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Accessory protein 5a is a major antagonist of the antiviral action of interferon against murine coronavirus.

ABSTRACT: The type I interferon (IFN) response plays an essential role in the control of in vivo infection by the coronavirus mouse hepatitis virus (MHV). However, in vitro, most strains of MHV are largely resistant to the action of this cytokine, suggesting that MHV encodes one or more functions that antagonize or evade the IFN system. A particular strain of MHV, MHV-S, exhibited orders-of-magnitude higher sensitivity to IFN than prototype strain MHV-A59. Through construction of interstrain chimeric recombinants, the basis for the enhanced IFN sensitivity of MHV-S was found to map entirely to the region downstream of the spike gene, at the 3' end of the genome. Sequence analysis revealed that the major difference between the two strains in this region is the absence of gene 5a from MHV-S. Creation of a gene 5a knockout mutant of MHV-A59 demonstrated that a major component of IFN resistance maps to gene 5a. Conversely, insertion of gene 5a, or its homologs from related group 2 coronaviruses, at an upstream genomic position in an MHV-A59/S chimera restored IFN resistance. This is the first demonstration of a coronavirus gene product that can protect that same virus from the antiviral state induced by IFN. Neither protein kinase R, which phosphorylates eukaryotic initiation factor 2, nor oligoadenylate synthetase, which activates RNase L, was differentially activated in IFN-treated cells infected with MHV-A59 or MHV-S. Thus, the major IFN-induced antiviral activities that are specifically inhibited by MHV, and possibly by other coronaviruses, remain to be identified.

SUBMITTER: Koetzner CA

PROVIDER: S-EPMC2916514 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:In the past two decades, the world has faced several infectious disease outbreaks. Ebola, Influenza A (H1N1), SARS, MERS, and Zika virus have had a massive global impact in terms of economic disruption, the strain on local and global public health. Most recently, the global outbreak of novel coronavirus 2019 (SARS-CoV-2) that causes COVID-19 is a newly discovered virus from the coronavirus family in Wuhan city, China, known to be a great threat to the public health systems. As of 15 April 2020, The Johns Hopkins University estimated that the COVID-19 affected more than two million people, resulting in a death toll above 130,000 around the world. Infected people in Europe and America correspond about 40% and 30% of the total reported cases respectively. At this moment only few Asian countries have controlled the disease, but a second wave of new infections is expected. Predicting inhibitor and target to the COVID-19 is an urgent need to protect human from the disease. Therefore, a protocol to identify anti-COVID-19 candidate based on computer-aided drug design is urgently needed. Thousands of compounds including approved drugs and drugs in the clinical trial are available in the literature. In practice, experimental techniques can measure the time and space average properties but they cannot be captured the structural variation of the COVID-19 during the interaction of inhibitor. Computer simulation is particularly suitable to complement experiments to elucidate conformational changes at the molecular level which are related to inhibition process of the COVID-19. Therefore, computational simulation is essential tool to elucidate the phenomenon. The structure-based virtual screening computational approach will be used to filter the best drugs from the literature, the investigate the structural variation of COVID-19 with the interaction of the best inhibitor is a fundamental step to design new drugs and vaccines which can combat the coronavirus. This mini-review will address novel coronavirus structure, mechanism of action, and trial test of antiviral drugs in the lab and patients with COVID-19.

Project description:Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory infections that can be life-threatening. To establish an infection and spread, MERS-CoV, like most other viruses, must navigate through an intricate network of antiviral host responses. Besides the well-known type I interferon (IFN-α/β) response, the protein kinase R (PKR)-mediated stress response is being recognized as an important innate response pathway. Upon detecting viral dsRNA, PKR phosphorylates eIF2α, leading to the inhibition of cellular and viral translation and the formation of stress granules (SGs), which are increasingly recognized as platforms for antiviral signaling pathways. It is unknown whether cellular infection by MERS-CoV activates the stress response pathway or whether the virus has evolved strategies to suppress this infection-limiting pathway. Here, we show that cellular infection with MERS-CoV does not lead to the formation of SGs. By transiently expressing the MERS-CoV accessory proteins individually, we identified a role of protein 4a (p4a) in preventing activation of the stress response pathway. Expression of MERS-CoV p4a impeded dsRNA-mediated PKR activation, thereby rescuing translation inhibition and preventing SG formation. In contrast, p4a failed to suppress stress response pathway activation that is independent of PKR and dsRNA. MERS-CoV p4a is a dsRNA binding protein. Mutation of the dsRNA binding motif in p4a disrupted its PKR antagonistic activity. By inserting p4a in a picornavirus lacking its natural PKR antagonist, we showed that p4a exerts PKR antagonistic activity also under infection conditions. However, a recombinant MERS-CoV deficient in p4a expression still suppressed SG formation, indicating the expression of at least one other stress response antagonist. This virus also suppressed the dsRNA-independent stress response pathway. Thus, MERS-CoV interferes with antiviral stress responses using at least two different mechanisms, with p4a suppressing the PKR-dependent stress response pathway, probably by sequestering dsRNA. MERS-CoV p4a represents the first coronavirus stress response antagonist described.

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Accessory protein 5a is a major antagonist of the antiviral action of interferon against murine coronavirus.

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