scholarly journals Cooperation between the Hepatitis C Virus p7 and NS5B Proteins Enhances Virion Infectivity

2015 ◽  
Vol 89 (22) ◽  
pp. 11523-11533 ◽  
Author(s):  
Mounavya Aligeti ◽  
Allison Roder ◽  
Stacy M. Horner
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Molecular Mechanisms ◽  
Genetic Interaction ◽  
Infectious Clone ◽  
Viral Rna ◽  
Rna Dependent Rna Polymerase ◽  
Adaptive Mutations ◽  
Viral Titers

ABSTRACTThe molecular mechanisms that govern hepatitis C virus (HCV) assembly, release, and infectivity are still not yet fully understood. In the present study, we sequenced a genotype 2A strain of HCV (JFH-1) that had been cell culture adapted in Huh-7.5 cells to produce nearly 100-fold-higher viral titers than the parental strain. Sequence analysis identified nine mutations in the genome, present within both the structural and nonstructural genes. The infectious clone of this virus containing all nine culture-adapted mutations had 10-fold-higher levels of RNA replication and RNA release into the supernatant but had nearly 1,000-fold-higher viral titers, resulting in an increased specific infectivity compared to wild-type JFH-1. Two mutations, identified in the p7 polypeptide and NS5B RNA-dependent RNA polymerase, were sufficient to increase the specific infectivity of JFH-1. We found that the culture-adapted mutation in p7 promoted an increase in the size of cellular lipid droplets following transfection of viral RNA. In addition, we found that the culture-adaptive mutations in p7 and NS5B acted synergistically to enhance the specific viral infectivity of JFH-1 by decreasing the level of sphingomyelin in the virion. Overall, these results reveal a genetic interaction between p7 and NS5B that contributes to virion specific infectivity. Furthermore, our results demonstrate a novel role for the RNA-dependent RNA polymerase NS5B in HCV assembly.IMPORTANCEHepatitis C virus assembly and release depend on viral interactions with host lipid metabolic pathways. Here, we demonstrate that the viral p7 and NS5B proteins cooperate to promote virion infectivity by decreasing sphingomyelin content in the virion. Our data uncover a new role for the viral RNA-dependent RNA polymerase NS5B and p7 proteins in contributing to virion morphogenesis. Overall, these findings are significant because they reveal a genetic interaction between p7 and NS5B, as well as an interaction with sphingomyelin that regulates virion infectivity. Our data provide new strategies for targeting host lipid-virus interactions as potential targets for therapies against HCV infection.

scholarly journals Combination of Antiviral Drugs to Inhibit SARS-CoV-2 Polymerase and Exonuclease as Potential COVID-19 Therapeutics

2021 ◽  
Author(s):  
Xuanting Wang ◽  
Carolina Q. Sacramento ◽  
Steffen Jockusch ◽  
Otávio Augusto Chaves ◽  
Chuanjuan Tao ◽  
...  
Keyword(s):  
Cell Culture ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Viral Rna ◽  
Combination Strategy ◽  
Rna Dependent Rna Polymerase ◽  
Culture Studies ◽  
Unique Structure ◽  
Combination Drugs

SARS-CoV-2 has an exonuclease-based proofreader, which removes nucleotide inhibitors such as Remdesivir that are incorporated into the viral RNA during replication, reducing the efficacy of these drugs for treating COVID-19. Combinations of inhibitors of both the viral RNA-dependent RNA polymerase and the exonuclease could overcome this deficiency. Here we report the identification of hepatitis C virus NS5A inhibitors Pibrentasvir and Ombitasvir as SARS-CoV-2 exonuclease inhibitors. In the presence of Pibrentasvir, RNAs terminated with the active forms of the prodrugs Sofosbuvir, Remdesivir, Favipiravir, Molnupiravir and AT-527 were largely protected from excision by the exonuclease, while in the absence of Pibrentasvir, there was rapid excision. Due to its unique structure, Tenofovir-terminated RNA was highly resistant to exonuclease excision even in the absence of Pibrentasvir. Viral cell culture studies also demonstrate significant synergy using this combination strategy. This study supports the use of combination drugs that inhibit both the SARS-CoV-2 polymerase and exonuclease for effective COVID-19 treatment.

scholarly journals Novel Nonnucleoside Inhibitor of Hepatitis C Virus RNA-Dependent RNA Polymerase

2004 ◽  
Vol 48 (12) ◽  
pp. 4813-4821 ◽  
Author(s):  
Anita Y. M. Howe ◽  
Johnathan Bloom ◽  
Carl J. Baldick ◽  
Christopher A. Benetatos ◽  
Huiming Cheng ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
High Throughput Screening ◽  
Viral Rna ◽  
Alpha Interferon ◽  
Hcv Rna ◽  
Binding Studies ◽  
Rna Dependent Rna Polymerase ◽  
Multiple Treatments

ABSTRACT A novel nonnucleoside inhibitor of hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), [(1R)-5-cyano-8-methyl-1-propyl-1,3,4,9-tetrahydropyano[3,4-b]indol-1-yl] acetic acid (HCV-371), was discovered through high-throughput screening followed by chemical optimization. HCV-371 displayed broad inhibitory activities against the NS5B RdRp enzyme, with 50% inhibitory concentrations ranging from 0.3 to 1.8 μM for 90% of the isolates derived from HCV genotypes 1a, 1b, and 3a. HCV-371 showed no inhibitory activity against a panel of human polymerases, including mitochondrial DNA polymerase gamma, and other unrelated viral polymerases, demonstrating its specificity for the HCV polymerase. A single administration of HCV-371 to cells containing the HCV subgenomic replicon for 3 days resulted in a dose-dependent reduction of the steady-state levels of viral RNA and protein. Multiple treatments with HCV-371 for 16 days led to a >3-log10 reduction in the HCV RNA level. In comparison, multiple treatments with a similar inhibitory dose of alpha interferon resulted in a 2-log10 reduction of the viral RNA level. In addition, treatment of cells with a combination of HCV-371 and pegylated alpha interferon resulted in an additive antiviral activity. Within the effective antiviral concentrations of HCV-371, there was no effect on cell viability and metabolism. The intracellular antiviral specificity of HCV-371 was demonstrated by its lack of activity in cells infected with several DNA or RNA viruses. Fluorescence binding studies show that HCV-371 binds the NS5B with an apparent dissociation constant of 150 nM, leading to high selectivity and lack of cytotoxicity in the antiviral assays.

Selection of DNA Aptamers That Bind the RNA-Dependent RNA Polymerase of Hepatitis C Virus and Inhibit Viral RNA SynthesisIn Vitro

2003 ◽  
Vol 13 (6) ◽  
pp. 455-463 ◽  
Author(s):  
Pantxika Bellecave ◽  
Marie-Line Andreola ◽  
Michel Ventura ◽  
Laura Tarrago-Litvak ◽  
Simon Litvak ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Viral Rna ◽  
Dna Aptamers ◽  
Rna Dependent Rna Polymerase ◽  
Selection Of

scholarly journals Specific Interaction between the Hepatitis C Virus NS5B RNA Polymerase and the 3′ End of the Viral RNA

1999 ◽  
Vol 73 (8) ◽  
pp. 7044-7049 ◽  
Author(s):  
Ju-Chien Cheng ◽  
Ming-Fu Chang ◽  
Shin C. Chang
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Rna Binding ◽  
Specific Interaction ◽  
Noncoding Region ◽  
Viral Rna ◽  
Coding Region ◽  
Rna Dependent Rna Polymerase ◽  
Ns5b Protein

ABSTRACT Hepatitis C virus (HCV) NS5B protein is the viral RNA-dependent RNA polymerase capable of directing RNA synthesis. In this study, an electrophoretic mobility shift assay demonstrated the interaction between a partially purified recombinant NS5B protein and a 3′ viral genomic RNA with or without the conserved 98-nucleotide tail. The NS5B-RNA complexes were specifically competed away by the unlabeled homologous RNA but not by the viral 5′ noncoding region and very poorly by the 3′ conserved 98-nucleotide tail. A 3′ coding region with conserved stem-loop structures rather than the 3′ noncoding region of the HCV genome is critical for the specific binding of NS5B. Nevertheless, no direct interaction between the 3′ coding region and the HCV NS5A protein was detected. Furthermore, two independent RNA-binding domains (RBDs) of NS5B were identified, RBD1, from amino acid residues 83 to 194, and RBD2, from residues 196 to 298. Interestingly, the conserved motifs of RNA-dependent RNA polymerase for putative RNA binding (220-DxxxxD-225) and template/primer position (282-S/TGxxxTxxxNS/T-292) are present in the RBD2. Nevertheless, the RNA-binding activity of RBD2 was abolished when it was linked to the carboxy-terminal half of the NS5B. These results provide some clues to understanding the initiation of HCV replication.

THE QSAR RESEARCH ON AURONE INHIBITORS OF HEPATITIS C VIRUS RNA-DEPENDENT RNA POLYMERASE BY APPLYING MULTI-DIMENSIONAL SCALING METHOD

2013 ◽  
Vol 06 (01) ◽  
pp. 1250062
Author(s):  
YONG-HONG HU ◽  
BAO-HUA ZHANG
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Hcv Rna ◽  
Training Set ◽  
Rna Dependent Rna Polymerase ◽  
Dimensional Scaling ◽  
Naturally Occurring ◽  
Virus Rna ◽  
Multi Dimensional Scaling

In this paper, we take naturally occurring 2-benzylidenebenzofuran-3-ones (aurones) inhibitors of hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) as an example to study the Multi-dimensional scaling (MDS) method for structure-activity relationship. By analyzing training set molecules, our MDS method combined with a PROXSCAL algorithm can predict inhibitory activity of most compounds correctly. Thus, a new sample's activity can be estimated and judged conveniently, and whether it should be synthesized can be known. The MDS method is applicable to optimize the structure for a compound and to provide suggestions for drug design.

scholarly journals De Novo Initiation of RNA Synthesis by the RNA-Dependent RNA Polymerase (NS5B) of Hepatitis C Virus

2000 ◽  
Vol 74 (2) ◽  
pp. 851-863 ◽  
Author(s):  
Guangxiang Luo ◽  
Robert K. Hamatake ◽  
Danielle M. Mathis ◽  
Jason Racela ◽  
Karen L. Rigat ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
Rna Synthesis ◽  
De Novo ◽  
Oligonucleotide Primer ◽  
Transferase Activity ◽  
Rdrp Activity ◽  
Rna Dependent Rna Polymerase ◽  
Hcv Ns5b

ABSTRACT Hepatitis C virus (HCV) NS5B protein possesses an RNA-dependent RNA polymerase (RdRp) activity, a major function responsible for replication of the viral RNA genome. To further characterize the RdRp activity, NS5B proteins were expressed from recombinant baculoviruses, purified to near homogeneity, and examined for their ability to synthesize RNA in vitro. As a result, a highly active NS5B RdRp (1b-42), which contains an 18-amino acid C-terminal truncation resulting from a newly created stop codon, was identified among a number of independent isolates. The RdRp activity of the truncated NS5B is comparable to the activity of the full-length protein and is 20 times higher in the presence of Mn2+ than in the presence of Mg2+. When a 384-nucleotide RNA was used as the template, two major RNA products were synthesized by 1b-42. One is a complementary RNA identical in size to the input RNA template (monomer), while the other is a hairpin dimer RNA synthesized by a “copy-back” mechanism. Substantial evidence derived from several experiments demonstrated that the RNA monomer was synthesized through de novo initiation by NS5B rather than by a terminal transferase activity. Synthesis of the RNA monomer requires all four ribonucleotides. The RNA monomer product was verified to be the result of de novo RNA synthesis, as two expected RNA products were generated from monomer RNA by RNase H digestion. In addition, modification of the RNA template by the addition of the chain terminator cordycepin at the 3′ end did not affect synthesis of the RNA monomer but eliminated synthesis of the self-priming hairpin dimer RNA. Moreover, synthesis of RNA on poly(C) and poly(U) homopolymer templates by 1b-42 NS5B did not require the oligonucleotide primer at high concentrations (≥50 μM) of GTP and ATP, further supporting a de novo initiation mechanism. These findings suggest that HCV NS5B is able to initiate RNA synthesis de novo.

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