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Perveen S, Yazdi AK, Hajian T, Li F, Vedadi M. Kinetic characterization of human mRNA guanine-N7 methyltransferase. Sci Rep 2024; 14:4509. [PMID: 38402266 PMCID: PMC10894281 DOI: 10.1038/s41598-024-55184-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Accepted: 02/21/2024] [Indexed: 02/26/2024] Open
Abstract
The 5'-mRNA-cap formation is a conserved process in protection of mRNA in eukaryotic cells, resulting in mRNA stability and efficient translation. In humans, two methyltransferases, RNA cap guanine-N7 methyltransferase (hRNMT) and cap-specific nucleoside-2'-O-methyltransferase 1 (hCMTr1) methylate the mRNA resulting in cap0 (N7mGpppN-RNA) and cap1 (N7mGpppN2'-Om-RNA) formation, respectively. Coronaviruses mimic this process by capping their RNA to evade human immune systems. The coronaviral nonstructural proteins, nsp14 and nsp10-nsp16, catalyze the same reactions as hRNMT and hCMTr1, respectively. These two viral enzymes are important targets for development of inhibitor-based antiviral therapeutics. However, assessing the selectivity of such inhibitors against human corresponding proteins is crucial. Human RNMTs have been implicated in proliferation of cancer cells and are also potential targets for development of anticancer therapeutics. Here, we report the development and optimization of a radiometric assay for hRNMT, full kinetic characterization of its activity, and optimization of the assay for high-throughput screening with a Z-factor of 0.79. This enables selectivity determination for a large number of hits from various screening of coronaviral methyltransferases, and also screening hRNMT for discovery of inhibitors and chemical probes that potentially could be used to further investigate the roles RNMTs play in cancers.
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Affiliation(s)
- Sumera Perveen
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | | | - Taraneh Hajian
- Ontario Institute for Cancer Research, 661 University Ave, Toronto, ON, M5G 0A3, Canada
| | - Fengling Li
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Masoud Vedadi
- Ontario Institute for Cancer Research, 661 University Ave, Toronto, ON, M5G 0A3, Canada.
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, M5S 1A8, Canada.
- QBI COVID-19 Research Group (QCRG), San Francisco, CA, 94158, USA.
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2
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Nayak A, Chavarria A, Sanders KN, Ghalei H, Khoshnevis S. Sinefungin, a natural nucleoside analog of S-adenosyl methionine, impairs the pathogenicity of Candida albicans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.12.562127. [PMID: 37873365 PMCID: PMC10592816 DOI: 10.1101/2023.10.12.562127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Candida albicans, an opportunistic fungal human pathogen, is a major threat to the healthcare system due to both infections in immunocompromised individuals and the emergence of antifungal resistance. Fungal infection caused by C. albicans, candidiasis, is a life-threatening condition in immunocompromised patients and the current treatments are mostly restricted to polyenes, azoles, and echinocandins. Use of these antifungals is limited by toxicity, drug-drug interactions, and the emergence of resistance, underscoring the importance of identifying novel therapeutic targets and the need for new treatment approaches. C. albicans can undergo a morphological transition from yeast to hyphae and this transition is central to C. albicans virulence. Here, we determine the impact of sinefungin, a natural nucleoside analog of S-adenosyl methionine, on the virulence of C. albicans strain SC5314 by evaluating treatment effects on the morphological transition, human epithelial cell adhesion, and biofilm formation. Our data indicate that sinefungin impairs pathogenic traits of C. albicans including hyphal lengthening, biofilm formation and the adhesion to the human epithelial cell lines, without adversely affecting human cells, therefore highlighting sinefungin as a potential avenue for therapeutic intervention. We determine that the formation of N6-methyladenosine (m6A) is particularly disturbed by sinefungin. More broadly, this study underscores the importance of considering the post-transcriptional control mechanisms of pathogenicity when designing therapeutic solutions to fungal infection.
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Affiliation(s)
- Anushka Nayak
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA
| | - Alejandro Chavarria
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA
| | - Kyla N. Sanders
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA
| | - Homa Ghalei
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA
| | - Sohail Khoshnevis
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA
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3
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Fischer TR, Meidner L, Schwickert M, Weber M, Zimmermann RA, Kersten C, Schirmeister T, Helm M. Chemical biology and medicinal chemistry of RNA methyltransferases. Nucleic Acids Res 2022; 50:4216-4245. [PMID: 35412633 PMCID: PMC9071492 DOI: 10.1093/nar/gkac224] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 03/17/2022] [Accepted: 04/08/2022] [Indexed: 12/24/2022] Open
Abstract
RNA methyltransferases (MTases) are ubiquitous enzymes whose hitherto low profile in medicinal chemistry, contrasts with the surging interest in RNA methylation, the arguably most important aspect of the new field of epitranscriptomics. As MTases become validated as drug targets in all major fields of biomedicine, the development of small molecule compounds as tools and inhibitors is picking up considerable momentum, in academia as well as in biotech. Here we discuss the development of small molecules for two related aspects of chemical biology. Firstly, derivates of the ubiquitous cofactor S-adenosyl-l-methionine (SAM) are being developed as bioconjugation tools for targeted transfer of functional groups and labels to increasingly visible targets. Secondly, SAM-derived compounds are being investigated for their ability to act as inhibitors of RNA MTases. Drug development is moving from derivatives of cosubstrates towards higher generation compounds that may address allosteric sites in addition to the catalytic centre. Progress in assay development and screening techniques from medicinal chemistry have led to recent breakthroughs, e.g. in addressing human enzymes targeted for their role in cancer. Spurred by the current pandemic, new inhibitors against coronaviral MTases have emerged at a spectacular rate, including a repurposed drug which is now in clinical trial.
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Affiliation(s)
- Tim R Fischer
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Laurenz Meidner
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Marvin Schwickert
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Marlies Weber
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Robert A Zimmermann
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Christian Kersten
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Tanja Schirmeister
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
| | - Mark Helm
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University Mainz, Staudingerweg 5, 55128Mainz, Germany
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4
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Reichert D, Schepers H, Simke J, Lechner H, Dörner W, Höcker B, Ravoo BJ, Rentmeister A. Computational design and experimental characterization of a photo-controlled mRNA-cap guanine-N7 methyltransferase. RSC Chem Biol 2021; 2:1484-1490. [PMID: 34704053 PMCID: PMC8495969 DOI: 10.1039/d1cb00109d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 06/25/2021] [Indexed: 11/21/2022] Open
Abstract
The spatial and temporal control of gene expression at the post-transcriptional level is essential in eukaryotic cells and developing multicellular organisms. In recent years optochemical and optogenetic tools have enabled the manipulation and investigation of many steps in the involved processes. However, examples for light-mediated control of eukaryotic mRNA processing and the responsible enzymes are still rare. In particular, methylation of the 5′ cap of mRNA is required for ribosome assembly, and the responsible guanine-N7 methyltransferase (MTase) from E. cuniculi (Ecm1) proved suitable for activating translation. Here, we report on a photoswitchable MTase obtained by bridging the substrate-binding cleft of Ecm1 with a tetra-ortho-methoxy-azobenzene. This azobenzene derivative is characterized by efficient trans-to-cis isomerization using red light at 615 nm. Starting from a cysteine-free Ecm1 variant (ΔCys), we used a computational approach to identify suitable conjugation sites for the azobenzene moiety. We created and characterized the four best-ranked variants, each featuring two appropriately positioned cysteines close to the substrate-binding cleft. Conjugating and crosslinking the azobenzene between C149/C155 in a designed Ecm1 variant (VAR3-Az) enabled light-dependent modulation of the MTase activity and showed a 50% higher activity for the cis form than the trans-form of the azobenzene conjugated to VAR3-Az. Guided by computational design, we engineered a light-dependent 5' cap guanine-N7 methyltransferase by bridging the substrate-binding cleft with an azobenzene derivative.![]()
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Affiliation(s)
- Dennis Reichert
- Institute of Biochemistry, University of Münster, Correnstraße 36 Münster 48149 Germany .,Cells in Motion Interfaculty Center, University of Münster Münster 48149 Germany
| | - Helena Schepers
- Institute of Biochemistry, University of Münster, Correnstraße 36 Münster 48149 Germany
| | - Julian Simke
- Organic Chemistry Institute, University of Münster, Corrensstraße 36 Münster 48149 Germany
| | - Horst Lechner
- Department for Biochemistry, University of Bayreuth, Universitätsstraße 30 Bayreuth 95447 Germany.,Institute of Biochemistry, Graz University of Technology, Petersgasse 10-12/II Graz 8010 Austria
| | - Wolfgang Dörner
- Institute of Biochemistry, University of Münster, Correnstraße 36 Münster 48149 Germany
| | - Birte Höcker
- Department for Biochemistry, University of Bayreuth, Universitätsstraße 30 Bayreuth 95447 Germany
| | - Bart Jan Ravoo
- Cells in Motion Interfaculty Center, University of Münster Münster 48149 Germany.,Organic Chemistry Institute, University of Münster, Corrensstraße 36 Münster 48149 Germany
| | - Andrea Rentmeister
- Institute of Biochemistry, University of Münster, Correnstraße 36 Münster 48149 Germany .,Cells in Motion Interfaculty Center, University of Münster Münster 48149 Germany
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5
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Reichert D, Mootz HD, Rentmeister A. Light-control of cap methylation and mRNA translation via genetic code expansion of Ecm1. Chem Sci 2021; 12:4383-4388. [PMID: 34163701 PMCID: PMC8179545 DOI: 10.1039/d1sc00159k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/04/2021] [Indexed: 12/24/2022] Open
Abstract
Gene expression is tightly regulated in all domains of life, with post-transcriptional regulation being more pronounced in higher eukaryotes. Optochemical and optogenetic approaches enable the actuation of many underlying processes by light, which is an excellent tool to exert spatio-temporal control. However, light-mediated control of eukaryotic mRNA processing and the respective enzymes has not been reported. We used genetic code expansion to install a photo-caged tyrosine (Y) in the active site of the cap methyltransferase Ecm1. This enzyme is responsible for guanine N7 methylation of the 5' cap, which is required for translation. Substituting Y284 with the photocaged ortho-nitrobenzyl-tyrosine (ONBY) almost completely abrogated the methylation activity of Ecm1. Irradiation with light removed the ONB group, restoring the native tyrosine and Ecm1 activity, yielding up to 97% conversion of the minimal substrate GpppA within 60 min after activation. Using luciferase- and eGFP-mRNAs as reporters, we could show that light actuates translation by inducing activation of Ecm1 ONBY284 in a eukaryotic in vitro translation system.
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Affiliation(s)
- Dennis Reichert
- Department of Chemistry, Institute of Biochemistry, University of Münster Correnstr. 36 48149 Münster Germany
- Cells in Motion Interfaculty Center, University of Münster 48149 Münster Germany
| | - Henning D Mootz
- Department of Chemistry, Institute of Biochemistry, University of Münster Correnstr. 36 48149 Münster Germany
| | - Andrea Rentmeister
- Department of Chemistry, Institute of Biochemistry, University of Münster Correnstr. 36 48149 Münster Germany
- Cells in Motion Interfaculty Center, University of Münster 48149 Münster Germany
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6
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Rosas-Lemus M, Minasov G, Shuvalova L, Inniss NL, Kiryukhina O, Brunzelle J, Satchell KJF. High-resolution structures of the SARS-CoV-2 2'- O-methyltransferase reveal strategies for structure-based inhibitor design. Sci Signal 2020; 13:eabe1202. [PMID: 32994211 PMCID: PMC8028745 DOI: 10.1126/scisignal.abe1202] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
There are currently no antiviral therapies specific for SARS-CoV-2, the virus responsible for the global pandemic disease COVID-19. To facilitate structure-based drug design, we conducted an x-ray crystallographic study of the SARS-CoV-2 nsp16-nsp10 2'-O-methyltransferase complex, which methylates Cap-0 viral mRNAs to improve viral protein translation and to avoid host immune detection. We determined the structures for nsp16-nsp10 heterodimers bound to the methyl donor S-adenosylmethionine (SAM), the reaction product S-adenosylhomocysteine (SAH), or the SAH analog sinefungin (SFG). We also solved structures for nsp16-nsp10 in complex with the methylated Cap-0 analog m7GpppA and either SAM or SAH. Comparative analyses between these structures and published structures for nsp16 from other betacoronaviruses revealed flexible loops in open and closed conformations at the m7GpppA-binding pocket. Bound sulfates in several of the structures suggested the location of the ribonucleic acid backbone phosphates in the ribonucleotide-binding groove. Additional nucleotide-binding sites were found on the face of the protein opposite the active site. These various sites and the conserved dimer interface could be exploited for the development of antiviral inhibitors.
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Affiliation(s)
- Monica Rosas-Lemus
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - George Minasov
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Ludmilla Shuvalova
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Nicole L Inniss
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Olga Kiryukhina
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
- Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Joseph Brunzelle
- Northwestern Synchrotron Research Center, Life Sciences Collaborative Access Team, Northwestern University, Argonne, IL 60439, USA
| | - Karla J F Satchell
- Department of Microbiology-Immunology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
- Center for Structural Genomics of Infectious Diseases, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
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7
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Bhattacharya A, Sharma M, Pakkinathan C, Rosen BP, Leprohon P, Ouellette M. Genomewide Analysis of Mode of Action of the S-Adenosylmethionine Analogue Sinefungin in Leishmania infantum. mSystems 2019; 4:e00416-19. [PMID: 31615876 PMCID: PMC6794121 DOI: 10.1128/msystems.00416-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 09/30/2019] [Indexed: 11/20/2022] Open
Abstract
To further our understanding of one-carbon metabolism in the protozoan parasite Leishmania, we conducted genomic screens to study how the parasite responded to sinefungin (SNF) selection. SNF is a structural analogue of S-adenosylmethionine (AdoMet), a key methyl group donor to a number of biomolecules. One screen consisted of sequencing SNF-resistant mutants generated by stepwise selection with gradually increasing drug concentrations. These studies demonstrated deletion of the AdoMet transporter (AdoMetT1) by intergenic recombination as a crucial loss-of-function marker for SNF resistance. The second screen consisted of Cos-seq, a gain-of-function cosmid-based genomewide functional screen with increasing SNF concentration coupled to next-generation sequencing. Cosmids enriched in that screen and sequenced led to the identification of (i) the AdoMet synthetase (METK) as the major SNF target, (ii) an mRNA [(guanine-N7)-methyltransferase (CMT1)], (iii) a leucine carboxyl methyltransferase (LCMT), (iv) two tryparedoxin genes, and (v) two protein phosphatase regulatory genes. Further functional exploration indicated that LCMT interacts with one phosphatase catalytic subunit (PP2AC) and that mutation of the C-terminal leucine residue of PP2AC affects sinefungin susceptibility. These holistic screens led to the identification of transporters, biosynthetic genes, RNA and protein methyltransferases, as well as phosphatases linked to AdoMet-mediated functions in Leishmania IMPORTANCE The two main cellular metabolic one-carbon donors are reduced folates and S-adenosylmethionine, whose biosynthetic pathways have proven highly effective in chemotherapeutic interventions in various cell types. Sinefungin, a nucleoside analogue of S-adenosylmethionine, was shown to have potent activity against the protozoan parasite Leishmania Here, we studied resistance to sinefungin using whole-genome approaches as a way to further our understanding of the role of S-adenosylmethionine in this parasite and to reveal novel potential drug targets. These approaches allowed the characterization of novel features related to S-adenosylmethionine function in Leishmania which could further help in the development of sinefungin-like compounds against this pathogenic parasite.
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Affiliation(s)
- Arijit Bhattacharya
- Division of Infectious Disease and Immunity, CHU de Quebec Research Center, Quebec, Quebec, Canada
- Department of Microbiology, Infectious Disease and Immunology, University Laval, Quebec, Quebec, Canada
| | - Mansi Sharma
- Division of Infectious Disease and Immunity, CHU de Quebec Research Center, Quebec, Quebec, Canada
- Department of Microbiology, Infectious Disease and Immunology, University Laval, Quebec, Quebec, Canada
| | - Charles Pakkinathan
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida, USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida, USA
| | - Philippe Leprohon
- Division of Infectious Disease and Immunity, CHU de Quebec Research Center, Quebec, Quebec, Canada
- Department of Microbiology, Infectious Disease and Immunology, University Laval, Quebec, Quebec, Canada
| | - Marc Ouellette
- Division of Infectious Disease and Immunity, CHU de Quebec Research Center, Quebec, Quebec, Canada
- Department of Microbiology, Infectious Disease and Immunology, University Laval, Quebec, Quebec, Canada
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8
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Antiviral effect of sinefungin on in vitro growth of feline herpesvirus type 1. J Antibiot (Tokyo) 2019; 72:981-985. [PMID: 31534199 DOI: 10.1038/s41429-019-0234-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 08/24/2019] [Accepted: 08/27/2019] [Indexed: 01/22/2023]
Abstract
Feline herpesvirus type 1 (FHV-1) causes a potentially fatal disease in cats. Through the use of virus inhibition and cytotoxicity assays, sinefungin, a nucleoside antibiotic, was assessed for its potential to inhibit the growth of FHV-1. Sinefungin inhibited in vitro growth of FHV-1 most significantly over other animal viruses, such as feline infectious peritonitis virus, equine herpesvirus, pseudorabies virus and feline calicivirus. Our results revealed that sinefungin specifically suppressed the replication of FHV-1 after its adsorption to the host feline kidney cells in a dose-dependent manner without obvious cytotoxicity to the host cells. This antibiotic can potentially offer a highly effective treatment for animals infected with FHV-1, providing alternative medication to currently available antiviral therapies.
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Screening and Identification of Microbial Derivatives for Inhibiting Legumain: An In silico Approach. JOURNAL OF PURE AND APPLIED MICROBIOLOGY 2018. [DOI: 10.22207/jpam.12.3.69] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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10
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Small methyltransferase RlmH assembles a composite active site to methylate a ribosomal pseudouridine. Sci Rep 2017; 7:969. [PMID: 28428565 PMCID: PMC5430550 DOI: 10.1038/s41598-017-01186-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 03/23/2017] [Indexed: 11/24/2022] Open
Abstract
Eubacterial ribosomal large-subunit methyltransferase H (RlmH) methylates 23S ribosomal RNA pseudouridine 1915 (Ψ1915), which lies near the ribosomal decoding center. The smallest member of the SPOUT superfamily of methyltransferases, RlmH lacks the RNA recognition domain found in larger methyltransferases. The catalytic mechanism of RlmH enzyme is unknown. Here, we describe the structures of RlmH bound to S-adenosyl-methionine (SAM) and the methyltransferase inhibitor sinefungin. Our structural and biochemical studies reveal catalytically essential residues in the dimer-mediated asymmetrical active site. One monomer provides the SAM-binding site, whereas the conserved C-terminal tail of the second monomer provides residues essential for catalysis. Our findings elucidate the mechanism by which a small protein dimer assembles a functionally asymmetric architecture.
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11
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Abstract
S-Adenosyl-L-methionine (SAM) is a sulfonium molecule with a structural hybrid of methionine and adenosine. As the second largest cofactor in the human body, its major function is to serve as methyl donor for SAM-dependent methyltransferases (MTases). The resultant transmethylation of biomolecules constitutes a significant biochemical mechanism in epigenetic regulation, cellular signaling, and metabolite degradation. Recently, numerous SAM analogs have been developed as synthetic cofactors to transfer the activated groups on MTase substrates for downstream ligation and identification. Meanwhile, new compounds built upon or derived from the SAM scaffold have been designed and tested as selective inhibitors for important MTase targets. Here, we summarized the recent development and application of SAM analogs as chemical biology tools for MTases.
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Affiliation(s)
- Jing Zhang
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, Georgia 30602, United States
| | - Yujun George Zheng
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, Georgia 30602, United States
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12
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Byszewska M, Śmietański M, Purta E, Bujnicki JM. RNA methyltransferases involved in 5' cap biosynthesis. RNA Biol 2015; 11:1597-607. [PMID: 25626080 PMCID: PMC4615557 DOI: 10.1080/15476286.2015.1004955] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
In eukaryotes and viruses that infect them, the 5′ end of mRNA molecules, and also many other functionally important RNAs, are modified to form a so-called cap structure that is important for interactions of these RNAs with many nuclear and cytoplasmic proteins. The RNA cap has multiple roles in gene expression, including enhancement of RNA stability, splicing, nucleocytoplasmic transport, and translation initiation. Apart from guanosine addition to the 5′ end in the most typical cap structure common to transcripts produced by RNA polymerase II (in particular mRNA), essentially all cap modifications are due to methylation. The complexity of the cap structure and its formation can range from just a single methylation of the unprocessed 5′ end of the primary transcript, as in mammalian U6 and 7SK, mouse B2, and plant U3 RNAs, to an elaborate m7Gpppm6,6AmpAmpCmpm3Um structure at the 5′ end of processed RNA in trypanosomes, which are formed by as many as 8 methylation reactions. While all enzymes responsible for methylation of the cap structure characterized to date were found to belong to the same evolutionarily related and structurally similar Rossmann Fold Methyltransferase superfamily, that uses the same methyl group donor, S-adenosylmethionine; the enzymes also exhibit interesting differences that are responsible for their distinct functions. This review focuses on the evolutionary classification of enzymes responsible for cap methylation in RNA, with a focus on the sequence relationships and structural similarities and dissimilarities that provide the basis for understanding the mechanism of biosynthesis of different caps in cellular and viral RNAs. Particular attention is paid to the similarities and differences between methyltransferases from human cells and from human pathogens that may be helpful in the development of antiviral and antiparasitic drugs.
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Sinefungin, a natural nucleoside analogue of S-adenosylmethionine, inhibits Streptococcus pneumoniae biofilm growth. BIOMED RESEARCH INTERNATIONAL 2014; 2014:156987. [PMID: 25050323 PMCID: PMC4094849 DOI: 10.1155/2014/156987] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/05/2014] [Accepted: 06/08/2014] [Indexed: 01/21/2023]
Abstract
Pneumococcal colonization and disease is often associated with biofilm formation, in which the bacteria exhibit elevated resistance both to antibiotics and to host defense systems, often resulting in infections that are persistent and difficult to treat. We evaluated the effect of sinefungin, a nucleoside analogue of S-adenosylmethionine, on pneumococcal in vitro biofilm formation and in vivo colonization. Sinefungin is bacteriostatic to pneumococci and significantly decreased biofilm growth and inhibited proliferation and structure of actively growing biofilms but did not alter growth or the matrix structure of established biofilms. Sinefungin significantly reduced pneumococcal colonization in rat middle ear. The quorum sensing molecule (autoinducer-2) production was significantly reduced by 92% in sinefungin treated samples. The luxS, pfs, and speE genes were downregulated in biofilms grown in the presence of sinefungin. This study shows that sinefungin inhibits pneumococcal biofilm growth in vitro and colonization in vivo, decreases AI-2 production, and downregulates luxS, pfs, and speE gene expressions. Therefore, the S-adenosylmethionine (SAM) inhibitors could be used as lead compounds for the development of novel antibiofilm agents against pneumococci.
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14
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Sun Y, Wang Z, Tao J, Wang Y, Wu A, Yang Z, Wang K, Shi L, Chen Y, Guo D. Yeast-based assays for the high-throughput screening of inhibitors of coronavirus RNA cap guanine-N7-methyltransferase. Antiviral Res 2014; 104:156-64. [PMID: 24530452 PMCID: PMC7119097 DOI: 10.1016/j.antiviral.2014.02.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 01/29/2014] [Accepted: 02/03/2014] [Indexed: 12/17/2022]
Abstract
A yeast-based system for screening of coronavirus N7-MTases inhibitors was developed. Sinefungin is not an ideal antiviral inhibitor. Three natural extracts were observed to specifically inhibit the N7-MTases of coronavirus.
The 5′-cap structure is a distinct feature of eukaryotic mRNAs and is important for RNA stability and protein translation by providing a molecular signature for the distinction of self or non-self mRNA. Eukaryotic viruses generally modify the 5′-end of their RNAs to mimic the cellular mRNA structure, thereby facilitating viral replication in host cells. However, the molecular organization and biochemical mechanisms of the viral capping apparatus typically differ from its cellular counterpart, which makes viral capping enzymes attractive targets for drug discovery. Our previous work showed that SARS coronavirus (SARS-CoV) non-structural protein 14 represents a structurally novel and unique guanine-N7-methyltransferase (N7-MTase) that is able to functionally complement yeast cellular N7-MTase. In the present study, we developed a yeast-based system for identifying and screening inhibitors against coronavirus N7-MTase using both 96-well and 384-well microtiter plates. The MTase inhibitors previously identified by in vitro biochemical assays were tested, and some, such as sinefungin, effectively suppressed N7-MTase in the yeast system. However, other compounds, such as ATA and AdoHcy, did not exert an inhibitory effect within a cellular context. These results validated the yeast assay system for inhibitor screening yet also demonstrated the difference between cell-based and in vitro biochemical assays. The yeast system was applied to the screening of 3000 natural product extracts, and three were observed to more potently inhibit the activity of coronavirus than human N7-MTase.
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Affiliation(s)
- Ying Sun
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Zidao Wang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Jiali Tao
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Yi Wang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Andong Wu
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China
| | - Ziwen Yang
- Biological Pesticide Engineering Research Center, Hubei Academy of Agricultural Science, Hubei 430072, PR China
| | - Kaimei Wang
- Biological Pesticide Engineering Research Center, Hubei Academy of Agricultural Science, Hubei 430072, PR China
| | - Liqiao Shi
- Biological Pesticide Engineering Research Center, Hubei Academy of Agricultural Science, Hubei 430072, PR China
| | - Yu Chen
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China.
| | - Deyin Guo
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, PR China.
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Tremblay-Létourneau M, Despins S, Bougie I, Bisaillon M. Virtual high-throughput screening identifies mycophenolic acid as a novel RNA capping inhibitor. PLoS One 2011; 6:e24806. [PMID: 21935470 PMCID: PMC3174198 DOI: 10.1371/journal.pone.0024806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 08/18/2011] [Indexed: 12/25/2022] Open
Abstract
The RNA guanylyltransferase (GTase) is involved in the synthesis of the m7Gppp-RNA cap structure found at the 5′ end of eukaryotic mRNAs. GTases are members of the covalent nucleotidyl transferase superfamily, which also includes DNA and RNA ligases. GTases catalyze a two-step reaction in which they initially utilize GTP as a substrate to form a covalent enzyme-GMP intermediate. The GMP moiety is then transferred to the diphosphate end of the RNA transcript in the second step of the reaction to form the Gppp-RNA structure. In the current study, we used a combination of virtual database screening, homology modeling, and biochemical assays to search for novel GTase inhibitors. Using this approach, we demonstrate that mycophenolic acid (MPA) can inhibit the GTase reaction by preventing the catalytic transfer of the GMP moiety onto an acceptor RNA. As such, MPA represents a novel type of inhibitor against RNA guanylyltransferases that inhibits the second step of the catalytic reaction. Moreover, we show that the addition of MPA to S. cerevisiae cells leads to a reduction of capped mRNAs. Finally, biochemical assays also demonstrate that MPA can inhibit DNA ligases through inhibition of the second step of the reaction. The biological implications of these findings for the MPA-mediated inhibition of members of the covalent nucleotidyl superfamily are discussed.
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Affiliation(s)
- Maude Tremblay-Létourneau
- RNA Group, Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Simon Despins
- RNA Group, Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Isabelle Bougie
- RNA Group, Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Martin Bisaillon
- RNA Group, Département de Biochimie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
- * E-mail:
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16
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Issur M, Picard‐Jean F, Bisaillon M. The RNA capping machinery as an anti-infective target. WILEY INTERDISCIPLINARY REVIEWS. RNA 2011; 2:184-92. [PMID: 21957005 PMCID: PMC7169851 DOI: 10.1002/wrna.43] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A number of different human pathogens code for their own enzymes involved in the synthesis of the RNA cap structure. Although the RNA cap structures originating from human and microbial enzymes are often identical, the subunit composition, structure and catalytic mechanisms of the microbial-encoded enzymes involved in the synthesis of the RNA cap structure are often significantly different from those of host cells. As a consequence, these pathogenic cap-forming enzymes are potential targets for antimicrobial drugs. During the past few years, experimental studies have started to demonstrate that inhibition of the RNA capping activity is a reasonable approach for the development of antimicrobial agents. The combination of structural, biochemical, and molecular modeling studies are starting to reveal novel molecules that can serve as starting blocks for the design of more potent and specific antimicrobial agents. Here, we examine various strategies that have been developed to inhibit microbial enzymes involved in the synthesis of the RNA cap structure, emphasizing the challenges remaining to design potent and selective drugs.
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Affiliation(s)
- Moheshwarnath Issur
- Département de Biochimie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Frédéric Picard‐Jean
- Département de Biochimie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
| | - Martin Bisaillon
- Département de Biochimie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada
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17
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Hu RH, Lin MC, Hsu YH, Meng M. Mutational effects of the consensus aromatic residues in the mRNA capping domain of Bamboo mosaic virus on GTP methylation and virus accumulation. Virology 2011; 411:15-24. [PMID: 21227477 DOI: 10.1016/j.virol.2010.12.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 10/29/2010] [Accepted: 12/14/2010] [Indexed: 10/18/2022]
Abstract
RNA viruses classified in the alphavirus-like superfamily possess a distinct capping domain, catalyzing GTP methylation and subsequent transfer of the m(7)GMP moiety from m(7)GTP to the 5'-diphosphate end of viral RNA. The H68A mutation in the capping domain of Bamboo mosaic virus enhanced GTP methylation but disabled the following transguanylation, making it possible to characterize the enzyme's methyltransferase activity separately. To explore the involvement of aromatic amino acids in substrate recognition, consensus aromatic residues in the viral domain were subjected to mutational analysis in the background of H68A. Several residues, including Y126, F144, F161, Y192, Y203, Y213, and W222, were found to be critical for GTP methylation and S-adenosylmethionine (AdoMet) binding. These mutations, except for Y213, also adversely affected the GTP binding, but less extensively. In general, the mutations decreasing the activity for GTP methylation also had correspondingly detrimental effects on virus accumulation.
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Affiliation(s)
- Rei-Hsing Hu
- Graduate Institute of Biotechnology, National Chung Hsing University, 250 Kuo-Kuang Rd, Taichung, Taiwan 40227, ROC
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18
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Chung KY, Dong H, Chao AT, Shi PY, Lescar J, Lim SP. Higher catalytic efficiency of N-7-methylation is responsible for processive N-7 and 2′-O methyltransferase activity in dengue virus. Virology 2010; 402:52-60. [DOI: 10.1016/j.virol.2010.03.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 12/30/2009] [Accepted: 03/03/2010] [Indexed: 01/06/2023]
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19
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Ghosh A, Lima CD. Enzymology of RNA cap synthesis. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:152-72. [PMID: 21956912 DOI: 10.1002/wrna.19] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The 5' guanine-N7 methyl cap is unique to cellular and viral messenger RNA (mRNA) and is the first co-transcriptional modification of mRNA. The mRNA cap plays a pivotal role in mRNA biogenesis and stability, and is essential for efficient splicing, mRNA export, and translation. Capping occurs by a series of three enzymatic reactions that results in formation of N7-methyl guanosine linked through a 5'-5' inverted triphosphate bridge to the first nucleotide of a nascent transcript. Capping of cellular mRNA occurs co-transcriptionally and in vivo requires that the capping apparatus be physically associated with the RNA polymerase II elongation complex. Certain capped mRNAs undergo further methylation to generate distinct cap structures. Although mRNA capping is conserved among viruses and eukaryotes, some viruses have adopted strategies for capping mRNA that are distinct from the cellular mRNA capping pathway.
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Affiliation(s)
- Agnidipta Ghosh
- Structural Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
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Fukuda K, Tamura T, Ito H, Yamamoto S, Ochi K, Inagaki K. Production improvement of antifungal, antitrypanosomal nucleoside sinefungin by rpoB mutation and optimization of resting cell system of Streptomyces incarnatus NRRL 8089. J Biosci Bioeng 2010; 109:459-65. [DOI: 10.1016/j.jbiosc.2009.10.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 10/17/2009] [Accepted: 10/22/2009] [Indexed: 10/20/2022]
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21
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Abstract
Disease caused by flavivirus infections is an increasing world health problem. Flavivirus nonstructural protein 5 (NS5) possesses enzymatic activities required for capping and synthesis of the viral RNA genome and is essential for virus replication. NS5 is comprised of two domains. The N-terminal domain binds GTP and can perform two biochemically distinct methylation reactions required for RNA cap formation. The C-terminal domain contains RNA-dependent RNA polymerase activity. As such, NS5 is an interesting target against which antiviral drugs could be developed and research toward this goal has accelerated our understanding of NS5 structure and function in recent years. The production and purification of recombinant versions of either the full-length NS5 or the two individual NS5 domains has led to detailed enzymatic studies on NS5 and the determination of structures of the two NS5 domains. In turn, studies using a combination of structural, biochemical, and reverse genetic approaches are revealing how NS5 performs its multifunctional roles in genome replication. Aside from its localization in the membrane-bound replication complex, NS5 can be found free in the cytoplasm and for some flaviviruses in the nucleus of virus-infected cells. NS5 is phosphorylated which may potentially regulate NS5 function and trafficking. Recently, NS5 of a number of flaviviruses has been shown to interact with cellular pathways involved in the host immune response, suggesting that NS5 may play a role in viral pathogenesis. This chapter reviews recent advances in our understanding of the multifunctional roles played by NS5 in the virus lifecycle.
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22
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Vaubourgeix J, Bardou F, Boissier F, Julien S, Constant P, Ploux O, Daffé M, Quémard A, Mourey L. S-adenosyl-N-decyl-aminoethyl, a potent bisubstrate inhibitor of mycobacterium tuberculosis mycolic acid methyltransferases. J Biol Chem 2009; 284:19321-30. [PMID: 19439410 PMCID: PMC2740557 DOI: 10.1074/jbc.m809599200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 03/26/2009] [Indexed: 11/06/2022] Open
Abstract
S-Adenosylmethionine-dependent methyltransferases (AdoMet-MTs) constitute a large family of enzymes specifically transferring a methyl group to a range of biologically active molecules. Mycobacterium tuberculosis produces a set of paralogous AdoMet-MTs responsible for introducing key chemical modifications at defined positions of mycolic acids, which are essential and specific components of the mycobacterial cell envelope. We investigated the inhibition of these mycolic acid methyltransferases (MA-MTs) by structural analogs of the AdoMet cofactor. We found that S-adenosyl-N-decyl-aminoethyl, a molecule in which the amino acid moiety of AdoMet is substituted by a lipid chain, inhibited MA-MTs from Mycobacterium smegmatis and M. tuberculosis strains, both in vitro and in vivo, with IC(50) values in the submicromolar range. By contrast, S-adenosylhomocysteine, the demethylated reaction product, and sinefungin, a general AdoMet-MT inhibitor, did not inhibit MA-MTs. The interaction between Hma (MmaA4), which is strictly required for the biosynthesis of oxygenated mycolic acids in M. tuberculosis, and the three cofactor analogs was investigated by x-ray crystallography. The high resolution crystal structures obtained illustrate the bisubstrate nature of S-adenosyl-N-decyl-aminoethyl and provide insight into its mode of action in the inhibition of MA-MTs. This study has potential implications for the design of new drugs effective against multidrug-resistant and persistent tubercle bacilli.
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Affiliation(s)
- Julien Vaubourgeix
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Fabienne Bardou
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Fanny Boissier
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Sylviane Julien
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Patricia Constant
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Olivier Ploux
- the Laboratoire de Biochimie des Micro-organismes: Enzymologie, Métabolisme, et Antibiotiques, Ecole Nationale Supérieure de Chimie de Paris, CNRS UMR 7573, F-75231 Paris, France
| | - Mamadou Daffé
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Annaïk Quémard
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
| | - Lionel Mourey
- From CNRS, Institut de Pharmacologie et de Biologie Structurale, Département Mécanismes Moléculaires des Infections Mycobactériennes, 205 Route de Narbonne, F-31077 Toulouse
- the Université de Toulouse, Université Paul Sabatier, Institut de Pharmacologie et de Biologie Structurale, F-31077 Toulouse, and
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Zheng S, Shuman S. Mutational analysis of vaccinia virus mRNA cap (guanine-N7) methyltransferase reveals essential contributions of the N-terminal peptide that closes over the active site. RNA (NEW YORK, N.Y.) 2008; 14:2297-2304. [PMID: 18799596 PMCID: PMC2578867 DOI: 10.1261/rna.1201308] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 07/23/2008] [Indexed: 05/26/2023]
Abstract
RNA guanine-N7 methyltransferase catalyzes the third step of eukaryal mRNA capping, the transfer of a methyl group from AdoMet to GpppRNA to form m(7)GpppRNA. Mutational and crystallographic analyses of cellular and poxvirus cap methyltransferases have yielded a coherent picture of a conserved active site and determinants of substrate specificity. Models of the Michaelis complex suggest a direct in-line mechanism of methyl transfer. Because no protein contacts to the guanine-N7 nucleophile, the AdoMet methyl carbon (Cepsilon) or the AdoHcy sulfur (Sdelta) leaving group were observed in ligand-bound structures of cellular cap methyltransferase, it was initially thought that the enzyme facilitates catalysis by optimizing proximity and geometry of the donor and acceptor. However, the structure of AdoHcy-bound vaccinia virus cap methyltransferase revealed the presence of an N-terminal "lid peptide" that closes over the active site and makes multiple contacts with the substrates, including the AdoMet sulfonium. This segment is disordered in the vaccinia apoenzyme and is not visible in the available structures of cellular cap methyltransferase. Here, we conducted a mutational analysis of the vaccinia virus lid peptide ((545)DKFRLNPEVSYFTNKRTRG(563)) entailing in vivo and in vitro readouts of the effects of alanine and conservative substitutions. We thereby identified essential functional groups that interact with the AdoMet sulfonium (Tyr555, Phe556), the AdoMet adenine (Asn550), and the cap triphosphate bridge (Arg560, Arg562). The results suggest that van der Waals contacts of Tyr555 and Phe556 to the AdoMet Sdelta and C epsilon atoms, and the electron-rich environment around the sulfonium, serve to stabilize the transition state of the transmethylation reaction.
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Affiliation(s)
- Sushuang Zheng
- Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10065, USA
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24
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Guianvarc'h D, Guangqi E, Drujon T, Rey C, Wang Q, Ploux O. Identification of inhibitors of the E. coli cyclopropane fatty acid synthase from the screening of a chemical library: In vitro and in vivo studies. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1652-8. [DOI: 10.1016/j.bbapap.2008.04.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 04/21/2008] [Accepted: 04/25/2008] [Indexed: 11/30/2022]
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25
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Zheng S, Shuman S. Structure-function analysis of vaccinia virus mRNA cap (guanine-N7) methyltransferase. RNA (NEW YORK, N.Y.) 2008; 14:696-705. [PMID: 18256245 PMCID: PMC2271365 DOI: 10.1261/rna.928208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The guanine-N7 methyltransferase domain of vaccinia virus mRNA capping enzyme is a heterodimer composed of a catalytic subunit and a stimulatory subunit. Structure-function analysis of the catalytic subunit by alanine scanning and conservative substitutions (49 mutations at 25 amino acids) identified 12 functional groups essential for methyltransferase activity in vivo, most of which were essential for cap methylation in vitro. Defects in cap binding were demonstrated for a subset of lethal mutants that displayed residual activity in vitro. We discuss our findings in light of a model of the Michaelis complex derived from crystal structures of AdoHcy-bound vaccinia cap methyltransferase and GTP-bound cellular cap methyltransferase. The structure-function data yield a coherent picture of the vaccinia cap methyltransferase active site and the determinants of substrate specificity and affinity.
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Affiliation(s)
- Sushuang Zheng
- Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10065, USA
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26
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Zheng S, Shuman S, Schwer B. Sinefungin resistance of Saccharomyces cerevisiae arising from Sam3 mutations that inactivate the AdoMet transporter or from increased expression of AdoMet synthase plus mRNA cap guanine-N7 methyltransferase. Nucleic Acids Res 2007; 35:6895-903. [PMID: 17932050 PMCID: PMC2175321 DOI: 10.1093/nar/gkm817] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The S-adenosylmethionine (AdoMet) analog sinefungin is a natural product antibiotic that inhibits nucleic acid methyltransferases and arrests the growth of unicellular eukarya and eukaryal viruses. The basis for the particular sensitivity of fungi and protozoa to sinefungin is not known. Here we report the isolation and characterization of spontaneous sinefungin-resistant mutants of the budding yeast Saccharomyces cerevisiae. In all cases, sinefungin resistance was attributable to a loss-of-function mutation in Sam3, the yeast high-affinity AdoMet transporter. Overexpression of wild-type Sam3 increased the sensitivity of yeast to growth inhibition by sinefungin. Thus, Sam3 is a tunable determinant of sinefungin potency. The shared ability of protozoan parasites to import AdoMet might determine sinefungin's anti-infective spectrum. Insights to the intracellular action of sinefungin stem from the finding that increased gene dosage of yeast AdoMet synthase plus cap guanine-N7 methyltransferase afforded greater resistance to sinefungin than either enzyme alone. These results are consistent with the proposal that mRNA cap methylation is a principal target of sinefungin's bioactivity.
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Affiliation(s)
- Sushuang Zheng
- Molecular Biology Program, Sloan-Kettering Institute and Microbiology, Weill Cornell Medical College, New York, NY 10065, USA
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27
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Takagi Y, Sindkar S, Ekonomidis D, Hall MP, Ho CK. Trypanosoma brucei encodes a bifunctional capping enzyme essential for cap 4 formation on the spliced leader RNA. J Biol Chem 2007; 282:15995-6005. [PMID: 17416901 DOI: 10.1074/jbc.m701569200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 5' end of kinetoplastid mRNA possesses a hypermethylated cap 4 structure, which is derived from standard m7GpppN (cap 0) with additional methylations at seven sites within the first four nucleosides on the spliced leader RNA. In addition to TbCe1 guanylyltransferase and TbCmt1 (guanine N-7) methyltransferase, Trypanosoma brucei encodes a second cap 0 forming enzyme. TbCgm1 (T. brucei cap guanylyltransferase-methyltransferase) is a novel bifunctional capping enzyme consisting of an amino-terminal guanylyltransferase domain and a carboxyl-terminal methyltransferase domain. Recombinant TbCgm1 transfers the GMP to spliced leader RNA (SL RNA) via a covalent enzyme-GMP intermediate, and methylates the guanine N-7 position of the GpppN-terminated RNA to form cap 0 structure. The two domains can function autonomously in vitro. TbCGM1 is essential for parasite growth. Silencing of TbCGM1 by RNA interference increased the abundance of uncapped SL RNA and lead to accumulation of hypomethylated SL RNA. In contrast, silencing of TbCE1 and TbCMT1 did not affect parasite growth or SL RNA capping. We conclude that TbCgm1 specifically cap SL RNA, and cap 0 is a prerequisite for subsequent methylation events leading to the formation of mature SL RNA.
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Affiliation(s)
- Yuko Takagi
- Department of Biological Sciences, State University of New York, Buffalo, New York 14260, USA
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28
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Li J, Chorba JS, Whelan SPJ. Vesicular stomatitis viruses resistant to the methylase inhibitor sinefungin upregulate RNA synthesis and reveal mutations that affect mRNA cap methylation. J Virol 2007; 81:4104-15. [PMID: 17301155 PMCID: PMC1866143 DOI: 10.1128/jvi.02681-06] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sinefungin (SIN), a natural S-adenosyl-L-methionine analog produced by Streptomyces griseolus, is a potent inhibitor of methyltransferases. We evaluated the effect of SIN on replication of vesicular stomatitis virus (VSV), a prototype of the nonsegmented negative-strand RNA viruses. The 241-kDa large polymerase (L) protein of VSV methylates viral mRNA cap structures at the guanine-N-7 (G-N-7) and ribose-2'-O (2'-O) positions. By performing transcription reactions in vitro, we show that both methylations are inhibited by SIN and that methylation was more sensitive at the G-N-7 than at 2'-O position. We further show that SIN inhibited growth of VSV in cell culture, reducing viral yield by 50-fold and diminishing plaque size. We isolated eight mutants that were resistant to SIN as judged by their growth characteristics. The SIN-resistant (SINR) viruses contained mutations in the L gene, the promoter for L gene expression provided by the conserved sequence elements of the G-L gene junction and the M gene. Five mutations resulted in amino acid substitutions to conserved regions II/III and VI of the L protein. For each mutant, we examined viral gene expression in cells and cap methylation in vitro. SINR mutants upregulated RNA synthesis in the presence of SIN, which may be responsible for their resistance. We also found that some SINR viruses with L gene mutations were defective in cap methylation in vitro, yet their methylases were less sensitive to SIN inhibition than those of the wild-type parent. These studies show that the VSV methylases are inhibited by SIN, and they define new regions of L protein that affect cap methylation. These studies also provide experimental evidence that inhibition of cap methylases is a potential strategy for development of antiviral therapeutics against nonsegmented negative-strand RNA viruses.
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Affiliation(s)
- Jianrong Li
- Harvard Medical School, Department of Microbiology and Molecular Genetics, 200 Longwood Ave., Boston, MA 02115, USA
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29
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Hausmann S, Ramirez A, Schneider S, Schwer B, Shuman S. Biochemical and genetic analysis of RNA cap guanine-N2 methyltransferases from Giardia lamblia and Schizosaccharomyces pombe. Nucleic Acids Res 2007; 35:1411-20. [PMID: 17284461 PMCID: PMC1865056 DOI: 10.1093/nar/gkl1150] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
RNA cap guanine-N2 methyltransferases such as Schizosaccharomyces pombe Tgs1 and Giardia lamblia Tgs2 catalyze methylation of the exocyclic N2 amine of 7-methylguanosine. Here we performed a mutational analysis of Giardia Tgs2, entailing an alanine scan of 17 residues within the minimal active domain. Alanine substitutions at Phe18, Thr40, Asp76, Asn103 and Asp140 reduced methyltransferase specific activity to <3% of wild-type Tgs2, thereby defining these residues as essential. Alanines at Pro142, Tyr148 and Pro185 reduced activity to 7–12% of wild-type. Structure–activity relationships at Phe18, Thr40, Asp76, Asn103, Asp140 and Tyr148, and at three other essential residues defined previously (Asp68, Glu91 and Trp143) were gleaned by testing the effects of 18 conservative substitutions. Our results engender a provisional map of the Tgs2 active site, which we discuss in light of crystal structures of related methyltransferases. A genetic analysis of S. pombe Tgs1 showed that it is nonessential. An S. pombe tgs1Δ strain grows normally, notwithstanding the absence of 2,2,7-trimethylguanosine caps on its U1, U2, U4 and U5 snRNAs. However, we find that S. pombe requires cap guanine-N7 methylation catalyzed by the enzyme Pcm1. Deletion of the pcm1+ gene was lethal, as were missense mutations in the Pcm1 active site. Thus, whereas m7G caps are essential in both S. pombe and S. cerevisiae, m2,2,7G caps are not.
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Affiliation(s)
- Stéphane Hausmann
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA and Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Alejandro Ramirez
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA and Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Susanne Schneider
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA and Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Beate Schwer
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA and Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Stewart Shuman
- Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10021, USA and Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA
- *To whom correspondence should be addressed.
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