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NS5B
About: NS5B is a research topic. Over the lifetime, 1314 publications have been published within this topic receiving 59534 citations.
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TL;DR: It is suggested that machine learning methods can facilitate the prediction of the NS5BIs potential for unknown sets of compounds and to determine the molecular descriptors associated with NS5 BIs.
Abstract: Non-structural proteins 5B (NS5B) play an important role in protein maturation and gene replication as an RNA dependent RNA polymerase in the hepatitis C virus (HCV). Inhibiting NS5B polymerase will prevent RNA replication and, therefore, it is significant for the treatment of HCV. It is becoming increasingly important to screen and predict molecules that have NS5B inhibitory activity by computational methods. This work explores several machine learning (ML) methods (support vector machine (SVM), k-nearest neighbor (k-NN), and C4.5 decision tree (C4.5 DT)) for the prediction of NS5B inhibitors (NS5BIs). This prediction system was tested using 1248 compounds (552 NS5BIs and 696 non- NS5BIs), which are significantly more diverse in chemical structure than those used in other studies. A feature selection method was used to improve the prediction accuracy and the selection of molecular descriptors responsible for distinguishing between NS5BIs and non-NS5BIs. The prediction accuracies were 81.4%-91.7% for the NS5BIs, 78.2%-87.2% for the non-NS5BIs, and 84.1%-85.0% overall based on the three kinds of machine learning methods. SVM gave the best accuracy of 91.7% for the NS5BIs, C4.5 gave the best accuracy of 87.2% for the non-NS5BIs, and k-NN gave the best overall accuracy of 85.0% for all the compounds. This work suggests that machine learning methods can facilitate the prediction of the NS5BIs potential for unknown sets of compounds and to determine the molecular descriptors associated with NS5BIs.
11 citations
TL;DR: It is found that NS5B also bound with human ribosomes, implicate a novel mechanism of coupling between replication and translation of the viral genome in the life cycle of HCV.
Abstract: Hepatitis C virus (HCV) non-structural protein 5B (NS5B) is an RNA replicase. We expressed full-length NS5B (591 amino acid residues) in Escherichia coli as a fusion protein with maltose binding protein (MBP-NS5B). MBP-NS5B was recovered in the soluble fraction after centrifugation at 40,000 × g and affinity-purified with amylose resin. The purified MBP-NS5B had a high-level of poly (A), oligo (U)-dependent UMP incorporation with a Km of 2 μm for UTP. Surprisingly, the enzymatically active MBP-NS5B was sedimented by ultracentrifugation at 160,000 × g. The pellet contained 16S and 23S ribosomal RNAs, suggesting that ribosomes were associated with MBP-NS5B. Ribosomes and MBP-NS5B were subsequently co-purified on amylose resin. Deletion study revealed that either the N-terminal (amino acid residues 1 107) or the C-terminal (amino acid residues 498–591) region of NS5B were sufficient for this association with ribosomes. We further found that NS5B also bound with human ribosomes. Our results implicate a novel mechanism of coupling between replication and translation of the viral genome in the life cycle of HCV.
11 citations
TL;DR: The trans-encapsidation system enables the production of HCV single-round infectious particles and can positively select variants, which should constitute a valuable tool in the development of replicon-based HCV vaccines.
Abstract: A trans-packaging system for hepatitis C virus (HCV) replicons lacking envelope glycoproteins was developed. The replicons were efficiently encapsidated into infectious particles after expression in trans of homologous HCV envelope proteins under the control of an adenoviral vector. Interestingly, expression in trans of core or core, p7 and NS2 with envelope proteins did not enhance trans-encapsidation. Expression of heterologous envelope proteins, in the presence or absence of heterologous core, p7 and NS2, did not rescue single-round infectious particle production. To increase the titre of homologous, single-round infectious particles in our system, successive cycles of trans-encapsidation and infection were performed. Four cycles resulted in a 100-fold increase in the yield of particles. Sequence analysis revealed a total of 16 potential adaptive mutations in two independent experiments. Except for a core mutation in one experiment, all the mutations were located in non-structural regions mainly in NS5A (four in domain III and two near the junction with the NS5B gene). Reverse genetics studies suggested that D2437A and S2443T adaptive mutations, which are located at the NS5A-B cleavage site did not affect viral replication, but enhanced the single-round infectious particles assembly only in trans-encapsidation model. In conclusion, our trans-encapsidation system enables the production of HCV single-round infectious particles. This system is adaptable and can positively select variants. The adapted variants promote trans-encapsidation and should constitute a valuable tool in the development of replicon-based HCV vaccines.
11 citations
TL;DR: The results suggested that this mutation of NS5B at least partly contributes to resistance to early viral clearance during interferon and ribavirin combination therapy.
Abstract: We previously reported the relationship between viral polymerase polymorphisms and the initial decline in viral load induced by interferon-alpha and ribavirin therapy in genotype 1b-related chronic hepatitis C patients. The presence of E124K and I85V of NS5B was closely associated with viral clearance at 8 weeks of treatment. The aim of this study was to investigate the mechanisms by which this polymorphism of NS5B protein affects early viral clearance. We used a replicon system derived from strain O, genotype 1b virus. Three mutants (V85I), (K124E), and (V85I/K124E) were introduced to the replicon. OR6c, a derivative of HuH7 cells, was transfected with the replicon including a luciferase reporter gene. Luciferase activities were measured 72 hr post-transfection. All three mutants showed higher luciferase activity than that of the wild type, and the V85I mutant showed the highest activity. This result was also confirmed by neomycin gene-containing replicons with same mutations. All replicons were down-regulated by ribavirin, but the level of reduction in the V85I mutant was the lowest. Our results suggested that this mutation at least partly contributes to resistance to early viral clearance during interferon and ribavirin combination therapy.
11 citations
TL;DR: Immunofluorescence and co-immunoprecipitation assays showed co-localization and interaction of BIK and NS5B, suggesting that BIK may be interacting with the HCV replication complex through NS5 B.
11 citations