Inhibition Of RNA Polymerase Research Articles

Molnupiravir and Combination of Nirmatrelvir and Ritonavir (PaxlovidTM) - Oral Anti-viral Drugs in COVID-19: A Systematic Review

The COVID-19 pandemic situation demands the discovery of newer drugs and/ or repurposing of the existing drugs. The anti-viral drugs approved for COVID-19 are remdesivir and favipiravir. Two more directly acting oral anti-viral drugs have been granted Emergency Use Authorization by US-FDA, molnupiravir on December 23, 2021, and nirmatrelvir and ritonavir (PaxlovidTM) on December 22, 2021. Molnupiravir, an RNA-dependent RNA polymerase (RdRp) inhibitor, has also been approved in the UK and is under review with other regulatory agencies. PaxlovidTM (a combination of the new anti-viral drugs nirmatrelvir and ritonavir) has been developed and approved by US-FDA and CDSCO, India. Nirmatrelvir acts by inhibiting 3CL (chymotrypsin-like) protease enzyme and it is combined with ritonavir to slow down its breakdown by cytochrome P450 enzymes and to increase the bioavailability. Both molnupiravir and PaxlovidTM have been approved for mild and moderate COVID-19 and in patients who have a higher risk of disease progression to severe disease including hospitalisation and death. This article systematically reviews the clinical trials of molnupiravir and PaxlovidTM that evaluated their efficacy and safety against COVID-19 in both published and unpublished literature.

T cell expansion is regulated by mutual regulation of ribosome biosynthesis and mTORC1 activity

Abstract The clonal expansion of T cells entails a swift and substantial repurposing of cellular physiology towards anabolic pathways to allow for a massive increase of cellular biomass for rapid cell division. Ribosomal biosynthesis is an essential and highly energy demanding process driven by the actvities of all RNA polymerases and ~300 proteins processing and modifying the rRNA and its precursors. How ribosomal biosynthesis is integrated into the process of T cell activation is incompletely understood. We have investigated how the mTOR complexes affect ribosomal biosynthesis, T cell proliferation and TCR signaling. We found that the proliferation of mTORC1-but not mTORC2-ablated T cells is slowed from three divisions per day to one with each consecutive division being delayed, mostly at the G1/S transition. mTORC1 signaling is affected by conventional TCR signaling pathways via PI3K while TCR sensitivity is hampered by mTORC1 inhibition. Upon activation the amount of RNA per cell increases at least 10-fold, which is reduced by half in mTORC1-ablated cells. RNA-seq data showed that this reduction affects all RNA biotypes and that rRNA processing is ineffective in activated T cells. Using 5’ ETS FISH probes of nascent pre-rRNA in imaging cytometry revealed that mTORC1 but not mTORC2 ablation reduces the number and the expansion of nucleoli while translation was not yet affected. Inhibiting RNA Polymerase I by chemical and genetic means blocked not only proliferation but mTORC1 signaling as well. Our data show that TCR signaling, mTORC1 activity and ribosomal biosynthesis are tightly interlinked and regulate each other. Supported by grants from the German Research Council (CRC1054-B07, OB150/7-1).

Exploration of natural compounds against the human mpox virus DNA-dependent RNA polymerase in silico

BackgroundLast year, the human monkeypox virus (hMPXV) emerged as an alarming threat to the community, with a detectable outbreak outside the African continent for the first time. According to The American Centers for Disease Control and Prevention (CDC), the virus is reported globally, with 86,746 confirmed cases (until April 08, 2023). DNA-dependent RNA polymerase (DdRp) is an essential protein for viral replication; hence it is a promising drug target for developing antiviral drugs against DNA viruses. Therefore, this study was conducted to search for natural compounds that could provide scaffolds for RNA polymerase inhibitors. MethodsIn this study, the DdRp structure of hMPXV was modeled and used to screen the natural compounds database (COCONUT). The virtual screening revealed 15 compounds able to tightly bind to the active site of the DdRp (binding energies less than −7.0 kcal/mol) compared to the physiological nucleotide, guanosine triphosphate (GTP). Molecular dynamics simulation was then performed on the top four hits and compared to GTP ResultsThe results revealed the potential of four compounds (comp289, comp295, comp441, and comp449) in binding the hMPXV DdRp active site with a comparable binding affinity (−17.06 ± 2.96, −11.6 ± 5.34, −14.85 ± 2.66, and −10.79 ± 4.49 kcal/mol) with GTP (−21.03 ± 7.55 kcal/mol) ConclusionThese findings may also pave the way for developing new hMPXV inhibitors based on natural product scaffolds. These results need further experimental validation but promising as it was validated by unbiased all-atom MD simulations and binding free energy calculations.

Remdesivir Efficacy and Tolerability in Children with COVID-19-Associated Allergic Comorbidities such as Asthma, Allergic Rhinitis, and Atopic Dermatitis.

In children, coronavirus disease 2019 (COVID-19) starts as a minor illness compared to adults, but during the ongoing COVID-19 pandemic, distinct SARS-CoV-2 variants and subvariants have changed options for therapies in both adults and children, especially for those with comorbidities such as allergies. On 25 April 2022, Remdesivir (RDV), a viral RNA-dependent RNA polymerase inhibitor, was approved by the Food and Drug Administration (FDA) for the treatment of pediatric patients 28 days and older, weighing ≥3 kg, hospitalized or non-hospitalized, who are at high risk of progression to severe forms of COVID-19. While RDV has been shown to have favorable effects in numerous types of research conducted on adults, such as shortening hospital stays, and has shown it has antiviral effects on various RNA viruses, there is a lack of findings regarding safety, tolerability, and efficacy of RDV in allergic pediatric patients since its initial FDA approval. This study aims to assess RDV's efficacy and tolerability in treating pediatric patients with mild and severe forms of COVID-19-associated allergies such as asthma, allergic rhinitis, and atopic dermatitis and how RDV affects the duration of hospitalization, especially for these comorbidities. The most recent pandemic wave among children rose due to the high transmissibility of the Omicron variant, and this study analyzed changes between July 2020 and September 2022 at the National Institute of Infectious Diseases "Prof. Dr. Matei Balș", Bucharest, Romania. Our retrospective study included 250 children <18 years old, 42 (16.8%) had allergies, 132 were males (52.8%), age group 0-5 years old (80%), with a positive viral test for SARS-CoV-2. Severity was categorized as mild (43.6%), moderate (53.2%), and severe (1.6%) COVID-19, and treatment with RDV was administered in 50.4% (126/250) of children included in the study. The presence of comorbidities, asthma (7.2%), allergic rhinitis (4.4%), and atopic dermatitis (4.4%), was associated with an increased risk of developing severe COVID-19 infection in children, p < 0.05. We did not register deaths and severe complications; all cases evolved favorably under the instituted treatment. Laboratory abnormalities in transaminase levels 53.97% (ALT) and 61.9% (AST) were grades 1 or 2 and did not require discontinuation of the antiviral treatment, p < 0.05. RDV in children reduced the duration and evolution of COVID-19 and decreased the length of hospitalization in group-associated allergies; p < 0.05. This article summarizes RDV's efficacy among children with COVID-19 and allergies when the clinical result was improved and reports positive effects on tolerability and reduced duration of hospitalization, especially in children with asthma, atopic dermatitis, and allergic rhinitis. More studies are needed to confirm our findings.

Targeting the vital non-structural proteins (NSP12, NSP7, NSP8 and NSP3) from SARS-CoV-2 and inhibition of RNA polymerase by natural bioactive compound naringenin as a promising drug candidate against COVID-19

The prevalence of SARS-CoV-2-induced respiratory infections is now a major challenge worldwide. There is currently no specific antiviral drug to prevent or treat this disease. Infection with COVID-19 seriously needs to find effective therapeutic agents. In the present study, naringenin, as a potential inhibitor candidate for RNA Polymerase SARS-CoV-2 was compared with remdesivir (FDA-approved drug) and GS-441,524 (Derivative of the drug remdesivir) by screening with wild-type and mutant SARS-CoV-2 NSP12 (NSP7-NSP8) and NSP3 interfaces, then complexes were simulated by molecular dynamics (MD) simulations to gain their stabilities. The docking results displayed ​scores of -3.45 kcal/mol and -4.32 kcal/mol against NSP12 and NSP3, respectively. Our results showed that naringenin had ΔG values more negative than the ΔG values of Remdesivir (RDV) and GS-441,524. Hence, naringenin was considered to be a potential inhibitor. Also, the number of hydrogen bonds of naringenin with NSP3 and later NSP12 are more than Remdesivir and its derivative. In this research, Mean root mean square deviation (RMSD) values of NSP3 and NSP12with naringenin ligand (5.55±1.58 nm to 3.45±0.56 nm and 0.238±0.01 to 0.242±0.021 nm, respectively showed stability in the presence of ligand. The root mean square fluctuations (RMSF) values of NSP3 and NSP12 amino acid units in the presence of naringenin in were 1.5 ± 0.31 nm and 0.118±0.058, respectively. Pharmacokinetic properties and prediction of absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of naringenin and RDV showed that ​these two compounds had no potential cytotoxicity.

Transient left bundle branch block associated with favipiravir treatment for coronavirus infection.

The coronavirus disease 2019 (COVID-19) may lead to a wide spectrum of clinical manifestations ranging from asymptomatic to symptomatic by having targets on various tissues such as lung parenchyma and myocardium (Shahrbaf et al., Cardiovasc Hematol Disord Drug Targets. 21(2):88-90, 2021). As an RNA-dependent RNApolymerase inhibitor, favipiravir has been proposed as a treatment in clinical studies done during the pandemic period (Furuta et al., Antiviral Res. 100(2):446-454, 2013). Although favipiravir is generally a safe medication, it may rarely cause cardiac adverse effects (Shahrbaf et al., Cardiovasc Hematol Disord Drug Targets. 21(2):88-90, 2021). To the best of our knowledge, favipiravir has not been reported to cause left bundle branch block (LBBB).

Bioactive compounds from Huashi Baidu decoction possess both antiviral and anti-inflammatory effects against COVID-19

The coronavirus disease 2019 (COVID-19) pandemic is an ongoing global health concern, and effective antiviral reagents are urgently needed. Traditional Chinese medicine theory-driven natural drug research and development (TCMT-NDRD) is a feasible method to address this issue as the traditional Chinese medicine formulae have been shown effective in the treatment of COVID-19. Huashi Baidu decoction (Q-14) is a clinically approved formula for COVID-19 therapy with antiviral and anti-inflammatory effects. Here, an integrative pharmacological strategy was applied to identify the antiviral and anti-inflammatory bioactive compounds from Q-14. Overall, a total of 343 chemical compounds were initially characterized, and 60 prototype compounds in Q-14 were subsequently traced in plasma using ultrahigh-performance liquid chromatography with quadrupole time-of-flight mass spectrometry. Among the 60 compounds, six compounds (magnolol, glycyrrhisoflavone, licoisoflavone A, emodin, echinatin, and quercetin) were identified showing a dose-dependent inhibition effect on the SARS-CoV-2 infection, including two inhibitors (echinatin and quercetin) of the main protease (Mpro), as well as two inhibitors (glycyrrhisoflavone and licoisoflavone A) of the RNA-dependent RNA polymerase (RdRp). Meanwhile, three anti-inflammatory components, including licochalcone B, echinatin, and glycyrrhisoflavone, were identified in a SARS-CoV-2-infected inflammatory cell model. In addition, glycyrrhisoflavone and licoisoflavone A also displayed strong inhibitory activities against cAMP-specific 3',5'-cyclic phosphodiesterase 4 (PDE4). Crystal structures of PDE4 in complex with glycyrrhisoflavone or licoisoflavone A were determined at resolutions of 1.54Å and 1.65Å, respectively, and both compounds bind in the active site of PDE4 with similar interactions. These findings will greatly stimulate the study of TCMT-NDRD against COVID-19.

Assessing the Orthogonality of Phage-Encoded RNA Polymerases for Tailored Synthetic Biology Applications in Pseudomonas Species.

The phage T7 RNA polymerase (RNAP) and lysozyme form the basis of the widely used pET expression system for recombinant expression in the biotechnology field and as a tool in microbial synthetic biology. Attempts to transfer this genetic circuitry from Escherichia coli to non-model bacterial organisms with high potential have been restricted by the cytotoxicity of the T7 RNAP in the receiving hosts. We here explore the diversity of T7-like RNAPs mined directly from Pseudomonas phages for implementation in Pseudomonas species, thus relying on the co-evolution and natural adaptation of the system towards its host. By screening and characterizing different viral transcription machinery using a vector-based system in P. putida., we identified a set of four non-toxic phage RNAPs from phages phi15, PPPL-1, Pf-10, and 67PfluR64PP, showing a broad activity range and orthogonality to each other and the T7 RNAP. In addition, we confirmed the transcription start sites of their predicted promoters and improved the stringency of the phage RNAP expression systems by introducing and optimizing phage lysozymes for RNAP inhibition. This set of viral RNAPs expands the adaption of T7-inspired circuitry towards Pseudomonas species and highlights the potential of mining tailored genetic parts and tools from phages for their non-model host.

Suramin binds and inhibits infection of SARS-CoV-2 through both spike protein-heparan sulfate and ACE2 receptor interactions

SARS-CoV-2 receptor binding domains (RBDs) interact with both the ACE2 receptor and heparan sulfate on the surface of host cells to enhance SARS-CoV-2 infection. We show that suramin, a polysulfated synthetic drug, binds to the ACE2 receptor and heparan sulfate binding sites on the RBDs of wild-type, Delta, and Omicron variants. Specifically, heparan sulfate and suramin had enhanced preferential binding for Omicron RBD, and suramin is most potent against the live SARS-CoV-2 Omicron variant (B.1.1.529) when compared to wild type and Delta (B.1.617.2) variants in vitro. These results suggest that inhibition of live virus infection occurs through dual SARS-CoV-2 targets of S-protein binding and previously reported RNA-dependent RNA polymerase inhibition and offers the possibility for this and other polysulfated molecules to be used as potential therapeutic and prophylactic options against COVID-19.

Abstract 4909: Molecular analysis of small cell lung cancer provides insights into mechanism of action underlying the novel drug combination of lurbinectedin and TIC10/ONC201

Abstract We previously explored the combination of novel imipridone TIC10/ONC201 and small molecule RNA polymerase inhibitor lurbinectedin as a potentially effective treatment regimen for small cell lung cancer (SCLC). Data from cell viability experiments demonstrated synergistic killing of SCLC cells with minimal death of healthy control cells. Analysis of intracellular proteins via Western blot indicated that combinatorial treatment induces the integrated stress response, DNA damage/cell cycle checkpoint responses, and increased apoptosis of tumor cells. We have utilized the Luminex 200 platform to perform analyses of cytokine levels in SCLC cell lines with various genetic alterations before and after ONC201 and lurbinectedin treatment. Our results revealed significant changes in cytokine levels following treatment indicating potential immunomodulatory and angioregulatory effects of ONC201 and lurbinectedin. CCL3, known to recruit and activate granulocytes, was found to be elevated by treatment with lurbinectedin, ONC201 and combination versus control. Angiopoietin 1, which contributes to blood vessel maturation, and angiopoietin 2, which promotes neovascularisation, were elevated by all drug treatments in H1882 SCLC cells. Our ongoing studies are further analysing the importance of specific cytokines in tumor vascularity and in recruitment and killing of SCLC cells by immune cells. Results from these experiments are helping to elucidate the molecular mechanisms underlying SCLC, its immune landscape, and treatment response. Citation Format: Ashley Sanchez Sevilla Uruchurtu, Nicholas Liguori, Leiqing Zhang, Kelsey Huntington, Lanlan Zhou, Young Lee, Abbas E. Abbas, Christopher G. Azzoli, Wafik S. El-Deiry. Molecular analysis of small cell lung cancer provides insights into mechanism of action underlying the novel drug combination of lurbinectedin and TIC10/ONC201. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4909.

Dietary phytochemicals against COVID‐19: A focus on thymoquinone

Dietary phytochemicals against COVID‐19: A focus on thymoquinone

Targeting mutant dicer tumorigenesis in pleuropulmonary blastoma via inhibition of RNA polymerase I

DICER1 mutations predispose to increased risk for various cancers, particularly pleuropulmonary blastoma (PPB), the commonest lung malignancy of childhood. There is a paucity of directly actionable molecular targets as these tumors are driven by loss-of-function mutations of DICER1. Therapeutic development for PPB is further limited by a lack of biologically and physiologically-representative disease models. Given recent evidence of Dicer's role as a haploinsufficient tumor suppressor regulating RNA polymerase I (Pol I), Pol I inhibition could abrogate mutant Dicer-mediated accumulation of stalled polymerases to trigger apoptosis. Hence, we developed a novel subpleural orthotopic PPB patient-derived xenograft (PDX) model that retained both RNase IIIa and IIIb hotspot mutations and recapitulated the cardiorespiratory physiology of intra-thoracic disease, and with it evaluated the tolerability and efficacy of first-in-class Pol I inhibitor CX-5461. In PDX tumors, CX-5461 significantly reduced H3K9 di-methylation and increased nuclear p53 expression, within 24 hours’ exposure. Following treatment at the maximum tolerated dosing regimen (12 doses, 30 mg/kg), tumors were smaller and less hemorrhagic than controls, with significantly decreased cellular proliferation, and increased apoptosis. As demonstrated in a novel intrathoracic tumor model of PPB, Pol I inhibition with CX-5461 could be a tolerable and clinically-feasible therapeutic strategy for mutant Dicer tumors, inducing antitumor effects by decreasing H3K9 methylation and enhancing p53-mediated apoptosis.

Computational identification of drug-like marine natural products as potential RNA polymerase inhibitors against Nipah virus

Nipah virus (NiV) has been an alarming threat to human populations in southern Asia for more than a decade. It is one of the most deadly viruses in the Mononegavirales order. Despite its high mortality rate and virulence, no chemotherapeutic agent or vaccine is publicly available. Hence, this work was conducted to computationally screen marine natural products database for drug-like potential inhibitors for the viral RNA-dependent RNA polymerase (RdRp). The structural model was subjected to molecular dynamics (MD) simulation to obtain the native ensemble of the protein. The CMNPDB dataset of marine natural products was filtered to retain only compounds following Lipinski's five rules. The molecules were energy minimized and docked into different conformers of the RdRp using AutoDock Vina. The best 35 molecules were rescored by GNINA, a deep learning-based docking software. The resulting nine compounds were evaluated for their pharmacokinetic profiles and medicinal chemistry properties. The best five compounds were subjected to MD simulation for 100 ns, followed by binding free energy estimation via Molecular Mechanics/ Generalized Born Surface Area (MM/GBSA) calculations. The results showed remarkable behavior of five hits as inferred by stable binding pose and orientation to block the exit channel of RNA synthesis products in the RdRp cavity. These hits are promising starting materials for in vitro validation and structural modifications to enhance the pharmacokinetic and medicinal chemistry properties for developing antiviral lead compounds.

Structural Insights into the Role of Pseudouridimycin Binding in Disruption of Bacterial RNA Polymerase Bridge Helix Conformational Arrangement.

The bridge helix (BH) is a crucial region in bacterial RNA polymerase (RNAP) catalysis. It plays an essential role in the nucleotide addition cycle (NAC) by performing many modulated rearrangements and conformational changes. Any changes in the bridge helix conformational arrangements could perturb the NAC. Pseudouridimycin (PUM) was recently reported as a new RNAP inhibitor. However, the crucial role of the bridge helix in the inhibitory activity of PUM remains unclear, hence the aim of this study. The PUM interaction and the structural dynamics of bacterial Bridge Helix upon PUM binding were investigated using various dynamic analysis approaches. Besides establishing the importance of the bridge helix residues in the binding of PUM, the findings of this study revealed that the adjacent binding of PUM induces a stabilized and structurally rigid bridge helix characterized by a reduction of individual residue flexibility, which could interfere with its role in the NAC. In addition, a hydrophobic structural rearrangement of the bridge helix is observed, evidenced by the burial and folding of residues into the hydrophobic core and a switch in the secondary structure of some regions of the bridge helix from the turn and bend to the alpha helix. The observed conformational disruption of the bridge helix upon binding of PUM also accounts for the reported inhibitory prowess and broad-spectrum activity as widely reported. Conclusion We believe findings from this study will further complement current drug discovery knowledge on disrupting bacterial RNAP machinery.

High-Throughput Screen Reveals the Structure-Activity Relationship of the Antimicrobial Lasso Peptide Ubonodin.

The Burkholderia cepacia complex (Bcc) is a group of bacteria including opportunistic human pathogens. Immunocompromised individuals and cystic fibrosis patients are especially vulnerable to serious infections by these bacteria, motivating the search for compounds with antimicrobial activity against the Bcc. Ubonodin is a lasso peptide with promising activity against Bcc species, working by inhibiting RNA polymerase in susceptible bacteria. We constructed a library of over 90 000 ubonodin variants with 2 amino acid substitutions and used a high-throughput screen and next-generation sequencing to examine the fitness of the entire library, generating the most comprehensive data set on lasso peptide activity so far. This screen revealed information regarding the structure-activity relationship of ubonodin over a large sequence space. Remarkably, the screen identified one variant with not only improved activity compared to wild-type ubonodin but also a submicromolar minimum inhibitory concentration (MIC) against a clinical isolate of the Bcc member Burkholderia cenocepacia. Ubonodin and several of the variants identified in this study had lower MICs against certain Bcc strains than those of many clinically approved antibiotics. Finally, the large library size enabled us to develop DeepLasso, a deep learning model that can predict the RNAP inhibitory activity of an ubonodin variant.

An update on current understanding of the epidemiology and management of the re-emerging endemic Lassa fever outbreaks

An update on current understanding of the epidemiology and management of the re-emerging endemic Lassa fever outbreaks

Antiviral effect and mechanism of Phillyrin and its reformulated FS21 against influenza.

Influenza virus causes significant morbidity and mortality with pandemic threat. Oleaceae Fructus Forsythiae is a medicinal herb. This study aimed to investigate antiviral effect of Phillyrin, a purified bioactive compound from this herb, and its reformulated preparation FS21 against influenza and its mechanism. Madin-Darby Canine Kidney (MDCK) cells were infected by one of six influenza viruses: five influenza A viruses (IAVs: three H1N1 and two H3N2) and one influenza B virus (IBV). Virus-induced cytopathic effects were observed and recorded under microscope. Viral replication and mRNA transcription were evaluated by quantitative polymerase chain reaction (qPCR) and protein expression by Western blot. Infectious virus production was assessed using TCID50 assay, and IC50 was calculated accordingly. Pretreatment and time-of-addition experiments with Phillyrin or FS21 added 1 h before or in early (0-3 h), mid (3-6 h), or late (6-9 h) stages of viral infection were performed to assess their antiviral effects. Mechanistic studies included hemagglutination and neuraminidase inhibition, viral binding and entry, endosomal acidification, and plasmid-based influenza RNA polymerase activity. Phillyrin and FS21 had potent antiviral effects against all six IAV and IBV in a dose-dependent manner. Mechanistic studies showed that both suppressed influenza viral RNA polymerase with no effect on virus-mediated hemagglutination inhibition, viral binding or entry, endosomal acidification, or neuraminidase activity. Phillyrin and FS21 have broad and potent antiviral effects against influenza viruses with inhibition of viral RNA polymerase as the distinct antiviral mechanism.

Amanitine poisoning - cases, management, therapy results

Mushroom poisoning continues to be a serious clinical problem. The most serious are intoxications with mushrooms containing cytotropic toxins with predominant injury of liver, kidneys and heart. The toxic properties of the phalloides are mainly due to α-amanitin, which is an inhibitor of RNA polymerase II. The clinical course of poisoning can be divided for 4 periods. The asymptomatic period usually lasts 6-24 hours after mushroom consumption. Then the period of the gastrointestinal disorder lasting on average 12-24 hours. The second latency period with apparent improvement of the patient's general condition lasting 12-24 hours is subjected to the stage, during which biochemical markers of hepatocyte activity appear. After a few days (usually on the 4-5th day) from poisoning, kidney function may occur (oliguria or anuria), and circulatory system disorders may also occur. Death usually occurs between 4-16 days after poisoning. The treatment of poisoning with amanita phalloides includes a number of procedures, including rapid removal of toxins, blocking the penetration of amatoxins into the hepatic cell, compensation of systemic metabolic disorders, and extracorporeal support of liver function.

A gene silencing screen uncovers diverse tools for targeted gene repression in Arabidopsis

DNA methylation has been utilized for target gene silencing in plants. However, it is not well understood whether other silencing pathways can be also used to manipulate gene expression. Here we performed a gain-of-function screen for proteins that could silence a target gene when fused to an artificial zinc finger. We uncovered many proteins that suppressed gene expression through DNA methylation, histone H3K27me3 deposition, H3K4me3 demethylation, histone deacetylation, inhibition of RNA polymerase II transcription elongation or Ser-5 dephosphorylation. These proteins also silenced many other genes with different efficacies, and a machine learning model could accurately predict the efficacy of each silencer on the basis of various chromatin features of the target loci. Furthermore, some proteins were also able to target gene silencing when used in a dCas9-SunTag system. These results provide a more comprehensive understanding of epigenetic regulatory pathways in plants and provide an armament of tools for targeted gene manipulation.

Remdesivir-Induced Bradycardia.

Remdesivir, a viral RNA-dependent RNA polymerase inhibitor, found extensive use in coronavirus disease 2019-infected patients because it curbs the viral load expansion. Among patients hospitalized as a result of lower respiratory tract infection, remdesivir proved to improve recovery time; however, remdesivir also can induce significant cytotoxic effects on cardiac myocytes. In this narrative review, we discuss the pathophysiological mechanism of remdesivir-induced bradycardia and diagnostic and management strategies for these patients. We conclude that further research is necessary to understand better the mechanism of bradycardia in coronavirus disease 2019 patients with or without cardiovascular disorder treated with remdesivir.