominant factor in targeting mRNAs into both P-bodies and stress granules, and during stress, when most mRNAs are untranslated, the composition of P-bodies reflects this broader translation repression.

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The Leader Protein of Theiler's Virus Prevents the Activation of PKR

Journal of Virology ◽

10.1128/jvi.01010-19 ◽

2019 ◽

Vol 93 (19) ◽

Cited By ~ 4

Author(s):

Fabian Borghese ◽

Frédéric Sorgeloos ◽

Teresa Cesaro ◽

Thomas Michiels

Keyword(s):

Stress Granule ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Wild Type Virus ◽

Granule Formation ◽

Double Stranded Rna ◽

Eif2α Phosphorylation ◽

Leader Protein ◽

Infected Cells ◽

L Proteins

ABSTRACT Leader (L) proteins encoded by cardioviruses are multifunctional proteins that contribute to innate immunity evasion. L proteins of Theiler’s murine encephalomyelitis virus (TMEV), Saffold virus (SAFV), and encephalomyocarditis virus (EMCV) were reported to inhibit stress granule assembly in infected cells. Here, we show that TMEV L can act at two levels in the stress granule formation pathway: on the one hand, it can inhibit sodium arsenite-induced stress granule assembly without preventing eIF2α phosphorylation and, thus, acts downstream of eIF2α; on the other hand, it can inhibit eucaryotic translation initiation factor 2 alpha kinase 2 (PKR) activation and the consequent PKR-mediated eIF2α phosphorylation. Interestingly, coimmunostaining experiments revealed that PKR colocalizes with viral double-stranded RNA (dsRNA) in cells infected with L-mutant viruses but not in cells infected with the wild-type virus. Furthermore, PKR coprecipitated with dsRNA from cells infected with L-mutant viruses significantly more than from cells infected with the wild-type virus. These data strongly suggest that L blocks PKR activation by preventing the interaction between PKR and viral dsRNA. In infected cells, L also rendered PKR refractory to subsequent activation by poly(I·C). However, no interaction was observed between L and either dsRNA or PKR. Taken together, our results suggest that, unlike other viral proteins, L indirectly acts on PKR to negatively regulate its responsiveness to dsRNA. IMPORTANCE The leader (L) protein encoded by cardioviruses is a very short multifunctional protein that contributes to evasion of the host innate immune response. This protein notably prevents the formation of stress granules in infected cells. Using Theiler’s virus as a model, we show that L proteins can act at two levels in the stress response pathway leading to stress granule formation, the most striking one being the inhibition of eucaryotic translation initiation factor 2 alpha kinase 2 (PKR) activation. Interestingly, the leader protein appears to inhibit PKR via a novel mechanism by rendering this kinase unable to detect double-stranded RNA, its typical activator. Unlike other viral proteins, such as influenza virus NS1, the leader protein appears to interact with neither PKR nor double-stranded RNA, suggesting that it acts indirectly to trigger the inhibition of the kinase.

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