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author:("Cho, unchan")
1.  Cordycepin is a novel chemical suppressor of Epstein-Barr virus replication 
Oncoscience  2014;1(12):866-881.
Cordyceps species are known to produce numerous active components and are used for diverse medicinal purposes because of their varied physiological activities, including their ability to protect the liver from damage as well as their anticancer, antidepressant, anti-inflammatory, hypoglycemic, antimicrobial effects. Cordycepin, an adenosine derivative, differs from adenosine in that its ribose lacks an oxygen atom at the 3′ position. Several research groups have reported that cordycepin has antiviral activity against several viruses including influenza virus, plant viruses, human immunodeficiency virus(HIV), murine leukemia virus, and Epstein-Barr virus (EBV). In this study, we identify the epigenetic mechanisms by which cordycepin exerts its anti-gammaherpesvirus effects. We show that cordycepin possesses antitumor and antiviral activity against gastric carcinoma and EBV, respectively. A comparison of the CD50 values of cordycepin and its analogs showed that the lack of a 2′-hydroxyl group in cordycepin was critical for its relatively potent cytotoxicity. Cordycepin treatment decreased the rate of early apoptosis in SNU719 cells by up to 64%, but increased late apoptosis/necrosis by up to 31%. Interestingly, cordycepin increased BCL7A methylation in SNU719 cells by up to 58% and decreased demethylation by up to 37%. Consistent with these changes in methylation, cordycepin treatment significantly downregulated most EBV genes tested. Under the same conditions, cordycepin significantly decreased the frequency of Q and F promoter usage, and H3K4me3 histone enrichment was significantly reduced at several important EBV genomic loci. Extracellular and intracellular EBV genome copy numbers were reduced by up to 55% and 30%, respectively, in response to 125 μM cordycepin treatment.
Finally, cordycepin significantly suppressed the transfer of EBV from LCL-EBV-GFP to AGS cells, indicating that EBV infection of gastric epithelial cells was inhibited. These results suggest that cordycepin has antiviral and antitumor activities against gammaherpesviruses and host cells latently infected with virus.
PMCID: PMC4303894  PMID: 25621301
Cordycepin; Epstein–Barr virus; gastric carcinoma; antiviral agent
2.  Aralia cordata Inhibits Triacylglycerol Biosynthesis in HepG2 Cells 
Journal of Medicinal Food  2013;16(12):1108-1114.
Abstract
Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first committed step in triacylglycerol (TAG) and phospholipid biosynthesis, and has been considered as one of the drug targets for treating hepatic steatosis, insulin resistance, and other metabolic disorders. The aim of this study was to investigate the GPAT inhibitors from natural products and to evaluate their effects. The methanol extract of Aralia cordata roots showed a strong inhibitory effect on the human GPAT1 activity. A further bioactivity-guided approach led to the isolation of ent-pimara-8(14),15-dien-19-oic acid, (PA), one of the major compounds of A. cordata, which suppressed the GPAT1 activity with IC50 value of 60.5 μM. PA markedly reduced de novo lysophosphatidic acid synthesis through inhibition of GPAT activity and therefore significantly decreased synthesis of TAG in the HepG2 cells. These results suggest that PA as well as A. cordata root extract could be beneficial in controlling lipid metabolism.
doi:10.1089/jmf.2012.2636
PMCID: PMC3868379  PMID: 24283275
Aralia cordata; ent-pimara-8(14),15-dien-19-oic acid; glycerol-3-phosphate acyltransferase; lysophophatidic acid; triacylglycerol
3.  Efficient lytic induction of kaposi's sarcoma-associated herpesvirus (KSHV) by the anthracyclines 
Oncotarget  2014;5(18):8515-8527.
Lytic induction of latent Kaposi's sarcoma-associated herpesvirus (KSHV) has been considered as a therapeutic option for efficient treatment of several KSHV-associated malignancies. Here, we developed a robust high-throughput screening system that allows an easy and quantitative measurement of lytic induction of latent KSHV and discovered three anthracyclines as potent inducers from screen of FDA-approved drugs. Lytic induction of latent KSHV by three compounds was verified by the significant induction of lytic genes and subsequent production of infectious KSHV. Importantly, lytic induction by three compounds was much more efficient than that by sodium butyrate, a well-characterized inducer of KSHV lytic cycle. Mechanistically, the anthracyclines caused lytic induction of KSHV through apoptosis induced by their DNA intercalation rather than topoisomerase II inhibition. Consequently, our results clearly demonstrated a role of anthracyclines as effective lytic inducers of KSHV and also provided a molecular basis of their use for efficient treatment of diseases associated with KSHV infection.
PMCID: PMC4226701  PMID: 25237786
Kaposi's sarcoma-associated herpesvirus (KSHV); Lytic induction; Anthracyclines; Apoptosis; DNA intercalation
4.  Antiviral activity of ginsenosides against coxsackievirus B3, enterovirus 71, and human rhinovirus 3 
Journal of Ginseng Research  2014;38(3):173-179.
Background
Ginsenosides are the major components responsible for the biochemical and pharmacological actions of ginseng, and have been shown to have various biological activities. In this study, we investigated the antiviral activities of seven ginsenosides [protopanaxatriol (PT) type: Re, Rf, and Rg2; protopanaxadiol (PD) type: Rb1, Rb2, Rc, and Rd)] against coxsackievirus B3 (CVB3), enterovirus 71 (EV71), and human rhinovirus 3 (HRV3).
Methods
Assays of antiviral activity and cytotoxicity were evaluated by the sulforhodamine B method using the cytopathic effect (CPE) reduction assay.
Results
The antiviral assays demonstrated that, of the seven ginsenosides, the PT-type ginsenosides (Re, Rf, and Rg2) possess significant antiviral activities against CVB3 and HRV3 at a concentration of 100 μg/mL. Among the PT-type ginsenosides, only ginsenoside Rg2 showed significant anti-EV71 activity with no cytotoxicity to cells at 100 μg/mL. The PD-type ginsenosides (Rb1, Rb2, Rc, and Rd), by contrast, did not show any significant antiviral activity against CVB3, EV71, and HRV3, and exhibited cytotoxic effects to virus-infected cells. Notably, the antiviral efficacies of PT-type ginsenosides were comparable to those of ribavirin, a commonly used antiviral drug.
Conclusion
Collectively, our findings suggest that the ginsenosides Re, Rf, and Rg2 have the potential to be effective in the treatment of CVB3, EV71, and HRV3 infection.
doi:10.1016/j.jgr.2014.04.003
PMCID: PMC4213867  PMID: 25378991
antiviral activity; CVB3; EV71; ginsenosides; HRV3
5.  Identification of a Novel Function of CX-4945 as a Splicing Regulator 
PLoS ONE  2014;9(4):e94978.
Alternative splicing is a nearly ubiquitous versatile process that controls gene expression and creates numerous protein isoforms with different functions from a single gene. The significance of alternative splicing has been confirmed by the increasing number of human diseases that are caused by misregulation of splicing events. Very few compounds, however, have been reported to act as inhibitors of alternative splicing, and their potential clinical use needs to be evaluated. Here, we report that CX-4945, a previously well-characterized inhibitor of casein kinase 2 (CK2) and a molecule currently in clinical trials (Phase II) for cancer treatment, regulates splicing in mammalian cells in a CK2-independent manner. Transcriptome-wide analysis using exon array also showed a widespread alteration in alternative splicing of numerous genes. We found that CX-4945 potently inhibits the Cdc2-like kinases (Clks) in vitro and in turn, leads to suppression of the phosphorylation of serine/arginine-rich (SR) proteins in mammalian cells. Surprisingly, the overall efficacy of CX-4945 on Clks (IC50 = 3–90 nM) was stronger than that of TG-003, the strongest inhibitor reported to date. Of the Clks, Clk2 was most strongly inhibited by CX-4945 in an ATP-competitive manner. Our research revealed an unexpected activity of the drug candidate CX-4945 as a potent splicing modulator and also suggested a potential application for therapy of diseases caused by abnormal splicing.
doi:10.1371/journal.pone.0094978
PMCID: PMC3990583  PMID: 24743259
6.  U1 snRNP Determines mRNA Length and Regulates Isoform Expression 
Cell  2012;150(1):53-64.
Summary
U1 snRNP (U1), in addition to its splicing role, protects pre-mRNAs from drastic premature termination by cleavage and polyadenylation (PCPA) at cryptic polyadenylation signals (PASs) in introns. Here, a high throughput sequencing strategy of differentially expressed transcripts (HIDE-seq), mapped PCPA sites genome-wide in divergent organisms. Surprisingly, while U1 depletion terminated most nascent gene transcripts within ~1 kb, moderate functional U1 level decreases, insufficient to inhibit splicing, dose-dependently shifted PCPA downstream, eliciting mRNA 3′ UTR shortening and proximal 3′ exon switching characteristic of activated immune and neuronal cells, stem cells and cancer. Activated neurons’ signature mRNA shortening could be recapitulated by U1 decrease and antagonized by U1 over-expression. Importantly, we show that rapid and transient transcriptional up-regulation inherent to neuronal activation physiology creates U1 shortage relative to pre-mRNAs. Additional experiments suggest co-transcriptional PCPA counteracted by U1 association with nascent-transcripts, a process we term telescripting, ensuring transcriptome integrity and regulating mRNA length.
doi:10.1016/j.cell.2012.05.029
PMCID: PMC3412174  PMID: 22770214
7.  Updates on the genetic variations of Norovirus in sporadic gastroenteritis in Chungnam Korea, 2009-2010 
Virology Journal  2012;9:29.
Previously, we explored the epidemic pattern and molecular characterization of noroviruses (NoVs) isolated in Chungnam, Korea in 2008, and the present study extended these observations to 2009 and 2010. In Korea, NoVs showed the seasonal prevalence from late fall to spring, and widely detected in preschool children and peoples over 60 years of age. Epidemiological pattern of NoV was similar in 2008 and in 2010, but pattern in 2009 was affected by pandemic influenza A/H1N1 2009 virus. NoV-positive samples were subjected to sequence determination of the capsid gene region, which resolved the isolated NoVs into five GI (2, 6, 7, 9 and 10) and eleven GII genotypes (1, 2, 3, 4, 6, 7, 8, 12, 13, 16 and 17). The most prevalent genotype was GII.4 and occupied 130 out of 211 NoV isolates (61.6%). Comparison of NoV GII.4 of prevalent genotype in these periods with reference strains of the same genotype was conducted to genetic analysis by a phylogenetic tree. The NoV GII.4 strains were segregated into seven distinct genetic groups, which are supported by high bootstrap values and previously reported clusters. All Korean NoV GII.4 strains belonged to either VI cluster or VII cluster. The divergence of nucleotide sequences within VI and VII intra-clusters was > 3.9% and > 3.5%, respectively. The "Chungnam(06-117)/2010" strain which was isolated in June 2010 was a variant that did not belong to cluster VI or VII and showed 5.8-8.2%, 6.2-8.1% nucleotide divergence with cluster VI and VII, respectively.
doi:10.1186/1743-422X-9-29
PMCID: PMC3312829  PMID: 22273062
8.  Translation-competent 48S complex formation on HCV IRES requires the RNA-binding protein NSAP1 
Nucleic Acids Research  2011;39(17):7791-7802.
Translation of many cellular and viral mRNAs is directed by internal ribosomal entry sites (IRESs). Several proteins that enhance IRES activity through interactions with IRES elements have been discovered. However, the molecular basis for the IRES-activating function of the IRES-binding proteins remains unknown. Here, we report that NS1-associated protein 1 (NSAP1), which augments several cellular and viral IRES activities, enhances hepatitis C viral (HCV) IRES function by facilitating the formation of translation-competent 48S ribosome–mRNA complex. NSAP1, which is associated with the solvent side of the 40S ribosomal subunit, enhances 80S complex formation through correct positioning of HCV mRNA on the 40S ribosomal subunit. NSAP1 seems to accomplish this positioning function by directly binding to both a specific site in the mRNA downstream of the initiation codon and a 40S ribosomal protein (or proteins).
doi:10.1093/nar/gkr509
PMCID: PMC3177222  PMID: 21715376
9.  Inactivation of the SMN complex by Oxidative Stress 
Molecular cell  2008;31(2):244-254.
Summary
The SMN complex is essential for the biogenesis of small nuclear ribonucleoproteins (snRNPs), the major constituents of the spliceosome. Deficiency in functional SMN protein causes spinal muscular atrophy (SMA), a common motor neuron degenerative disease of severity commensurate with SMN levels, and correspondingly, snRNP assembly decrease. We developed a high throughput screen for snRNP assembly modifiers and discovered that reactive oxygen species (ROS) inhibit SMN complex activity in a dose-dependent manner. ROS-generating compounds, e.g, the environmental toxins menadione and β-lapachone (in vivo IC50=0.45 μM) also cause intermolecular disulfide crosslinking of SMN. Both the oxidative inactivation and SMN crosslinking can be reversed by reductants. We identified two cysteines that form SMN-SMN disulfide crosslinks, defining specific contact points in oligomeric SMN. Thus, the SMN complex is a redox-sensitive assemblyosome and a novel ROS target, suggesting that it may play a role in oxidative stress pathophysiology, which is associated with many degenerative diseases.
doi:10.1016/j.molcel.2008.06.004
PMCID: PMC2867055  PMID: 18657506
10.  BiP Internal Ribosomal Entry Site Activity Is Controlled by Heat-Induced Interaction of NSAP1† ▿  
Molecular and Cellular Biology  2007;27(1):368-383.
TheBiP protein, a stress response protein, plays an important role in the proper folding and assembly of nascent protein and in the scavenging of misfolded proteins in the endoplasmic reticulum lumen. Translation of BiP is directed by an internal ribosomal entry site (IRES) in the 5′ nontranslated region of the BiP mRNA. BiP IRES activity increases when cells are heat stressed. Here we report that NSAP1 specifically enhances the IRES activity of BiP mRNA by interacting with the IRES element. Overexpression of NSAP1 in 293T cells increased the IRES activity of BiP mRNA, whereas knockdown of NSAP1 by small interfering RNA (siRNA) reduced the IRES activity of BiP mRNA. The amount of NSAP1 bound to the BiP IRES increased under heat stress conditions, and the IRES activity of BiP mRNA was increased. Moreover, the increase in BiP IRES activity with heat treatment was not observed in cells lacking NSAP1 after siRNA treatment. BiP mRNAs were redistributed from the heavy polysome to the light polysome in NSAP1 knockdown cells. Together, these data indicate that NSAP1 modulates IRES-dependent translation of BiP mRNA through an RNA-protein interaction under heat stress conditions.
doi:10.1128/MCB.00814-06
PMCID: PMC1800651  PMID: 17074807
11.  Polypyrimidine Tract-Binding Protein Enhances the Internal Ribosomal Entry Site-Dependent Translation of p27Kip1 mRNA and Modulates Transition from G1 to S Phase 
Molecular and Cellular Biology  2005;25(4):1283-1297.
The p27Kip1 protein plays a critical role in the regulation of cell proliferation through the inhibition of cyclin-dependent kinase activity. Translation of p27Kip1 is directed by an internal ribosomal entry site (IRES) in the 5′ nontranslated region of p27Kip1 mRNA. Here, we report that polypyrimidine tract-binding protein (PTB) specifically enhances the IRES activity of p27Kip1 mRNA through an interaction with the IRES element. We found that addition of PTB to an in vitro translation system and overexpression of PTB in 293T cells augmented the IRES activity of p27Kip1 mRNA but that knockdown of PTB by introduction of PTB-specific small interfering RNAs (siRNAs) diminished the IRES activity of p27Kip1 mRNA. Moreover, the G1 phase in the cell cycle (which is maintained in part by p27Kip1) was shortened in cells depleted of PTB by siRNA knockdown. 12-O-Tetradecanoylphorbol-13-acetate (TPA)-induced differentiation in HL60 cells was used to examine PTB-induced modulation of p27Kip1 protein synthesis during differentiation. The IRES activity of p27Kip1 mRNA in HL60 cells was increased by TPA treatment (with a concomitant increase in PTB protein levels), but the levels of p27Kip1 mRNA remained unchanged. Together, these data suggest that PTB modulates cell cycle and differentiation, at least in part, by enhancing the IRES activity of p27Kip1 mRNA.
doi:10.1128/MCB.25.4.1283-1297.2005
PMCID: PMC548013  PMID: 15684381
12.  A Cellular RNA-Binding Protein Enhances Internal Ribosomal Entry Site-Dependent Translation through an Interaction Downstream of the Hepatitis C Virus Polyprotein Initiation Codon 
Molecular and Cellular Biology  2004;24(18):7878-7890.
Translational initiation of hepatitis C virus (HCV) mRNA occurs by internal entry of ribosomes into an internal ribosomal entry site (IRES) at the 5′ nontranslated region. A region encoding the N-terminal part of the HCV polyprotein has been shown to augment the translation of HCV mRNA. Here we show that a cellular protein, NS1-associated protein 1 (NSAP1), augments HCV mRNA translation through a specific interaction with an adenosine-rich protein-coding region within the HCV mRNA. The overexpression of NSAP1 specifically enhanced HCV IRES-dependent translation, and knockdown of NSAP1 by use of a small interfering RNA specifically inhibited the translation of HCV mRNA. An HCV replicon RNA capable of mimicking the HCV proliferation process in host cells was further used to confirm that NSAP1 enhances the translation of HCV mRNA. These results suggest the existence of a novel mechanism of translational enhancement that acts through the interaction of an RNA-binding protein with a protein coding sequence.
doi:10.1128/MCB.24.18.7878-7890.2004
PMCID: PMC515056  PMID: 15340051
13.  Translation of Polioviral mRNA Is Inhibited by Cleavage of Polypyrimidine Tract-Binding Proteins Executed by Polioviral 3Cpro 
Journal of Virology  2002;76(5):2529-2542.
The translation of polioviral mRNA occurs through an internal ribosomal entry site (IRES). Several RNA-binding proteins, such as polypyrimidine tract-binding protein (PTB) and poly(rC)-binding protein (PCBP), are required for the poliovirus IRES-dependent translation. Here we report that a poliovirus protein, 3Cpro (and/or 3CDpro), cleaves PTB isoforms (PTB1, PTB2, and PTB4). Three 3Cpro target sites (one major target site and two minor target sites) exist in PTBs. PTB fragments generated by poliovirus infection are redistributed to the cytoplasm from the nucleus, where most of the intact PTBs are localized. Moreover, these PTB fragments inhibit polioviral IRES-dependent translation in a cell-based assay system. We speculate that the proteolytic cleavage of PTBs may contribute to the molecular switching from translation to replication of polioviral RNA.
PMCID: PMC135932  PMID: 11836431
14.  Nonstructural Protein 5A of Hepatitis C Virus Inhibits the Function of Karyopherin β3 
Journal of Virology  2000;74(11):5233-5241.
It has been suggested that nonstructural protein 5A (NS5A) of hepatitis C virus (HCV) plays a role in the incapacitation of interferon by inactivation of RNA-dependent protein kinase PKR. In order to further investigate the role of NS5A, we tried to identify cellular proteins interacting with NS5A by using the yeast two-hybrid system. The karyopherin β3 gene was isolated from a human liver cell library as a protein interacting with NS5A. The protein-protein interaction between NS5A and karyopherin β3 was confirmed by in vitro binding assay and an in vivo coimmunoprecipitation method. The effect of NS5A on the karyopherin β3 activity was investigated using a yeast cell line containing mutations in both PSE1 and KAP123, genes that are homologous to the human karyopherin β3 gene. Human karyopherin β3 complemented the loss of the PSE1 and KAP123 functions, supporting growth of the double mutant cells. However, expression of NS5A hampered the growth of the double mutant cells supplemented with human karyopherin β3. On the other hand, expression of NS5A by itself had no effect on the growth of the double mutant expressing wild-type yeast PSE1. This indicates that NS5A may inhibit karyopherin β3 function via protein-protein interaction. The role of NS5A in HCV replication is discussed.
PMCID: PMC110877  PMID: 10799599

Results 1-14 (14)