How do flavivirus-infected cells resist arsenite-induced stress granule formation?

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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Disruption of Stress Granule Formation by the Multifunctional Cricket Paralysis Virus 1A Protein

Journal of Virology ◽

10.1128/jvi.01779-16 ◽

2016 ◽

Vol 91 (5) ◽

Cited By ~ 12

Author(s):

Anthony Khong ◽

Craig H. Kerr ◽

Clarence H. L. Yeung ◽

Kathleen Keatings ◽

Arabinda Nayak ◽

...

Keyword(s):

Virus Infection ◽

Stress Granule ◽

Granule Formation ◽

Viral Translation ◽

Content Type ◽

Cellular Processes ◽

Cellular Environment ◽

Viral Yield ◽

Infected Cells ◽

Paralysis Virus

ABSTRACT Stress granules (SGs) are cytosolic ribonucleoprotein aggregates that are induced during cellular stress. Several viruses modulate SG formation, suggesting that SGs have an impact on virus infection. However, the mechanisms and impact of modulating SG assembly in infected cells are not completely understood. In this study, we identify the dicistrovirus cricket paralysis virus 1A (CrPV-1A) protein that functions to inhibit SG assembly during infection. Moreover, besides inhibiting RNA interference, CrPV-1A also inhibits host transcription, which indirectly modulates SG assembly. Thus, CrPV-1A is a multifunctional protein. We identify a key R146A residue that is responsible for these effects, and mutant CrPV(R146A) virus infection is attenuated in Drosophila melanogaster S2 cells and adult fruit flies and results in increased SG formation. Treatment of CrPV(R146A)-infected cells with actinomycin D, which represses transcription, restores SG assembly suppression and viral yield. In summary, CrPV-1A modulates several cellular processes to generate a cellular environment that promotes viral translation and replication. IMPORTANCE RNA viruses encode a limited set of viral proteins to modulate an array of cellular processes in order to facilitate viral replication and inhibit antiviral defenses. In this study, we identified a viral protein, called CrPV-1A, within the dicistrovirus cricket paralysis virus that can inhibit host transcription, modulate viral translation, and block a cellular process called stress granule assembly. We also identified a specific amino acid within CrPV-1A that is important for these cellular processes and that mutant viruses containing mutations of CrPV-1A attenuate virus infection. We also demonstrate that the CrPV-1A protein can also modulate cellular processes in human cells, suggesting that the mode of action of CrPV-1A is conserved. We propose that CrPV-1A is a multifunctional, versatile protein that creates a cellular environment in virus-infected cells that permits productive virus infection.

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Critical role for G3BP1 in infectious bursal disease virus (IBDV)-induced stress granule formation and viral replication

Veterinary Microbiology ◽

10.1016/j.vetmic.2020.108806 ◽

2020 ◽

Vol 248 ◽

pp. 108806

Author(s):

Dianzheng Zhao ◽

Jiaxin Li ◽

Yongqiang Wang ◽

Xiaoqi Li ◽

Li Gao ◽

...

Keyword(s):

Viral Replication ◽

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Critical Role ◽

Stress Granule ◽

Infectious Bursal Disease ◽

Granule Formation ◽

Induced Stress ◽

Bursal Disease

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Stable Formation of Compositionally Unique Stress Granules in Virus-Infected Cells

Journal of Virology ◽

10.1128/jvi.01320-09 ◽

2009 ◽

Vol 84 (7) ◽

pp. 3654-3665 ◽

Cited By ~ 82

Author(s):

Joanna Piotrowska ◽

Spencer J. Hansen ◽

Nogi Park ◽

Katarzyna Jamka ◽

Peter Sarnow ◽

...

Keyword(s):

Oxidative Stress ◽

Heat Shock ◽

Viral Infections ◽

De Novo ◽

Stress Granules ◽

Stress Granule ◽

Initiation Factor ◽

Granule Formation ◽

Infected Cells ◽

Positive Strand Rna

ABSTRACT Stress granules are sites of mRNA storage formed in response to a variety of stresses, including viral infections. Here, the mechanisms and consequences of stress granule formation during poliovirus infection were examined. The results indicate that stress granules containing T-cell-restricted intracellular antigen 1 (TIA-1) and mRNA are stably constituted in infected cells despite lacking intact RasGAP SH3-domain binding protein 1 (G3BP) and eukaryotic initiation factor 4G. Fluorescent in situ hybridization revealed that stress granules in infected cells do not contain significant amounts of viral positive-strand RNA. Infection does not prevent stress granule formation in response to heat shock, indicating that poliovirus does not block de novo stress granule formation. A mutant TIA-1 protein that prevents stress granule formation during oxidative stress also prevents formation in infected cells. However, stress granule formation during infection is more dependent upon ongoing transcription than is formation during oxidative stress or heat shock. Furthermore, Sam68 is recruited to stress granules in infected cells but not to stress granules formed in response to oxidative stress or heat shock. These results demonstrate that stress granule formation in poliovirus-infected cells utilizes a transcription-dependent pathway that results in the appearance of stable, compositionally unique stress granules.

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