scholarly journals Hepatitis C Virus Translation Regulation

2020 ◽  
Vol 21 (7) ◽  
pp. 2328 ◽  
Author(s):  
Michael Niepmann ◽  
Gesche K. Gerresheim
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Translation Initiation ◽  
Core Protein ◽  
Mrna Translation ◽  
Start Codon ◽  
Translation Regulation ◽  
Hcv Rna ◽  
Entry Site ◽  
Initiation Factors

Translation of the hepatitis C virus (HCV) RNA genome is regulated by the internal ribosome entry site (IRES), located in the 5’-untranslated region (5′UTR) and part of the core protein coding sequence, and by the 3′UTR. The 5′UTR has some highly conserved structural regions, while others can assume different conformations. The IRES can bind to the ribosomal 40S subunit with high affinity without any other factors. Nevertheless, IRES activity is modulated by additional cis sequences in the viral genome, including the 3′UTR and the cis-acting replication element (CRE). Canonical translation initiation factors (eIFs) are involved in HCV translation initiation, including eIF3, eIF2, eIF1A, eIF5, and eIF5B. Alternatively, under stress conditions and limited eIF2-Met-tRNAiMet availability, alternative initiation factors such as eIF2D, eIF2A, and eIF5B can substitute for eIF2 to allow HCV translation even when cellular mRNA translation is downregulated. In addition, several IRES trans-acting factors (ITAFs) modulate IRES activity by building large networks of RNA-protein and protein–protein interactions, also connecting 5′- and 3′-ends of the viral RNA. Moreover, some ITAFs can act as RNA chaperones that help to position the viral AUG start codon in the ribosomal 40S subunit entry channel. Finally, the liver-specific microRNA-122 (miR-122) stimulates HCV IRES-dependent translation, most likely by stabilizing a certain structure of the IRES that is required for initiation.

scholarly journals Geneticin Stabilizes the Open Conformation of the 5′ Region of Hepatitis C Virus RNA and Inhibits Viral Replication

2015 ◽  
Vol 60 (2) ◽  
pp. 925-935 ◽  
Author(s):  
Ascensión Ariza-Mateos ◽  
Rosa Díaz-Toledano ◽  
Timothy M. Block ◽  
Samuel Prieto-Vega ◽  
Alex Birk ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Therapeutic Potential ◽  
Kinetic Studies ◽  
Rnase P ◽  
Start Codon ◽  
Hcv Rna ◽  
Rnase Iii ◽  
Entry Site ◽  
Content Type

ABSTRACTThe aminoglycoside Geneticin (G418) is known to inhibit cell culture proliferation, via virus-specific mechanisms, of two different virus genera from the familyFlaviviridae. Here, we tried to determine whether Geneticin can selectively alter the switching of the nucleotide 1 to 570 RNA region of hepatitis C virus (HCV) and, if so, whether this inhibits viral growth. Two structure-dependent RNases known to specifically cleave HCV RNA were tested in the presence or absence of the drug. One was theSynechocystissp. RNase P ribozyme, which cleaves the tRNA-like domain around the AUG start codon under high-salt buffer conditions; the second wasEscherichia coliRNase III, which recognizes a double-helical RNA switch element that changes the internal ribosome entry site (IRES) from a closed (C) conformation to an open (O) one. While the drug did not affect RNase P activity, it did inhibit RNase III in the micromolar range. Kinetic studies indicated that the drug favors the switch from the C to the O conformation of the IRES by stabilizing the distal double-stranded element and inhibiting further processing of the O form. We demonstrate that, because the RNA in this region is highly conserved and essential for virus survival, Geneticin inhibits HCV Jc1 NS3 expression, the release of the viral genomic RNA, and the propagation of HCV in Huh 7.5 cells. Our study highlights the crucial role of riboswitches in HCV replication and suggests the therapeutic potential of viral-RNA-targeted antivirals.

scholarly journals Lower concentration of La protein required for internal ribosome entry on hepatitis C virus RNA than on poliovirus RNA

1999 ◽  
Vol 80 (9) ◽  
pp. 2319-2327 ◽  
Author(s):  
Takeshi Isoyama ◽  
Nobuhiko Kamoshita ◽  
Kotaro Yasui ◽  
Atsushi Iwai ◽  
Kazuko Shiroki ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Translation Initiation ◽  
Internal Ribosomal Entry Site ◽  
Translation System ◽  
Hcv Rna ◽  
Entry Site ◽  
La Protein ◽  
Reticulocyte Lysates ◽  
Hcv Ires

Translation initiation of poliovirus and hepatitis C virus (HCV) RNA occurs by entry of ribosomes to the internal RNA sequence, called the internal ribosomal entry site (IRES). Both IRES bind to the La protein and are thought to require the protein for their translation initiation activity, although they are greatly different in both the primary and predicted secondary structures. To compare the La protein requirement for these IRES, we took advantage of I-RNA from the yeast Saccharomyces cerevisiae, which has been reported to bind to La protein and block poliovirus IRES-mediated translation initiation. In a cell-free translation system prepared from HeLa cells, yeast I-RNA inhibited translation initiation on poliovirus RNA as expected, but did not significantly inhibit translation initiation on HCV RNA. However, the translation initiation directed by either IRES was apparently inhibited by I-RNA in rabbit reticulocyte lysates, in which La protein is limiting. I-RNA-mediated inhibition of HCV IRES-dependent translation in rabbit reticulocyte lysates was reversed by exogenous addition of purified recombinant La protein of smaller amounts than necessary to reverse poliovirus IRES-dependent translation. These results suggest that HCV IRES requires lower concentrations of La protein for its function than does poliovirus IRES. Immunofluorescence studies showed that HCV infection appeared not to affect the subcellular localization of La protein, which exists mainly in the nucleus, although La protein redistributed to the cytoplasm after poliovirus infection. The data are compatible with the low requirement of La protein for HCV IRES activity.

scholarly journals Inhibition of hepatitis C virus replication and internal ribosome entry site-dependent translation by an RNA molecule

2009 ◽  
Vol 90 (7) ◽  
pp. 1659-1669 ◽  
Author(s):  
Cristina Romero-López ◽  
Raquel Díaz-González ◽  
Alicia Barroso-delJesus ◽  
Alfredo Berzal-Herranz
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Internal Ribosome Entry Site ◽  
Hammerhead Ribozyme ◽  
Start Codon ◽  
Hcv Rna ◽  
Entry Site ◽  
Subgenomic Replicon ◽  
Stem Loop ◽  
Internal Ribosome Entry

Hepatitis C virus (HCV) protein synthesis is mediated by a highly conserved internal ribosome entry site (IRES), mostly located at the 5′ untranslatable region (UTR) of the viral genome. The translation mechanism is different from that used by cellular cap-mRNAs, making IRESs an attractive target site for new antiviral drugs. The present work characterizes a chimeric RNA molecule (HH363-50) composed of two inhibitors: a hammerhead ribozyme targeting position 363 of the HCV genome and an aptamer directed towards the essential stem–loop structure in domain IV of the IRES region (which contains the translation start codon). The inhibitor RNA interferes with the formation of a translationally active complex, stalling its progression at the level of 80S particle formation. This action is likely related to the effective and specific blocking of HCV IRES-dependent translation achieved in Huh-7 cells. The inhibitor HH363-50 also reduces HCV RNA levels in a subgenomic replicon system. The present findings suggest that HH363-50 could be an effective anti-HCV compound and highlight the possibilities of antiviral agents based on RNA molecules.

scholarly journals Differential Effects on the Hepatitis C Virus (HCV) Internal Ribosome Entry Site by Vitamin B12 and the HCV Core Protein

2004 ◽  
Vol 78 (21) ◽  
pp. 12075-12081 ◽  
Author(s):  
Dongsheng Li ◽  
William B. Lott ◽  
John Martyn ◽  
Gholamreza Haqshenas ◽  
Eric J. Gowans
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Internal Ribosome Entry Site ◽  
Core Protein ◽  
Vitamin B ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Hcv Core Protein ◽  
Hcv Ires

ABSTRACT To investigate the role of the hepatitis C virus internal ribosome entry site (HCV IRES) domain IV in translation initiation and regulation, two chimeric IRES elements were constructed to contain the reciprocal domain IV in the otherwise HCV and classical swine fever virus IRES elements. This permitted an examination of the role of domain IV in the control of HCV translation. A specific inhibitor of the HCV IRES, vitamin B12, was shown to inhibit translation directed by all IRES elements which contained domain IV from the HCV and the GB virus B IRES elements, whereas the HCV core protein could only suppress translation from the wild-type HCV IRES. Thus, the mechanisms of translation inhibition by vitamin B12 and the core protein differ, and they target different regions of the IRES.

scholarly journals Hepatitis C virus depends on E-cadherin as an entry factor and regulates its expression in epithelial-to-mesenchymal transition

2016 ◽  
Vol 113 (27) ◽  
pp. 7620-7625 ◽  
Author(s):  
Qisheng Li ◽  
Catherine Sodroski ◽  
Brianna Lowey ◽  
Cameron J. Schweitzer ◽  
Helen Cha ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Cell Surface ◽  
Viral Entry ◽  
Epithelial To Mesenchymal Transition ◽  
Hcv Infection ◽  
Hcv Rna ◽  
Entry Site ◽  
Mesenchymal Transition ◽  
E Cadherin

Hepatitis C virus (HCV) enters the host cell through interactions with a cascade of cellular factors. Although significant progress has been made in understanding HCV entry, the precise mechanisms by which HCV exploits the receptor complex and host machinery to enter the cell remain unclear. This intricate process of viral entry likely depends on additional yet-to-be-defined cellular molecules. Recently, by applying integrative functional genomics approaches, we identified and interrogated distinct sets of host dependencies in the complete HCV life cycle. Viral entry assays using HCV pseudoparticles (HCVpps) of various genotypes uncovered multiple previously unappreciated host factors, including E-cadherin, that mediate HCV entry. E-cadherin silencing significantly inhibited HCV infection in Huh7.5.1 cells, HepG2/miR122/CD81 cells, and primary human hepatocytes at a postbinding entry step. Knockdown of E-cadherin, however, had no effect on HCV RNA replication or internal ribosomal entry site (IRES)-mediated translation. In addition, an E-cadherin monoclonal antibody effectively blocked HCV entry and infection in hepatocytes. Mechanistic studies demonstrated that E-cadherin is closely associated with claudin-1 (CLDN1) and occludin (OCLN) on the cell membrane. Depletion of E-cadherin drastically diminished the cell-surface distribution of these two tight junction proteins in various hepatic cell lines, indicating that E-cadherin plays an important regulatory role in CLDN1/OCLN localization on the cell surface. Furthermore, loss of E-cadherin expression in hepatocytes is associated with HCV-induced epithelial-to-mesenchymal transition (EMT), providing an important link between HCV infection and liver cancer. Our data indicate that a dynamic interplay among E-cadherin, tight junctions, and EMT exists and mediates an important function in HCV entry.

scholarly journals Enhanced virus translation enables miR-122-independent Hepatitis C Virus propagation

2021 ◽  
Author(s):  
Mamata Panigrahi ◽  
Michael Palmer ◽  
Joyce A Wilson
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Virus Replication ◽  
Rna Structure ◽  
Genome Stability ◽  
Internal Ribosomal Entry Site ◽  
Terminal Region ◽  
Translation Regulation ◽  
Virus Propagation ◽  
Entry Site

The 5’UTR of the Hepatitis C Virus genome forms RNA structures that regulate virus replication and translation. The region contains a viral internal ribosomal entry site and a 5’ terminal region. Binding of the liver specific miRNA, miR-122, to two conserved binding sites in the 5’ terminal region regulates viral replication, translation, and genome stability, and is essential for efficient virus replication, but its precise mechanism of its action is still under debate. A current hypothesis is that miR-122 binding stimulates viral translation by facilitating the viral 5’ UTR to form the translationally active HCV IRES RNA structure. While miR-122 is essential for detectable virus replication in cell culture, several viral variants with 5’ UTR mutations exhibit low level replication in the absence of miR-122. We show that HCV mutants capable of replicating independently of miR-122 also replicate independently of other microRNAs generated by the canonical miRNA synthesis pathway. Further, we also show that the mutant genomes display an enhanced translation phenotype that correlates with their ability to replicate independently of miR-122. Finally, we provide evidence that translation regulation is the major role for miR-122, and show that miR-122-independent HCV replication can be rescued to miR-122-dependent levels by the combined impacts of 5’ UTR mutations that stimulate translation, and by stabilizing the viral genome by knockdown of host exonucleases and phosphatases that degrade the genome. Thus, we provide a model suggesting that translation stimulation and genome stabilization are the primary roles for miR-122 in the virus life cycle.

scholarly journals Cytokine-Modulated Natural Killer Cells Differentially Regulate the Activity of the Hepatitis C Virus

2018 ◽  
Vol 19 (9) ◽  
pp. 2771 ◽  
Author(s):  
Yoo Cho ◽  
Hwan Lee ◽  
Hyojeung Kang ◽  
Hyosun Cho
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Nk Cells ◽  
Natural Killer ◽  
Core Protein ◽  
Lymphoid Cells ◽  
Hcv Rna ◽  
Cell Infection ◽  
Hcv Core Protein

HCV genotype 2a strain JFH-1 replicates and produces viral particles efficiently in human hepatocellular carcinoma (huh) 7.5 cells, which provide a stable in vitro cell infection system for the hepatitis C virus (HCVcc system). Natural killer (NK) cells are large lymphoid cells that recognize and kill virus-infected cells. In this study, we investigated the interaction between NK cells and the HCVcc system. IL-10 is a typical immune regulatory cytokine that is produced mostly by NK cells and macrophages. IL-21 is one of the main cytokines that stimulate the activation of NK cells. First, we used anti-IL-10 to neutralize IL-10 in a coculture of NK cells and HCVcc. Anti-IL-10 treatment increased the maturation of NK cells by enhancing the frequency of the CD56+dim population in NK-92 cells. However, with anti-IL-10 treatment of NK cells in coculture with J6/JFH-1-huh 7.5 cells, there was a significant decrease in the expression of STAT1 and STAT5 proteins in NK-92 cells and an increase in the HCV Core and NS3 proteins. In addition, rIL-21 treatment increased the frequency of the CD56+dim population in NK-92 cells, Also, there was a dramatic increase in the expression of STAT1 and STAT5 proteins in rIL-21 pre-stimulated NK cells and a decrease in the expression of HCV Core protein in coculture with J6/JFH-1-huh 7.5 cells. In summary, we found that the functional activation of NK cells can be modulated by anti-IL-10 or rIL-21, which controls the expression of HCV proteins as well as HCV RNA replication.

scholarly journals Expression of hepatitis C virus proteins in epithelial intestinal cells in vivo

2004 ◽  
Vol 85 (9) ◽  
pp. 2515-2523 ◽  
Author(s):  
Séverine Deforges ◽  
Alexey Evlashev ◽  
Magali Perret ◽  
Mireille Sodoyer ◽  
Stéphane Pouzol ◽  
...  
Keyword(s):  
Small Intestine ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Core Protein ◽  
Lipoprotein Metabolism ◽  
Hcv Rna ◽  
Hybrid Particles ◽  
Hepatitis C Infection ◽  
Hcv Antibody

Previous work on hepatitis C virus (HCV) led to the discovery of a new form of virus particle associating virus and lipoprotein elements. These hybrid particles (LVP for lipo-viro-particles) are enriched in triglycerides and contain at least apolipoprotein B (apoB), HCV RNA and core protein. These findings suggest that LVP synthesis could occur in liver and intestine, the two main organs specialized in the production of apoB-containing lipoprotein. To identify the site of LVP production, the genetic diversity and phylogenetic relationship of HCV quasispecies from purified LVP, whole serum and liver biopsies from chronically infected patients were studied. HCV quasispecies from LVP and liver differed significantly, suggesting that LVP were not predominantly synthesized in the liver but might also originate in the intestine. The authors therefore searched for the presence of HCV in the small intestine. Paraffin-embedded intestinal biopsies from 10 chronically HCV-infected patients and from 12 HCV RNA-negative controls (10 anti-HCV antibody-negative and two anti-HCV antibody-positive patients) were tested for HCV protein expression. HCV NS3 and NS5A proteins were stained in small intestine epithelial cells in four of the 10 chronically infected patients, and not in controls. Cells expressing HCV proteins were apoB-producing enterocytes but not mucus-secreting cells. These data indicate that the small intestine can be infected by HCV, and identify this organ as a potential reservoir and replication site. This further emphasizes the interaction between lipoprotein metabolism and HCV, and offers new insights into hepatitis C infection and pathophysiology.

scholarly journals Characterization of Low- and Very-Low-Density Hepatitis C Virus RNA-Containing Particles

2002 ◽  
Vol 76 (14) ◽  
pp. 6919-6928 ◽  
Author(s):  
P. André ◽  
F. Komurian-Pradel ◽  
S. Deforges ◽  
M. Perret ◽  
J. L. Berland ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Apolipoprotein B ◽  
Core Protein ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hcv Rna ◽  
Low Density ◽  
Density Fractions

ABSTRACT The presence of hepatitis C virus (HCV) RNA-containing particles in the low-density fractions of plasma has been associated with high infectivity. However, the nature of circulating HCV particles and their association with immunoglobulins or lipoproteins as well as the characterization of cell entry have all been subject to conflicting reports. For a better analysis of HCV RNA-containing particles, we quantified HCV RNA in the low-density fractions of plasma corresponding to the very-low-density lipoprotein (VLDL), intermediate-density lipoprotein, and low-density lipoprotein (LDL) fractions from untreated chronically HCV-infected patients. HCV RNA was always found in at least one of these fractions and represented 8 to 95% of the total plasma HCV RNA. Surprisingly, immunoglobulins G and M were also found in the low-density fractions and could be used to purify the HCV RNA-containing particles (lipo-viro-particles [LVP]). Purified LVP were rich in triglycerides; contained at least apolipoprotein B, HCV RNA, and core protein; and appeared as large spherical particles with a diameter of more than 100 nm and with internal structures. Delipidation of these particles resulted in capsid-like structures recognized by anti-HCV core protein antibody. Purified LVP efficiently bind and enter hepatocyte cell lines, while serum or whole-density fractions do not. Binding of these particles was competed out by VLDL and LDL from noninfected donors and was blocked by anti-apolipoprotein B and E antibodies, whereas upregulation of the LDL receptor increased their internalization. These results suggest that the infectivity of LVP is mediated by endogenous proteins rather than by viral components providing a mechanism of escape from the humoral immune response.

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