Natural product inhibition of SARS-CoV-2 guanine-N7 RNA cap methyltransferase shows potent cellular antiviral efficacy
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PROVIDER: PRJNA1190932 | ENA |
REPOSITORIES: ENA
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Project description:SARS-CoV-2 virus mimics host mRNA by capping its viral RNA to promote replication and evade host immune sensing. SARS-CoV-2 NSP14 is the N7-guanosine methyltransferase (N7-MTase) responsible for RNA cap-0 formation. Targeting NSP14 for antiviral drug development is an under-explored but promising strategy. Here we conducted a high-throughput screening on natural products library derived from Chinese herbal medicine to discover Emodin as a SARS-CoV-2 NSP14 inhibitor. Exploring Emodin derivatives, Questin was identified with potent cellular inhibitory activity (EC50=249 nM) against SARS-CoV-2, which inhibits NSP14 in an RNA cap competitive manner, making it one the most potent anti-coronaviral natural products. Mechanistically, besides catalyzing viral RNA capping, NSP14 by itself could remodel host transcriptome such as enriching CREBBP, a key host factor in cellular cyclic AMP response pathway, to promote viral infection. As a result, targeting NSP14 by Questin significantly impairs viral Replication & Translation step and reverses host transcriptome remodeled by NSP14. We next validated Questin as a promising lead with significantly improved toxicity upon acute exposure in zebrafish larvae. Taken together, our study not only demonstrates Questin as a potent drug lead for clinical antiviral application, but also highlights multiple antiviral potentials of NSP14 as therapeutic target.
2024-12-31 | GSE282879 | GEO
Project description: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.
| S-EPMC2271365 | biostudies-literature
Project description:The project aims to identify the RNA binding proteins that can specifically bind to mRNA internal modification N7-methylguanosine (m7G). N7-methylguanosine (m7G) methylation has been long identified as the essential cap modification for eukaryotic mRNA, but later has been identified internally in various types of RNAs, including tRNA, rRNA, miRNA, and mRNA. While the METTL1/WDR4 complex, responsible for tRNA m7G installation, has been suggested to be responsible for internal mRNA modification as well, little is known about the proteins that can identify and interact with m7G. To better understand its interaction with RNA binding proteins and further define its regulatory function in mRNA metabolism, we performed the experiment to pulldown proteins with different binding affinity on unmodified G and m7G and subject the enriched fractions to mass spectrometry.
2024-09-03 | PXD049390 | Pride
Project description:Coronaviruses possess a cap structure at the 5' ends of viral genomic RNA and subgenomic RNAs, which is generated through consecutive methylations by virally encoded guanine-N7-methyltransferase (N7-MTase) and 2'-O-methyltransferase (2'-O-MTase). The coronaviral N7-MTase is unique for its physical linkage with an exoribonuclease (ExoN) harbored in nonstructural protein 14 (nsp14) of coronaviruses. In this study, the structure-function relationships of the N7-MTase were analyzed by deletion and site-directed mutagenesis of severe acute respiratory syndrome coronavirus (SARS-CoV) nsp14. The results showed that the ExoN domain is closely involved in the activity of the N7-MTase, suggesting that coronavirus N7-MTase is different from all other viral N7-MTases, which are separable from other structural domains located in the same polypeptide. Two of the 12 critical residues identified to be essential for the N7-MTase were located at the N terminus of the core ExoN domain, reinforcing a role of the ExoN domain in the N7-MTase activity of nsp14. The other 10 critical residues were distributed throughout the N7-MTase domain but localized mainly in the S-adenosyl-l-methionine (SAM)-binding pocket and key structural elements of the MTase fold of nsp14. The sequence motif DxGxPxA (amino acids [aa] 331 to 338) was identified as the key part of the SAM-binding site. These results provide insights into the structure and functional mechanisms of coronaviral nsp14 N7-MTase.
| S-EPMC3648086 | biostudies-literature
Project description: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.
| S-EPMC8495969 | biostudies-literature
Project description:SARS-CoV-2, the cause of the currently ongoing COVID-19 pandemic, encodes its own mRNA capping machinery. Insights into this capping system may provide new ideas for therapeutic interventions and drug discovery. In this work, we employ a previously developed Py-FLINT screening approach to study the inhibitory effects of compounds against the cap guanine N7-methyltransferase enzyme, which is involved in SARS-CoV-2 mRNA capping. We screened five commercially available libraries (7039 compounds in total) to identify 83 inhibitors with IC50 < 50 μM, which were further validated using RP HPLC and dot blot assays. Novel fluorescence anisotropy binding assays were developed to examine the targeted binding site. The inhibitor structures were analyzed for structure-activity relationships in order to define common structural patterns. Finally, the most potent inhibitors were tested for antiviral activity on SARS-CoV-2 in a cell based assay.
| S-EPMC8299157 | biostudies-literature
Project description:Small-molecule inhibition of SARS-CoV-2 guanine-N7 RNA cap methyltransferase
| PRJNA1035531 | ENA
Project description: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.
| S-EPMC7119097 | biostudies-literature
Project description: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.
| S-EPMC7291971 | biostudies-literature
Project description:The order Nidovirales is a diverse group of (+)RNA viruses, classified together based on their common genome organisation and conserved replicative enzymes, despite drastic differences in size and complexity. One such difference pertains to the mechanisms and enzymes responsible for generation of the proposed viral 5' RNA cap. Within the Coronaviridae family, two separate methytransferases (MTase), nsp14 and nsp16, perform the RNA-cap N7-guanine and 2'-OH methylation respectively for generation of the proposed m7GpppNm type I cap structure. For the majority of other families within the Nidovirales order, the presence, structure and key enzymes involved in 5' capping are far less clear. These viruses either lack completely an RNA MTase signature sequence, or lack an N7-guanine methyltransferase signature sequence, obscuring our understanding about how RNA-caps are N7-methylated for these families. Here, we report the discovery of a putative Rossmann fold RNA methyltransferase in 10 Tobaniviridae members in Orf1a, an unusual genome locus for this gene. Multiple sequence alignments and structural analyses lead us to propose this novel gene as a typical RNA-cap N7-guanine MTase with substrate specificity and active-site organization similar to the canonical eukaryotic RNA-cap N7-guanine MTase.
| S-EPMC7107822 | biostudies-literature