Publications by authors named "Hironori Nishitsuji"

45 Publications

Amino Acid Polymorphism in Hepatitis B Virus Associated With Functional Cure.

Cell Mol Gastroenterol Hepatol 2021 Aug 2. Epub 2021 Aug 2.

Department of Virology II, National Institute of Infectious Diseases, Tokyo. Electronic address:

Background & Aims: To provide an adequate treatment strategy for chronic hepatitis B, it is essential to know which patients are expected to have a good prognosis and which patients do not require therapeutic intervention. Previously, we identified the substitution of isoleucine to leucine at amino acid 97 (I97L) in the hepatitis B core region as a key predictor among patients with stable hepatitis. In this study, we attempted to identify the point at which I97L affects the hepatitis B virus (HBV) life cycle and to elucidate the underlying mechanisms governing the stabilization of hepatitis.

Methods: To confirm the clinical features of I97L, we used a cohort of hepatitis B e antigen-negative patients with chronic hepatitis B infected with HBV-I97 wild-type (wt) or HBV-I97L. The effects of I97L on viral characteristics were evaluated by in vitro HBV production and infection systems with the HBV reporter virus and cell culture-generated HBV.

Results: The ratios of reduction in hepatitis B surface antigen and HBV DNA were higher in patients with HBV-I97L than in those with HBV-I97wt. HBV-I97L exhibited lower infectivity than HBV-I97wt in both infection systems with reporter HBV and cell culture-generated HBV. HBV-I97L virions exhibiting low infectivity primarily contained a single-stranded HBV genome. The lower efficiency of cccDNA synthesis was demonstrated after infection of HBV-I97L or transfection of the molecular clone of HBV-I97L.

Conclusions: The I97L substitution reduces the level of cccDNA through the generation of immature virions with single-stranded genomes. This I97L-associated low efficiency of cccDNA synthesis may be involved in the stabilization of hepatitis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jcmgh.2021.07.013DOI Listing
August 2021

Identification of Two Critical Neutralizing Epitopes in the Receptor Binding Domain of Hepatitis B Virus preS1.

J Virol 2020 Dec 9. Epub 2020 Dec 9.

Department of Virology II, National Institute of Infectious Diseases

Hepatitis B virus (HBV) infection is a major public health problem. Human hepatocytes are infected with HBV via binding between the preS1 region in the large envelope protein of HBV and sodium taurocholate cotransporting polypeptide. Although several monoclonal antibodies (MAbs) that recognize the receptor binding domain in preS1 and neutralize HBV infection have been isolated, details of neutralizing epitopes are not understood. In this study, we generated 13 MAbs targeting the preS1 receptor binding domain from preS1-specific memory B cells derived from DNA immunized mice. The MAbs were classified into three groups according to the epitope regions, designated epitopes I-III. A virus neutralization assay revealed that MAbs recognizing epitopes I and III neutralized HBV infection, suggesting that these domains are critical epitopes for viral neutralization. In addition, a neutralization assay against multiple genotypes of HBV revealed that epitope I is a semi-pangenotypic neutralizing epitope, whereas epitope III is a genotype-specific epitope. We also showed that neutralizing MAbs against preS1 could neutralize HBV bearing vaccine-induced escape mutation. These findings provide insight into novel immunoprophylaxis for the prevention and treatment of HBV infection. The HBV preS1 2-47 aa region (preS1/2-47) is essential for virus binding with sodium taurocholate cotransporting polypeptide. Several MAbs targeting preS1/2-47 have been reported to neutralize HBV infection; however, which region in preS1/2-47 contains the critical neutralizing epitope for HBV infection is unclear. Here, we generated several MAbs targeting preS1/2-47 and found that MAbs recognizing the N- or C-terminus of preS1/2-47 remarkably neutralized HBV infection. We further confirmed the neutralizing activity of anti-preS1 MAbs against HBV with vaccine escape mutation. These data clarified the relationship between the antibody epitope and the virus neutralizing activity and also suggested the potential ability of a vaccine antigen containing the preS1 region to overcome the weakness of current HB vaccines comprising the small S protein.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01680-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8092832PMC
December 2020

Reduction of severe acute respiratory syndrome coronavirus-2 infectivity by admissible concentration of ozone gas and water.

Microbiol Immunol 2021 Jan 14;65(1):10-16. Epub 2020 Dec 14.

Department of Nephrology, Fujita Health University School of Medicine, Toyoake, Japan.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing the global coronavirus disease 2019 (COVID-19) pandemic. Because complete elimination of SARS-CoV-2 appears difficult, decreasing the risk of transmission is important. Treatment with 0.1 and 0.05 ppm ozone gas for 10 and 20 hr, respectively, decreased SARS-CoV-2 infectivity by about 95%. The magnitude of the effect was dependent on humidity. Treatment with 1 and 2 mg/L ozone water for 10 s reduced SARS-CoV-2 infectivity by about 2 and 3 logs, respectively. Our results suggest that low-dose ozone, in the form of gas and water, is effective against SARS-CoV-2.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1348-0421.12861DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7753712PMC
January 2021

Modulation of hepatitis B virus infection by epidermal growth factor secreted from liver sinusoidal endothelial cells.

Sci Rep 2020 09 1;10(1):14349. Epub 2020 Sep 1.

Institute for Quantitative Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032, Japan.

Hepatocytes derived from human iPSCs are useful to study hepatitis B virus (HBV) infection, however infection efficiency is rather poor. In order to improve the efficiency of HBV infection to iPSC-derived hepatocytes, we set a co-culture of hepatocytes with liver non-parenchymal cells and found that liver sinusoidal endothelial cells (LSECs) enhanced HBV infection by secreting epidermal growth factor (EGF). While EGF receptor (EGFR) is known as a co-receptor for HBV, we found that EGF enhanced HBV infection at a low dose of EGF, whereas EGF at a high dose suppressed HBV infection. EGFR is internalized by clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE) pathways depending on the dose of EGF. At a high dose of EGF, the endocytosed EGFR via CIE is degraded in the lysosome. This study is the first to provide evidence that HBV is endocytosed via CME and CIE pathways at a low and high dose of EGF, respectively. In conclusion, we developed an in vitro system of HBV infection using iPSC-derived liver cells, and show that EGF secreted from LSECs modulates HBV infection in a dose dependent manner.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-71453-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7462976PMC
September 2020

Orchestration of Intracellular Circuits by G Protein-Coupled Receptor 39 for Hepatitis B Virus Proliferation.

Int J Mol Sci 2020 Aug 7;21(16). Epub 2020 Aug 7.

Genome Medical Science Project, Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Chiba 272-8516, Japan.

Hepatitis B virus (HBV), a highly persistent pathogen causing hepatocellular carcinoma (HCC), takes full advantage of host machinery, presenting therapeutic targets. Here we aimed to identify novel druggable host cellular factors using the reporter HBV we have recently generated. In an RNAi screen of G protein-coupled receptors (GPCRs), GPCR39 (GPR39) appeared as the top hit to facilitate HBV proliferation. Lentiviral overexpression of active GPR39 proteins and an agonist enhanced HBV replication and transcriptional activities of viral promoters, inducing the expression of CCAAT/enhancer binding protein (CEBP)-β (CEBPB). Meanwhile, GPR39 was uncovered to activate the heat shock response, upregulating the expression of proviral heat shock proteins (HSPs). In addition, glioma-associated oncogene homologue signaling, a recently reported target of GPR39, was suggested to inhibit HBV replication and eventually suppress expression of CEBPB and HSPs. Thus, GPR39 provirally governed intracellular circuits simultaneously affecting the carcinopathogenetic gene functions. GPR39 and the regulated signaling networks would serve as antiviral targets, and strategies with selective inhibitors of GPR39 functions can develop host-targeted antiviral therapies preventing HCC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21165661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7460832PMC
August 2020

N-Terminal PreS1 Sequence Regulates Efficient Infection of Cell-Culture-Generated Hepatitis B Virus.

Hepatology 2021 02 31;73(2):520-532. Epub 2020 Oct 31.

Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan.

Background And Aims: An efficient cell-culture system for hepatitis B virus (HBV) is indispensable for research on viral characteristics and antiviral reagents. Currently, for the HBV infection assay in cell culture, viruses derived from HBV genome-integrated cell lines of HepG2.2.15 or HepAD-38 are commonly used. However, these viruses are not suitable for the evaluation of polymorphism-dependent viral characteristics or resistant mutations against antiviral reagents. HBV obtained by the transient transfection of the ordinary HBV molecular clone has limited infection efficiencies in cell culture.

Approach And Results: We found that an 11-amino-acid deletion (d11) in the preS1 region enhances the infectivity of cell-culture-generated HBV (HBVcc) to sodium taurocholate cotransporting polypeptide-transduced HepG2 (HepG2/NTCP) cells. Infection of HBVcc derived from a d11-introduced genotype C strain (GTC-d11) was ~10-fold more efficient than infection of wild-type GTC (GTC-wt), and the number of infected cells was comparable between GTC-d11- and HepG2.2.15-derived viruses when inoculated with the same genome equivalents. A time-dependent increase in pregenomic RNA and efficient synthesis of covalently closed circular DNA were detected after infection with the GTC-d11 virus. The involvement of d11 in the HBV large surface protein in the enhanced infectivity was confirmed by an HBV reporter virus and hepatitis D virus infection system. The binding step of the GTC-d11 virus onto the cell surface was responsible for this efficient infection.

Conclusions: This system provides a powerful tool for studying the infection and propagation of HBV in cell culture and also for developing the antiviral strategy against HBV infection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/hep.31308DOI Listing
February 2021

Engineering Cellular Biosensors with Customizable Antiviral Responses Targeting Hepatitis B Virus.

iScience 2020 Mar 26;23(3):100867. Epub 2020 Feb 26.

Department of Microbiology, Yokohama City University School of Medicine, 3-9 Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan. Electronic address:

SynNotch receptor technology is a versatile tool that uses the regulatory notch core portion with an extracellular scFv and an intracellular transcription factor that enables to program customized input and output functions in mammalian cells. In this study, we designed a novel synNotch receptor comprising scFv against HBs antigen linked with an intracellular artificial transcription factor and exploited it for viral sensing and cellular immunotherapy. The synNotch receptor expressing cells sensed HBV particles and membrane-bound HBs antigens and responded by expressing reporter molecules, secNL or GFP. We also programmed these cells to dispense antiviral responses such as type I interferon and anti-HBV neutralizing mouse-human chimeric antibodies. Our data reveal that synNotch receptor signaling works for membrane-bound ligands such as enveloped viral particles and proteins borne on liposomal vesicles. This study establishes the concepts of "engineered immunity" where the synNotch platform is utilized for cellular immunotherapy against viral infections.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.isci.2020.100867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7113479PMC
March 2020

Anti-viral effects of interferon-λ3 on hepatitis B virus infection in cell culture.

Hepatol Res 2020 Mar 5;50(3):283-291. Epub 2020 Jan 5.

Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan.

Aim: Interferon (IFN)-λ3 is known to have antiviral effects against various pathogens. Recently, it has been reported that the production of IFN-λ3 in colon cells after the administration of nucleotide analogs is expected to reduce hepatitis B surface antigen in chronic hepatitis B patients. Here, we aimed to prove the antiviral effects of IFN-λ3 on hepatitis B virus (HBV) by using an in vitro HBV production and infection system.

Methods: We used HepG2.2.15-derived HBV as an inoculum and the replication-competent molecular clone of HBV as a replication model.

Results: By administering IFN-λ3 to HepG2 cells transfected with the HBV molecular clone, the production of hepatitis B surface antigen and hepatitis B core-related antigen was reduced dose-dependently. IFN-λ3 treatment also reduced the number of HBV-positive cells and the synthesis of covalently closed circular DNA after infection of HepG2.2.15-derived HBV to sodium taurocholate cotransporting polypeptide-transduced HepG2 cells. The inhibitory effect on HBV infection by IFN-λ3 was confirmed by using a recombinant a HBV reporter virus system. To elucidate the underlying mechanisms of the anti-HBV effect of IFN-λ3, we assessed the transcription of HBV RNA and the production of core-associated HBV DNA in HBV molecular clone-transfected HepG2 cells, and found that both parameters were reduced by IFN-λ3.

Conclusions: We observed that the administration of IFN-λ3 inhibits HBV infection and the production of HBV proteins at the HBV RNA transcription level. This finding provides novel insight into the treatment of chronic hepatitis B patients with the administration or induction of IFN-λ3.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/hepr.13449DOI Listing
March 2020

A new hepatoma cell line exhibiting high susceptibility to hepatitis B virus infection.

Biochem Biophys Res Commun 2019 07 24;515(1):156-162. Epub 2019 May 24.

Department of Tumor Virology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama, 700-8558, Japan. Electronic address:

Hepatitis B virus (HBV) infection, which increases the risk of cirrhosis and hepatocellular carcinoma and requires lifelong treatment, has become a major global health problem. However, host factors essential to the HBV life cycle are still unclear, and the development of new drugs is needed. Cells derived from the human hepatoma cell line HepG2 and engineered to overexpress sodium taurocholate cotransporting polypeptide (NTCP: a receptor for HBV), termed HepG2/NTCP cells, are widely used as the cell-based HBV infection and replication systems for HBV research. We recently found that human hepatoma cell line Li23-derived cells overexpressing NTCP (A8 cells subcloned from Li23 cells), whose gene expression profile was distinct from that of HepG2/NTCP cells, were also sensitive to HBV infection. However, the HBV susceptibility of A8 cells was around 1/100 that of HepG2/NTCP cells. Since we considered that plural cell assay systems will be needed for the objective evaluation of anti-HBV reagents, as we previously demonstrated in hepatitis C virus research, we here attempted to develop a new Li23 cell-derived assay system equivalent to that using HepG2/NTCP cells. By repeated subcloning of A8 cells, we successfully established a new cell line (A8.15.78.10) exhibiting high HBV susceptibility equal to that of HepG2/NTCP cells. Characterization of A8.15.78.10 cells revealed that the increase of HBV susceptibility was correlated with increases in the protein and glycosylation levels of NTCP, and with decreased expression of STING, a factor contributing to innate immunity. Finally, we performed a comparative evaluation of HBV entry inhibitors (cyclosporin A and rosiglitazone) by an HBV/secNL reporter assay using A8.15.78.10 cells or HepG2/NTCP cells. The results confirmed that cyclosporin A exhibited anti-HBV activity in both cell lines, as previously reported. However, we found that rosiglitazone did not show the anti-HBV activity in A8.15.78.10 cells, although it worked in HepG2/NTCP cells as previously reported. This suggested that the difference in anti-HBV activity between cyclosporin A and rosiglitazone was due to the different types of cells used for the assay. In conclusion, plural assay systems using different types of cells are required for the objective and impartial evaluation of anti-HBV reagents.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbrc.2019.05.126DOI Listing
July 2019

Multiple antiviral activities of the antimalarial and anti-hepatitis C drug candidates N-89 and N-251.

Biochem Biophys Rep 2018 Sep 1;15:1-6. Epub 2018 Jun 1.

Department of Tumor Virology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.

The chemically synthesized endoperoxide compound N-89 and its derivative N-251 were shown to have potent antimalarial activity. We previously demonstrated that N-89 and N-251 potently inhibited the RNA replication of hepatitis C virus (HCV), which belongs to the family. Since antimalarial and anti-HCV mechanisms have not been clarified, we were interested whether N-89 and N-251 possessed the activity against viruses other than HCV. In this study, we examined the effects of N-89 and N-251 on other flaviviruses (dengue virus and Japanese encephalitis virus) and hepatitis viruses (hepatitis B virus and hepatitis E virus). Our findings revealed that N-89 and N-251 moderately inhibited the RNA replication of Japanese encephalitis virus and hepatitis E virus, although we could not detect those anti-dengue virus activities. We also observed that N-89 and N-251 moderately inhibited the replication of hepatitis B virus at the step after viral translation. These results suggest the possibility that N-89 and N-251 act on some common host factor(s) that are necessary for viral replications, rather than the possibility that N-89 and N-251 directly act on the viral proteins except for HCV. We describe a new type of antiviral reagents, N-89 and N-251, which are applicable to multiple different viruses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbrep.2018.05.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6047365PMC
September 2018

Serum miRNAs Predicting Sustained HBs Antigen Reduction 48 Weeks after Pegylated Interferon Therapy in HBe Antigen-Negative Patients.

Int J Mol Sci 2018 Jul 2;19(7). Epub 2018 Jul 2.

Department of Gastroenterology and Neurology, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Miki, Kita, Kagawa 761-0793, Japan.

The therapeutic goal for hepatitis B virus (HBV) infection is HBs antigen (HBsAg) seroclearance, which is achieved through 48-week pegylated interferon (Peg-IFN) therapy. This study aimed to identify predictive biomarkers for sustained HBsAg reduction by analyzing serum microRNAs. Twenty-two consecutive chronic HBV infection patients negative for HBe antigen (HBeAg) with HBV-DNA levels <5 log copies/mL, alanine aminotransferase (ALT) <100 U/L, and compensated liver functions, were enrolled. The patients were subcutaneously injected with Peg-IFNα-2a weekly for 48 weeks (treatment period), followed by the 48-week observation period. HBsAg 1-log drop relative to baseline levels recorded at the end of the observation period was considered effective. Sera were obtained at weeks 0 and 24 during the treatment period analyzed for microRNAs. The microRNA (miRNA) antiviral activity was evaluated in vitro using Huh7/sodium taurocholate cotransporting polypeptide (NTCP) cells. As a result, six patients achieved the HBsAg 1-log drop after the observation periods. Comparison of serum microRNA levels demonstrated that high miR-6126 levels at week 24 predicted HBsAg 1-log drop. Furthermore, miR-6126 reduced HBsAg in culture medium supernatants and intracellular HBV-DNA quantities in Huh7/NTCP cells. In conclusion, high serum miR-6126 levels during Peg-IFN therapy predicted the HBsAg 1-log drop 48 weeks after the completion of therapy. In vitro assays revealed that miR-6126 was able to suppress HBsAg production and HBV replication.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms19071940DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073286PMC
July 2018

Development of a cell-based assay to identify hepatitis B virus entry inhibitors targeting the sodium taurocholate cotransporting polypeptide.

Oncotarget 2018 May 4;9(34):23681-23694. Epub 2018 May 4.

Department of Microbiology, Yokohama City University School of Medicine, Kanagawa 236-0004, Japan.

Sodium taurocholate cotransporting polypeptide (NTCP) is a major entry receptor of hepatitis B virus (HBV) and one of the most attractive targets for anti-HBV drugs. We developed a cell-mediated drug screening method to monitor NTCP expression on the cell surface by generating a HepG2 cell line with tetracycline-inducible expression of NTCP and a monoclonal antibody that specifically detects cell-surface NTCP. Using this system, we screened a small molecule library for compounds that protected against HBV infection by targeting NTCP. We found that glabridin, a licorice-derived isoflavane, could suppress viral infection by inducing caveolar endocytosis of cell-surface NTCP with an IC of ~40 μM. We also found that glabridin could attenuate the inhibitory effect of taurocholate on type I interferon signaling by depleting the level of cell-surface NTCP. These results demonstrate that our screening system could be a powerful tool for discovering drugs targeting HBV entry.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.18632/oncotarget.25348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5955094PMC
May 2018

TIP60 Complex Inhibits Hepatitis B Virus Transcription.

J Virol 2018 03 26;92(6). Epub 2018 Feb 26.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Chiba, Japan.

Hepatitis B virus (HBV) is a global major health problem, with over one million deaths annually caused by chronic liver damage. Understanding host factors that modulate HBV replication may aid the development of anti-HBV therapies. Our recent genome-wide small interfering RNA screen using recombinant HBV demonstrated that TIP60 inhibited HBV infection. Here, we show that TIP60 complex contributes to anti-HBV defense. The TIP60 complex bound to the HBV promoter and suppressed HBV transcription driven by the precore/core promoter. The silencing of EP400, TRRAP, BAF53a, RUVBL1, and RUVBL2, which form the TIP60 complex, also resulted in increased HBV transcription. These results contribute to our enhanced understanding of the molecular mechanism of HBV transcription associated with the chromatin structure of HBV covalently closed circular DNA (cccDNA). Exploiting these intrinsic cellular defenses might help develop new anti-HBV agents. Investigating the molecular mechanism of HBV replication is important to understand the persistent nature of HBV infection and to aid the development of new HBV agents, which are currently limited to HBV polymerase inhibitors. Previously, we developed a new reporter HBV. By screening host factors using this recombinant virus, we identified several gene products that regulate HBV infection, including TIP60. Here, we showed that TIP60, a catalytic subunit of the NuA4 complex, inhibited HBV replication. Depletion of TIP60 increased the level of HBV mRNA. Moreover, TIP60 localized in the HBV cccDNA chromatin complex catalyzed the acetylation of histone H4 to recruit Brd4. These results suggest that TIP60, in concert with other cellular factors, plays an important role in the regulation of the HBV chromatin structure by acting as a critical component of the intrinsic antiviral defense, which sheds new light on the regulation of HBV replication.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01788-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5827368PMC
March 2018

Investigating the hepatitis B virus life cycle using engineered reporter hepatitis B viruses.

Cancer Sci 2018 Jan 7;109(1):241-249. Epub 2017 Dec 7.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Japan.

Chronic infection with hepatitis B virus (HBV) increases the risk of developing fibrosis, cirrhosis or hepatocellular carcinoma. Current therapies are limited to type-I interferons and/or nucleos(t)ide analogues; however, these are only partially effective. The development of novel anti-HBV agents for new treatment strategies has been hampered by the lack of a suitable system that allows the in vitro replication of HBV. Studies of virus infection/replication at the molecular level using wild-type HBV are labor-intensive and time-consuming. To overcome these problems, we previously constructed a recombinant reporter HBV bearing the NanoLuc gene and showed its usefulness in identifying factors that affect HBV proliferation. Because this system mimics the early stage of the HBV life cycle faithfully, we conducted a quantitative analysis of HBV infectivity to several human hepatocyte cell lines as well as the effect of dimethyl sulfoxide and HBV protein X on the early stage of HBV proliferation using this system. Furthermore, we developed a system to produce a reporter HBV expressing a pol gene. These reporter HBV may provide an opportunity to enhance our understanding of the HBV life cycle and aid strategies for the development of new anti-HBV agents.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cas.13440DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5765299PMC
January 2018

Molecular characterization of AID-mediated reduction of hepatitis B virus transcripts.

Virology 2017 10 2;510:281-288. Epub 2017 Aug 2.

Department of Molecular Genetics, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan. Electronic address:

Hepatitis B virus (HBV) is the major cause of liver cirrhosis and hepatocellular carcinoma. After entering a hepatocyte, HBV forms a nuclear viral episome and produces pregenomic (pg) RNA with a stem-loop structure called an epsilon, which acts to signal encapsidation. We previously demonstrated that TGF-β upregulates activation-induced cytidine deaminase (AID) expression in hepatocytes, which in turn downregulates HBV transcripts by recruiting the RNA exosome complex. The molecular mechanism underlying AID-mediated HBV RNA reduction remains largely unclear. Here we used a pgRNA reporter system having a reporter gene within pgRNA to identify sis- and trans-acting elements in AID-mediated HBV RNA reduction. We found that the epsilon RNA and C-terminus of AID are required for AID-mediated HBV RNA reduction. Importantly, this reduction was reproduced in a hydrodynamic HBV transfection mouse model. The molecular mechanism of AID-mediated HBV RNA reduction is discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.virol.2017.07.035DOI Listing
October 2017

Identification of KX2-391 as an inhibitor of HBV transcription by a recombinant HBV-based screening assay.

Antiviral Res 2017 08 15;144:138-146. Epub 2017 Jun 15.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, 1-7-1, Kohnodai, Ichikawa, Chiba, 272-8516, Japan.

Antiviral therapies for chronic hepatitis B virus (HBV) infection that are currently applicable for clinical use are limited to nucleos(t)ide analogs targeting HBV polymerase activity and pegylated interferon alpha (PEG-IFN). Towards establishing an effective therapy for HBV related diseases, it is important to develop a new anti-HBV agent that suppresses and eradicates HBV. This study used recombinant HBV encoding NanoLuc to screen anti-HBV compounds from 1827 US Food and Drug Administration approved compounds and identified several compounds that suppressed HBV infection. Among them, KX2-391, a non-ATP-competitive inhibitor of SRC kinase and tubulin polymerization, was identified as a lead candidate for an anti-HBV drug. Treatment of sodium taurocholate cotransporting polypeptide (NTCP) transduced-HepG2 (HepG2-NTCP) or primary human hepatocytes with KX2-391 suppressed HBV replication in a dose-dependent manner. The anti-HBV activity of KX2-391 appeared not to depend on SRC kinase activity because siRNA for SRC mRNA did not impair the HBV infection/replication. The anti-HBV activity of KX2-391 depended on the inhibitory effect of tubulin polymerization similar to other tubulin polymerization inhibitors, some of which were shown to inhibit HBV replication. KX2-391 inhibited HBV transcription driven by a HBV precore promoter in an HBV X protein-independent manner but did not inhibit the activity of HBV-S1, -S2, -X or cytomegalovirus promoters. Treatment with KX2-391 reduced the expression of several various factors including hepatocyte nuclear factor-4a.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.antiviral.2017.06.005DOI Listing
August 2017

Development of a Hepatitis B Virus Reporter System to Monitor the Early Stages of the Replication Cycle.

J Vis Exp 2017 02 1(120). Epub 2017 Feb 1.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine.

Currently, it is possible to construct recombinant forms of various viruses, such as human immunodeficiency virus 1 (HIV-1) and hepatitis C virus (HCV), that carry foreign genes such as a reporter or marker protein in their genomes. These recombinant viruses usually faithfully mimic the life cycle of the original virus in infected cells and exhibit the same host range dependence. The development of a recombinant virus enables the efficient screening of inhibitors and the identification of specific host factors. However, to date the construction of recombinant hepatitis B virus (HBV) has been difficult because of various experimental limitations. The main limitation is the compact genome size of HBV, and a fairly strict genome size that does not exceed 1.3 genome sizes, that must be packaged into virions. Thus, the size of a foreign gene to be inserted should be smaller than 0.4 kb if no deletion of the genome DNA is to be performed. Therefore, to overcome this size limitation, the deletion of some HBV DNA is required. Here, we report the construction of recombinant HBV encoding a reporter gene to monitor the early stage of the HBV replication cycle by replacing part of the HBV core-coding region with the reporter gene by deleting part of the HBV pol coding region. Detection of recombinant HBV infection, monitored by the reporter activity, was highly sensitive and less expensive than detection using the currently available conventional methods to evaluate HBV infection. This system will be useful for a number of applications including high-throughput screening for the identification of anti-HBV inhibitors, host factors and virus-susceptible cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3791/54849DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5407679PMC
February 2017

Long noncoding RNA #32 contributes to antiviral responses by controlling interferon-stimulated gene expression.

Proc Natl Acad Sci U S A 2016 09 31;113(37):10388-93. Epub 2016 Aug 31.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Chiba 272-8516, Japan.

Despite the breadth of knowledge that exists regarding the function of long noncoding RNAs (lncRNAs) in biological phenomena, the role of lncRNAs in host antiviral responses is poorly understood. Here, we report that lncRNA#32 is associated with type I IFN signaling. The silencing of lncRNA#32 dramatically reduced the level of IFN-stimulated gene (ISG) expression, resulting in sensitivity to encephalomyocarditis virus (EMCV) infection. In contrast, the ectopic expression of lncRNA#32 significantly suppressed EMCV replication, suggesting that lncRNA#32 positively regulates the host antiviral response. We further demonstrated the suppressive function of lncRNA#32 in hepatitis B virus and hepatitis C virus infection. lncRNA#32 bound to activating transcription factor 2 (ATF2) and regulated ISG expression. Our results reveal a role for lncRNA#32 in host antiviral responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1525022113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5027408PMC
September 2016

Human induced pluripotent stem cell-derived hepatic cell lines as a new model for host interaction with hepatitis B virus.

Sci Rep 2016 07 8;6:29358. Epub 2016 Jul 8.

Department of Gastroenterology and Hepatology, Tokyo Medical and Dental University, Tokyo, Japan.

Hepatitis B virus (HBV) is not eradicated by current antiviral therapies due to persistence of HBV covalently closed circular DNA (cccDNA) in host cells, and thus development of novel culture models for productive HBV infection is urgently needed, which will allow the study of HBV cccDNA eradication. To meet this need, we developed culture models of HBV infection using human induced pluripotent stem cell-derived hepatocyte lineages, including immature proliferating hepatic progenitor-like cell lines (iPS-HPCs) and differentiated hepatocyte-like cells (iPS-Heps). These cells were susceptible to HBV infection, produced HBV particles, and maintained innate immune responses. The infection efficiency of HBV in iPS-HPCs predominantly depended on the expression levels of sodium taurocholate cotransporting polypeptide (NTCP), and was low relative to iPS-Heps: however, long-term culture of iPS-Heps was difficult. To provide a model for HBV persistence, iPS-HPCs overexpressing NTCP were established. The long-term persistence of HBV cccDNA was detected in iPS-HPCs overexpressing NTCP, and depended on the inhibition of the Janus-kinase signaling pathway. In conclusion, this study provides evidence that iPS-derived hepatic cell lines can be utilized for novel HBV culture models with genetic variation to investigate the interactions between HBV and host cells and the development of anti-HBV strategies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep29358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4937433PMC
July 2016

Hepatitis C virus utilizes VLDLR as a novel entry pathway.

Proc Natl Acad Sci U S A 2016 Jan 23;113(1):188-93. Epub 2015 Dec 23.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Chiba, 272-8516 Japan;

Various host factors are involved in the cellular entry of hepatitis C virus (HCV). In addition to the factors previously reported, we discovered that the very-low-density lipoprotein receptor (VLDLR) mediates HCV entry independent of CD81. Culturing Huh7.5 cells under hypoxic conditions significantly increased HCV entry as a result of the expression of VLDLR, which was not expressed under normoxic conditions in this cell line. Ectopic VLDLR expression conferred susceptibility to HCV entry of CD81-deficient Huh7.5 cells. Additionally, VLDLR-mediated HCV entry was not affected by the knockdown of cellular factors known to act as HCV receptors or HCV entry factors. Because VLDLR is expressed in primary human hepatocytes, our results suggest that VLDLR functions in vivo as an HCV receptor independent of canonical CD81-mediated HCV entry.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1506524113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4711846PMC
January 2016

ATP1B3 Protein Modulates the Restriction of HIV-1 Production and Nuclear Factor κ Light Chain Enhancer of Activated B Cells (NF-κB) Activation by BST-2.

J Biol Chem 2016 Feb 22;291(9):4754-62. Epub 2015 Dec 22.

the Department of Life and Environmental Sciences and Research Institute, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino-shi, Chiba 275-0016, Japan, and

Here, we identify ATP1B3 and fibrillin-1 as novel BST-2-binding proteins. ATP1B3 depletion in HeLa cells (BST-2-positive cells), but not 293T cells (BST-2-negative cells), induced the restriction of HIV-1 production in a BST-2-dependent manner. In contrast, fibrillin-1 knockdown reduced HIV-1 production in 293T and HeLa cells in a BST-2-independent manner. Moreover, NF-κB activation was enhanced by siATP1B3 treatment in HIV-1- and HIV-1ΔVpu-infected HeLa cells. In addition, ATP1B3 silencing induced high level BST-2 expression on the surface of HeLa cells. These results indicate that ATP1B3 is a co-factor that accelerates BST-2 degradation and reduces BST-2-mediated restriction of HIV-1 production and NF-κB activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M115.679357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4813497PMC
February 2016

Novel reporter system to monitor early stages of the hepatitis B virus life cycle.

Cancer Sci 2015 Nov 16;106(11):1616-24. Epub 2015 Oct 16.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Japan.

A recombinant hepatitis B virus (HBV) expressing NanoLuc (NL) (HBV/NL) was produced by cotransfecting a plasmid containing a 1.2-fold HBV genome carrying the NL gene with a plasmid bearing a packaging-defective 1.2-fold HBV genome into a human hepatoma cell line, HepG2. We found that NL activity in HBV/NL-infected primary hepatocytes or sodium taurocholate cotransporting polypeptide-transduced human hepatocyte-derived cell lines increased linearly for several days after infection and was concordant with HBV RNA levels in the cells. Treatment of the virus-infected cells with HBV inhibitors reduced NL activity in a dose-dependent manner. Detection of HBV/NL infection, monitored by NL activity, was highly sensitive and less expensive than detection using the conventional method to evaluate HBV infection. In addition, because we also studied host factors, this system is applicable not only for studying the HBV life cycle, but also for exploring agent(s) that regulate HBV proliferation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cas.12799DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4714683PMC
November 2015

ZNF10 inhibits HIV-1 LTR activity through interaction with NF-κB and Sp1 binding motifs.

FEBS Lett 2015 Jul 19;589(15):2019-25. Epub 2015 Jun 19.

Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan; Research Institute, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan. Electronic address:

Kruppel-associated box-containing zinc finger (KRAB-ZNF) genes constitute the single largest gene family of transcriptional repressors in the genomes of higher organisms. In this study, we isolated 52 cDNA clones of KRAB-ZFPs from U1 cell lines and screened them to identify which were capable of regulating HIV-1 gene expression. We identified 5 KRAB-ZFPs that suppressed ⩾50% of HIV-1 LTR. Of the 5 identified KRAB-ZFPs, the expression of ZNF10 significantly enhanced the transcriptional repression activity of the LTR compared with other ZNFs. In addition, the depletion of endogenous ZNF10 led to the activation of HIV-1 LTR. The repressor activity of ZNF10 was required for TRIM28, SETDB1 and HP1-gamma binding. These results indicate that ZNF10 could be involved in a potent intrinsic antiretroviral defense.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.febslet.2015.06.013DOI Listing
July 2015

A new role for PGA1 in inhibiting hepatitis C virus-IRES-mediated translation by targeting viral translation factors.

Antiviral Res 2015 May 7;117:1-9. Epub 2015 Feb 7.

Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan; High Technology Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan; Research Institute, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan. Electronic address:

Previous studies have demonstrated that cyclopentenone prostaglandins (cyPGs) inhibit the replication of a wide variety of DNA and RNA viruses in different mammalian cell types. We investigated a new role for prostaglandin A1 (PGA1) in the inhibition of hepatitis C virus (HCV)-IRES-mediated translation. PGA1 exhibited dose-dependent inhibitory effects on HCV translation in HCV replicon cells. Furthermore, repetitive PGA1 treatment demonstrated the potential to safely induce the suppression of HCV translation. We also validated a new role for PGA1 in the inhibition of HCV-IRES-mediated translation by targeting cellular translation factors, including the small ribosomal subunit (40S) and eukaryotic initiation factors (eIFs). In pull-down assays, biotinylated PGA1 co-precipitated with the entire HCV IRES RNA/eIF3-40S subunit complex. Moreover, the interactions between PGA1 and the elongation factors and ribosomal subunit were dependent upon HCV IRES RNA binding, and the PGA1/HCV IRES RNA/eIF3-40S subunit complex inhibited HCV-IRES-mediated translation. The novel mechanism revealed in this study may aid in the search for more effective anti-HCV drugs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.antiviral.2015.01.013DOI Listing
May 2015

The RNA-editing enzyme APOBEC1 requires heterogeneous nuclear ribonucleoprotein Q isoform 6 for efficient interaction with interleukin-8 mRNA.

J Biol Chem 2014 Sep 6;289(38):26226-26238. Epub 2014 Aug 6.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, 1-7-1, Kohnodai, Ichikawa, Chiba 272-8516, Japan.

Apolipoprotein B mRNA-editing enzyme, catalytic polypeptide 1 (APOBEC1) is an intestine-specific RNA-binding protein. However, inflammation or exposure to DNA-damaging agents can induce ectopic APOBEC1 expression, which can result in hepatocellular hyperplasia in animal models. To identify its RNA targets, FLAG-tagged APOBEC1 was immunoprecipitated from transfected HuH7.5 hepatocellular carcinoma cells and analyzed using DNA microarrays. The interleukin-8 (IL8) mRNA was the most abundant co-precipitated RNA. Exogenous APOBEC1 expression increased IL8 production by extending the half-life of the IL8 mRNA. A cluster of AU-rich elements in the 3'-UTR of IL8 was essential to the APOBEC1-mediated increase in IL8 production. Notably, IL8 mRNA did not co-immunoprecipitate with APOBEC1 from lysates of other cell types at appreciable levels; therefore, other factors may enhance the association between APOBEC1 and IL8 mRNA in a cell type-specific manner. A yeast two-hybrid analysis and siRNA screen were used to identify proteins that enhance the interaction between APOBEC1 and IL8 mRNA. Heterogeneous nuclear ribonucleoprotein Q (hnRNPQ) was essential to the APOBEC1/IL8 mRNA association in HuH7.5 cells. Of the seven hnRNPQ isoforms, only hnRNPQ6 enabled APOBEC1 to bind to IL8 mRNA when overexpressed in HEK293 cells, which expressed the lowest level of endogenous hnRNPQ6 among the cell types examined. The results of a reporter assay using a luciferase gene fused to the IL8 3'-UTR were consistent with the hypothesis that hnRNPQ6 is required for APOBEC1-enhanced IL8 production. Collectively, these data indicate that hnRNPQ6 promotes the interaction of APOBEC1 with IL8 mRNA and the subsequent increase in IL8 production.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M114.563221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176254PMC
September 2014

Induction of heat-shock protein 70 by prostaglandin A₁ inhibits HIV-1 Vif-mediated degradation of APOBEC3G.

Antiviral Res 2013 Sep 4;99(3):307-11. Epub 2013 Jul 4.

Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan; Department of Virology II, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.

Previous studies have demonstrated that cyclopentenone prostaglandins (cyPGs) inhibit human immunodeficiency virus type 1 (HIV-1) replication in various cell types. This antiviral activity has been associated with the induction of heat-shock protein 70 (HSP70) in infected cells. We investigated a new role of prostaglandin A₁ (PGA₁) in the replication of HIV-1 in non-permissive cells. Because overexpression of HSP70 blocks the viral infectivity factor (Vif)-mediated degradation of APOBEC3G (A3G) via the ubiquitin-proteasome pathway, we examined the effects of PGA₁ on A3G and HIV-1 replication. The induction of HSP70 synthesis by PGA₁ blocked Vif-mediated A3G degradation and enhanced the incorporation of A3G into both wild-type and Vif-deficient viruses. Furthermore, we determined the viral titer of HIV-1 particles produced from PGA₁-treated 293T cells. The induction of HSP70 synthesis by PGA₁ significantly reduced the viral titer in the presence of A3G. Additionally, the p24 Gag antigen levels were dramatically reduced in non-permissive cells treated once or repeatedly with PGA₁. Thus, we showed that PGA₁ inhibits HIV-1 replication, at least in part, by blocking Vif-mediated A3G degradation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.antiviral.2013.06.017DOI Listing
September 2013

Hepatitis C virus infection induces inflammatory cytokines and chemokines mediated by the cross talk between hepatocytes and stellate cells.

J Virol 2013 Jul 15;87(14):8169-78. Epub 2013 May 15.

Research Center for Hepatitis and Immunology, National Center for Global Health and Medicine, Ichikawa, Chiba, Japan.

Inflammatory cytokines and chemokines play important roles in inflammation during viral infection. Hepatitis C virus (HCV) is a hepatotropic RNA virus that is closely associated with chronic liver inflammation, fibrosis, and hepatocellular carcinoma. During the progression of HCV-related diseases, hepatic stellate cells (HSCs) contribute to the inflammatory response triggered by HCV infection. However, the underlying molecular mechanisms that mediate HSC-induced chronic inflammation during HCV infection are not fully understood. By coculturing HSCs with HCV-infected hepatocytes in vitro, we found that HSCs stimulated HCV-infected hepatocytes, leading to the expression of proinflammatory cytokines and chemokines such as interleukin-6 (IL-6), IL-8, macrophage inflammatory protein 1α (MIP-1α), and MIP-1β. Moreover, we found that this effect was mediated by IL-1α, which was secreted by HSCs. HCV infection enhanced production of CCAAT/enhancer binding protein (C/EBP) β mRNA, and HSC-dependent IL-1α production contributed to the stimulation of C/EBPβ target cytokines and chemokines in HCV-infected hepatocytes. Consistent with this result, knockdown of mRNA for C/EBPβ in HCV-infected hepatocytes resulted in decreased production of cytokines and chemokines after the addition of HSC conditioned medium. Induction of cytokines and chemokines in hepatocytes by the HSC conditioned medium required a yet to be identified postentry event during productive HCV infection. The cross talk between HSCs and HCV-infected hepatocytes is a key feature of inflammation-mediated, HCV-related diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.00974-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3700210PMC
July 2013

ZBRK1 represses HIV-1 LTR-mediated transcription.

FEBS Lett 2012 Oct 17;586(20):3562-8. Epub 2012 Aug 17.

Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan.

The identification of cellular proteins that interact with the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) provides a basic understanding of HIV-1 gene expression, which is the major determinant regulating virus replication. We show that ZBRK1 negatively regulates the HIV-1 LTR. Ectopic expression of ZBRK1 represses transcriptional activity of the HIV-1 LTR, whereas the depletion of endogenous ZBRK1 leads to activation of the HIV-1 LTR. The repressor activity of ZBRK1 is required for TRIM28 binding. Furthermore, ZBRK1 is bound to the HIV-1 LTR in vivo. These results indicate that ZBRK1 could be involved in a potent intrinsic antiretroviral defense.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.febslet.2012.08.010DOI Listing
October 2012

The interaction between human initiation factor eIF3 subunit c and heat-shock protein 90: a necessary factor for translation mediated by the hepatitis C virus internal ribosome entry site.

Virus Res 2012 Jan 14;163(1):390-5. Epub 2011 Oct 14.

Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino-shi, Chiba 275-0016, Japan.

Heat-shock protein 90 (Hsp90) is a molecular chaperone that plays a key role in the conformational maturation of various transcription factors and protein kinases in signal transduction. The hepatitis C virus (HCV) internal ribosome entry site (IRES) RNA drives translation by directly recruiting the 40S ribosomal subunits that bind to eukaryotic initiation factor 3 (eIF3). Our data indicate that Hsp90 binds indirectly to eIF3 subunit c by interacting with it through the HCV IRES RNA, and the functional consequence of this Hsp90-eIF3c-HCV-IRES RNA interaction is the prevention of ubiquitination and the proteasome-dependent degradation of eIF3c. Hsp90 activity interference by Hsp90 inhibitors appears to be the result of the dissociation of eIF3c from Hsp90 in the presence of HCV IRES RNA and the resultant induction of the degradation of the free forms of eIF3c. Moreover, the interaction between Hsp90 and eIF3c is dependent on HCV IRES RNA binding. Furthermore, we demonstrate, by knockdown of eIF3c, that the silencing of eIF3c results in inhibitory effects on translation of HCV-derived RNA but does not affect cap-dependent translation. These results indicate that the interaction between Hsp90 and eIF3c may play an important role in HCV IRES-mediated translation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.virusres.2011.10.003DOI Listing
January 2012

Identification of amino acid residues in HIV-1 reverse transcriptase that are critical for the proteolytic processing of Gag-Pol precursors.

FEBS Lett 2011 Nov 12;585(21):3372-7. Epub 2011 Oct 12.

Department of Life and Environmental Sciences, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan.

The efficient processing of human immunodeficiency virus type 1 Gag-Pol requires not only protease activity but also specific reverse transcriptase (RT) and integrase sequences. However, the critical amino acid residues of the HIV-1 Pol gene involved in protease-mediated Gag-Pol processing have not been precisely defined. Here, we found that the substitution of Thr-128 or Tyr-146 with Ala markedly impaired the proteolytic processing of the MA/CA, p66/p51 and RT/IN sites but did not affect the normal processing of other sites. Moreover, a Thr-128 or Tyr-146 mutation in RT abolished RT dimerization in vitro. These results suggest that Thr-128 and Tyr-146 within the RT region play important roles in protease-mediated Gag-Pol processing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.febslet.2011.09.034DOI Listing
November 2011
-->