Very-long-chain fatty acid metabolic capacity of 17-beta-hydroxysteroid dehydrogenase type 12 (HSD17B12) promotes replication of hepatitis C virus and related flaviviruses.

Flaviviridae infections represent a major global health burden. By deciphering mechanistic aspects of hepatitis C virus (HCV)-host interactions, one could discover common strategy for inhibiting the replication of related flaviviruses. By elucidating the HCV interactome, we identified the 17-beta-hydroxysteroid dehydrogenase type 12 (HSD17B12) as a human hub of the very-long-chain fatty acid (VLCFA) synthesis pathway and core interactor.

Importin β1 targeting by hepatitis C virus NS3/4A protein restricts IRF3 and NF-κB signaling of IFNB1 antiviral response.

In this study, newly identified host interactors of hepatitis C virus (HCV) proteins were assessed for a role in modulating the innate immune response. The analysis revealed enrichment for components of the nuclear transport machinery and the crucial interaction with NS3/4A protein in suppression of interferon-β (IFNB1) induction. Using a comprehensive microscopy-based high-content screening approach combined to the gene silencing of nuclear transport factors, we showed that NS3/4A-interacting proteins control the nucleocytoplasmic trafficking of IFN regulatory factor 3 (IRF3) and NF-κB p65 upon Sendai virus (SeV) infection.

Correction: Spliceosome SNRNP200 Promotes Viral RNA Sensing and IRF3 Activation of Antiviral Response.

[This corrects the article DOI: 10.1371/journal.ppat.

Association of a Network of Interferon-Stimulated Genes with a Locus Encoding a Negative Regulator of Non-conventional IKK Kinases and IFNB1.

Functional genomic analysis of gene expression in mice allowed us to identify a quantitative trait locus (QTL) linked in trans to the expression of 190 gene transcripts and in cis to the expression of only two genes, one of which was Ypel5. Most of the trans-expression QTL genes were interferon-stimulated genes (ISGs), and their expression in mouse macrophage cell lines was stimulated in an IFNB1-dependent manner by Ypel5 silencing. In human HEK293T cells, YPEL5 silencing enhanced the induction of IFNB1 by pattern recognition receptors and phosphorylation of TBK1/IKBKE kinases, whereas co-immunoprecipitation experiments revealed that YPEL5 interacted physically with IKBKE.

Spliceosome SNRNP200 Promotes Viral RNA Sensing and IRF3 Activation of Antiviral Response.

Spliceosomal SNRNP200 is a Ski2-like RNA helicase that is associated with retinitis pigmentosa 33 (RP33). Here we found that SNRNP200 promotes viral RNA sensing and IRF3 activation through the ability of its amino-terminal Sec63 domain (Sec63-1) to bind RNA and to interact with TBK1. We show that SNRNP200 relocalizes into TBK1-containing cytoplasmic structures upon infection, in contrast to the RP33-associated S1087L mutant, which is also unable to rescue antiviral response of SNRNP200 knockdown cells.

Elucidating novel hepatitis C virus-host interactions using combined mass spectrometry and functional genomics approaches.

More than 170 million people worldwide are infected with the hepatitis C virus (HCV), for which future therapies are expected to rely upon a combination of oral antivirals. For a rapidly evolving virus like HCV, host-targeting antivirals are an attractive option. To decipher the role of novel HCV-host interactions, we used a proteomics approach combining immunoprecipitation of viral-host protein complexes coupled to mass spectrometry identification and functional genomics RNA interference screening of HCV partners.

A host YB-1 ribonucleoprotein complex is hijacked by hepatitis C virus for the control of NS3-dependent particle production.

Hepatitis C virus (HCV) orchestrates the different stages of its life cycle in time and space through the sequential participation of HCV proteins and cellular machineries; hence, these represent tractable molecular host targets for HCV elimination by combination therapies. We recently identified multifunctional Y-box-binding protein 1 (YB-1 or YBX1) as an interacting partner of NS3/4A protein and HCV genomic RNA that negatively regulates the equilibrium between viral translation/replication and particle production. To identify novel host factors that regulate the production of infectious particles, we elucidated the YB-1 interactome in human hepatoma cells by a quantitative mass spectrometry approach.

Genome-wide RNAi screen reveals a new role of a WNT/CTNNB1 signaling pathway as negative regulator of virus-induced innate immune responses.

To identify new regulators of antiviral innate immunity, we completed the first genome-wide gene silencing screen assessing the transcriptional response at the interferon-β (IFNB1) promoter following Sendai virus (SeV) infection. We now report a novel link between WNT signaling pathway and the modulation of retinoic acid-inducible gene I (RIG-I)-like receptor (RLR)-dependent innate immune responses. Here we show that secretion of WNT2B and WNT9B and stabilization of β-catenin (CTNNB1) upon virus infection negatively regulate expression of representative inducible genes IFNB1, IFIT1 and TNF in a CTNNB1-dependent effector mechanism.

Tollip-induced down-regulation of MARCH1.

In addition to their classical antigen presenting functions, MHC class II molecules potentiate the TLR-triggered production of pro-inflammatory cytokines. Here, we have addressed the effect of Tollip and MARCH1 on the regulation of MHC II trafficking and TLR signaling. Our results show that MARCH1-deficient mice splenocytes are impaired in their capacity to produce pro-inflammatory cytokines in response to poly(I:C) and that TLR3 and MHC II molecules interact in the endocytic pathway.

Regulators of innate immunity as novel targets for panviral therapeutics.

Interferons (IFNs) have long been used as an immunomodulatory therapy for a large array of acute and chronic viral infections. However, IFN therapies have been plagued by severe side effects. The discovery of pathogen recognition receptors (PRR) rejuvenated the interest for immunomodulatory therapies.

Y-box-binding protein 1 interacts with hepatitis C virus NS3/4A and influences the equilibrium between viral RNA replication and infectious particle production.

The hepatitis C virus (HCV) NS3/4A protein has several essential roles in the virus life cycle, most probably through dynamic interactions with host factors. To discover cellular cofactors that are co-opted by HCV for its replication, we elucidated the NS3/4A interactome using mass spectrometry and identified Y-box-binding protein 1 (YB-1) as an interacting partner of NS3/4A protein and HCV genomic RNA. Importantly, silencing YB-1 expression decreased viral RNA replication and severely impaired the propagation of the infectious HCV molecular clone JFH-1.

Hepatitis C Virus NS3/4A Protease Inhibitors: A Light at the End of the Tunnel.

Hepatitis C virus (HCV) infection is a serious and growing threat to human health. The current treatment provides limited efficacy and is poorly tolerated, highlighting the urgent medical need for novel therapeutics. The membrane-targeted NS3 protein in complex with the NS4A comprises a serine protease domain (NS3/4A protease) that is essential for viral polyprotein maturation and contributes to the evasion of the host innate antiviral immunity by HCV.

MAVS dimer is a crucial signaling component of innate immunity and the target of hepatitis C virus NS3/4A protease.

The mitochondrial antiviral signaling (MAVS) protein plays a central role in innate antiviral immunity. Upon recognition of a virus, intracellular receptors of the RIG-I-like helicase family interact with MAVS to trigger a signaling cascade. In this study, we investigate the requirement of the MAVS structure for enabling its signaling by structure-function analyses and resonance energy transfer approaches in live cells.

Interleukin-10-induced MARCH1 mediates intracellular sequestration of MHC class II in monocytes.

IL-10 is a potent anti-inflammatory cytokine interfering with antigen presentation by inducing the intracellular sequestration of MHC class II (MHC-II) molecules. Here we studied the contribution of membrane-associated RING-CH (MARCH) ubiquitin ligase family members to the IL-10-induced down-regulation of MHC-II molecules. We found that MARCH1 and MARCH8 proteins are the most potent family members for the down-regulation of MHC-II surface expression in transfected cells, but only MARCH1 mRNA expression is strongly induced by IL-10 in human primary monocytes.

Synthesis, structural characterization, and biological studies of new antimony(III) complexes with thiones. The influence of the solvent on the geometry of the complexes.

Five new antimony(III) complexes with the heterocyclic thiones 2-mercapto-benzimidazole (MBZIM), 5-ethoxy-2-mercapto-benzimidazole (EtMBZIM), and 2-mercapto-thiazolidine (MTZD) of formulas {[SbCl(2)(MBZIM)4]+.Cl-.2H(2)O.

Synthesis, structural characterization, and biological studies of six- and five-coordinate organotin(IV) complexes with the thioamides 2-mercaptobenzothiazole, 5-chloro-2-mercaptobenzothiazole, and 2-mercaptobenzoxazole.

Organotin(IV) complexes with the formulas [(C6H5)3Sn(mbzt)] (1), [(C6H5)3Sn(cmbzt)] (3), and [(C6H5)2Sn(cmbzt)2] (4) (Hmbzt = 2-mercaptobenzothiazole and Hcmbzt = 5-chloro-2-mercaptobenzothiazole) have been synthesized and characterized by elemental analysis; FT-IR, Raman, 1H, 13C, and 119Sn NMR, and Mössbauer spectroscopic techniques; and X-ray crystallography at various temperatures. The crystal structures of complexes 1, 3, and 4 were determined by X-ray diffraction at room temperature [295(1) or 293(2) K]. The complexes [(C6H5)3Sn(mbzo)] (2) and [(n-C4H9)2Sn(cmbzt)2] (5) (Hmbzo = 2-mercaptobenzoxazole) were synthesized by new improved methods, and their structures were determined at low temperature [100(1) K] and compared to those solved at room temperature.

Synthesis and structures of Se analogues of the antithyroid drug 6-n-propyl-2-thiouracil and its alkyl derivatives: formation of dimeric Se-Se compounds and deselenation reactions of charge-transfer adducts of diiodine.

Four selenium analogues of the antithyroid drug 6-n-propyl-2-thiouracil (PTU), of formulae RSeU, (R = methyl (Me) (1), ethyl (Et) (2), n-propyl (nPr) (3), and isopropyl (iPr) 4), have been synthesized. Reaction of 1-4 with diiodine in a 1:1 molar ratio in dichloromethane results in the formation of [(RSeU)I(2)] (R = methyl (5), ethyl (6), n-propyl (7) and isopropyl (8)). All compounds have been characterized by elemental analysis, FT-Raman, FT-IR, UV/Vis, (1)H-, (13)C-, (77)Se-1D and -2D NMR spectroscopy, and ESI-MS spectrometric techniques.

Translation of the F protein of hepatitis C virus is initiated at a non-AUG codon in a +1 reading frame relative to the polyprotein.

The hepatitis C virus (HCV) genome contains an internal ribosome entry site (IRES) followed by a large open reading frame coding for a polyprotein that is cleaved into 10 proteins. An additional HCV protein, the F protein, was recently suggested to result from a +1 frameshift by a minority of ribosomes that initiated translation at the HCV AUG initiator codon of the polyprotein. In the present study, we reassessed the mechanism accounting for the synthesis of the F protein by measuring the expression in cultured cells of a luciferase reporter gene with an insertion encompassing the IRES plus the beginning of the HCV-coding region preceding the luciferase-coding sequence.

Efficiency of a programmed -1 ribosomal frameshift in the different subtypes of the human immunodeficiency virus type 1 group M.

The synthesis of the Gag-Pol polyprotein, the precursor of the enzymes of the human immunodeficiency virus type 1 (HIV-1), requires a programmed -1 ribosomal frameshift. This frameshift has been investigated so far only for subtype B of HIV-1 group M. In this subtype, the frameshift stimulatory signal was found to be a two-stem helix, in which a three-purine bulge interrupts the two stems.

The frameshift stimulatory signal of human immunodeficiency virus type 1 group O is a pseudoknot.

Human immunodeficiency virus type 1 (HIV-1) requires a programmed -1 ribosomal frameshift to produce Gag-Pol, the precursor of its enzymatic activities. This frameshift occurs at a slippery sequence on the viral messenger RNA and is stimulated by a specific structure, downstream of the shift site. While in group M, the most abundant HIV-1 group, the frameshift stimulatory signal is an extended bulged stem-loop, we show here, using a combination of mutagenesis and probing studies, that it is a pseudoknot in group O.

Characterization of the frameshift stimulatory signal controlling a programmed -1 ribosomal frameshift in the human immunodeficiency virus type 1.

Synthesis of the Gag-Pol protein of the human immunodeficiency virus type 1 (HIV-1) requires a programmed -1 ribosomal frameshifting when ribosomes translate the unspliced viral messenger RNA. This frameshift occurs at a slippery sequence followed by an RNA structure motif that stimulates frameshifting. This motif is commonly assumed to be a simple stem-loop for HIV-1.