An mRNA cap-binding complex in giant viruses controls protein synthesis
Ontology highlight
ABSTRACT:
ORGANISM(S): Acanthamoeba castellanii
PROVIDER: GSE290007 | GEO | 2025/12/04
REPOSITORIES: GEO
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Project description:Plitidepsin is an antitumoral drug safe for treating COVID-19 infection that impairs SARS-CoV-2 replication by targeting the translation elongation factor eEF1A. Here we show that plitidepsin decreased all SARS-CoV-2 transcripts along the early translation of viral R1AB polyproteins and the late synthesis of structural viral proteins. It also reduced de novo cap-dependent translation of viral and non-viral RNAs but affected less than 13% of the host proteome, thus preserving cellular viability. In response to plitidepsin, cells upregulated EIF2AK3 and additional proteins that reduce translation. Other proteins supported proteostasis via ribosome synthesis and cap-independent translation routes, which relied on eIF4G2, PABPC1, and readers such as IGF2BP2. While cap- or internal ribosome entry sites (IRES)-mediated translation pathways were inhibited by plitidepsin, impact on N6-methyladenosine (m6A) translation was limited. The molecular landscape reprogrammed by cells treated with plitidepsin predicted a potential broad-spectrum activity against viruses translated via cap- or IRES-dependent pathways that were suppressed by m6A. In agreement, plitidepsin inhibited the replication of members from the Coronaviridae, Flaviviridae, Pneumoviridae and Herpesviridae families. Yet, it failed to block retroviruses that exploit m6A synthesis routes and are inhibited by drugs against specific m6A readers such as IGF2BP2. By deciphering the molecular fingerprint of cells treated with host-directed therapies targeting protein translation, we identified a rational approach to select for broad-spectrum antivirals with complementary activities and potential to counteract future pandemic viruses.
2024-12-18 | GSE270367 | GEO
Project description:Virus infection may shut off host protein synthesis in order to achieve the replicative advantage over host cells. It is well known that human pathogenic viruses, particularly the picornaviruses, can block host protein synthesis by cleavage or inhibition of eukaryotic initiation factors (eIFs). In this study we found a novel mechanism that microRNA (miRNA) is involved in viral pathogenesis. Infection of enteroviruses can disturb the expression of host miRNAs, in which miR-141 is up-regulated and inhibits host protein synthesis by post-transcriptional repression of the target gene eIF4E, a key element for cap-dependent translation of host proteins. Knockdown of miR-141 by a specific siRNA, antagomiR-141, could restore host eIF4E expression, delay the occurrence of cytopathic effect (CPE), and impair virus propagation. We demonstrated that EV71 infection could increase early growth response 1 (EGR1) expression which induced miR-141 causing the eIF4E suppression; while silencing of EGR1 attenuated virus production. Our results suggest that enterovirus infection causes the EGR1-mediated upregulation of host miR-141, further lead to the translational switch from cap-dependent to cap-independent protein synthesis in the host cells, an environmental beneficial for viral propagation. This novel mechanism may highlight a new approach for future development of antiviral therapy. Enteroviruses in the Picornaviridae family are important human pathogens which can cause fatal diseases, including cardiopulmonary failure, aseptic meningitis, paralysis, myocarditis, and encephalomyelitis. Virus infection may induce shutoff of host protein synthesis, particularly in picornavirus, whose protein translation is cap-independent. It is known that poliovirus 2A protease cleaves eIF4G, a scaffold component of mammalian cell translational complex, leading to the shut down of host protein synthesis. Nevertheless, the cleavage of eIF4G may not be sufficient for the complete shutoff of host protein synthesis. Previous studies showed that cleavage of polyA-binding protein (PABP) by viral protease 3C and dephosphorylation of the translational repressor, eIF4E binding protein 1 (4E-BP1), also contribute to this process. The cap-binding protein, eIF4E, is the most crucial factor in determining whether cap-dependent or -independent translation takes place. The mechanism by which viral infection modulates host cell protein synthesis through interfering eIF4E expression is not yet known. miRNAs are a newly discovered class of small non-protein-coding RNAs that may act via endogenous RNA interference. Our understanding of its role in the dynamic interplay between virus and host components is quite limited. Since both virus infection and miRNAs could hinder cellular protein synthesis, whether miRNAs are involved during virus infection in shutting off host protein synthesis is still unknown. To address this issue, we analyze the altered gene and microRNA expression after EV71 infection. ***This submission represents the mRNA expression component of the study only***
2011-01-03 | E-GEOD-15323 | biostudies-arrayexpress
Project description:We report a novel mechanism of gene origination in the segmented negative sense viruses (sNSVs), including IAV and LASV. During replication, these viruses use "snatched" host caps to prime their own transcription (cap-snatching). We show that a proportion of cap-snatched host sequences contain translational start codons (AUGs), that are recognized by the host ribosome. This allows for the translation of host and viral “untranslated regions” (UTRs) to create N-terminally extended viral proteins or entirely novel polypeptides by genetic overprinting.
2020-05-31 | GSE148122 | GEO
Project description:Multiple processes exist in a cell to ensure continuousproduction of essential proteins either through cap-dependent or cap-independent translation processes. Viruses depend on the host translation machinery for viral protein synthesis. Therefore, viruses have evolved clever strategies to utilize the host translation machinery. Earlier studies have shown that genotype1 hepatitis E virus (g1-HEV) utilizes both cap-dependent and cap-independent translation machineries for its replication and proliferation. Cap-independent translation in g1-HEV is driven by an eighty seven nucleotide-long RNA element which acts as a noncanonical, internal ribosome entry site like (IRESl) element. Here, we have identified the RNA-protein interactome of the HEV IRESl element and characterized the functional significance of some of its components. Our study reveals indispensable roles of host ribosomal proteinRPL5 and DHX9 (RNA helicase A) in mediating efficient translation from the IRESlelement and establish the function of HEV IRESl as a bonafide internal ribosome entry site.
2023-06-25 | PXD031009 | Pride
Project description:Virus infection may shut off host protein synthesis in order to achieve the replicative advantage over host cells. It is well known that human pathogenic viruses, particularly the picornaviruses, can block host protein synthesis by cleavage or inhibition of eukaryotic initiation factors (eIFs). In this study we found a novel mechanism that microRNA (miRNA) is involved in viral pathogenesis. Infection of enteroviruses can disturb the expression of host miRNAs, in which miR-141 is up-regulated and inhibits host protein synthesis by post-transcriptional repression of the target gene eIF4E, a key element for cap-dependent translation of host proteins. Knockdown of miR-141 by a specific siRNA, antagomiR-141, could restore host eIF4E expression, delay the occurrence of cytopathic effect (CPE), and impair virus propagation. We demonstrated that EV71 infection could increase early growth response 1 (EGR1) expression which induced miR-141 causing the eIF4E suppression; while silencing of EGR1 attenuated virus production. Our results suggest that enterovirus infection causes the EGR1-mediated upregulation of host miR-141, further lead to the translational switch from cap-dependent to cap-independent protein synthesis in the host cells, an environmental beneficial for viral propagation. This novel mechanism may highlight a new approach for future development of antiviral therapy.
2011-01-03 | GSE15323 | GEO
Project description:RNA viruses are a major threat to global human health. The life cycles of many highly pathogenic RNA viruses like influenza A virus (IAV) and Lassa virus depends on host mRNA, as viral polymerases cleave 5′m7G-capped host transcripts to prime viral mRNA synthesis (‘cap-snatching’). We hypothesized that start codons within cap-snatched host transcripts could drive the expression of chimeric human-viral coding sequences. Here, we report the existence of this mechanism of gene origination (‘start-snatching’), which creates, depending on the translatability of the viral UTRs, human-virus protein chimeras either as N-terminally extended viral proteins or entirely novel polypeptides by genetic overprinting. We show that both types of chimeric proteins are made in IAV-infected cells, can generate T cell responses and contribute to virulence. Our results indicate that IAV, and likely a multitude of other human-, animal- and plant-viruses, use this host-dependent mechanism to expand their proteome diversity during infection.
2020-05-15 | GSE148245 | GEO
Project description:Influenza A virus (IAV) is a major respiratory pathogen that causes severe illness and mortality worldwide. IAV critically depends on host factors for multiple functions that are not encoded by the viral genome. Notably, the IAV RNA-dependent RNA polymerase (RdRP) complex lacks intrinsic 7-methylguanosine (m7G) capping activity and instead “snatches” the 5’m7G caps and the adjacent 10-15nts of host transcripts to prime viral mRNA production, allowing viral transcripts to be recognized by the host translation machinery. We developed a new approach to simultaneously assay the 5’ ends of host and viral transcripts in infected cells and identify the host capsnatch origins for viral mRNAs. We used this technique to study the progression of IAV infection in nuclear and cytoplasmic compartiments and determined that the RdRP complex has specific sequence preferences that results in preferential capsnatching and avoidance of sub-populations of host RNAs, which can be reverted by the addition of a cap-snatch inhibitor. Notably, genes avoided by CapSnatch Seq have biological functions enriched for mRNA processing, translation, and viral replication. This selectivity and functional enrichment of avoided genes is conserved among capsnatching viruses including Influenza B Virus and Lymphocytic Choriomeningitis Virus, despite differences in RdRP domains and subcellular locations of RNA substrates. This suggests that this preference convergently arose as a viral strategy to allow cap-snatching viruses to avoid targeting genes necessary for its own replication.
2017-08-09 | GSE85474 | GEO
Project description:Viral infection often triggers eukaryotic initiator factor 2α (eIF2α) phosphorylation, leading to global 5’-cap-dependent translation inhibition. RSV encodes messenger RNAs (mRNAs) mimicking 5’-cap structures of host mRNAs and thus inhibition of cap-dependent translation initiation would likely also reduce viral translation. We confirmed that RSV limits widespread translation initiation inhibition and unexpectedly found that the fraction of ribosomes within polysomes increases during infection, indicating higher ribosome loading on mRNAs during infection. We found that AU-rich host transcripts that are less efficiently translated under normal conditions become more efficient at recruiting ribosomes, similar to RSV transcripts. Viral transcripts are transcribed in cytoplasmic inclusion bodies, where the viral AU-rich binding protein M2-1 has been shown to bind viral transcripts and shuttle them into the cytoplasm. We further demonstrated that M2-1 is found on polysomes, and that M2-1 might deliver host AU-rich transcripts for translation.
2024-09-03 | GSE268742 | GEO
Project description:Viruses rely on the host translation machinery to synthesize their own proteins. Consequently, they have evolved varied mechanisms to co-opt host translation for their survival. SARS-CoV-2 relies on a non-structural protein, NSP1, for shutting down host translation. Despite this, it is currently unknown how viral proteins and host factors critical for viral replication can escape a global shutdown of host translation. Here, using a novel FACS-based assay called MeTAFlow, we report a dose-dependent reduction in both nascent protein synthesis and mRNA abundance in cells expressing NSP1. We perform RNA-Seq and matched ribosome profiling experiments to identify gene-specific changes both at the mRNA expression and translation level. We discover a functionally-coherent subset of human genes preferentially translated in the context of NSP1 expression. These genes include the translation machinery components, RNA binding proteins, and others important for viral pathogenicity. Importantly, we also uncover potential mechanisms of preferential translation through the presence of shared sites for specific RNA binding proteins and a remarkable enrichment for 5′ terminal oligo-pyrimidine tracts. Collectively, the present study suggests fine tuning of host gene expression and translation by NSP1 despite its global repressive effect on host protein synthesis.
2020-10-01 | GSE158374 | GEO
Project description:The presence of translation-related proteins has long been seen as a critical distinction between viruses and cellular life, the discovery of giant viruses has challenged this standard. We prove that the potential eukaryotic translation initiation factor 4A (eIF4A, Mb0671) encoded by the Megavirus baoshan (M. baoshan), a member of the Mimiviridae family, possesses ATPase activity and RNA-binding capacity. Mb0671 is important for viral adaptation to the host, localizes to the cytoplasm, and is found in mature virions. Proteomics reveals that Mb0671 can manipulate host protein synthesis, compared to wild-type cells, the cellular proteins that are significantly upregulated in A. castellaniia cells overexpressing Mb0671 are significantly enriched in the spliceosome, biosynthesis of amino acids, ribosome biogenesis in eukaryotes, SNARE interactions in vesicular transport, DNA replication, autophagy and mTOR signaling pathway. Proteomics also revealed Mb0671 plays an important role in RNA processing and transport, gene expression regulation in host cells. Proteomics reveals that overexpression of Mb0671 significantly affects the synthesis of viral proteins. Indirect interactions between Mb0671 and the host's eIF4A, along with other interactions primarily with ribosomal and translation-related proteins, suggest that Mb0671 may form a complex with host translation proteins to perform translation functions. Our findings indicate that the virus-encoded translation factor Mb0671 plays an important role in viral protein synthesis, suggesting that these unusual viruses may possess a special translation mechanism in which Mb0671 could play a key role.
2024-10-03 | PXD056594 |