Relevance of Ebola virus VP35 homo-dimerization on the type I interferon cascade inhibition

Ebola virus high lethality relies on its ability to efficiently bypass the host innate antiviral response, which senses the viral dsRNA through the RIG-I receptor and induces type I interferon α/β production. In the bypassing action, the Ebola virus protein VP35 plays a pivotal role at multiple levels of the RIG-I cascade, masking the viral 5′-triphosphorylated dsRNA from RIG-I, and interacting with other cascade components. The VP35 type I interferon inhibition is exerted by the C-terminal domain, while the N-terminal domain, containing a coiled-coil region, is primarily required for oligomerization. However, mutations at key VP35 residues L90/93/107A (VP35-3m) in the coiled-coil region were reported to affect oligomerization and reduce type I interferon antagonism, indicating a possible but unclear role of homo-oligomerization on VP35 interaction with the RIG-I pathway components. In this work, we investigated the VP35 dimerization thermodynamics and its contribution to type I interferon antagonism by computational and biological methods. Focusing on the coiled-coil region, we combined coarse-grained and all-atom simulations on wild type VP35 and VP35-3m homo-dimerization. According to our results, wild type VP35 coiled-coil is able to self-assemble into dimers, while VP35-3m coiled-coil shows poor propensity to even dimerize. Free-energy calculations confirmed the key role of L90, L93 and L107 in stabilizing the coiled-coil homo-dimeric structure. In vitro type I interferon antagonism studies, using full-length wild type VP35 and VP35-3m, revealed that VP35 homo-dimerization is an essential preliminary step for dsRNA binding, which appears to be the main factor of the VP35 RIG-I cascade inhibition, while it is not essential to block the other steps.

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Role of middle-east respiratory syndrome coronavirus membrane and open reading frame 8b proteins in type I interferon antagonism

10.5353/th_991044058291903414 ◽

2018 ◽

Author(s):

Lok-yin, Roy Wong

Keyword(s):

Middle East ◽

Type I Interferon ◽

Middle East Respiratory Syndrome ◽

Open Reading Frame ◽

Type I ◽

Reading Frame ◽

Interferon Antagonism

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The Abstruse Side of Type I Interferon Immunotherapy for COVID-19 Cases with Comorbidities

Journal of Respiration ◽

10.3390/jor1010005 ◽

2021 ◽

Vol 1 (1) ◽

pp. 49-59

Author(s):

Selvakumar Subbian

Keyword(s):

Infectious Diseases ◽

Disease Severity ◽

Type I Interferon ◽

Host Factors ◽

Type I ◽

The Novel ◽

Inflammatory Drugs ◽

Precautionary Measures ◽

Inducible Genes

The Coronavirus Disease-2019 (COVID-19) pandemic, caused by the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has claimed 1.2 million people globally since December 2019. Although the host factors underpinning COVID-19 pathology are not fully understood, type I interferon (IFN-I) response is considered crucial for SARS-CoV-2 pathogenesis. Perturbations in IFN-I signaling and associated interferon-inducible genes (ISG) are among the primary disease severity indicators in COVID-19. Consequently, IFN-I therapy, either alone or in- combination with existing antiviral or anti-inflammatory drugs, is tested in many ongoing clinical trials to reduce COVID-19 mortality. Since signaling by the IFN-I family of molecules regulates host immune response to other infectious and non-infectious diseases, any imbalance in this family of cytokines would impact the clinical outcome of COVID-19, as well as other co-existing diseases. Therefore, it is imperative to evaluate the beneficial-versus-detrimental effects of IFN-I immunotherapy for COVID-19 patients with divergent disease severity and other co-existing conditions. This review article summarizes the role of IFN-I signaling in infectious and non-infectious diseases of humans. It highlights the precautionary measures to be considered before administering IFN-I to COVID-19 patients having other co-existing disorders. Finally, suggestions are proposed to improve IFN-I immunotherapy to COVID-19.

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Induction of Dendritic Cell Production of Type I and Type III Interferons by Wild-Type and Vaccine Strains of Measles Virus: Role of Defective Interfering RNAs

Journal of Virology ◽

10.1128/jvi.00261-13 ◽

2013 ◽

Vol 87 (14) ◽

pp. 7816-7827 ◽

Cited By ~ 20

Author(s):

R. Shivakoti ◽

M. Siwek ◽

D. Hauer ◽

K. L. W. Schultz ◽

D. E. Griffin

Keyword(s):

Dendritic Cell ◽

Measles Virus ◽

Type I ◽

Wild Type ◽

Cell Production ◽

Type Iii

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Retrovirus-induced interference with collagen I gene expression in Mov13 fibroblasts is maintained in the absence of DNA methylation

Molecular and Cellular Biology ◽

10.1128/mcb.11.1.47-54.1991 ◽

1991 ◽

Vol 11 (1) ◽

pp. 47-54

Author(s):

H Chan ◽

S Hartung ◽

M Breindl

Keyword(s):

Gene Expression ◽

Dna Methylation ◽

Chromatin Structure ◽

Transcriptional Activity ◽

Xenopus Laevis Oocytes ◽

Regulatory Sequences ◽

Type I ◽

Wild Type ◽

Col1a1 Gene

We have studied the role of DNA methylation in repression of the murine alpha 1 type I collagen (COL1A1) gene in Mov13 fibroblasts. In Mov13 mice, a retroviral provirus has inserted into the first intron of the COL1A1 gene and blocks its expression at the level of transcriptional initiation. We found that regulatory sequences in the COL1A1 promoter region that are involved in the tissue-specific regulation of the gene are unmethylated in collagen-expressing wild-type fibroblasts and methylated in Mov13 fibroblasts, confirming and extending earlier observations. To directly assess the role of DNA methylation in the repression of COL1A1 gene transcription, we treated Mov13 fibroblasts with the demethylating agent 5-azacytidine. This treatment resulted in a demethylation of the COL1A1 regulatory sequences but failed to activate transcription of the COL1A1 gene. Moreover, the 5-azacytidine treatment induced a transcription-competent chromatin structure in the retroviral sequences but not in the COL1A1 promoter. In DNA transfection and microinjection experiments, we found that the provirus interfered with transcriptional activity of the COL1A1 promoter in Mov13 fibroblasts but not in Xenopus laevis oocytes. In contrast, the wild-type COL1A1 promoter was transcriptionally active in Mov13 fibroblasts. These experiments showed that the COL1A1 promoter is potentially transcriptionally active in the presence of proviral sequences and that Mov13 fibroblasts contain the trans-acting factors required for efficient COL1A1 gene expression. Our results indicate that the provirus insertion in Mov13 can inactivate COL1A1 gene expression at several levels. It prevents the developmentally regulated establishment of a transcription-competent methylation pattern and chromatin structure of the COL1A1 domain and, in the absence of DNA methylation, appears to suppress the COL1A1 promoter in a cell-specific manner, presumably by assuming a dominant chromatin structure that may be incompatible with transcriptional activity of flanking cellular sequences.

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