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Abstract
This review on natural products containing a tropolonoid motif highlights analytical methods applied for structural identification and biosynthetic pathway analysis, the ecological context and the pharmacological potential of this compound class.
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Affiliation(s)
- Huijuan Guo
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute
- 07745 Jena
- Germany
| | - David Roman
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute
- 07745 Jena
- Germany
| | - Christine Beemelmanns
- Leibniz Institute for Natural Product Research and Infection Biology – Hans Knöll Institute
- 07745 Jena
- Germany
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2
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Tkachev VV, Sayapin YA, Gusakov EA, Kolodina AA, Dorogan IV, Shilov GV, Aldoshin SM, Minkin VI. Synthesis and Molecular Structures of (3-Hydroxy, 3-Chloro, 3-Arylamino)-N-acetyl-3-arylaminotropones. CRYSTALLOGR REP+ 2018. [DOI: 10.1134/s1063774518010200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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3
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Lomonosova E, Daw J, Garimallaprabhakaran AK, Agyemang NB, Ashani Y, Murelli RP, Tavis JE. Efficacy and cytotoxicity in cell culture of novel α-hydroxytropolone inhibitors of hepatitis B virus ribonuclease H. Antiviral Res 2017. [PMID: 28633989 DOI: 10.1016/j.antiviral.2017.06.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Chronic Hepatitis B virus (HBV) infection is a major worldwide public health problem. Current direct-acting anti-HBV drugs target the HBV DNA polymerase activity, but the equally essential viral ribonuclease H (RNaseH) activity is unexploited as a drug target. Previously, we reported that α-hydroxytropolone compounds can inhibit the HBV RNaseH and block viral replication. Subsequently, we found that our biochemical RNaseH assay underreports efficacy of the α-hydroxytropolones against HBV replication. Therefore, we conducted a structure-activity analysis of 59 troponoids against HBV replication in cell culture. These studies revealed that antiviral efficacy is diminished by larger substitutions on the tropolone ring, identified key components in the substitutions needed for high efficacy, and revealed that cytotoxicity correlates with increased lipophilicity of the α-hydroxytropolones. These data provide key guidance for further optimization of the α-hydroxytropolone scaffold as novel HBV RNaseH inhibitors.
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Affiliation(s)
- Elena Lomonosova
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, USA; Saint Louis University Liver Center, Saint Louis, MO, USA
| | - Jil Daw
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, USA
| | | | - Nana B Agyemang
- Department of Chemistry, Brooklyn College, City University of New York, Brooklyn, NY, USA
| | - Yashkumar Ashani
- Department of Chemistry, Brooklyn College, City University of New York, Brooklyn, NY, USA
| | - Ryan P Murelli
- Department of Chemistry, Brooklyn College, City University of New York, Brooklyn, NY, USA; PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, USA
| | - John E Tavis
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, USA; Saint Louis University Liver Center, Saint Louis, MO, USA.
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4
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Schutte-Smith M, Eselem Bungu PS, Steyl G, Roodt A. Crystal structure of 3,5,7-tris(morpholinomethyl)tropolone·0.67 hydrate, C 22H 33N 3O 5·0.67H 2O. Z KRIST-NEW CRYST ST 2016. [DOI: 10.1515/ncrs-2016-0083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
C22H33N3O5·0.67H2O, monoclinic, P21/c, a = 11.9915(6) Å, b = 18.9934(10) Å, c = 10.5332(5) Å, β = 112.155(2)°, V = 2221.91(19) Å3, Z = 4, R
gt(F) = 0.0417, wR
ref(F
2) = 0.1139, T = 100(2) K.
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Affiliation(s)
- Marietjie Schutte-Smith
- Department of Chemistry , University of the Free State , P.O. Box 339, Bloemfontein 9301, South Africa
| | | | - Gideon Steyl
- Department of Chemistry , University of the Free State , Bloemfontein 9301, South Africa
| | - Andreas Roodt
- Department of Chemistry , University of the Free State , Bloemfontein 9301, South Africa
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5
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Gorle S, Maddila S, Chokkakula S, Lavanya P, Singh M, Jonnalagadda SB. Synthesis, Biological Activity of Pyrimidine Linked with Morpholinophenyl Derivatives. J Heterocycl Chem 2015. [DOI: 10.1002/jhet.2498] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Sridevi Gorle
- Discipline of Biochemistry, School of Life Sciences; University of KwaZulu-Natal; Westville Campus, Chiltern Hills Durban 4000 South Africa
| | - Suresh Maddila
- School of Chemistry and Physics; University of KwaZulu-Natal; Westville Campus, Chilten Hills, Private Bag 54001 Durban 4000 South Africa
| | - Santosh Chokkakula
- School of Life and Health Sciences; Adikavi Nannaya University; Rajahmundry 533296 India
| | - Palakondu Lavanya
- Department of Chemistry; Annamacharya Institute of Technology and Sciences J.N.T. University; Tirupati 517 502 Andhra Pradesh India
| | - Moganavelli Singh
- Discipline of Biochemistry, School of Life Sciences; University of KwaZulu-Natal; Westville Campus, Chiltern Hills Durban 4000 South Africa
| | - Sreekanth B. Jonnalagadda
- School of Chemistry and Physics; University of KwaZulu-Natal; Westville Campus, Chilten Hills, Private Bag 54001 Durban 4000 South Africa
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LaPlante SR, Padyana AK, Abeywardane A, Bonneau P, Cartier M, Coulombe R, Jakalian A, Wildeson-Jones J, Li X, Liang S, McKercher G, White P, Zhang Q, Taylor SJ. Integrated Strategies for Identifying Leads That Target the NS3 Helicase of the Hepatitis C Virus. J Med Chem 2014; 57:2074-90. [DOI: 10.1021/jm401432c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Steven R. LaPlante
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
| | | | | | - Pierre Bonneau
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
| | - Mireille Cartier
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
| | - René Coulombe
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
| | - Araz Jakalian
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
| | | | | | | | - Ginette McKercher
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
| | - Peter White
- Departments of Chemistry and Biological Sciences, Boehringer Ingelheim (Canada) Ltd, R&D, 2100 Cunard Street, Laval, Québec H7S 2G5, Canada
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7
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Hepatitis C virus NS3 inhibitors: current and future perspectives. BIOMED RESEARCH INTERNATIONAL 2013; 2013:467869. [PMID: 24282816 PMCID: PMC3825274 DOI: 10.1155/2013/467869] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 09/08/2013] [Indexed: 12/24/2022]
Abstract
Currently, hepatitis C virus (HCV) infection is considered a serious health-care problem all over the world. A good number of direct-acting antivirals (DAAs) against HCV infection are in clinical progress including NS3-4A protease inhibitors, RNA-dependent RNA polymerase inhibitors, and NS5A inhibitors as well as host targeted inhibitors. Two NS3-4A protease inhibitors (telaprevir and boceprevir) have been recently approved for the treatment of hepatitis C in combination with standard of care (pegylated interferon plus ribavirin). The new therapy has significantly improved sustained virologic response (SVR); however, the adverse effects associated with this therapy are still the main concern. In addition to the emergence of viral resistance, other targets must be continually developed. One such underdeveloped target is the helicase portion of the HCV NS3 protein. This review article summarizes our current understanding of HCV treatment, particularly with those of NS3 inhibitors.
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Holler TP, Parkinson T, Pryde DC. Targeting the non-structural proteins of hepatitis C virus: beyond hepatitis C virus protease and polymerase. Expert Opin Drug Discov 2013; 4:293-314. [PMID: 23489127 DOI: 10.1517/17460440902762802] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Chronic hepatitis C virus (HCV) infection is a main cause of cirrhosis of the liver and hepatocellular carcinoma. The standard of care is a combination of pegylated interferon with ribavirin, a regimen that has undesirable side effects and is frequently ineffective. Compounds targeting HCV protease and polymerase are in late-stage clinical trials and have been extensively reviewed elsewhere. OBJECTIVE To review and evaluate the progress towards finding novel HCV antivirals targeting HCV proteins beyond the already precedented NS3 protease and NS5B polymerase. METHODS Searches of CAplus and Medline databases were combined with information from key conferences. This review focuses on NS2/3 serine protease, NS3 helicase activity and the non-structural proteins 4A, 4B and 5A. CONCLUSIONS Use of the replicon model of HCV replication and biochemical assays of specific targets has allowed screening of vast libraries of compounds, but resulted in clinical candidates from only NS4A and NS5A. The field is hindered by a lack of good chemical matter that inhibits the remaining enzymes from HCV, and a lack of understanding of the functions of non-structural proteins 4A, 4B and 5A in the replication of HCV.
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Affiliation(s)
- Tod P Holler
- Associate Research Fellow Pfizer Global Research and Development, Antiviral Biology, Ramsgate Road, Sandwich, Kent CT13 9NJ, UK +44 130 464 6387 ; +44 130 465 1819 ;
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9
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Tormos R, Bosca F. Antineoplastic tropolone derivatives as useful biomarkers: fluorescence enhancement upon binding to biological targets. RSC Adv 2013. [DOI: 10.1039/c3ra42122h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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11
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12
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Legrand-Abravanel F, Nicot F, Izopet J. New NS5B polymerase inhibitors for hepatitis C. Expert Opin Investig Drugs 2010; 19:963-75. [DOI: 10.1517/13543784.2010.500285] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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13
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Najda-Bernatowicz A, Krawczyk M, Stankiewicz-Drogoń A, Bretner M, Boguszewska-Chachulska AM. Studies on the anti-hepatitis C virus activity of newly synthesized tropolone derivatives: identification of NS3 helicase inhibitors that specifically inhibit subgenomic HCV replication. Bioorg Med Chem 2010; 18:5129-36. [PMID: 20579888 DOI: 10.1016/j.bmc.2010.05.066] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Revised: 05/21/2010] [Accepted: 05/25/2010] [Indexed: 10/19/2022]
Abstract
We synthesized new tropolone derivatives substituted with cyclic amines: piperidine, piperazine or pyrrolidine. The most active anti-helicase compound (IC50=3.4 microM), 3,5,7-tri[(4'-methylpiperazin-1'-yl)methyl]tropolone (2), inhibited RNA replication by 50% at 46.9 microM (EC50) and exhibited the lowest cytotoxicity (CC50)>1 mM resulting in a selectivity index (SI=CC50/EC50)>21. The most efficient replication inhibitor, 3,5,7-tri[(4'-methylpiperidin-1'-yl)methyl]tropolone (6), inhibited RNA replication with an EC50 of 32.0 microM and a SI value of 17.4, whereas 3,5,7-tri[(3'-methylpiperidin-1'-yl)methyl]tropolone (7) exhibited a slightly lower activity with an EC50 of 35.6 microM and a SI of 9.8.
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14
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Abstract
The development of techniques based on fluorescence has made it possible to create new types of assays that represent an advantageous alternative to old tests relying on radioactivity. Such a novel approach has been applied to develop a high-throughput assay to measure the helicase activity of the hepatitis C virus (HCV) NS3 protein and the inhibitory potential of several classes of compounds. The NS3 helicase is one of the most promising targets of anti-HCV-oriented screening of compounds due to the urgent need for more effective and tolerable drugs. The 96- or 384-well microplate assay that we developed is based on the use of a quenched double-stranded DNA substrate labeled with a fluorophore (Cy3 or FAM) and with a Black Hole Quencher 1 or 2. It allows for direct (real-time) measurements of substrate unwinding and inhibition of unwinding by anti-helicase compounds. After a few modifications of buffers and assay conditions this method can be applied to various variants of HCV helicase and other proteins with helicase activities.
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15
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Stankiewicz-Drogoń A, Dörner B, Erker T, Boguszewska-Chachulska AM. Synthesis of new acridone derivatives, inhibitors of NS3 helicase, which efficiently and specifically inhibit subgenomic HCV replication. J Med Chem 2010; 53:3117-26. [PMID: 20337460 DOI: 10.1021/jm901741p] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new goup of acridone derivatives, obtained by reaction of acridone-4-carboxylic acid derivatives with aromatic amines, was tested to determine the inhibitory properties toward the NS3 helicase of hepatitis C virus (HCV). Six compounds inhibited the NS3 helicase at low concentrations (IC(50) from 1.5 to 20 microM). The acridone derivatives probably act via intercalation into double-stranded nucleic acids with a strong specificity for double-stranded RNA, although an interaction with the enzyme cannot be excluded. Testing in the subgenomic HCV replicon system revealed that compounds 10 and 13 are efficient RNA replication inhibitors, with EC(50) of 3.5 and 1 microM and therapeutic indexes of >28 and 20, respectively. Compound 16, with EC(50) < 1 microM and TI > 1000, is extremely specific and practically noncytotoxic at the concentrations tested, proving that the acridone derivatives may be regarded as potential antiviral agents. Although the mechanism of action of 16 in the replicon system remains unclear, it is the key lead compound for further development of anti-HCV drugs.
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16
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Delang L, Coelmont L, Neyts J. Antiviral therapy for hepatitis C virus: beyond the standard of care. Viruses 2010; 2:826-866. [PMID: 21994657 PMCID: PMC3185663 DOI: 10.3390/v2040826] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 03/09/2010] [Accepted: 03/17/2010] [Indexed: 02/06/2023] Open
Abstract
Hepatitis C virus (HCV) represents a major health burden, with an estimated 180 million chronically infected individuals worldwide. These patients are at increased risk of developing liver cirrhosis and hepatocellular carcinoma. Infection with HCV is the leading cause of liver transplantation in the Western world. Currently, the standard of care (SoC) consists of pegylated interferon alpha (pegIFN-α) and ribavirin (RBV). However this therapy has a limited efficacy and is associated with serious side effects. Therefore more tolerable, highly potent inhibitors of HCV replication are urgently needed. Both Specifically Targeted Antiviral Therapy for HCV (STAT-C) and inhibitors that are believed to interfere with the host-viral interaction are discussed.
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Affiliation(s)
| | | | - Johan Neyts
- Rega Institute for Medical Research, KULeuven, Minderbroedersstraat 10, 3000 Leuven, Belgium; E-Mails: (L.D.); (L.C.)
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17
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Koufaki M, Theodorou E, Alexi X, Nikoloudaki F, Alexis MN. Synthesis of tropolone derivatives and evaluation of their in vitro neuroprotective activity. Eur J Med Chem 2010; 45:1107-12. [DOI: 10.1016/j.ejmech.2009.12.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 07/30/2009] [Accepted: 12/03/2009] [Indexed: 11/28/2022]
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Real-time monitoring of RNA helicase activity using fluorescence resonance energy transfer in vitro. Biochem Biophys Res Commun 2010; 393:131-6. [PMID: 20117090 DOI: 10.1016/j.bbrc.2010.01.100] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Accepted: 01/23/2010] [Indexed: 11/20/2022]
Abstract
We have developed a continuous fluorescence assay based on fluorescence resonance energy transfer (FRET) for the monitoring of RNA helicase activity in vitro. The assay is tested using the hepatitis C virus (HCV) NS3 helicase as a model. We prepared a double-stranded RNA (dsRNA) substrate with a 5' fluorophore-labeled strand hybridized to a 3' quencher-labeled strand. When the dsRNA is unwound by helicase, the fluorescence of the fluorophore is emitted following the separation of the strands. Unlike in conventional gel-based assays, this new assay eliminates the complex and time-consuming steps, and can be used to simply measure the real-time kinetics in a single helicase reaction. Our results demonstrate that Alexa Fluor 488 and BHQ1 are an effective fluorophore-quencher pair, and this assay is suitable for the quantitative measurement of the RNA helicase activity of HCV NS3. Moreover, we found that several extracts of marine organisms exhibited different inhibitory effects on the RNA and DNA helicase activities of HCV NS3. We propose that this assay will be useful for monitoring the detailed kinetics of RNA unwinding mechanisms and screening RNA helicase inhibitors at high throughput.
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Quer J, Buti M, Cubero M, Guardia J, Esteban R, Esteban JI. New strategies for the treatment of hepatitis C virus infection and implications of resistance to new direct-acting antiviral agents. Infect Drug Resist 2010; 3:133-45. [PMID: 21694902 PMCID: PMC3108733 DOI: 10.2147/idr.s7136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Indexed: 12/22/2022] Open
Abstract
Persistent hepatitis C virus (HCV) infection is a leading cause of chronic hepatitis, cirrhosis, and hepatocellular carcinoma and the major indication for liver transplantation in adults. Current standard of care treatment (SOC) with pegylated-interferon-α 2 and ribavirin (RBV) has a limited efficacy and is associated with significant side effects frequently associated with poor compliance or treatment discontinuation, requiring specialized and frequent monitoring. To overcome the limited efficacy of SOC, more than 50 direct-acting antiviral agents (DAA) designed to target viral-encoded proteins essential in the HCV life cycle are currently under development. The rapid selection of resistant mutants associated with the quasispecies nature of HCV with high mutation and replication rates is one of the main challenges for the new HCV therapies. Predictive host and viral factors together with combination of DAAs with or without IFN and/or RBV need to be accurately evaluated to design the most effective individualized treatment strategy within the shortest time interval and with minimum side effects.
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Affiliation(s)
- Josep Quer
- Liver Unit, Internal Medicine Hospital Universitari Vall d'Hebron, Institut de Recerca (VHIR), Barcelona, Spain
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21
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Li Y, Chang M, Sun M, Li W, Gao W. Synthesis of Novel Bromo-substituted Flavone-like Troponoid Compounds from Oxidation Cyclization of 3-Cinnamoyl-5,7-dibromotropolones Using I2/DMSO/H2SO4System. CHINESE J CHEM 2009. [DOI: 10.1002/cjoc.200990348] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Belon CA, Frick DN. Helicase inhibitors as specifically targeted antiviral therapy for hepatitis C. Future Virol 2009; 4:277-293. [PMID: 20161209 PMCID: PMC2714653 DOI: 10.2217/fvl.09.7] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The hepatitis C virus (HCV) leads to chronic liver disease and affects more than 2% of the world's population. Complications of the disease include fibrosis, cirrhosis and hepatocellular carcinoma. Current therapy for chronic HCV infection, a combination of ribavirin and pegylated IFN-alpha, is expensive, causes profound side effects and is only moderately effective against several common HCV strains. Specifically targeted antiviral therapy for hepatitis C (STAT-C) will probably supplement or replace present therapies. Leading compounds for STAT-C target the HCV nonstructural (NS)5B polymerase and NS3 protease, however, owing to the constant threat of viral resistance, other targets must be continually developed. One such underdeveloped target is the helicase domain of the HCV NS3 protein. The HCV helicase uses energy derived from ATP hydrolysis to separate based-paired RNA or DNA. This article discusses unique features of the HCV helicase, recently discovered compounds that inhibit HCV helicase catalyzed reactions and HCV cellular replication, and new methods to monitor helicase action in a high-throughput format.
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Affiliation(s)
- Craig A Belon
- New York Medical College, Department of Biochemistry & Molecular Biology, Valhalla, NY 10595, USA, Tel.: +1 914 594 3537; Fax: +1 914 594 4058;
| | - David N Frick
- New York Medical College, Department of Biochemistry & Molecular Biology, Valhalla, NY 10595, USA, Tel.: +1 914 594 4190; Fax: +1 914 594 4058;
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Hill TN, Steyl G. Dicarbon-yl[2-hydr-oxy-3,5,7-tris-(mor-pho-linomethyl)cyclo-hepta-2,4,6-trien-onato(1-)-κO,O]rhodium(I). Acta Crystallogr Sect E Struct Rep Online 2008; 64:m1580-1. [PMID: 21581182 PMCID: PMC2960118 DOI: 10.1107/s160053680803780x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Accepted: 11/14/2008] [Indexed: 11/29/2022]
Abstract
In the title compound, [Rh(C(22)H(32)N(3)O(5))(CO)(2)], the Rh(I) atom is coordinated by two carbonyl ligands and two tropolonate O atoms in a distorted square-planar geometry. It is an example of a new type of tropolone derivative that has not been characterized via solid-state methods. Weak intra-molecular C-H⋯N and inter-molecular C-H⋯O hydrogen bonds, and π-π stacking inter-actions between the tropolone rings [centroid-centroid distance = 3.590 (8) Å] are observed in the crystal structure.
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Affiliation(s)
- Tania N. Hill
- Department of Chemistry, University of the Free State, Bloemfontein 9300, South Africa
| | - G. Steyl
- Department of Chemistry, University of the Free State, Bloemfontein 9300, South Africa
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24
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Belon CA, Frick DN. Monitoring helicase activity with molecular beacons. Biotechniques 2008; 45:433-40, 442. [PMID: 18855770 DOI: 10.2144/000112834] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A high-throughput, fluorescence-based helicase assay using molecular beacons is described. The assay is tested using the NS3 helicase encoded by the hepatitis C virus (HCV) and is shown to accurately monitor helicase action on both DNA and RNA. In the assay, a ssDNA oligonucleotide molecular beacon, featuring a fluorescent moiety attached to one end and a quencher attached to the other, is annealed to a second longer DNA or RNA oligonucleotide. Upon strand separation by a helicase and ATP, the beacon strand forms an intramolecular hairpin that brings the tethered fluorescent and quencher molecules into juxtaposition, quenching fluorescence. Unlike currently available real-time helicase assays, the molecular beacon-based helicase assay is irreversible. As such, it does not require the addition of extra DNA strands to prevent products from re-annealing. Several variants of the new assay are described and experimentally verified using both Cy3 and Cy5 beacons, including one based on a sequence from the HCV genome. The HCV genome-based molecular beacon helicase assay is used to demonstrate how such an assay can be used in high-throughput screens and to analyze HCV helicase inhibitors.
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Affiliation(s)
- Craig A Belon
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
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25
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Stankiewicz-Drogon A, Palchykovska LG, Kostina VG, Alexeeva IV, Shved AD, Boguszewska-Chachulska AM. New acridone-4-carboxylic acid derivatives as potential inhibitors of hepatitis C virus infection. Bioorg Med Chem 2008; 16:8846-52. [PMID: 18801660 DOI: 10.1016/j.bmc.2008.08.074] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 08/22/2008] [Accepted: 08/28/2008] [Indexed: 12/11/2022]
Abstract
A new class of compounds--acridone derivatives--was tested using the direct fluorometric helicase activity assay to determine the inhibitory properties of the derivatives towards the NS3 helicase of Hepatitis C virus (HCV). The compounds were also tested as putative transcription inhibitors of in vitro transcription based on the DNA-dependent T7 RNA polymerase. Most of the acridone derivatives tested were transcription inhibitors; however, only four of them inhibited the NS3 helicase at low concentrations (IC(50) from 3 microM to 20 microM) and were therefore selected for further studies on the mechanism of inhibition. The acridone derivatives probably act via intercalation into double-stranded nucleic acids but they may also interact directly with viral enzymes. Selected carboxamides were tested in the subgenomic HCV replicon system. Two of the compounds: N-(pyridin-4-yl)-amide and N-(pyridin-2-yl)-amide of acridone-4-carboxylic acid are efficient RNA replication inhibitors with selectivity indexes of 19.4 and 40.5, respectively, proving that the acridone derivatives may be regarded as potential antiviral agents.
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26
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NS3 Peptide, a novel potent hepatitis C virus NS3 helicase inhibitor: its mechanism of action and antiviral activity in the replicon system. Antimicrob Agents Chemother 2007; 52:393-401. [PMID: 18039921 DOI: 10.1128/aac.00961-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hepatitis C virus (HCV) chronic infections represent one of the major and still unresolved health problems because of low efficiency and high cost of current therapy. Therefore, our studies centered on a viral protein, the NS3 helicase, whose activity is indispensable for replication of the viral RNA, and on its peptide inhibitor that corresponds to a highly conserved arginine-rich sequence of domain 2 of the helicase. The NS3 peptide (p14) was expressed in bacteria. Its 50% inhibitory activity in a fluorometric helicase assay corresponded to 725 nM, while the ATPase activity of NS3 was not affected. Nuclear magnetic resonance (NMR) studies of peptide-protein interactions using the relaxation filtering technique revealed that p14 binds directly to the full-length helicase and its separately expressed domain 1 but not to domain 2. Changes in the NMR chemical shift of backbone amide nuclei ((1)H and (15)N) of domain 1 or p14, measured during complex formation, were used to identify the principal amino acids of both domain 1 and the peptide engaged in their interaction. In the proposed interplay model, p14 contacts the clefts between domains 1 and 2, as well as between domains 1 and 3, preventing substrate binding. This interaction is strongly supported by cross-linking experiments, as well as by kinetic studies performed using a fluorometric assay. The antiviral activity of p14 was tested in a subgenomic HCV replicon assay that showed that the peptide at micromolar concentrations can reduce HCV RNA replication.
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Borowski P, Lang M, Haag A, Baier A. Tropolone and its derivatives as inhibitors of the helicase activity of hepatitis C virus nucleotide triphosphatase/helicase. Antivir Chem Chemother 2007; 18:103-9. [PMID: 17542155 DOI: 10.1177/095632020701800206] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In this report, we demonstrate the interaction of the non-structural protein 3 (NS3) of hepatitis C virus (HCV) with alkaloide tropolone (2-hydroxy-2,4,6-heptatriene-1-one) and its derivatives. The compounds were biochemically screened separately against the ATPase and helicase activities of HCV NS3. In the investigations presented, alkaIoide tropolone and its derivatives significantly inhibited the helicase activity of the viral protein when using a DNA substrate, with 50% inhibitory concentration values within a low micromolar range. The results using the RNA substrate were unexpected--none of the tropolone derivatives excerted any modulating influence towards the unwinding activity. Surprisingly, no influence of the nucleoside triphosphatase (NTPase) turnover was observed. Evidence is presented confirming that these compounds do not act by blocking the NTP-binding site, but by occupying an additional allosteric regulatory site. Further mechanisms of action, particularly of some of the derivatives, are discussed.
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Affiliation(s)
- Peter Borowski
- Department of Molecular Biology, Institute of Environmental Protection, John Paul II Catholic University of Lublin, Lublin, Poland.
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Abstract
Helicases are a ubiquitous class of enzymes involved in nearly all aspects of DNA and RNA metabolism. Despite recent progress in understanding their mechanism of action, limited resolution has left inaccessible the detailed mechanisms by which these enzymes couple the rearrangement of nucleic acid structures to the binding and hydrolysis of ATP. Observing individual mechanistic cycles of these motor proteins is central to understanding their cellular functions. Here we follow in real time, at a resolution of two base pairs and 20 ms, the RNA translocation and unwinding cycles of a hepatitis C virus helicase (NS3) monomer. NS3 is a representative superfamily-2 helicase essential for viral replication, and therefore a potentially important drug target. We show that the cyclic movement of NS3 is coordinated by ATP in discrete steps of 11 +/- 3 base pairs, and that actual unwinding occurs in rapid smaller substeps of 3.6 +/- 1.3 base pairs, also triggered by ATP binding, indicating that NS3 might move like an inchworm. This ATP-coupling mechanism is likely to be applicable to other non-hexameric helicases involved in many essential cellular functions. The assay developed here should be useful in investigating a broad range of nucleic acid translocation motors.
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Affiliation(s)
- David N Frick
- Department of Biochemistry & Molecular Biology, New York Medical College, Valhalla, NY, USA
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