scholarly journals The Interaction of Viperin with Hepatitis C Virus Non-Structural Protein 5A Inhibits the Catalytic Activity of Viperin

2019 ◽  
Author(s):  
Soumi Ghosh ◽  
Ayesha M. Patel ◽  
Timothy J. Grunkemeyer ◽  
Arti B. Dumbrepatil ◽  
Kelcie Zegalia ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Specific Activity ◽  
Regulatory Protein ◽  
Protein A ◽  
Structural Protein ◽  
Radical Sam ◽  
Replication Complex ◽  
Wide Range ◽  
Radical Sam Enzyme

AbstractThe radical SAM enzyme viperin exerts a wide range of antiviral effects through both the synthesis of the antiviral nucleotide 3’-deoxy-3’, 4’-didehydro-CTP (ddhCTP) and through its interactions with various cellular and viral proteins. Here we investigate the interaction of viperin with hepatitis C virus non-structural protein 5A (NS5A) and the host sterol regulatory protein, vesicle-associated membrane protein A (VAP-33). NS5A and VAP-33 form part of the viral replication complex that is essential for copying the RNA genome of the virus. Using transfected enzymes in HEK293T cells, we show that viperin binds to both NS5A and VAP-33 independently and that this interaction is dependent on all three proteins being localized to the ER membrane. Co-expression of viperin with VAP-33 and NS5A was found to reduce NS5A levels, most likely by increasing the rate of proteasomal degradation. However, co-expression of viperin with VAP-33 and NS5A also reduces the specific activity of viperin by ~ 3-fold. This observation suggests that NS5A may have evolved to bind viperin as a strategy to reduce ddhCTP synthesis, thereby reducing possibility of the replication complex introducing this chain-terminating nucleotide during genome synthesis.

scholarly journals Nonstructural Protein 5A (NS5A) and Human Replication Protein A Increase the Processivity of Hepatitis C Virus NS5B Polymerase ActivityIn Vitro

2014 ◽  
Vol 89 (1) ◽  
pp. 165-180 ◽  
Author(s):  
Nagraj Mani ◽  
Alexander Yuzhakov ◽  
Olga Yuzhakov ◽  
Joyce T. Coll ◽  
Jim Black ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protein A ◽  
Replication Protein A ◽  
Replication Protein ◽  
Host Proteins ◽  
Rolling Circle ◽  
Replication Complex ◽  
Replication System

ABSTRACTThe precise role(s) and topological organization of different factors in the hepatitis C virus (HCV) RNA replication complex are not well understood. In order to elucidate the role of viral and host proteins in HCV replication, we have developed a novelin vitroreplication system that utilizes a rolling-circle RNA template. Under close-to-physiological salt conditions, HCV NS5BΔ21, an RNA-dependent RNA polymerase, has poor affinity for the RNA template. Human replication protein A (RPA) and HCV NS5A recruit NS5BΔ21 to the template. Subsequently, NS3 is recruited to the replication complex by NS5BΔ21, resulting in RNA synthesis stimulation by helicase. Both RPA and NS5A(S25-C447), but not NS5A(S25-K215), enabled the NS5BΔ21-NS3 helicase complex to be stably associated with the template and synthesize RNA product in a highly processive mannerin vitro. This newin vitroHCV replication system is a useful tool that may facilitate the study of other replication factors and aid in the discovery of novel inhibitors of HCV replication.IMPORTANCEThe molecular mechanism of hepatitis C virus (HCV) replication is not fully understood, but viral and host proteins collaborate in this process. Using a rolling-circle RNA template, we have reconstituted anin vitroHCV replication system that allows us to interrogate the role of viral and host proteins in HCV replication and delineate the molecular interactions. We showed that HCV NS5A(S25-C447)and cellular replication protein A (RPA) functionally cooperate as a processivity factor to stimulate HCV replication by HCV NS5BΔ21 polymerase and NS3 helicase. This system paves the way to test other proteins and may be used as an assay for discovery of HCV inhibitors.

scholarly journals Non-structural protein 4A of Hepatitis C virus accumulates on mitochondria and renders the cells prone to undergoing mitochondria-mediated apoptosis

2006 ◽  
Vol 87 (7) ◽  
pp. 1935-1945 ◽  
Author(s):  
Yuki Nomura-Takigawa ◽  
Motoko Nagano-Fujii ◽  
Lin Deng ◽  
Sohei Kitazawa ◽  
Satoshi Ishido ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Replication ◽  
Hcv Rna ◽  
Structural Protein ◽  
Cellular Functions ◽  
Replication Complex ◽  
Huh7 Cells ◽  
Infected Cells ◽  
Rna Replicon

Non-structural protein 4A (NS4A) of Hepatitis C virus (HCV) functions as a cofactor for NS3 by forming a complex with it to augment its enzymic activities. NS4A also forms a complex with other HCV proteins, such as NS4B/NS5A, to facilitate the formation of the viral RNA replication complex on the endoplasmic reticulum (ER) membrane. In addition to its essential role in HCV replication, NS4A is thought to be involved in viral pathogenesis by affecting cellular functions. In this study, it was demonstrated that NS4A was localized not only on the ER, but also on mitochondria when expressed either alone or together with NS3 in the form of the NS3/4A polyprotein and in the context of HCV RNA replication in Huh7 cells harbouring an HCV RNA replicon. Moreover, NS4A expression altered the intracellular distribution of mitochondria significantly and caused mitochondrial damage, as evidenced by the collapsed mitochondrial transmembrane potential and release of cytochrome c into the cytoplasm, which led ultimately to induction of apoptosis through activation of caspase-3, but not caspase-8. Consistently, Huh7 cells expressing NS3/4A and those harbouring an HCV RNA replicon were shown to be more prone to undergoing actinomycin D-induced, mitochondria-mediated apoptosis, compared with the control Huh7 cells. Taken together, these results suggest the possibility that HCV exerts cytopathic effect (CPE) on the infected cells under certain conditions and that NS4A is responsible, at least in part, for the conditional CPE in HCV-infected cells.

scholarly journals Dual topology of the processed hepatitis C virus protein NS4B is influenced by the NS5A protein

2006 ◽  
Vol 87 (11) ◽  
pp. 3263-3272 ◽  
Author(s):  
Marika Lundin ◽  
Hannah Lindström ◽  
Caroline Grönwall ◽  
Mats A. A. Persson
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protein A ◽  
Virus Protein ◽  
Structural Protein ◽  
Expression Studies ◽  
N Terminus ◽  
Hepatitis C Virus Proteins ◽  
Membrane Changes

Among the least-known hepatitis C virus proteins is the non-structural protein 4B (NS4B). It localizes to the endoplasmic reticulum (ER) membrane and induces membrane changes, resulting in a membranous web that is reported to be the locale for virus replication. A model was presented previously for the topology of recombinant HCV NS4B of the 1a genotype based on in vitro data. In this model, the N-terminal tail of a considerable fraction of the NS4B molecules was translocated into the ER lumen via a post-translational process, giving the protein a dual transmembrane topology. It is now reported that translocation of the N terminus also occurs for processed NS4B expressed in cells in the context of the polyprotein. In the presence of NS5A, however, a lower degree of translocation was observed, which may indicate that NS5A influences the topology of NS4B. In vitro expression studies of NS4B from all major genotypes demonstrated that translocation of the N terminus to the ER lumen is conserved across genotypes. This clearly suggests an important function for this feature. Furthermore, when disrupting a previously reported amphipathic helix (AH) in the N terminus of NS4B, translocation was inhibited. As a disrupted AH also abolished the ability of NS4B to rearrange membranes, these data indicate for the first time an association between translocation of the N terminus and membrane rearrangement. Finally, the present experiments also confirm the predicted location of the first luminal loop to be around aa 112.

scholarly journals Effect of directly acting anti-viral agents on immunological imprints in chronic HCV-4a patients: interleukin-10 and vascular endothelial growth factor genes expression level

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Iman S. Naga ◽  
Amel Abdel Fattah Kamel ◽  
Said Ahmed Ooda ◽  
Hadeer Muhammad Fath Elbab ◽  
Rania Mohamed El-Sharkawy
Keyword(s):  
Gene Expression ◽  
Vascular Endothelial Growth Factor ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Growth Factor ◽  
Angiogenic Factor ◽  
Vascular Endothelial ◽  
Wide Range ◽  
Chronic Hcv ◽  
Endothelial Growth Factor

Abstract Background Hepatitis C virus infection is a global health challenge with Egypt being one of the highly affected countries. IL-10 has been suggested as a suitable marker to assess necroinflammation and to monitor the progression of liver damage. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor playing a central role in many physiological as well as pathological processes. Several factors can be predictive of the response to treatment and achievement of SVR; some of which are host-related, and others are virus-related. The gene expression of IL-10 and VEGF have multiple effects for treatment response. The aim of the present work was to study the effect of treatment with directly acting agents (DAA) on the expression of VEGF and IL-10 genes in chronic hepatitis C virus-infected Egyptian genotype-4a patients. Twenty-five HCV subjects where evaluated for IL-10 and VEGF gene expression before and after treatment with DAA. Results IL-10 expression was downregulated in 92% of the cases. VEGF expression was heterogeneous showing spreading of values along a wide range with 64% of the cases being downregulated. Conclusion DAAs do not completely reverse the immunological imprints established upon chronic HCV infection.

scholarly journals Resistance Analysis of the Hepatitis C Virus NS3 Protease Inhibitor Asunaprevir

2012 ◽  
Vol 56 (7) ◽  
pp. 3670-3681 ◽  
Author(s):  
Fiona McPhee ◽  
Jacques Friborg ◽  
Steven Levine ◽  
Chaoqun Chen ◽  
Paul Falk ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Protease Inhibitor ◽  
Clinical Studies ◽  
Replication Capacity ◽  
Replication Complex ◽  
Hcv Genotype ◽  
Genotype 1A ◽  
Genotype 1B ◽  
Ns3 Protease

ABSTRACTAsunaprevir (BMS-650032) is a potent hepatitis C virus (HCV) NS3 protease inhibitor demonstrating efficacy in alfa interferon-sparing, direct-acting antiviral dual-combination regimens (together with the NS5A replication complex inhibitor daclatasvir) in patients chronically infected with HCV genotype 1b. Here, we describe a comprehensivein vitrogenotypic and phenotypic analysis of asunaprevir-associated resistance against genotypes 1a and 1b using HCV replicons and patient samples obtained from clinical studies of short-term asunaprevir monotherapy. During genotype 1a resistance selection using HCV replicons, the primary NS3 protease substitutions identified were R155K, D168G, and I170T, which conferred low- to moderate-level asunaprevir resistance (5- to 21-fold) in transient-transfection susceptibility assays. For genotype 1b, a higher level of asunaprevir-associated resistance was observed at the same selection pressures, ranging from 170- to 400-fold relative to the wild-type control. The primary NS3 protease substitutions identified occurred predominantly at amino acid residue D168 (D168A/G/H/V/Y) and were associated with high-level asunaprevir resistance (16- to 280-fold) and impaired replication capacity. In asunaprevir single-ascending-dose and 3-day multiple-ascending-dose studies in HCV genotype 1a- or 1b-infected patients, the predominant pre-existing NS3 baseline polymorphism was NS3-Q80K. This substitution impacted initial virologic response rates in a single-ascending-dose study, but its effects after multiple doses were more ambiguous. Interestingly, for patient NS3 protease sequences containing Q80 and those containing K80, susceptibilities to asunaprevir were comparable when tested in an enzyme assay. No resistance-associated variants emerged in these clinical studies that significantly impacted susceptibility to asunaprevir. Importantly, asunaprevir-resistant replicons remained susceptible to an NS5A replication complex inhibitor, consistent with a role for asunaprevir in combination therapies.

scholarly journals Cell Transformation and Proteome Alteration in QSG7701 Cells Transfected with Hepatitis C Virus Non-structural Protein 3

2007 ◽  
Vol 39 (10) ◽  
pp. 751-762 ◽  
Author(s):  
Qiongqiong HE ◽  
Ruixue CHENG ◽  
Zhuchu CHEN ◽  
Xuxian XIAO ◽  
Zhiqiang XIAO ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Cell Transformation ◽  
Structural Protein

Association between variants in the interferon lambda 4 locus and substitutions in the hepatitis C virus non-structural protein 5A

2015 ◽  
Vol 63 (3) ◽  
pp. 554-563 ◽  
Author(s):  
Sakura Akamatsu ◽  
C. Nelson Hayes ◽  
Hidenori Ochi ◽  
Takuro Uchida ◽  
Hiromi Kan ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Structural Protein ◽  
Interferon Lambda

Mechanism of Zinc Ejection by Disulfiram in Nonstructural Protein 5A

2021 ◽  
Author(s):  
Ashfaq Ur Rehman ◽  
Guodong Zheng ◽  
Bozitao Zhong ◽  
Duan Ni ◽  
Jia-Yi Li ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Nonstructural Protein ◽  
Structural Protein ◽  
Positive Strand ◽  
Positive Strand Rna ◽  
Nonstructural Protein 5A

Hepatitis C virus (HCV) is a notorious member of the enveloped, positive-strand RNA flavivirus family. Non-structural protein 5A (NS5A) plays a key role in HCV replication and assembly. NS5A is...

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