Project description:Influenza A virus is mainly transmitted through the respiratory route and can cause severe illness in humans. Proteins encoded by influenza A virus can interact with cellular factors and dysregulate host biological processes to facilitate viral replication and pathogenicity. The influenza viral PA protein is not only a subunit of influenza viral polymerase but also a virulence factor involved in pathogenicity during infection. To explore the role of the influenza virus PA protein in regulating host biological processes, we conducted immunoprecipitation and LC-MS/MS to globally identify cellular factors that interact with the PA proteins of the influenza A H1N1, 2009 pandemic H1N1, H3N2, and H7N9 viruses. The results demonstrated that proteins located in the mitochondrion, proteasome, and nucleus are associated with the PA protein. We further discovered that the PA protein is located in mitochondria by immunofluorescence and mitochondrial fractionation and that overexpression of the PA protein reduces mitochondrial respiration. In addition, our results revealed the interaction between PA and the mitochondrial matrix protein PYCR2 and the antiviral role of PYCR2 during influenza A virus replication. Moreover, we found that the PA protein could also trigger autophagy and disrupt mitochondrial homeostasis. Overall, our research revealed the impacts of the influenza A virus PA protein on mitochondrial function and autophagy.
Project description:The nuclear RNA exosome is an essential multi-subunit complex that controls RNA homeostasis. Congenital mutations in exosome genes are associated with neurodegenerative diseases. Here, we show that transient depletion of nuclear RNA exosome subunits in epithelial cells inhibits influenza virus replication. Similarly, viral biogenesis was suppressed in cells derived from mice with conditional ablation of the RNA exosome subunit Exosc3. Furthermore, patient-derived cells with a congenital EXOSC3 mutation were less susceptible to influenza virus infection. Using proteomics and next generation sequencing during infection, we show that the viral polymerase complex (PA, PB2, PB1) co-opts the nuclear RNA exosome complex and cellular RNAs en route to 3’ end degradation. Mechanistically, the nuclear RNA exosome coordinates the initial steps of viral transcription with RNAPII at host promoters. Exosome deficiency uncouples chromatin targeting of the viral polymerase complex and the formation of cellular:viral RNA hybrids, which are essential RNA intermediates that license transcription of antisense genomic viral RNAs. Overall, we discovered a critical nexus between an essential component of the influenza virus (polymerase) and an essential component of the cell (exosome), alteration of which leads to breakage of host-pathogen symmetry and a lose-lose scenario (viral impairment and neurodegeneration).
2017-05-08 | GSE96677 | GEO
Project description:Deep mutational scanning of influenza H3N2 neuraminidase
Project description:Here, we present a systematic and quantitative test of the hypothesis that the composition and activities of the endoplasmic reticulum (ER) proteostasis network impact mutational tolerance of secretory pathway client proteins. We focus on influenza hemagluttinin (HA), a viral coat protein that folds in the host’s ER via a complex but well-characterized pathway. By integrating chemical methods to modulate the unfolded protein response with deep mutational scanning to assess mutational tolerance, we discover that upregulation of ER chaperones broadly enhances HA mutational tolerance across numerous sites and secondary/tertiary structure elements, including sites targeted by host antibodies. Remarkably, this host chaperone-enhanced mutational tolerance is observed at the same HA sites where mutational tolerance is most reduced by propagation at a fever-like temperature. Thus, host ER proteostasis mechanisms and temperature modulate HA mutational tolerance in opposite directions. This finding has important implications for influenza evolution, because influenza immune escape is contingent on HA possessing sufficient mutational tolerance to acquire antibody resistance while still maintaining the capacity to fold and function. More broadly, this work provides the first experimental evidence that the composition and activities of the ER proteostasis network critically define the mutational tolerance and, therefore, the evolution of secretory pathway client proteins.
Project description:Influenza A virus encodes promoters in both the sense and antisense orientations. These support the generation of new genomes, antigenomes, and mRNA transcripts. Characterization of the influenza promoters using minimal replication assays—transfections with viral polymerase, nucleoprotein, and a genomic template—defined their sequence as 13nt at the 5’ end of the viral genomic RNA (U13) and 12nt at the 3’ end (U12).Other than a single position the U12 and U13 sequences are identical between all eight RNA molecules that comprise the segmented influenza genome.Nevertheless, each segment can exhibit different transcriptional dynamics despite possessing identical promoters.Minimal replication assays lack the influenza protein NS2, which can modulate transcription and replication differentially between influenza segments.This suggests that NS2 expression may redefine the influenza A virus promoter.In this work we assess how internal regions of sequence in two genomic segments, HA and PB1, may contribute to NS2-dependent replication as well as map such interactions down to individual nucleotides in PB1. We find that the expression of NS2 significantly alters sequence requirements for efficient replication beyond the identical U12 and U13 sequence, providing a mechanism for the divergent replication and transcription dynamics across the influenza A virus genome.
Project description:During influenza A virus (IAV) infections, viral proteins are targeted by cellular E3 ligases for modification with ubiquitin. Here, we decipher and functionally explore the ubiquitin landscape of the IAV polymerase during infection of human alveolar epithelial cells by applying mass spectrometry analysis of immuno-purified K-ε-GG- (di-glycyl)-remnant-bearing peptides. We identified 59 modified lysines across all three subunits of the viral polymerase of which 17 distinctively affected mRNA transcription, vRNA replication and the generation of recombinant viruses via non-proteolytic mechanisms. Moreover, our results demonstrate that the ubiquitinated residue K578 in the PB1 thumb domain is crucial for the dynamic structural transitions of the viral polymerase that are required for vRNA replication. Mutations K578A and K578R impeded the steps of cRNA stabilization and vRNA transcription, respectively, and affected NP binding as well as polymerase dimerization. Collectively, our results indicate that ubiquitin-mediated disruption of the charge-dependent interaction between PB1-K578 and PB2-E72 is required to coordinate polymerase dimerization and facilitate vRNA replication, which demonstrates that IAV exploit the cellular ubiquitin system to modulate the activity of the viral polymerase for the regulation of viral replication.
Project description:This study used virological, histological, and global gene expression from an experimental murine model of influenza infection to study the contribution of a specific mutation in the PB1-F2 protein (PB1-F2 N66S) of influenza A to viral pathogenesis.
Project description:This SuperSeries is composed of the following subset Series: GSE36461: MiRNA profiling during infection with H1N1 influenza A virus (A/Mexico/InDRE4487/H1N1/2009) GSE36462: MiRNA profiling during infection with H7N7 influenza A virus (A/Ck/Germany/R28/H7N7/2003) GSE36553: mRNA profiling during infection with H1N1 influenza A virus (A/Mexico/InDRE4487/H1N1/2009) Refer to individual Series