Topic
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 demonstrated that a recombinant NS5B protein with an amino terminal sequence of ASMSYSWTG has RNA-dependent RNA polymerase (RDRP) activity and should assist in understanding the mechanism of HCV replication and the identification of specific enzyme inhibitors.
61 citations
TL;DR: C-terminal nucleolin inhibited the NS5B RdRP activity in a dose-dependent manner, which indicates the binding ability of nucleolin may be involved inNS5B functions.
61 citations
TL;DR: Evidence is provided that the enhancement of HCV IRES-dependent translation mediated by the 3′UTR is negatively controlled by the CRE region in the human hepatoma cell lines Huh-7 and Hep-G2 in a time-dependent manner, supporting the existence of a functional high order structure in the HCV genome that involves two evolutionarily conserved RNA elements.
Abstract: Hepatitis C virus (HCV) translation is mediated by an internal ribosome entry site (IRES) located at the 5′ end of the genomic RNA. The 3′ untranslatable region (3′UTR) stimulates translation by the recruitment of protein factors that simultaneously bind to the 5′ end of the viral genome. This leads to the formation of a macromolecular complex with a closed loop conformation, similar to that described for the cap-translated mRNAs. We previously demonstrated the existence of a long-range RNA–RNA interaction involving subdomain IIId of the IRES region and the stem–loop 5BSL3.2 of the CRE element at the 3′ end of the viral genome. The present study provides evidence that the enhancement of HCV IRES-dependent translation mediated by the 3′UTR is negatively controlled by the CRE region in the human hepatoma cell lines Huh-7 and Hep-G2 in a time-dependent manner. Domain 5BSL3.2 is the major partner in this process. Mutations in this motif lead to an increase in IRES activity by up to eightfold. These data support the existence of a functional high order structure in the HCV genome that involves two evolutionarily conserved RNA elements, domain IIId in the IRES and stem–loop 5BSL3.2 in the CRE region. This interaction could have a role in the circularisation of the viral genome.
61 citations
TL;DR: To reduce ADA-mediated deamination, cyclic 1-aryl-1,3-propanyl prodrugs of the corresponding nucleoside monophosphate (NMP) were prepared, anticipating cytochrome P450 3A-mediated oxidative cleavage to the NMP in hepatocytes, and a 2',3'-carbonate prodrug moiety proved to be a successful strategy.
Abstract: 2'-C-Methyladenosine exhibits impressive inhibitory activity in the cell-based hepatitis C virus (HCV) subgenomic replicon assay, by virtue of intracellular conversion to the corresponding nucleoside triphosphate (NTP) and inhibition of NS5B RNA-dependent RNA polymerase (RdRp). However, rapid degradation by adenosine deaminase (ADA) limits its overall therapeutic potential. To reduce ADA-mediated deamination, we prepared cyclic 1-aryl-1,3-propanyl prodrugs of the corresponding nucleoside monophosphate (NMP), anticipating cytochrome P450 3A-mediated oxidative cleavage to the NMP in hepatocytes. Lead compounds identified in a primary rat hepatocyte screen were shown to result in liver levels of NTP predictive of efficacy after intravenous dosing to rats. The oral bioavailability of the initial lead was below 5%; therefore, additional analogues were synthesized and screened for liver NTP levels after oral administration to rats. Addition of a 2',3'-carbonate prodrug moiety proved to be a successful strategy, and the 1-(4-pyridyl)-1,3-propanyl prodrug containing a 2',3'-carbonate moiety displayed oral bioavailability of 39%.
61 citations
TL;DR: Honokiol, a small active molecular compound extracted from magnolia, has been shown to inhibit hepatitis C virus (HCV) infection in vitro.
Abstract: Background
Honokiol, a small active molecular compound extracted from magnolia, has recently been shown to inhibit hepatitis C virus (HCV) infection in vitro.
Aims
This study further characterized aspects of the HCV lifecycle affected by the antiviral functions of honokiol.
Methods
The influence of honokiol on HCV infection, entry, translation and replication was assessed in Huh-7.5.1 cells using cell culture-derived HCV (HCVcc), HCV pseudo-type (HCVpp) and sub-genomic replicons.
Results
Honokiol had strong antiviral effect against HCVcc infection at non-toxic concentrations. Combined with interferon-α, its inhibitory effect on HCVcc was more profound than that of ribavirin. Honokiol inhibited the cell entry of lentiviral particles pseudo-typed with glycoproteins from HCV genotypes 1a, 1b, and 2a, but not of the vesicular stomatitis virus. It had inefficient activity on HCV internal ribosome entry site (IRES)-translation at concentrations with significant anti-HCVcc effects. The expression levels of components of replication complex, NS3, NS5A and NS5B, were down-regulated by honokiol in a dose-dependent manner. It also inhibited HCV replication dose dependently in both genotypes 1b and 2a sub-genomic replicons.
Conclusions
Honokiol inhibits HCV infection by targeting cell entry and replication and, only at a concentration >30 μM, IRES-mediated translation of HCV life cycle. Based on its high therapeutic index (LD50/EC90 = 5.4), honokiol may be a promising drug for the treatment of HCV infection.
60 citations