title: Hepatitis C virus (HCV) induces formation of stress granules whose proteins regulate HCV RNA replication and virus assembly and egress.
abstract: Stress granules (SGs) are cytoplasmic structures that are induced in response to environmental stress, including viral infections. Here we report that hepatitis C virus (HCV) triggers the appearance of SGs in a PKR- and interferon (IFN)-dependent manner. Moreover, we show an inverse correlation between the presence of stress granules and the induction of IFN-stimulated proteins, i.e., MxA and USP18, in HCV-infected cells despite high-level expression of the corresponding MxA and USP18 mRNAs, suggesting that interferon-stimulated gene translation is inhibited in stress granule-containing HCV-infected cells. Finally, in short hairpin RNA (shRNA) knockdown experiments, we found that the stress granule proteins T-cell-restricted intracellular antigen 1 (TIA-1), TIA1-related protein (TIAR), and RasGAP-SH3 domain binding protein 1 (G3BP1) are required for efficient HCV RNA and protein accumulation at early time points in the infection and that G3BP1 and TIA-1 are required for intracellular and extracellular infectious virus production late in the infection, suggesting that they are required for virus assembly. In contrast, TIAR downregulation decreases extracellular infectious virus titers with little effect on intracellular RNA content or infectivity late in the infection, suggesting that it is required for infectious particle release. Collectively, these results illustrate that HCV exploits the stress granule machinery at least two ways: by inducing the formation of SGs by triggering PKR phosphorylation, thereby downregulating the translation of antiviral interferon-stimulated genes, and by co-opting SG proteins for its replication, assembly, and egress.
authors.affiliation: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Urtzi
authors.initials: U
authors.lastname: Garaigorta
authors.forename: Markus H
authors.initials: MH
authors.lastname: Heim
authors.forename: Bryan
authors.initials: B
authors.lastname: Boyd
authors.forename: Stefan
authors.initials: S
authors.lastname: Wieland
authors.forename: Francis V
authors.initials: FV
authors.lastname: Chisari
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D003594:Cytoplasmic Granules / Q000378:metabolism*; D004265:DNA Helicases; D015536:Down-Regulation; D010450:Endopeptidases / Q000096:biosynthesis / Q000235:genetics; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D057809:HEK293 Cells; D016174:Hepacivirus / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D006801:Humans; D016899:Interferon-beta / Q000378:metabolism* / Q000494:pharmacology; D064547:Myxovirus Resistance Proteins; D039102:Poly(A)-Binding Proteins / Q000378:metabolism; D000075223:Poly-ADP-Ribose Binding Proteins; D014176:Protein Biosynthesis; D020365:RNA Helicases; D034622:RNA Interference; D000067776:RNA Recognition Motif Proteins; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering; D012367:RNA, Viral / Q000096:biosynthesis* / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000074019:T-Cell Intracellular Antigen-1; D043222:Ubiquitin Thiolesterase; D019065:Virus Assembly; D057074:Virus Release; D014779:Virus Replication / Q000187:drug effects; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D039102:Poly(A)-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D000067776:RNA Recognition Motif Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D000074019:T-Cell Intracellular Antigen-1; C071558:TIA1 protein, human; C076751:TIAL1 protein, human; D016899:Interferon-beta; D019892:eIF-2 Kinase; D010450:Endopeptidases; C485560:USP18 protein, human; D043222:Ubiquitin Thiolesterase; D019204:GTP-Binding Proteins; D004265:DNA Helicases; C116070:G3BP1 protein, human; D020365:RNA Helicases