Identification of a Functional, CRM-1-Dependent Nuclear Export Signal in Hepatitis C Virus Core Protein

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease worldwide. HCV core protein is involved in nucleocapsid formation, but it also interacts with multiple cytoplasmic and nuclear molecules and plays a crucial role in the development of liver disease and hepatocarcinogenesis. The core protein is found mostly in the cytoplasm during HCV infection, but also in the nucleus in patients with hepatocarcinoma and in core-transgenic mice. HCV core contains nuclear localization signals (NLS), but no nuclear export signal (NES) has yet been identified

pISTil: a pipeline for yeast two-hybrid Interaction Sequence Tags identification and analysis

High-throughput screening of protein-protein interactions opens new systems biology perspectives for the comprehensive understanding of cell physiology in normal and pathological conditions. In this context, yeast two-hybrid system appears as a promising approach to efficiently reconstruct protein interaction networks at the proteome-wide scale. This protein interaction screening method generates a large amount of raw sequence data, i.e. the ISTs (Interaction Sequence Tags), which urgently need appropriate tools for their systematic and standardised analysis.Journal Articleinfo:eu-repo/semantics/publishe

Measles virus V protein blocks Jak1-mediated phosphorylation of STAT1 to escape IFN-α/β signaling

AbstractViruses have evolved various strategies to escape the antiviral activity of type I interferons (IFN-α/β). For measles virus, this function is carried by the polycistronic gene P that encodes, by an unusual editing strategy, for the phosphoprotein P and the virulence factor V (MV-V). MV-V prevents STAT1 nuclear translocation by either sequestration or phosphorylation inhibition, thereby blocking IFN-α/β pathway. We show that both the N- and C-terminal domains of MV-V (PNT and VCT) contribute to the inhibition of IFN-α/β signaling. Using the two-hybrid system and co-affinity purification experiments, we identified STAT1 and Jak1 as interactors of MV-V and demonstrate that MV-V can block the direct phosphorylation of STAT1 by Jak1. A deleterious mutation within the PNT domain of MV-V (Y110H) impaired its ability to interact and block STAT1 phosphorylation. Thus, MV-V interacts with at least two components of IFN-α/β receptor complex to block downstream signaling

Study of Human RIG-I Polymorphisms Identifies Two Variants with an Opposite Impact on the Antiviral Immune Response

International audienceBACKGROUND: RIG-I is a pivotal receptor that detects numerous RNA and DNA viruses. Thus, its defectiveness may strongly impair the host antiviral immunity. Remarkably, very little information is available on RIG-I single-nucleotide polymorphisms (SNPs) presenting a functional impact on the host response. METHODOLOGY/PRINCIPAL FINDINGS: Here, we studied all non-synonymous SNPs of RIG-I using biochemical and structural modeling approaches. We identified two important variants: (i) a frameshift mutation (P(229)fs) that generates a truncated, constitutively active receptor and (ii) a serine to isoleucine mutation (S(183)I), which drastically inhibits antiviral signaling and exerts a down-regulatory effect, due to unintended stable complexes of RIG-I with itself and with MAVS, a key downstream adapter protein. CONCLUSIONS/SIGNIFICANCE: Hence, this study characterized P(229)fs and S(183)I SNPs as major functional RIG-I variants and potential genetic determinants of viral susceptibility. This work also demonstrated that serine 183 is a residue that critically regulates RIG-I-induced antiviral signaling

IRGM Is a Common Target of RNA Viruses that Subvert the Autophagy Network

Autophagy is a conserved degradative pathway used as a host defense mechanism against intracellular pathogens. However, several viruses can evade or subvert autophagy to insure their own replication. Nevertheless, the molecular details of viral interaction with autophagy remain largely unknown. We have determined the ability of 83 proteins of several families of RNA viruses (Paramyxoviridae, Flaviviridae, Orthomyxoviridae, Retroviridae and Togaviridae), to interact with 44 human autophagy-associated proteins using yeast two-hybrid and bioinformatic analysis. We found that the autophagy network is highly targeted by RNA viruses. Although central to autophagy, targeted proteins have also a high number of connections with proteins of other cellular functions. Interestingly, immunity-associated GTPase family M (IRGM), the most targeted protein, was found to interact with the autophagy-associated proteins ATG5, ATG10, MAP1CL3C and SH3GLB1. Strikingly, reduction of IRGM expression using small interfering RNA impairs both Measles virus (MeV), Hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV-1)-induced autophagy and viral particle production. Moreover we found that the expression of IRGM-interacting MeV-C, HCV-NS3 or HIV-NEF proteins per se is sufficient to induce autophagy, through an IRGM dependent pathway. Our work reveals an unexpected role of IRGM in virus-induced autophagy and suggests that several different families of RNA viruses may use common strategies to manipulate autophagy to improve viral infectivity

NRP/Optineurin Cooperates with TAX1BP1 to Potentiate the Activation of NF-κB by Human T-Lymphotropic Virus Type 1 Tax Protein

Nuclear factor (NF)-κB is a major survival pathway engaged by the Human T-Lymphotropic Virus type 1 (HTLV-1) Tax protein. Tax1 activation of NF-κB occurs predominantly in the cytoplasm, where Tax1 binds NF-κB Essential Modulator (NEMO/IKKγ) and triggers the activation of IκB kinases. Several independent studies have shown that Tax1-mediated NF-κB activation is dependent on Tax1 ubiquitination. Here, we identify by co-immunoprecipitation assays NEMO-Related Protein (NRP/Optineurin) as a binding partner for Tax1 in HTLV-1 infected and Tax1/NRP co-expressing cells. Immunofluorescence studies reveal that Tax1, NRP and NEMO colocalize in Golgi-associated structures. The interaction between Tax1 and NRP requires the ubiquitin-binding activity of NRP and the ubiquitination sites of Tax1. In addition, we observe that NRP increases the ubiquitination of Tax1 along with Tax1-dependent NF-κB signaling. Surprisingly, we find that in addition to Tax1, NRP interacts cooperatively with the Tax1 binding protein TAX1BP1, and that NRP and TAX1BP1 cooperate to modulate Tax1 ubiquitination and NF-κB activation. Our data strongly suggest for the first time that NRP is a critical adaptor that regulates the assembly of TAX1BP1 and post-translationally modified forms of Tax1, leading to sustained NF-κB activation

Virus-host protein interactions in RNA viruses.

International audienceRNA viruses exhibit small-sized genomes that only encode a limited number of viral proteins, but still establish complex networks of interactions with host cell components. Here we summarize recent reports that aim at understanding general features of RNA virus infection networks at the protein level

Maturation anormale et activité cytotoxique des cellules dendritiques infectées par le virus de la rougeole

LYON-ENS Sciences (693872304) / SudocSudocFranceF

Stimuler la réponse interféron de type I avec des petites molécules : le renouveau d’une vieille idée

Les interférons de type I jouent un rôle central dans la mise en place d’une réponse immunitaire innée contre les infections virales et les cellules tumorales. Peu après leur découverte en 1957, plusieurs équipes ont recherché des petites molécules capables d’induire l’expression de ces cytokines à des fins thérapeutiques. Un ensemble de composés actifs chez la souris ont ainsi été identifiés, mais en raison de leur relative inefficacité chez l’homme pour des raisons incomprises à l’époque, ces travaux ont été abandonnés et sont tombés dans l’oubli. Ces dernières années, la caractérisation des récepteurs impliqués dans la reconnaissance des pathogènes, des voies de signalisation qu’ils activent, ainsi que la découverte des cellules dendritiques plasmacytoïdes ont révolutionné notre compréhension de l’immunité innée. Ces découvertes et les nouvelles technologies de criblages à haut débit ont ravivé l’intérêt pour les petites molécules capables d’induire les interférons de type I. Les preuves de leur efficacité thérapeutique chez l’homme sont attendues très prochainement