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Rabie AM, Eltayb WA. Potent Dual Polymerase/Exonuclease Inhibitory Activities of Antioxidant Aminothiadiazoles Against the COVID-19 Omicron Virus: A Promising In Silico/In Vitro Repositioning Research Study. Mol Biotechnol 2024; 66:592-611. [PMID: 36690820 PMCID: PMC9870775 DOI: 10.1007/s12033-022-00551-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Accepted: 08/10/2022] [Indexed: 01/25/2023]
Abstract
Recently, natural and synthetic nitrogenous heterocyclic antivirals topped the scene as first choices for the treatment of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and their accompanying disease, the coronavirus disease 2019 (COVID-19). Meanwhile, the mysterious evolution of a new strain of SARS-CoV-2, the Omicron variant and its sublineages, caused a new defiance in the continual COVID-19 battle. Hitting the two principal coronaviral-2 multiplication enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) synchronously using the same ligand is a highly effective novel dual pathway to hinder SARS-CoV-2 reproduction and stop COVID-19 progression irrespective of the SARS-CoV-2 variant type since RdRps and ExoNs are widely conserved among all SARS-CoV-2 strains. Herein, the present computational/biological study screened our previous small libraries of nitrogenous heterocyclic compounds, searching for the most ideal drug candidates predictably able to efficiently act through this double approach. Theoretical filtration gave rise to three promising antioxidant nitrogenous heterocyclic compounds of the 1,3,4-thiadiazole type, which are CoViTris2022, Taroxaz-26, and ChloViD2022. Further experimental evaluation proved for the first time, utilizing the in vitro anti-RdRp/ExoN and anti-SARS-CoV-2 bioassays, that ChloViD2022, CoViTris2022, and Taroxaz-26 could effectively inhibit the replication of the new virulent strains of SARS-CoV-2 with extremely minute in vitro anti-RdRp and anti-SARS-CoV-2 EC50 values of 0.17 and 0.41 μM for ChloViD2022, 0.21 and 0.69 μM for CoViTris2022, and 0.23 and 0.73 μM for Taroxaz-26, respectively, transcending the anti-COVID-19 drug molnupiravir. The preliminary in silico outcomes greatly supported these biochemical results, proposing that the three molecules potently strike the key catalytic pockets of the SARS-CoV-2 (Omicron variant) RdRp's and ExoN's vital active sites. Moreover, the idealistic pharmacophoric hallmarks of CoViTris2022, Taroxaz-26, and ChloViD2022 molecules relatively make them typical dual-action inhibitors of SARS-CoV-2 replication and proofreading, with their highly flexible structures open for various kinds of chemical derivatization. To cut it short, the present pivotal findings of this comprehensive work disclosed the promising repositioning potentials of the three 2-aminothiadiazoles, CoViTris2022, Taroxaz-26, and ChloViD2022, to successfully interfere with the crucial biological interactions of the coronaviral-2 polymerase/exoribonuclease with the four principal RNA nucleotides, and, as a result, cure COVID-19 infection, encouraging us to rapidly start the three drugs' broad preclinical/clinical anti-COVID-19 evaluations.
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Affiliation(s)
- Amgad M Rabie
- Dr. Amgad Rabie's Research Lab. for Drug Discovery (DARLD), Mansoura City, Mansoura, 35511, Dakahlia Governorate, Egypt.
- Head of Drug Discovery & Clinical Research Department, Dikernis General Hospital (DGH), Magliss El-Madina Street, Dikernis City, Dikernis, 35744, Dakahlia Governorate, Egypt.
| | - Wafa A Eltayb
- Biotechnology Department, Faculty of Science and Technology, Shendi University, Shendi, Nher Anile, Sudan.
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2
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El Hassab MA, Eldehna WM, Al-Rashood ST, Alharbi A, Eskandrani RO, Alkahtani HM, Elkaeed EB, Abou-Seri SM. Multi-stage structure-based virtual screening approach towards identification of potential SARS-CoV-2 NSP13 helicase inhibitors. J Enzyme Inhib Med Chem 2022; 37:563-572. [PMID: 35012384 PMCID: PMC8757614 DOI: 10.1080/14756366.2021.2022659] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 11/24/2022] Open
Abstract
On account of its crucial role in the virus life cycle, SARS-COV-2 NSP13 helicase enzyme was exploited as a promising target to identify a novel potential inhibitor using multi-stage structure-based drug discovery approaches. Firstly, a 3D pharmacophore was generated based on the collected data from a protein-ligand interaction fingerprint (PLIF) study using key interactions between co-crystallised fragments and the NSP13 helicase active site. The ZINC database was screened through the generated 3D-pharmacophore retrieving 13 potential hits. All the retrieved hits exceeded the benchmark score of the co-crystallised fragments at the molecular docking step and the best five-hit compounds were selected for further analysis. Finally, a combination between molecular dynamics simulations and MM-PBSA based binding free energy calculations was conducted on the best hit (compound FWM-1) bound to NSP13 helicase enzyme, which identified FWM-1 as a potential potent NSP13 helicase inhibitor with binding free energy equals -328.6 ± 9.2 kcal/mol.
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Affiliation(s)
- Mahmoud A. El Hassab
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, King Salman International University (KSIU), Ras Sudr, Egypt
| | - Wagdy M. Eldehna
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Kafrelsheikh University, Kafrelsheikh, Egypt
| | - Sara T. Al-Rashood
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Amal Alharbi
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Razan O. Eskandrani
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Hamad M. Alkahtani
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Eslam B. Elkaeed
- Department of Pharmaceutical Sciences, College of Pharmacy, AlMaarefa University, Riyadh, Saudi Arabia
| | - Sahar M. Abou-Seri
- Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Cairo University, Cairo, Egypt
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3
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Ahmed-Belkacem R, Hausdorff M, Delpal A, Sutto-Ortiz P, Colmant AMG, Touret F, Ogando NS, Snijder EJ, Canard B, Coutard B, Vasseur JJ, Decroly E, Debart F. Potent Inhibition of SARS-CoV-2 nsp14 N7-Methyltransferase by Sulfonamide-Based Bisubstrate Analogues. J Med Chem 2022; 65:6231-6249. [PMID: 35439007 PMCID: PMC9045040 DOI: 10.1021/acs.jmedchem.2c00120] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Indexed: 12/15/2022]
Abstract
Enzymes involved in RNA capping of SARS-CoV-2 are essential for the stability of viral RNA, translation of mRNAs, and virus evasion from innate immunity, making them attractive targets for antiviral agents. In this work, we focused on the design and synthesis of nucleoside-derived inhibitors against the SARS-CoV-2 nsp14 (N7-guanine)-methyltransferase (N7-MTase) that catalyzes the transfer of the methyl group from the S-adenosyl-l-methionine (SAM) cofactor to the N7-guanosine cap. Seven compounds out of 39 SAM analogues showed remarkable double-digit nanomolar inhibitory activity against the N7-MTase nsp14. Molecular docking supported the structure-activity relationships of these inhibitors and a bisubstrate-based mechanism of action. The three most potent inhibitors significantly stabilized nsp14 (ΔTm ≈ 11 °C), and the best inhibitor demonstrated high selectivity for nsp14 over human RNA N7-MTase.
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Affiliation(s)
| | - Marcel Hausdorff
- IBMM,
University of Montpellier, CNRS, ENSCM, 34293 Montpellier, cedex 5, France
| | - Adrien Delpal
- AFMB,
University of Aix-Marseille, CNRS, 13288 Marseille, cedex 9, France
| | | | - Agathe M. G. Colmant
- IHU
Méditerranée Infection, Unité Virus Emergents, University of Aix-Marseille, IRD 190, INSERM 1207, 13005 Marseille, France
| | - Franck Touret
- IHU
Méditerranée Infection, Unité Virus Emergents, University of Aix-Marseille, IRD 190, INSERM 1207, 13005 Marseille, France
| | - Natacha S. Ogando
- Department
of Medical Microbiology, Leiden University
Medical Center, 2333 ZA Leiden, The Netherlands
| | - Eric J. Snijder
- Department
of Medical Microbiology, Leiden University
Medical Center, 2333 ZA Leiden, The Netherlands
| | - Bruno Canard
- AFMB,
University of Aix-Marseille, CNRS, 13288 Marseille, cedex 9, France
| | - Bruno Coutard
- IHU
Méditerranée Infection, Unité Virus Emergents, University of Aix-Marseille, IRD 190, INSERM 1207, 13005 Marseille, France
| | - Jean-Jacques Vasseur
- IBMM,
University of Montpellier, CNRS, ENSCM, 34293 Montpellier, cedex 5, France
| | - Etienne Decroly
- AFMB,
University of Aix-Marseille, CNRS, 13288 Marseille, cedex 9, France
| | - Françoise Debart
- IBMM,
University of Montpellier, CNRS, ENSCM, 34293 Montpellier, cedex 5, France
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Baddock HT, Brolih S, Yosaatmadja Y, Ratnaweera M, Bielinski M, Swift L, Cruz-Migoni A, Fan H, Keown JR, Walker AP, Morris G, Grimes J, Fodor E, Schofield C, Gileadi O, McHugh P. Characterization of the SARS-CoV-2 ExoN (nsp14ExoN-nsp10) complex: implications for its role in viral genome stability and inhibitor identification. Nucleic Acids Res 2022; 50:1484-1500. [PMID: 35037045 PMCID: PMC8860572 DOI: 10.1093/nar/gkab1303] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 12/15/2021] [Accepted: 12/22/2021] [Indexed: 12/19/2022] Open
Abstract
The SARS-CoV-2 coronavirus is the causal agent of the current global pandemic. SARS-CoV-2 belongs to an order, Nidovirales, with very large RNA genomes. It is proposed that the fidelity of coronavirus (CoV) genome replication is aided by an RNA nuclease complex, comprising the non-structural proteins 14 and 10 (nsp14-nsp10), an attractive target for antiviral inhibition. Our results validate reports that the SARS-CoV-2 nsp14-nsp10 complex has RNase activity. Detailed functional characterization reveals nsp14-nsp10 is a versatile nuclease capable of digesting a wide variety of RNA structures, including those with a blocked 3'-terminus. Consistent with a role in maintaining viral genome integrity during replication, we find that nsp14-nsp10 activity is enhanced by the viral RNA-dependent RNA polymerase complex (RdRp) consisting of nsp12-nsp7-nsp8 (nsp12-7-8) and demonstrate that this stimulation is mediated by nsp8. We propose that the role of nsp14-nsp10 in maintaining replication fidelity goes beyond classical proofreading by purging the nascent replicating RNA strand of a range of potentially replication-terminating aberrations. Using our developed assays, we identify drug and drug-like molecules that inhibit nsp14-nsp10, including the known SARS-CoV-2 major protease (Mpro) inhibitor ebselen and the HIV integrase inhibitor raltegravir, revealing the potential for multifunctional inhibitors in COVID-19 treatment.
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Affiliation(s)
- Hannah T Baddock
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Sanja Brolih
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Yuliana Yosaatmadja
- Centre for Medicines Discovery, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Malitha Ratnaweera
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Marcin Bielinski
- Chemistry Research Laboratory, Department of Chemistry and the Ineos Oxford Institute for Antimicrobial Research, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - Lonnie P Swift
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Abimael Cruz-Migoni
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Haitian Fan
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Jeremy R Keown
- Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, University of Oxford, Oxford OX3 7BN, UK
| | - Alexander P Walker
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Garrett M Morris
- Department of Statistics, University of Oxford, 24-29 St Giles', Oxford OX1 3LB, UK
| | - Jonathan M Grimes
- Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, University of Oxford, Oxford OX3 7BN, UK
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Didcot OX11 0DE, UK
| | - Ervin Fodor
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Christopher J Schofield
- Chemistry Research Laboratory, Department of Chemistry and the Ineos Oxford Institute for Antimicrobial Research, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - Opher Gileadi
- Centre for Medicines Discovery, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Peter J McHugh
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
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5
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Grodzki M, Bluhm AP, Schaefer M, Tagmount A, Russo M, Sobh A, Rafiee R, Vulpe CD, Karst SM, Norris MH. Genome-scale CRISPR screens identify host factors that promote human coronavirus infection. Genome Med 2022; 14:10. [PMID: 35086559 PMCID: PMC8792531 DOI: 10.1186/s13073-022-01013-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 01/10/2022] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND The COVID-19 pandemic has resulted in 275 million infections and 5.4 million deaths as of December 2021. While effective vaccines are being administered globally, there is still a great need for antiviral therapies as antigenically novel SARS-CoV-2 variants continue to emerge across the globe. Viruses require host factors at every step in their life cycle, representing a rich pool of candidate targets for antiviral drug design. METHODS To identify host factors that promote SARS-CoV-2 infection with potential for broad-spectrum activity across the coronavirus family, we performed genome-scale CRISPR knockout screens in two cell lines (Vero E6 and HEK293T ectopically expressing ACE2) with SARS-CoV-2 and the common cold-causing human coronavirus OC43. Gene knockdown, CRISPR knockout, and small molecule testing in Vero, HEK293, and human small airway epithelial cells were used to verify our findings. RESULTS While we identified multiple genes and functional pathways that have been previously reported to promote human coronavirus replication, we also identified a substantial number of novel genes and pathways. The website https://sarscrisprscreens.epi.ufl.edu/ was created to allow visualization and comparison of SARS-CoV2 CRISPR screens in a uniformly analyzed way. Of note, host factors involved in cell cycle regulation were enriched in our screens as were several key components of the programmed mRNA decay pathway. The role of EDC4 and XRN1 in coronavirus replication in human small airway epithelial cells was verified. Finally, we identified novel candidate antiviral compounds targeting a number of factors revealed by our screens. CONCLUSIONS Overall, our studies substantiate and expand the growing body of literature focused on understanding key human coronavirus-host cell interactions and exploit that knowledge for rational antiviral drug development.
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Affiliation(s)
- Marco Grodzki
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Andrew P Bluhm
- Department of Geography, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Moritz Schaefer
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Abderrahmane Tagmount
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Max Russo
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
- Present address: Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA
| | - Amin Sobh
- Univeristy of Florida Heath Cancer Center, University of Florida, Gainesville, FL, USA
| | - Roya Rafiee
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Chris D Vulpe
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Stephanie M Karst
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL, USA.
| | - Michael H Norris
- Department of Geography, College of Liberal Arts and Sciences, University of Florida, Gainesville, FL, USA.
- Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
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6
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Basu S, Mak T, Ulferts R, Wu M, Deegan T, Fujisawa R, Tan KW, Lim CT, Basier C, Canal B, Curran JF, Drury LS, McClure AW, Roberts EL, Weissmann F, Zeisner TU, Beale R, Cowling VH, Howell M, Labib K, Diffley JF. Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of Nsp14 RNA cap methyltransferase. Biochem J 2021; 478:2481-2497. [PMID: 34198328 PMCID: PMC8286817 DOI: 10.1042/bcj20210219] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 05/05/2021] [Accepted: 05/10/2021] [Indexed: 12/15/2022]
Abstract
The COVID-19 pandemic has presented itself as one of the most critical public health challenges of the century, with SARS-CoV-2 being the third member of the Coronaviridae family to cause a fatal disease in humans. There is currently only one antiviral compound, remdesivir, that can be used for the treatment of COVID-19. To identify additional potential therapeutics, we investigated the enzymatic proteins encoded in the SARS-CoV-2 genome. In this study, we focussed on the viral RNA cap methyltransferases, which play key roles in enabling viral protein translation and facilitating viral escape from the immune system. We expressed and purified both the guanine-N7 methyltransferase nsp14, and the nsp16 2'-O-methyltransferase with its activating cofactor, nsp10. We performed an in vitro high-throughput screen for inhibitors of nsp14 using a custom compound library of over 5000 pharmaceutical compounds that have previously been characterised in either clinical or basic research. We identified four compounds as potential inhibitors of nsp14, all of which also showed antiviral capacity in a cell-based model of SARS-CoV-2 infection. Three of the four compounds also exhibited synergistic effects on viral replication with remdesivir.
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Affiliation(s)
- Souradeep Basu
- Cell Cycle Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Tiffany Mak
- Cell Cycle Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Rachel Ulferts
- Cell Biology of Infection Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Mary Wu
- High Throughput Screening, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Tom Deegan
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Ryo Fujisawa
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Kang Wei Tan
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Chew Theng Lim
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Clovis Basier
- Cell Cycle Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Berta Canal
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Joseph F. Curran
- Cell Cycle Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Lucy S. Drury
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Allison W. McClure
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Emma L. Roberts
- Cell Cycle Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Florian Weissmann
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Theresa U. Zeisner
- Cell Cycle Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Rupert Beale
- Cell Biology of Infection Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Victoria H. Cowling
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Michael Howell
- High Throughput Screening, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Karim Labib
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - John F.X. Diffley
- Chromosome Replication Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
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7
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Canal B, McClure AW, Curran JF, Wu M, Ulferts R, Weissmann F, Zeng J, Bertolin AP, Milligan JC, Basu S, Drury LS, Deegan TD, Fujisawa R, Roberts EL, Basier C, Labib K, Beale R, Howell M, Diffley JF. Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of nsp14/nsp10 exoribonuclease. Biochem J 2021; 478:2445-2464. [PMID: 34198326 PMCID: PMC8286829 DOI: 10.1042/bcj20210198] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/05/2021] [Accepted: 05/10/2021] [Indexed: 01/18/2023]
Abstract
SARS-CoV-2 is a coronavirus that emerged in 2019 and rapidly spread across the world causing a deadly pandemic with tremendous social and economic costs. Healthcare systems worldwide are under great pressure, and there is an urgent need for effective antiviral treatments. The only currently approved antiviral treatment for COVID-19 is remdesivir, an inhibitor of viral genome replication. SARS-CoV-2 proliferation relies on the enzymatic activities of the non-structural proteins (nsp), which makes them interesting targets for the development of new antiviral treatments. With the aim to identify novel SARS-CoV-2 antivirals, we have purified the exoribonuclease/methyltransferase (nsp14) and its cofactor (nsp10) and developed biochemical assays compatible with high-throughput approaches to screen for exoribonuclease inhibitors. We have screened a library of over 5000 commercial compounds and identified patulin and aurintricarboxylic acid (ATA) as inhibitors of nsp14 exoribonuclease in vitro. We found that patulin and ATA inhibit replication of SARS-CoV-2 in a VERO E6 cell-culture model. These two new antiviral compounds will be valuable tools for further coronavirus research as well as potentially contributing to new therapeutic opportunities for COVID-19.
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Affiliation(s)
- Berta Canal
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Allison W. McClure
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Joseph F. Curran
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Mary Wu
- High Throughput Screening, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Rachel Ulferts
- Cell Biology of Infection Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Florian Weissmann
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Jingkun Zeng
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Agustina P. Bertolin
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Jennifer C. Milligan
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Souradeep Basu
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Lucy S. Drury
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Tom D. Deegan
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Ryo Fujisawa
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Emma L. Roberts
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Clovis Basier
- Cell Cycle Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Karim Labib
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life Sciences, University of Dundee, Dundee DD1 5EH, U.K
| | - Rupert Beale
- Cell Biology of Infection Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - Michael Howell
- High Throughput Screening, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
| | - John F.X. Diffley
- Chromosome Replication Laboratory, the Francis Crick Institute, 1 Midland Road, London NW1 1AT, U.K
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8
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Pearson LA, Green CJ, Lin D, Petit AP, Gray DW, Cowling VH, Fordyce EA. Development of a High-Throughput Screening Assay to Identify Inhibitors of the SARS-CoV-2 Guanine-N7-Methyltransferase Using RapidFire Mass Spectrometry. SLAS Discov 2021; 26:749-756. [PMID: 33724070 PMCID: PMC7967019 DOI: 10.1177/24725552211000652] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 02/08/2021] [Accepted: 02/16/2021] [Indexed: 01/11/2023]
Abstract
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) represents a significant threat to human health. Despite its similarity to related coronaviruses, there are currently no specific treatments for COVID-19 infection, and therefore there is an urgent need to develop therapies for this and future coronavirus outbreaks. Formation of the cap at the 5' end of viral RNA has been shown to help coronaviruses evade host defenses. Nonstructural protein 14 (nsp14) is responsible for N7-methylation of the cap guanosine in coronaviruses. This enzyme is highly conserved among coronaviruses and is a bifunctional protein with both N7-methyltransferase and 3'-5' exonuclease activities that distinguish nsp14 from its human equivalent. Mutational analysis of SARS-CoV nsp14 highlighted its role in viral replication and translation efficiency of the viral genome. In this paper, we describe the characterization and development of a high-throughput assay for nsp14 utilizing RapidFire technology. The assay has been used to screen a library of 1771 Food and Drug Administration (FDA)-approved drugs. From this, we have validated nitazoxanide as a selective inhibitor of the methyltransferase activity of nsp14. Although modestly active, this compound could serve as a starting point for further optimization.
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Affiliation(s)
- Lesley-Anne Pearson
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, UK
| | - Charlotte J. Green
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, UK
| | - De Lin
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, UK
| | - Alain-Pierre Petit
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, UK
| | - David W. Gray
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, UK
| | - Victoria H. Cowling
- Centre for Gene Regulation and Expression, School of Life Sciences, University of Dundee, Dundee, UK
| | - Euan A.F. Fordyce
- Drug Discovery Unit, School of Life Sciences, University of Dundee, Dundee, UK
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9
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Ngwe Tun MM, Morita K, Ishikawa T, Urata S. The Antiviral Effect of the Chemical Compounds Targeting DED/EDh Motifs of the Viral Proteins on Lymphocytic Choriomeningitis Virus and SARS-CoV-2. Viruses 2021; 13:1220. [PMID: 34202565 PMCID: PMC8310078 DOI: 10.3390/v13071220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/14/2021] [Accepted: 06/23/2021] [Indexed: 01/01/2023] Open
Abstract
Arenaviruses and coronaviruses include several human pathogenic viruses, such as Lassa virus, Lymphocytic choriomeningitis virus (LCMV), SARS-CoV, MERS-CoV, and SARS-CoV-2. Although these viruses belong to different virus families, they possess a common motif, the DED/EDh motif, known as an exonuclease (ExoN) motif. In this study, proof-of-concept studies, in which the DED/EDh motif in these viral proteins, NP for arenaviruses, and nsp14 for coronaviruses, could be a drug target, were performed. Docking simulation studies between two structurally different chemical compounds, ATA and PV6R, and the DED/EDh motifs in these viral proteins indicated that these compounds target DED/EDh motifs. The concentration which exhibited modest cell toxicity was used with these compounds to treat LCMV and SARS-CoV-2 infections in two different cell lines, A549 and Vero 76 cells. Both ATA and PV6R inhibited the post-entry step of LCMV and SARS-CoV-2 infection. These studies strongly suggest that DED/EDh motifs in these viral proteins could be a drug target to combat two distinct viral families, arenaviruses and coronaviruses.
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Affiliation(s)
- Mya Myat Ngwe Tun
- Department of Virology, Institute of Tropical Medicine and Leading Program, Graduate School of Biomedical Science, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan; (M.M.N.T.); (K.M.)
| | - Kouichi Morita
- Department of Virology, Institute of Tropical Medicine and Leading Program, Graduate School of Biomedical Science, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan; (M.M.N.T.); (K.M.)
| | - Takeshi Ishikawa
- Department of Chemistry, Biotechnology and Chemical Engineering, Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065, Japan
| | - Shuzo Urata
- National Research Center for the Control and Prevention of Infectious Diseases (CCPID), Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
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10
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Ahmed-Belkacem R, Sutto-Ortiz P, Guiraud M, Canard B, Vasseur JJ, Decroly E, Debart F. Synthesis of adenine dinucleosides SAM analogs as specific inhibitors of SARS-CoV nsp14 RNA cap guanine-N7-methyltransferase. Eur J Med Chem 2020; 201:112557. [PMID: 32563813 PMCID: PMC7291971 DOI: 10.1016/j.ejmech.2020.112557] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 05/26/2020] [Accepted: 06/08/2020] [Indexed: 12/18/2022]
Abstract
The spreading of new viruses is known to provoke global human health threat. The current COVID-19 pandemic caused by the recently emerged coronavirus SARS-CoV-2 is one significant and unfortunate example of what the world will have to face in the future with emerging viruses in absence of appropriate treatment. The discovery of potent and specific antiviral inhibitors and/or vaccines to fight these massive outbreaks is an urgent research priority. Enzymes involved in the capping pathway of viruses and more specifically RNA N7- or 2′O-methyltransferases (MTases) are now admitted as potential targets for antiviral chemotherapy. We designed bisubstrate inhibitors by mimicking the transition state of the 2′-O-methylation of the cap RNA in order to block viral 2′-O MTases. This work resulted in the synthesis of 16 adenine dinucleosides with both adenosines connected by various nitrogen-containing linkers. Unexpectedly, all the bisubstrate compounds were barely active against 2′-O MTases of several flaviviruses or SARS-CoV but surprisingly, seven of them showed efficient and specific inhibition against SARS-CoV N7-MTase (nsp14) in the micromolar to submicromolar range. The most active nsp14 inhibitor identified is as potent as but particularly more specific than the broad-spectrum MTase inhibitor, sinefungin. Molecular docking suggests that the inhibitor binds to a pocket formed by the S-adenosyl methionine (SAM) and cap RNA binding sites, conserved among SARS-CoV nsp14. These dinucleoside SAM analogs will serve as starting points for the development of next inhibitors for SARS-CoV-2 nsp14 N7-MTase.
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Affiliation(s)
| | - Priscila Sutto-Ortiz
- AFMB, CNRS, Aix-Marseille University, UMR 7257, 163 Avenue de Luminy, Marseille, France
| | - Mathis Guiraud
- IBMM, CNRS, University of Montpellier, ENSCM, Montpellier, France
| | - Bruno Canard
- AFMB, CNRS, Aix-Marseille University, UMR 7257, 163 Avenue de Luminy, Marseille, France
| | | | - Etienne Decroly
- AFMB, CNRS, Aix-Marseille University, UMR 7257, 163 Avenue de Luminy, Marseille, France.
| | - Françoise Debart
- IBMM, CNRS, University of Montpellier, ENSCM, Montpellier, France.
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11
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Wood ER, Bledsoe R, Chai J, Daka P, Deng H, Ding Y, Harris-Gurley S, Kryn LH, Nartey E, Nichols J, Nolte RT, Prabhu N, Rise C, Sheahan T, Shotwell JB, Smith D, Tai V, Taylor JD, Tomberlin G, Wang L, Wisely B, You S, Xia B, Dickson H. The Role of Phosphodiesterase 12 (PDE12) as a Negative Regulator of the Innate Immune Response and the Discovery of Antiviral Inhibitors. J Biol Chem 2015; 290:19681-96. [PMID: 26055709 PMCID: PMC4528132 DOI: 10.1074/jbc.m115.653113] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 05/20/2015] [Indexed: 11/06/2022] Open
Abstract
2',5'-Oligoadenylate synthetase (OAS) enzymes and RNase-L constitute a major effector arm of interferon (IFN)-mediated antiviral defense. OAS produces a unique oligonucleotide second messenger, 2',5'-oligoadenylate (2-5A), that binds and activates RNase-L. This pathway is down-regulated by virus- and host-encoded enzymes that degrade 2-5A. Phosphodiesterase 12 (PDE12) was the first cellular 2-5A- degrading enzyme to be purified and described at a molecular level. Inhibition of PDE12 may up-regulate the OAS/RNase-L pathway in response to viral infection resulting in increased resistance to a variety of viral pathogens. We generated a PDE12-null cell line, HeLaΔPDE12, using transcription activator-like effector nuclease-mediated gene inactivation. This cell line has increased 2-5A levels in response to IFN and poly(I-C), a double-stranded RNA mimic compared with the parental cell line. Moreover, HeLaΔPDE12 cells were resistant to viral pathogens, including encephalomyocarditis virus, human rhinovirus, and respiratory syncytial virus. Based on these results, we used DNA-encoded chemical library screening to identify starting points for inhibitor lead optimization. Compounds derived from this effort raise 2-5A levels and exhibit antiviral activity comparable with the effects observed with PDE12 gene inactivation. The crystal structure of PDE12 complexed with an inhibitor was solved providing insights into the structure-activity relationships of inhibitor potency and selectivity.
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Affiliation(s)
| | | | - Jing Chai
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Philias Daka
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Hongfeng Deng
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Yun Ding
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | | | | | | | | | | | - Ninad Prabhu
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Cecil Rise
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Timothy Sheahan
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - J Brad Shotwell
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | - Vince Tai
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | | | | | | | - Shihyun You
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Bing Xia
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Hamilton Dickson
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
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12
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Moon SL, Anderson JR, Kumagai Y, Wilusz CJ, Akira S, Khromykh AA, Wilusz J. A noncoding RNA produced by arthropod-borne flaviviruses inhibits the cellular exoribonuclease XRN1 and alters host mRNA stability. RNA 2012; 18:2029-40. [PMID: 23006624 PMCID: PMC3479393 DOI: 10.1261/rna.034330.112] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 08/17/2012] [Indexed: 05/25/2023]
Abstract
All arthropod-borne flaviviruses generate a short noncoding RNA (sfRNA) from the viral 3' untranslated region during infection due to stalling of the cellular 5'-to-3' exonuclease XRN1. We show here that formation of sfRNA also inhibits XRN1 activity. Cells infected with Dengue or Kunjin viruses accumulate uncapped mRNAs, decay intermediates normally targeted by XRN1. XRN1 repression also resulted in the increased overall stability of cellular mRNAs in flavivirus-infected cells. Importantly, a mutant Kunjin virus that cannot form sfRNA but replicates to normal levels failed to affect host mRNA stability or XRN1 activity. Expression of sfRNA in the absence of viral infection demonstrated that sfRNA formation was directly responsible for the stabilization of cellular mRNAs. Finally, numerous cellular mRNAs were differentially expressed in an sfRNA-dependent fashion in a Kunjin virus infection. We conclude that flaviviruses incapacitate XRN1 during infection and dysregulate host mRNA stability as a result of sfRNA formation.
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Affiliation(s)
- Stephanie L. Moon
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA
| | - John R. Anderson
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Yutaro Kumagai
- Laboratory of Host Defense, Immunology Frontier Research Center, Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
| | - Carol J. Wilusz
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Shizuo Akira
- Laboratory of Host Defense, Immunology Frontier Research Center, Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
| | - Alexander A. Khromykh
- Australian Infectious Disease Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Jeffrey Wilusz
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA
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13
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Zimanyi CM, Ando N, Brignole EJ, Asturias FJ, Stubbe J, Drennan CL. Tangled up in knots: structures of inactivated forms of E. coli class Ia ribonucleotide reductase. Structure 2012; 20:1374-83. [PMID: 22727814 PMCID: PMC3459064 DOI: 10.1016/j.str.2012.05.009] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 05/16/2012] [Accepted: 05/17/2012] [Indexed: 11/19/2022]
Abstract
Ribonucleotide reductases (RNRs) provide the precursors for DNA biosynthesis and repair and are successful targets for anticancer drugs such as clofarabine and gemcitabine. Recently, we reported that dATP inhibits E. coli class Ia RNR by driving formation of RNR subunits into α4β4 rings. Here, we present the first X-ray structure of a gemcitabine-inhibited E. coli RNR and show that the previously described α4β4 rings can interlock to form an unprecedented (α4β4)2 megacomplex. This complex is also seen in a higher-resolution dATP-inhibited RNR structure presented here, which employs a distinct crystal lattice from that observed in the gemcitabine-inhibited case. With few reported examples of protein catenanes, we use data from small-angle X-ray scattering and electron microscopy to both understand the solution conditions that contribute to concatenation in RNRs as well as present a mechanism for the formation of these unusual structures.
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Affiliation(s)
- Christina M. Zimanyi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Nozomi Ando
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Edward J. Brignole
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139
| | | | - JoAnne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Catherine L. Drennan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139
- Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
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14
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Rymarquis LA, Souret FF, Green PJ. Evidence that XRN4, an Arabidopsis homolog of exoribonuclease XRN1, preferentially impacts transcripts with certain sequences or in particular functional categories. RNA 2011; 17:501-11. [PMID: 21224377 PMCID: PMC3039149 DOI: 10.1261/rna.2467911] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 11/30/2010] [Indexed: 05/19/2023]
Abstract
One of the major players controlling RNA decay is the cytoplasmic 5'-to-3' exoribonuclease, which is conserved among eukaryotic organisms. In Arabidopsis, the 5'-to-3' exoribonuclease XRN4 is involved in disease resistance, the response to ethylene, RNAi, and miRNA-mediated RNA decay. Curiously, XRN4 appears to display selectivity among its substrates because certain 3' cleavage products formed by miRNA-mediated decay, such as from ARF10 mRNA, accumulate in the xrn4 mutant, whereas others, such as from AGO1, do not. To examine the nature of this selectivity, transcripts that differentially accumulate in xrn4 were identified by combining PARE and Affymetrix arrays. Certain functional categories, such as stamen-associated proteins and hydrolases, were over-represented among transcripts decreased in xrn4, whereas transcripts encoding nuclear-encoded chloroplast-targeted proteins and nucleic acid-binding proteins were over-represented in transcripts increased in xrn4. To ascertain if RNA sequence influences the apparent XRN4 selectivity, a series of chimeric constructs was generated in which the miRNA-complementary sites and different portions of the surrounding sequences from AGO1 and ARF10 were interchanged. Analysis of the resulting transgenic plants revealed that the presence of a 150 nucleotide sequence downstream from the ARF10 miRNA-complementary site conferred strong accumulation of the 3' cleavage products in xrn4. In addition, sequence analysis of differentially accumulating transcripts led to the identification of 27 hexamer motifs that were over-represented in transcripts or miRNA-cleavage products accumulating in xrn4. Taken together, the data indicate that specific mRNA sequences, like those in ARF10, and mRNAs from select functional categories are attractive targets for XRN4-mediated decay.
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Affiliation(s)
- Linda A Rymarquis
- Department of Plant and Soil Sciences, University of Delaware, Delaware 19716, USA
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15
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Slomovic S, Schuster G. Stable PNPase RNAi silencing: its effect on the processing and adenylation of human mitochondrial RNA. RNA 2008; 14:310-323. [PMID: 18083837 PMCID: PMC2212247 DOI: 10.1261/rna.697308] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Accepted: 10/24/2007] [Indexed: 05/25/2023]
Abstract
Polynucleotide phosphorylase (PNPase) is a diverse enzyme, involved in RNA polyadenylation, degradation, and processing in prokaryotes and organelles. However, in human mitochondria, PNPase is located in the intermembrane space (IMS), where no mitochondrial RNA (mtRNA) is known to be present. In order to determine the nature and degree of its involvement in mtRNA metabolism, we stably silenced PNPase by establishing HeLa cell lines expressing PNPase short-hairpin RNA (shRNA). Processing and polyadenylation of mt-mRNAs were significantly affected, but, to different degrees in different genes. For instance, the stable poly(A) tails at the 3' ends of COX1 transcripts were abolished, while COX3 poly(A) tails remained unaffected and ND5 and ND3 poly(A) extensions increased in length. Despite the lack of polyadenylation at the 3' end, COX1 mRNA and protein accumulated to normal levels, as was the case for all 13 mt-encoded proteins. Interestingly, ATP depletion also altered poly(A) tail length, demonstrating that adenylation of mtRNA can be manipulated by indirect, environmental means and not solely by direct enzymatic activity. When both PNPase and the mitochondrial poly(A)-polymerase (mtPAP) were concurrently silenced, the mature 3' end of ND3 mRNA lacked poly(A) tails but retained oligo(A) extensions. Furthermore, in mtPAP-silenced cells, truncated adenylated COX1 molecules, considered to be degradation intermediates, were present but harbored significantly shorter tails. Together, these results suggest that an additional mitochondrial polymerase, yet to be identified, is responsible for the oligoadenylation of mtRNA and that PNPase, although located in the IMS, is involved, most likely by indirect means, in the processing and polyadenylation of mtRNA.
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Affiliation(s)
- Shimyn Slomovic
- Department of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel
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16
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Liu WF, Zhang A, He GJ, Yan YB. The R3H domain stabilizes poly(A)-specific ribonuclease by stabilizing the RRM domain. Biochem Biophys Res Commun 2007; 360:846-51. [PMID: 17624302 DOI: 10.1016/j.bbrc.2007.06.139] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Accepted: 06/28/2007] [Indexed: 11/29/2022]
Abstract
Poly(A)-specific ribonuclease (PARN), a key enzyme involved in eukaryotic mRNA decay, contains one catalytic domain and two RNA-binding domains. Here we found that at least one RNA-binding domain is required for the substrate binding, but not for the catalysis of PARN. The removal of the R3H domain led to a dramatic decrease in PARN stability and a change in the aggregation kinetic regime, while only minor effects were observed for the removal of the RRM domain or both RNA-binding domains. Thus the R3H domain might stabilize PARN by acting as a protector or intermolecular chaperone of the RRM domain.
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Affiliation(s)
- Wei-Feng Liu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China
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17
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Kong J, Liebhaber SA. A cell type-restricted mRNA surveillance pathway triggered by ribosome extension into the 3' untranslated region. Nat Struct Mol Biol 2007; 14:670-6. [PMID: 17572684 DOI: 10.1038/nsmb1256] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 04/27/2007] [Indexed: 11/09/2022]
Abstract
The accuracy of eukaryotic gene expression is monitored at multiple levels. Surveillance pathways have been identified that degrade messenger RNAs containing nonsense mutations, harboring stalled ribosomes or lacking termination codons. Here we report a previously uncharacterized surveillance pathway triggered by ribosome extension into the 3' untranslated region. This ribosome extension-mediated decay, REMD, accounts for marked repression of protein synthesis from a human alpha-globin gene containing a prevalent antitermination mutation. REMD can be mechanistically distinguished from other surveillance pathways by its functional linkage to accelerated deadenylation, by its independence from the NMD factor Upf1 and by cell-type restriction. This unusual pathway of mRNA surveillance is likely to act as a modifier of additional genetic defects and may reflect post-transcriptional controls particular to erythroid and other differentiated cell lineages.
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Affiliation(s)
- Jian Kong
- Department of Genetics and Department of Medicine, University of Pennsylvania School of Medicine, 415 Curie Blvd., CRB 430, Philadelphia, Pennsylvania 19104, USA
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18
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Liu WF, Zhang A, Cheng Y, Zhou HM, Yan YB. Effect of magnesium ions on the thermal stability of human poly(A)-specific ribonuclease. FEBS Lett 2007; 581:1047-52. [PMID: 17306797 DOI: 10.1016/j.febslet.2007.02.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Revised: 02/02/2007] [Accepted: 02/05/2007] [Indexed: 12/01/2022]
Abstract
Poly(A)-specific ribonuclease (PARN), a member of the DEDD family, is a key enzyme involved in the deadenylation of mRNA in higher eukaryotic cells. In this research, it was found that Mg(2+) could protect PARN against thermal inactivation by increasing the midpoint of inactivation and decreasing the inactivation rate. This protective effect was unique to Mg(2+) in a concentration-dependent manner. However, the thermal unfolding and aggregation was promoted by the addition of Mg(2+) at high temperatures. These results revealed that Mg(2+) might have dual effects on PARN stability: protecting the active site but endangering the overall structural stability.
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Affiliation(s)
- Wei-Feng Liu
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China
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19
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Abstract
A direct relationship exists between aging and increasing incidences of chronic diseases. In fact, with most age-associated diseases individuals manifest an underlying chronic inflammatory state as evidenced by local infiltration of inflammatory cells, such as macrophages, and higher circulatory levels of pro-inflammatory cytokines, complement components and adhesion molecules. Consequently, treatment with anti-inflammatory agents provide symptomatic relief to several aging-associated diseases, even as remote as Alzheimer's or Parkinson's disease, indicating that chronic inflammation may play a substantial role in the pathogenesis of these disease states. The molecular mechanisms underlying this chronic inflammatory condition during cellular senescence is presently unclear. Cellular damage by oxygen free radicals is a primary driving force for aging and increased activation of redox-regulated transcription factors, such as NF-kappaB that regulate the expression of pro-inflammatory molecules, has been documented in aged animals/individuals versus their young counterparts. Human polynucleotide phosphorylase (hPNPase(old-35)), a RNA degradation enzyme shown to be upregulated during differentiation and cellular senescence, may represent a molecular link between aging and its associated inflammation. hPNPase(old-35) promotes reactive oxygen species (ROS) production, activates the NF-kappaB pathway and initiates the production of pro-inflammatory cytokines, such as IL-6 and IL-8. In these contexts, inhibition of hPNPase(old-35) may represent a novel molecular target for intervening in aging-associated chronic diseases.
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Affiliation(s)
- Devanand Sarkar
- Department of Pathology, Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University Medical Center, New York, NY 10032, USA
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20
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Abstract
Poly(A)-specific ribonuclease (PARN) is a cap-interacting and poly(A)-specific 3'-exoribonuclease. Here we have investigated how the cap binding complex (CBC) affects human PARN activity. We showed that CBC, via its 80-kDa subunit (CBP80), inhibited PARN, suggesting that CBC can regulate mRNA deadenylation. The CBC-mediated inhibition of PARN was cap-independent, and in keeping with this, the CBP80 subunit alone inhibited PARN. Our data suggested a new function for CBC, identified CBC as a potential regulator of PARN, and emphasized the importance of communication between the two extreme ends of the mRNA as a key strategy to regulate mRNA degradation. Based on our data, we have proposed a model for CBC-mediated regulation of PARN, which relies on an interaction between CBP80 and PARN. Association of CBC with PARN might have importance in the regulated recruitment of PARN to the nonsense-mediated decay pathway during the pioneer round of translation.
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21
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Fujita Y, Kasuya A, Matsushita Y, Suga M, Kizuka M, Iijima Y, Ogita T. Structural elucidation of A-74528, an inhibitor for 2′,5′-phosphodiesterase isolated from Streptomyces sp. Bioorg Med Chem Lett 2005; 15:4317-21. [PMID: 16061376 DOI: 10.1016/j.bmcl.2005.06.047] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 06/14/2005] [Accepted: 06/15/2005] [Indexed: 10/25/2022]
Abstract
A-74528 (1) is a metabolite of Streptomyces sp. discovered in the screening for 2',5'-oligoadenylate phosphodiesterase inhibitors. The planar structure of 1 was mainly elucidated by NMR techniques including natural abundance INADEQUATE, and the relative configuration and the conformation were elucidated by the analyses of NOEs and assessment of dihedral angles predicted by QUANTA/CHARMm computations and coupling constants. It was proved that 1 is a highly fused polyketide with a side-chain branching site that never appeared before from the nature.
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Affiliation(s)
- Yoko Fujita
- Sankyo R&D Facility, Sankyo Co. Ltd., 2-58, Hiromachi 1-chome, Shinagawa-ku, Tokyo 140-8710, Japan
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Kubota K, Nakahara K, Ohtsuka T, Yoshida S, Kawaguchi J, Fujita Y, Ozeki Y, Hara A, Yoshimura C, Furukawa H, Haruyama H, Ichikawa K, Yamashita M, Matsuoka T, Iijima Y. Identification of 2'-phosphodiesterase, which plays a role in the 2-5A system regulated by interferon. J Biol Chem 2004; 279:37832-41. [PMID: 15231837 DOI: 10.1074/jbc.m400089200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 2-5A system is one of the major pathways for antiviral and antitumor functions that can be induced by interferons (IFNs). The 2-5A system is modulated by 5'-triphosphorylated, 2',5'-phosphodiester-linked oligoadenylates (2-5A), which are synthesized by 2',5'-oligoadenylate synthetases (2',5'-OASs), inactivated by 5'-phosphatase and completely degraded by 2'-phosphodiesterase (2'-PDE). Generated 2-5A activates 2-5A-dependent endoribonuclease, RNase L, which induces RNA degradation in cells and finally apoptosis. Although 2',5'-OASs and RNase L have been molecularly cloned and studied well, the identification of 2'-PDE has remained elusive. Here, we describe the first identification of 2'-PDE, the third key enzyme of the 2-5A system. We found a putative 2'-PDE band on SDS-PAGE by successive six-step chromatographies from ammonium sulfate precipitates of bovine liver and identified a partial amino acid sequence of the human 2'-PDE by mass spectrometry. Based on the full-length sequence of the human 2'-PDE obtained by in silico expressed sequence tag assembly, the gene was cloned by reverse transcription-PCR. The recombinant human 2'-PDE expressed in mammalian cells certainly cleaved the 2',5'-phosphodiester bond of 2-5A trimer and 2-5A analogs. Because no sequences with high homology to this human 2'-PDE were found, the human 2'-PDE was considered to be a unique enzyme without isoform. Suppression of 2'-PDE by a small interfering RNA and a 2'-PDE inhibitor resulted in significant reduction of viral replication, whereas overexpression of 2'-PDE protected cells from IFN-induced antiproliferative activity. These observations identify 2'-PDE as a key regulator of the 2-5A system and as a potential novel target for antiviral and antitumor treatments.
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Affiliation(s)
- Kazuishi Kubota
- Biomedical Research Laboratories, Sankyo Co., Ltd., 1-2-58, Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.
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23
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Abstract
Aminoglycosides are known to bind and perturb the function of catalytic RNA. Here we show that they also are potent inhibitors of protein-based catalysis using Escherichia coli Klenow polymerase (pol) and mammalian poly(A)-specific ribonuclease (PARN) as model enzymes. The inhibition was pH dependent and released in a competitive manner by Mg2+. Kinetic analysis showed that neomycin B behaved as a mixed noncompetitive inhibitor. Iron-mediated hydroxyl radical cleavage was used to show that neomycin B interfered with metal-ion binding in the active sites of both enzymes. Our analysis suggests a mechanism of inhibition where the aminoglycoside binds in the active site of the enzyme and thereby displaces catalytically important divalent metal ions. The potential causes of aminoglycoside toxicity and the usage of aminoglycosides to probe, characterize, and perturb metalloenzymes are discussed.
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Affiliation(s)
- Yan-Guo Ren
- Department of Cell and Molecular Biology, Uppsala University, SE-751 24 Uppsala, Sweden
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24
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Slobin LI. 5'-->3'-exoribonuclease from rabbit reticulocytes. Methods Enzymol 2002; 342:282-92. [PMID: 11586901 DOI: 10.1016/s0076-6879(01)42552-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Affiliation(s)
- L I Slobin
- Department of Biochemistry, University of Mississippi School of Medicine, Jackson, Mississippi 39216, USA
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25
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Affiliation(s)
- V J Cannistraro
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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26
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Villa T, Ceradini F, Bozzoni I. Identification of a novel element required for processing of intron-encoded box C/D small nucleolar RNAs in Saccharomyces cerevisiae. Mol Cell Biol 2000; 20:1311-20. [PMID: 10648617 PMCID: PMC85272 DOI: 10.1128/mcb.20.4.1311-1320.2000] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Processing of intron-encoded box C/D small nucleolar RNAs (snoRNAs) in metazoans through both the splicing-dependent and -independent pathways requires the conserved core motif formed by boxes C and D and the adjoining 5'-3'-terminal stem. By comparative analysis, we found that five out of six intron-encoded box C/D snoRNAs in yeast do not possess a canonical terminal stem. Instead, complementary regions within the flanking host intron sequences have been identified in all these cases. Here we show that these sequences are essential for processing of U18 and snR38 snoRNAs and that they compensate for the lack of a canonical terminal stem. We also show that the Rnt1p endonuclease, previously shown to be required for the processing of many snoRNAs encoded by monocistronic or polycistronic transcriptional units, is not required for U18 processing. Our results suggest a role of the complementary sequences in the early recognition of intronic snoRNA substrates and point out the importance of base pairing in favoring the communication between boxes C and D at the level of pre-snoRNA molecules for efficient assembly with snoRNP-specific factors.
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Affiliation(s)
- T Villa
- Istituto Pasteur, Fondazione Cenci-Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università di Roma "La Sapienza," 00185 Rome, Italy
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Cannistraro VJ, Kennell D. The reaction mechanism of ribonuclease II and its interaction with nucleic acid secondary structures. Biochim Biophys Acta 1999; 1433:170-87. [PMID: 10446370 DOI: 10.1016/s0167-4838(99)00136-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Ribonuclease II is a processive 3'- to 5'-exoribonuclease in Escherichia coli with two binding sites: a catalytic site associated with the first few 3'-nucleotides and an anchor site binding nucleotides approximately 15 to 25 from the 3'-end. When RNase II degrades single-stranded helical poly(C), the enzyme-substrate complex dissociates at discrete intervals of 12 nucleotides. RNase II stalled at the last rC of single-stranded 3'-(rC)(n)(dC)(m) oligonucleotides. The more residues released, the faster the stalled complex dissociated and the less it inhibited RNase II activity, i.e. the enzyme-substrate association weakened progressively. Using phosphodiesterase I (PDE I) as a probe, a method was developed to identify cytidine residues in (32)P-oligonucleotides interacting with a protein. PAGE bands corresponding to nucleotides 1-6 from the 3'-end were consistent with interaction at the catalytic site, and following a gap, bands approximately 15 to 25 from the 3'-end, with anchor site association. Both 3' and 5' binding were necessary to maintain the complex. Of most significance, the original anchor site nucleotides remained fixed at the anchor site while the 3'-end was pulled, or threaded, through the catalytic site, i.e. the substrate did not 'slide' through the enzyme. DNA oligonucleotides with double-stranded stem-loops were good competitive inhibitors of RNase II. A 3'-single-stranded arm was essential, while optimal binding required both 5'- and 3'-arms. PDE I probing indicated that the nucleotides at the anchor site were specified by the spatial distance from the catalytic site, and on only one of the duplex strands. When degradation of a structured RNA paused or stopped, the RNase II-product commenced cycles of dissociation-reassociation. Duplex strand binding by RNase II made complex DNA or RNA structures accessible to degradation by other nucleases and further verified the PDE I footprinting method.
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Affiliation(s)
- V J Cannistraro
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis MO, 63110, USA
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28
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Abstract
Hal2p is an enzyme that converts pAp (adenosine 3',5' bisphosphate), a product of sulfate assimilation, into 5' AMP and Pi. Overexpression of Hal2p confers lithium resistance in yeast, and its activity is inhibited by submillimolar amounts of Li+ in vitro. Here we report that pAp accumulation in HAL2 mutants inhibits the 5'-->3' exoribonucleases Xrn1p and Rat1p. Li+ treatment of a wild-type yeast strain also inhibits the exonucleases, as a result of pAp accumulation due to inhibition of Hal2p; 5' processing of the 5.8S rRNA and snoRNAs, degradation of pre-rRNA spacer fragments and mRNA turnover are inhibited. Lithium also inhibits the activity of RNase MRP by a mechanism which is not mediated by pAp. A mutation in the RNase MRP RNA confers Li+ hypersensitivity and is synthetically lethal with mutations in either HAL2 or XRN1. We propose that Li+ toxicity in yeast is due to synthetic lethality evoked between Xrn1p and RNase MRP. Similar mechanisms may contribute to the effects of Li+ on development and in human neurobiology.
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Affiliation(s)
- B Dichtl
- EMBL, Gene Expression Programme, Postfach 10.2209, 69012 Heidelberg, Germany
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29
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Coutts M, Krowczynska A, Brawerman G. Protection of mRNA against nucleases in cytoplasmic extracts of mouse sarcoma ascites cells. Biochim Biophys Acta 1993; 1173:49-56. [PMID: 8485153 DOI: 10.1016/0167-4781(93)90241-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mRNA present in extracts of mouse sarcoma 180 (S-180) ascites cells is relatively resistant to degradation when compared to added tracer ribosomal RNA. Deproteinized mRNA added to the extract is about as resistant as the endogenous mRNA, an indication that the protection is not due to any protein present in the endogenous mRNP structure. A major determinant of protection lies at the 5' end of RNA chains, where the presence of a triphosphate or a cap enhances the stability of mRNA transcripts. Addition of poly(A) to a capped transcript had little effect on stability. Stabilization by the cap structure is apparently not due to association of transcripts with a cap-binding protein. The discrimination in RNA decay rates appears to be based on interaction of the different RNA species with an exonuclease, which represents the predominant ribonuclease activity in the extract. Other major cytoplasmic nucleases are suppressed by an RNase inhibitor that is present in excess.
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Affiliation(s)
- M Coutts
- Department of Biochemistry, Tufts University Health Sciences Schools, Boston, MA 02111
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Severin ES, Itkes AV, Kartasheva ON, Tunitskaya VL, Turpaev KT, Kafiani CA. Regulation of 2-5 A phosphodiesterase activity by cAMP-dependent phosphorylation: mechanism and biological role. Adv Enzyme Regul 1985; 23:365-76. [PMID: 3000146 DOI: 10.1016/0065-2571(85)90056-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The results of the present study permit the explanation of one of the mechanisms of the interconnection between the regulatory systems of cAMP and 2-5A. cAMP-dependent regulation of 2'-PDE was found to involve phosphorylation of the specific protein inhibitor. Originally, a similar way of regulation of the enzyme activity was discovered for protein phosphatase I. This enzyme has a specific protein inhibitor type 1, which is phosphorylated by cAMP-dependent protein kinase and is activated by phosphorylation (18). It is interesting that the molecular weights of 2'-PDE protein inhibitor and of the inhibitor type 1 of protein phosphatase I are essentially the same. There is also a certain similarity between the above described mechanism and phosphorylation of the regulatory subunit of cAMP-dependent protein kinase type 2. The regulatory subunit can also act as a protein inhibitor of the enzyme and change its properties as a result of phosphorylation (19). The results obtained permit as well a more detailed explanation for cAMP-dependent inhibition of cell proliferation. Evidently, cAMP elevation causes activation of cAMP-dependent phosphorylation which, in turn, leads to the induction of 2-5A synthetase and inhibition of 2'-PDE. As a result of variations in the activities of these enzymes, the level of 2-5A rises. The latter brings about the changes characteristic of the resting state. They involve activation of RNase L and the succeeding acceleration of RNA hydrolysis, inhibition of protein synthesis and cell proliferation. The resting state is characterized by a rapid turnover of macromolecules due to their intensive degradation (20). The above described scheme suggested that the rapid turnover of RNA during inhibition of cell proliferation can be partially accounted for by activation of 2-5A-dependent RNase L. Thus, it can be thought that at least one of the mechanisms of the antiproliferative effect of cAMP-dependent phosphorylation of proteins involves cAMP-dependent elevation of intracellular 2-5A. Evidently, a number of properties of the resting cells are determined by the elevated content of 2-5A. Finally, it should be noted that the interconnection between the systems of cAMP and 2-5A is a multiple process. We have earlier demonstrated (12) that 2-5A activates cAMP phosphodiesterase in NIH 3T3 cell homogenates. These data suggest that the mutual regulation of cAMP and 2-5A levels involves the negative feedback mechanism (Fig. 8).
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31
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Itkes AV, Kartasheva ON, Kafiani CA, Severin ES. Inhibition of 2'-phosphodiesterase by cAMP-dependent protein kinase. Involvement of phosphorylation of protein inhibitor. FEBS Lett 1984; 176:65-8. [PMID: 6092139 DOI: 10.1016/0014-5793(84)80912-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
2'-Phosphodiesterase from NIH 3T3 cells was purified about 530-fold. Treatment of the cell lysate with the cAMP-dependent protein kinase causing the 2'-phosphodiesterase inhibition did not result in phosphorylation of the enzyme itself. The kinase was found to phosphorylate a specific 18-kDa protein, the phosphorylated form of this protein being the inhibitor of 2'-phosphodiesterase.
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