eIF2A mediates translation of hepatitis C viral mRNA under stress conditions

Kim, Joon Hyun; Park, Sung Mi; Park, Ji Hoon; Keum, Sun Ju; Jang, Sung Key

doi:10.1038/emboj.2011.146

Cited by 110 publications

(147 citation statements)

References 50 publications

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“…result is in agreement with the observation that HCV triggers the phosphorylation of PKR and eIF2␣ as a means to attenuate protein expression, including that by ISGs (38,125,126). However, the difference in shutoff among viral populations was not consistently reflected in the ratio of phosphorylated to nonphosphorylated forms of PKR and eIF2␣ ( Fig.…”

Section: Discussionsupporting

confidence: 81%

Response of Hepatitis C Virus to Long-Term Passage in the Presence of Alpha Interferon: Multiple Mutations and a Common Phenotype

Perales

Beach

Gallego

et al. 2013

J Virol

163

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H epatitis C virus (HCV) infects an estimated 180 million people worldwide, and about 75% of newly infected patients progress toward a chronic infection, which constitutes a risk for severe liver diseases such as cirrhosis and hepatocarcinoma (1-4). HCV is a hepacivirus in the Flaviviridae family characterized by the error-prone replication and quasispecies dynamics typical of RNA viruses (2,(5)(6)(7). No vaccine is available to prevent HCV infections or disease, and the current standard of care treatment consists of the combination of pegylated alpha interferon (IFN-␣) and the purine nucleoside analogue ribavirin (1-␤-D-ribofuranosyl-1-H-1,2,4-triazole-3-carboxamide) (8-10). Type I interferons (IFNs) such as IFN-␣ are members of a family of cytokines that constitute key components of the innate immune response to viruses, and their induction results in an antiviral state of the cell and suppression of viral replication (11)(12)(13)(14). Ribavirin is currently used to treat a number of human viral infections, and it can display multiple mechanisms of action, including enhancement of Th1 antiviral immune responses, upregulation of IFN-stimulated genes (ISGs), depletion of GTP pools, or viral RNA mutagenesis (see reviews in references 15, 16 and 17). However, on average only about 60% of the chronically infected patients show a sustained virological response to treatment with IFN-␣ plus ribavirin that results in virus clearance (18-21). The molecular and physiological bases of the therapeutic activity of the current combination treatment with IFN-␣ plus ribavirin are poorly understood. It might be possible to establish new treatment protocols based on recently developed directly acting antiviral agents (DAAs), with or without .Highly variable viruses exploit a number of strategies to counteract selective constraints intended to prevent their replication (reviewed in reference 7). Mutations that confer resistance to DAAs generally map in the target protein or in a protein that interacts with the target (28-30). However, the complexity of the cellular IFN response pathway is expected to require greater diversity of viral resistance mutations. Current evidence suggests that the response of HCV to IFN-␣-based therapy is influenced by several host (i.e., interleukin-28B [IL-28B] gene polymorphisms) and viral genetic (i.e., viral genotype and population complexity) factors (31-37).The advent of cell culture systems for sustained replication of HCV offers new prospects to approach the evolutionary dynamics of HCV and the host cell-virus relationship, including the anti-HCV activity of IFN-␣. Using these systems, Garaigorta and Chisari documented that HCV-induced protein kinase R (PKR) phosphorylation inhibited translation of IFN-stimulated genes (ISGs) in infected hepatocytes (38). Here we describe the adaptation of the HCV replication system of genotype 2a (39-41) to perform serial passages of HCV in the Huh-7.5 hepatocyte cell line with sustained, efficient viral replication for at least 100 serial passages. This cell ...

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Section: Discussionsupporting

confidence: 81%

Response of Hepatitis C Virus to Long-Term Passage in the Presence of Alpha Interferon: Multiple Mutations and a Common Phenotype

Perales

Beach

Gallego

et al. 2013

J Virol

163

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“…17 Similarly, eIF2A was found to facilitate translation of HCV mRNA under stress conditions. 18 Recently, eIF2A was shown to control tumor suppressor PTEN translation, which requires a CUG-centered palindromic motif for this process. 20 PTEN is involved in embryonic development, tissue homeostasis, metabolism, and tumor suppression.…”

Section: Discussionmentioning

confidence: 99%

“…eIF2A was originally suggested to function in the same pathway and promote eIF2-independent recruitment of Met-tRNAMet i to 40S ribosomal subunits in parallel with eIF2, or in the absence of eIF2. 3,4,[15][16][17][18] The double deletion eIF2A/eIF5B and eIF2A/eIF4E-ts mutant Saccharomyces cerevisiae strains displayed a severe slow growth phenotype. 15,16 The phenotype of these mutants and the biochemical localization of the eIF2A on the 40S ribosomal subunits and 80S ribosomes further suggested that eIF2A participates in translation initiation.…”

Section: Introductionmentioning

confidence: 99%

The eIF2A knockout mouse

et al. 2016

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Eukaryotic initiation factor 2A (eIF2A) is a 65-kDa protein that was first identified in the early 1970s as a factor capable of stimulating initiator methionyl-tRNAi (Met-tRNA Met i ) binding to 40S ribosomal subunits in vitro. However, in contrast to the eIF2, which stimulates Met-tRNA Met i binding to 40S ribosomal subunits in a GTP-dependent manner, eIF2A didn't reveal any GTP-dependence, but instead was found to direct binding of the Met-tRNA Met i to 40S ribosomal subunits in a codon-dependent manner. eIF2A appears to be highly conserved across eukaryotic species, suggesting conservation of function in evolution. The yeast Saccharomyces cerevisae eIF2A null mutant revealed no apparent phenotype, however, it was found that in yeast eIF2A functions as a suppressor of internal ribosome entry site (IRES)-mediated translation. It was thus suggested that eIF2A my act by impinging on the expression of specific mRNAs. Subsequent studies in mammalian cell systems implicated eIF2A in non-canonical (non-AUG-dependent) translation initiation events involving near cognate UUG and CUG codons. Yet, the role of eIF2A in cellular functions remains largely enigmatic. As a first step toward characterization of the eIF2A function in mammalian systems in vivo, we have obtained homozygous eIF2A-total knockout (KO) mice, in which a gene trap cassette was inserted between eIF2A exons 1 and 2 disrupting expression of all exons downstream of the insertion. The KO mice strain is viable and to date displays no apparent phenotype. We believe that the eIF2A KO mice strain will serve as a valuable tool for researchers studying non-canonical initiation of translation in vivo.

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“…To test the potential of JNS2A to rescue the PKR-mediated translation inhibition, we constructed a bicistronic reporter (Fig. 4A), which contained the firefly luciferase (FLuc) translated in a cap-dependent manner that is sensitive to eIF2␣ phosphorylation, and the Renilla luciferase (RLuc) translated under the control of HCV IRES element, which is resistant to eIF2␣ phosphorylation (37). The relative luciferase activity of FLuc normalized to that of RLuc represents the level of translation blocked by eIF2␣ phosphorylation.…”

Section: Phosphorylation Of Eif2␣ and Pkr Was Detected At Late Stagesmentioning

confidence: 99%

Blocking Double-Stranded RNA-Activated Protein Kinase PKR by Japanese Encephalitis Virus Nonstructural Protein 2A

Liang

et al. 2012

J Virol

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Japanese encephalitis virus (JEV) is an enveloped flavivirus with a single-stranded, positive-sense RNA genome encoding three structural and seven nonstructural proteins. To date, the role of JEV nonstructural protein 2A (NS2A) in the viral life cycle is largely unknown. The interferon (IFN)-induced double-stranded RNA (dsRNA)-activated protein kinase (PKR) phosphorylates the eukaryotic translation initiation factor 2α subunit (eIF2α) after sensing viral RNA and results in global translation arrest as an important host antiviral defense response. In this study, we found that JEV NS2A could antagonize PKR-mediated growth inhibition in a galactose-inducible PKR-expressing yeast system. In human cells, PKR activation, eIF2α phosphorylation, and the subsequent translational inhibition and cell death triggered by dsRNA and IFN-α were also repressed by JEV NS2A. Moreover, among the four eIF2α kinases, NS2A specifically blocked the eIF2α phosphorylation mediated by PKR and attenuated the PKR-promoted cell death induced by the chemotherapeutic drug doxorubicin. A single point mutation of NS2A residue 33 from Thr to Ile (T33I) abolished the anti-PKR potential of JEV NS2A. The recombinant JEV mutant carrying the NS2A-T33I mutation showed reduced in vitro growth and in vivo virulence phenotypes. Thus, JEV NS2A has a novel function in blocking the host antiviral response of PKR during JEV infection.

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eIF2A mediates translation of hepatitis C viral mRNA under stress conditions

Cited by 110 publications

References 50 publications

Response of Hepatitis C Virus to Long-Term Passage in the Presence of Alpha Interferon: Multiple Mutations and a Common Phenotype

Response of Hepatitis C Virus to Long-Term Passage in the Presence of Alpha Interferon: Multiple Mutations and a Common Phenotype

The eIF2A knockout mouse

Blocking Double-Stranded RNA-Activated Protein Kinase PKR by Japanese Encephalitis Virus Nonstructural Protein 2A

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