Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ribavirin (Rebetol) is an antiviral agent used in combination with interferon alpha-2b (IFN alpha-2b) for the treatment of chronic hepatitis C. Ribavirin has been reported to have a broad-spectrum antiviral activity mainly against RNA viruses. The effect of ribavirin was potentiated when administered in combination with IFN alpha-2b in an antiviral assay using bovine viral diarrhea virus as a surrogate for hepatitis C virus (HCV). Inhibition of host inosine monophosphate dehydrogenase and inhibition of RNA-dependent RNA polymerase (RdRp) of RNA viruses have been reported as the modes of action of ribavirin. Recently, ribavirin has been shown to induce mutation as template for newly generated RNA after uptake in RNA by RdRp of poliovirus, which is an RNA virus as in the case of HCV. It has also been shown that the infectivity of viruses is drastically reduced by the very slight increase in mutations induced by ribavirin. This effect as a mutagen on RNA viruses is a novel mode of ribavirin, and it is thought necessary to classify ribavirin into a new antiviral drug class.
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PMID:[Novel mode of action of ribavirin (Rebetol), a drug for the treatment of chronic hepatitis C: inducting the mutation of RNA viruses]. 1252 71

Bluetongue virus (BTV) is a double-stranded RNA virus of the Reoviridae family. The VP1 protein of BTV is the viral RNA-dependent RNA polymerase (RdRp), which is responsible for the replication of the viral genome. Currently there is no structural information available for VP1. By manual alignment of BTV, Reovirus and other viral RdRps we have generated a model for the structure of VP1, the RdRp of BTV. The structure can be divided into three domains: an N-terminal domain, a C-terminal domain, and a central polymerase domain. Mutation of the putative catalytic site in the central polymerase domain by site-directed mutagenesis abrogated in vitro replicase activity. Each of the domains was expressed individually and subsequently partially purified to obtain direct evidence for the location of polymerase activity and the nucleoside triphosphate binding site. The nucleoside triphosphate binding site was located by showing that CTP only bound to the full-length protein or to the polymerase domain and not to either of the other two domains. None of the domains had catalytic activity when tested individually or in tandem but when all three domains were mixed together the RdRp activity was reconstituted. This is the first report of the reconstitution of a functional viral RdRp in vitro from individual domains.
Biopolymers 2007 May
PMID:Reconstitution of bluetongue virus polymerase activity from isolated domains based on a three-dimensional structural model. 1732 25

One of the possible mechanisms of antiviral action of ribavirin (1-beta- d-ribofuranosyl-1,2,4-triazole-3-carboxamide, 1) is the accumulation of mutations in viral genomic RNA. The ambiguous incorporation of 5'-triphosphate of ribavirin (RTP, 8) by a viral RNA-dependent RNA polymerase (RdRp) is a key step of the mutation induction. We synthesized three ribavirin analogues that possess hydrophobic groups, 4-iodo-1-beta- d-ribofuranosylpyrazole-3-carboxamide ( 7a), 4-propynyl-1-beta- d-ribofuranosylpyrazole-3-carboxamide ( 7b), and 4-phenylethynyl-1-beta-D-ribofuranosylpyrazole-3-carboxamide ( 7c), and the corresponding triphosphates ( 9a, 9b, and 9c, respectively). Steady-state kinetics analysis of the incorporation of these triphosphate analogues by a poliovirus RdRp, 3D (pol), revealed that while the incorporation efficiency of 9a was comparable to RTP, 9b and 9c showed lower efficiency than RTP. Antipolioviral activity of 7a and 7b was much more moderate than ribavirin, and 7c showed no antipolioviral activity. Effects of substituting groups on the incorporation efficiency by 3D (pol) and a strategy for a rational design of more active ribavirin analogues are discussed.
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PMID:Effects of introduction of hydrophobic group on ribavirin base on mutation induction and anti-RNA viral activity. 1806 41

Canine distemper virus (CDV) is a highly contagious pathogen of carnivores. In dogs, the disease is characterized by high lethality rates and no specific antiviral therapy is available. The aim of this study was to verify the in vitro antiviral activity of the 5-ethynyl-1-beta-d-ribofuranosylimidazole-4-carboxamide (EICAR) and to compare it with the 1-(beta-d-ribofuranosyl)-1,2,4-triazole-3-carboxamide (ribavirin, RBV). EICAR was more active than RBV against CDV replication, while both molecules exhibited low selectivity indexes. A reversal of their antiviral activity was observed after addition of guanosine, suggesting their involvement in the inhibition of the inosine monophosphate dehydrogenase enzyme (IMPDH). RBV and EICAR had a time- and concentration-dependent anti-CDV activity, mainly displayed during the first 10h post-infection. The involvement of the inhibition of the viral RNA-dependent RNA polymerase (vRdRp) is discussed, as well as the role of CDV as a model to study more potent and selective antiviral molecules active against other Paramyxoviridae.
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PMID:Antiviral efficacy of EICAR against canine distemper virus (CDV) in vitro. 1978 26

Favipiravir (T-705; 6-fluoro-3-hydroxy-2-pyrazinecarboxamide) is an anti-viral agent that selectively and potently inhibits the RNA-dependent RNA polymerase (RdRp) of RNA viruses. Favipiravir was discovered through screening chemical library for anti-viral activity against the influenza virus by Toyama Chemical Co., Ltd. Favipiravir undergoes an intracellular phosphoribosylation to be an active form, favipiravir-RTP (favipiravir ribofuranosyl-5'-triphosphate), which is recognized as a substrate by RdRp, and inhibits the RNA polymerase activity. Since the catalytic domain of RdRp is conserved among various types of RNA viruses, this mechanism of action underpins a broader spectrum of anti-viral activities of favipiravir. Favipiravir is effective against a wide range of types and subtypes of influenza viruses, including strains resistant to existing anti-influenza drugs. Of note is that favipiravir shows anti-viral activities against other RNA viruses such as arenaviruses, bunyaviruses and filoviruses, all of which are known to cause fatal hemorrhagic fever. These unique anti-viral profiles will make favipiravir a potentially promising drug for specifically untreatable RNA viral infections.
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PMID:Favipiravir (T-705), a broad spectrum inhibitor of viral RNA polymerase. 2876 16

Favipiravir was initially developed as an antiviral drug against influenza and is currently used in clinical trials against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection (COVID-19). This agent is presumably involved in RNA chain termination during influenza virus replication, although the molecular interactions underlying its potential impact on the coronaviruses including SARS-CoV-2, SARS-CoV, and Middle East respiratory syndrome coronavirus (MERS-CoV) remain unclear. We performed in silico studies to elucidate detailed molecular interactions between favipiravir and the SARS-CoV-2, SARS-CoV, MERS-CoV, and influenza virus RNA-dependent RNA polymerases (RdRp). As a result, no interactions between favipiravir ribofuranosyl-5'-triphosphate (F-RTP), the active form of favipiravir, and the active sites of RdRps (PB1 proteins) from influenza A (H1N1)pdm09 virus were found, yet the agent bound to the tunnel of the replication genome of PB1 protein leading to the inhibition of replicated RNA passage. In contrast, F-RTP bound to the active sites of coronavirus RdRp in the presence of the agent and RdRp. Further, the agent bound to the replicated RNA terminus in the presence of agent, magnesium ions, nucleotide triphosphate, and RdRp proteins. These results suggest that favipiravir exhibits distinct mechanisms of action against influenza virus and various coronaviruses.
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PMID:Detailed Molecular Interactions of Favipiravir with SARS-CoV-2, SARS-CoV, MERS-CoV, and Influenza Virus Polymerases In Silico. 3309 45

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA-dependent RNA polymerase (RdRp) is a well-characterized therapeutic target which is a key player driving the viral replication and transcription machinery. The recent elucidation of the experimental structure of SARS-CoV-2 RdRp enzyme complexed with triphosphate form of Remdesivir (RTP) has opened an avenue for structure-based identification of potent inhibitors. Given the high mortality rate of the coronavirus disease 2019 (COVID-19) and lack of effective therapeutics against it, an alternative for safe and speedy drug discovery needs to be sought after. One promising strategy could be to explore the possibility for repurposing the Food and Drug Administration (FDA) approved antiviral drugs and antiviral phytocompounds. In the present study, a set of FDA approved antiviral drugs and antiviral phytocompounds were screened for their ability to bind within the RdRp enzyme active pocket. The top 3 hits among the FDA approved drugs were Paritaprevir (D33), Rilpivirine (D19) and Simeprevir (D31) which scored binding energies between -8.08 kcal/mol and -10.46 kcal/mol. Emetine (P5), 7,4-di-O-galloyltricetifavan (P28) and Oleanolic acid (P17) were the top three phytocompounds hits and exhibited binding energies ranging from -7.81 kcal/mol to -8.17 kcal/mol. These drugs and phytocompounds were able to establish hydrogen bonds with the catalytic residues-Asp760 and Asp761 and hydrophobic interactions with neighbouring residues. Further, the physicochemical properties of the molecules were evaluated. These identified potential inhibitors warrant further experimental investigations before their acceptance as drug candidates for the treatment of the disease.
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PMID:The potential of Paritaprevir and Emetine as inhibitors of SARS-CoV-2 RdRp. 3328 78