Biology subjects

Watashi, K.

Publications and source records attributed to Watashi, K..

23 records · Page 2Linked to original sources

bioRxiv2020

MafF is an anti-viral host factor that suppresses transcription from Hepatitis B Virus and Epstein Barr Virus promoters

Hepatitis B Virus (HBV) is a stealth virus that exhibits only minimal induction of the interferon system that is required for both innate and adaptive immune responses. However, 90% of acutely infected adults can clear the virus, suggesting the presence of additional mechanisms that facilitate viral clearance. Herein, we report that Maf bZIP transcription factor F (MafF) promotes host defense against infection with HBV. Using siRNA library and an HBV/NL reporter virus, we screened to identify anti-HBV host factors. Our data showed that silencing of MafF led to a 6-fold increase in luciferase activity after HBV/NL infection. Overexpression of MafF reduced HBV core promoter transcriptional activity, which was relieved upon mutating the putative MafF binding region. Loss of MafF expression by CRISPR/CAS9 (in HepG2-hNTCP-C4 cells) or siRNA silencing (in primary hepatocytes [PXB]), induced HBV core and HBV pregenomic RNA (pgRNA) levels, respectively, after HBV infection. MafF physically binds to HBV core promoter and competitively inhibits HNF-4 binding to an overlapping sequence in HBV enhancer II sequence (EnhII) as seen by ChIP analysis. MafF expression was induced by IL-1{beta}/TNF- treatment in both HepG2 and PXB cells, in an NF-{kappa}B-dependent manner. Consistently, MafF expression levels were significantly enhanced and positively correlated with the levels of these cytokines in patients with chronic HBV infection, especially in the immune clearance phase. ImportanceHBV is a leading cause of chronic liver diseases, infecting about 250 million people worldwide. HBV has developed strategies to escape interferon-dependent innate immune responses. Hence, the identification of other anti-HBV mechanisms is important for understanding HBV pathogenesis, and developing anti-HBV strategies. MafF was shown to suppress transcription from HBV core promoter, leading to a significant suppression of HBV life cycle. Furthermore, MafF expression was induced in chronic HBV patients and in primary human hepatocytes (PXB). This induction correlated with the levels of inflammatory cytokines (IL-1{beta} and TNF-). These data suggest that the induction of MafF contributes to the hosts antiviral defense by suppressing transcription from selected viral promoters. Our data shed light on a novel role for MafF as anti-HBV host restriction factor.

microbiology↗

bioRxiv2020

Multidrug treatment with nelfinavir and cepharanthine against COVID-19

Antiviral treatments targeting the emerging coronavirus disease 2019 (COVID-19) are urgently required. We screened a panel of already-approved drugs in a cell culture model of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and identified two new antiviral agents: the HIV protease inhibitor Nelfinavir and the anti-inflammatory drug Cepharanthine. In silico modeling shows Nelfinavir binds the SARS-CoV-2 main protease consistent with its inhibition of viral replication, whilst Cepharanthine inhibits viral attachment and entry into cells. Consistent with their different modes of action, in vitro assays highlight a synergistic effect of this combined treatment to limit SARS-CoV-2 proliferation. Mathematical modeling in vitro antiviral activity coupled with the known pharmacokinetics for these drugs predicts that Nelfinavir will facilitate viral clearance. Combining Nelfinavir/Cepharanthine enhanced their predicted efficacy to control viral proliferation, to ameliorate both the progression of disease and risk of transmission. In summary, this study identifies a new multidrug combination treatment for COVID-19.

microbiology↗

bioRxiv2020

Required concentration index quantifies effective drug combinations against HCV infection

Successful clinical drug development requires rational design of combination treatments based on preclinical data. Anti-HCV drugs exhibit significant diversity in antiviral effect. Dose-response assessments can be used to determine parameters profiling the diverse antiviral effect during combination treatment. In the current study, a combined experimental and mathematical approaches were used to compare and score different combinations of anti-hepatitis C virus (HCV) treatments. A "required concentration index" was generated and used to rank the antiviral profile of possible double- and triple-drug combinations against HCV genotype 1 and 2. Rankings varied based on target HCV genotype. Interestingly, multidrug (double and triple) treatment not only augmented antiviral activity, but also reduced genotype-specific efficacy, suggesting another advantage of multidrug treatment. The current study provides a quantitative method for profiling drug combinations against viral genotypes, to better inform clinical drug development.

systems biology↗

bioRxiv2019

Two strategies underlying the trade-off of hepatitis C virus proliferation: stay-at-home or leaving-home?

Viruses proliferate through both genome replication inside infected cells and transmission to new target cells or to new hosts. Each viral genome molecule in infected cells is used either for amplifying the intracellular genome as a template (\"stay-at-home strategy\") or for packaging into progeny virions to be released extracellularly (\"leaving-home strategy\"). The balance between these strategies is important for both initial growth and transmission of viruses. In this study, we used hepatitis C virus (HCV) as a model system to study the functions of viral genomic RNA in both RNA replication in cells and in progeny virus assembly and release. Using viral infection assays combined with mathematical modelling, we characterized the dynamics of two different HCV strains (JFH-1, a clinical isolate, and Jc1-n, a laboratory strain), which have different viral assembly and release characteristics. We found that 1.27% and 3.28% of JFH-1 and Jc1-n intracellular viral RNAs, respectively, are used for producing and releasing progeny virions. Analysis of the Malthusian parameter of the HCV genome (i.e., initial growth rate) and the number of de novo infections (i.e., initial transmissibility) suggests that the leaving-home strategy provides a higher level of initial transmission for Jc1-n, while, in contrast, the stay-at-home strategy provides a higher initial growth rate for JFH-1. Thus, theoretical-experimental analysis of viral dynamics enables us to better understand the proliferation strategies of viruses. Ours is the first study to analyze stay-leave trade-offs during the viral life cycle and their significance for viral proliferation.

evolutionary biology↗

bioRxiv2018

A Single Adaptive Mutation in Sodium Taurocholate Cotransporting Polypeptide Induced by Hepadnaviruses Determines Virus Species-specificity

Hepatitis B virus (HBV) and its hepadnavirus relatives infect a wide range of vertebrates from fish to human. Hepadnaviruses and their hosts have a long history of acquiring adaptive mutations. However, there are no reports providing direct molecular evidence for such a coevolutionary \"arms race\" between hepadnaviruses and their hosts. Here, we present evidence suggesting the adaptive evolution of the sodium taurocholate cotransporting polypeptide (NTCP), an HBV receptor, has been influenced by virus infection. Evolutionary analysis of the NTCP-encoding genes from 20 mammals showed that most NTCP residues are highly conserved among species, exhibiting evolution under negative selection (dN/dS < 1); this observation implies that the evolution of NTCP is restricted by maintaining its original protein function. However, 0.7 % of NTCP amino acid (aa) residues exhibit rapid evolution under positive selection (dN/dS > 1). Notably, a substitution at aa 158, a positively selected residue, converting the human NTCP to a monkey-type sequence abrogated the capacity to support HBV infection; conversely, a substitution at this residue converting the monkey Ntcp to the human sequence was sufficient to confer HBV susceptibility. Together, these observations suggested that positive selection at aa 158 was induced by virus infection. Moreover, the aa 158 sequence determined attachment of the HBV envelope protein to host cell, demonstrating the mechanism whereby HBV infection would create positive selection at this residue in NTCP. In summary, we provide the first evidence in agreement with the function of hepadnavirus as a driver for inducing an adaptive mutation in host receptor.\n\nImportanceHepatitis B virus (HBV) and its hepadnavirus relatives infect a wide range of vertebrates, with a long infectious history (hundreds of millions of years). Such a long history generally allows adaptive mutations in hosts to escape from infection, while simultaneously allowing adaptive mutations in viruses to overcome host barriers. However, there is no published molecular evidence for such a coevolutionary \"arms race\" between hepadnaviruses and hosts. In the present study, we performed coevolutionary phylogenetic analysis between hepadnaviruses and the sodium taurocholate cotransporting polypeptide (NTCP), an HBV receptor, combined with virological experimental assays for investigating the biological significance of NTCP sequence variation. Our data provide the first molecular evidences supporting that HBV-related hepadnaviruses drive adaptive evolution in the NTCP sequence, including a mechanistic explanation of how NTCP mutations determine host viral susceptibility. Our novel insights enhance our understanding of how hepadnaviruses evolved with their hosts, permitting the acquisition of strong species-specificity.

evolutionary biology↗