Inhibition of SUV39H1 reduces tumor angiogenesis via Notch1 in oral squamous cell carcinoma.

Targeting tumor angiogenesis is an important approach in advanced tumor therapy. Here we investigated the effect of the suppressor of variegation 3-9 homolog 1 (SUV39H1) on tumor angiogenesis in oral squamous cell carcinoma (OSCC). The GEPIA database was used to analyze the expression of SUV39H1 in various cancer tissues. The expression of SUV39H1 in OSCC was detected by immunohistochemistry, and the correlation between SUV39H1 and Notch1 and microvascular density (MVD) was analyzed. The effect of SUV39H1 inhibition on OSCC was investigated in vivo by chaetocin treatment. The migration and tube formation of vascular endothelial cells by conditioned culture-medium of different treatments of oral squamous cell cells were measured. The transcriptional level of SUV39H1 is elevated in various cancer tissues. The transcription level of SUV39H1 in head and neck squamous cell carcinoma was significantly higher than that in control. Immunohistochemistry result showed increased SUV39H1 expression in OSCC, which was significantly correlated with T staging. The expression of SUV39H1 was significantly correlated with Notch1 and CD31. In vivo experiment chaetocin treatment significantly inhibit the growth of tumor, and reduce SUV39H1, Notch1, CD31 expression. The decreased expression of SUV39H1 in OSCC cells lead to the decreased expression of Notch1 and VEGF proteins, as well as the decreased migration and tube formation ability of vascular endothelial cells. Inhibition of Notch1 further enhance this effect. Our results suggest inhibition of SUV39H1 may affect angiogenesis by regulating Notch1 expression. This study provides a foundation for SUV39H1 as a potential therapeutic target for OSCC.

In vitro biological evaluation and in silico insights into the antiviral activity of standardized olive leaves extract against SARS-CoV-2.

There is still a great global need for efficient treatments for the management of SARS-CoV-2 illness notwithstanding the availability and efficacy of COVID-19 vaccinations. Olive leaf is an herbal remedy with a potential antiviral activity that could improve the recovery of COVID-19 patients. In this work, the olive leaves major metabolites were screened in silico for their activity against SARS-CoV-2 by molecular docking on several viral targets such as methyl transferase, helicase, Plpro, Mpro, and RdRp. The results of in silico docking study showed that olive leaves phytoconstituents exhibited strong potential antiviral activity against SARS-CoV-2 selected targets. Verbacoside demonstrated a strong inhibition against methyl transferase, helicase, Plpro, Mpro, and RdRp (docking scores = -17.2, -20, -18.2, -19.8, and -21.7 kcal/mol.) respectively. Oleuropein inhibited 5rmm, Mpro, and RdRp (docking scores = -15, -16.6 and -18.6 kcal/mol., respectively) respectively. Apigenin-7-O-glucoside exhibited activity against methyl transferase and RdRp (docking score = -16.1 and -19.4 kcal/mol., respectively) while Luteolin-7-O-glucoside inhibited Plpro and RdRp (docking score = -15.2 and -20 kcal/mol., respectively). The in vitro antiviral assay was carried out on standardized olive leaf extract (SOLE) containing 20% oleuropein and IC50 was calculated. The results revealed that 20% SOLE demonstrated a moderate antiviral activity against SARS-CoV-2 with IC50 of 118.3 µg /mL. Accordingly, olive leaf could be a potential herbal therapy against SARS-CoV-2 but more in vivo and clinical investigations are recommended.

Cheminformatics approach to identify andrographolide derivatives as dual inhibitors of methyltransferases (nsp14 and nsp16) of SARS-CoV-2.

The Covid-19 pandemic outbreak has accelerated tremendous efforts to discover a therapeutic strategy that targets severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to control viral infection. Various viral proteins have been identified as potential drug targets, however, to date, no specific therapeutic cure is available against the SARS-CoV-2. To address this issue, the present work reports a systematic cheminformatic approach to identify the potent andrographolide derivatives that can target methyltransferases of SARS-CoV-2, i.e. nsp14 and nsp16 which are crucial for the replication of the virus and host immune evasion. A consensus of cheminformatics methodologies including virtual screening, molecular docking, ADMET profiling, molecular dynamics simulations, free-energy landscape analysis, molecular mechanics generalized born surface area (MM-GBSA), and density functional theory (DFT) was utilized. Our study reveals two new andrographolide derivatives (PubChem CID: 2734589 and 138968421) as natural bioactive molecules that can form stable complexes with both proteins via hydrophobic interactions, hydrogen bonds and electrostatic interactions. The toxicity analysis predicts class four toxicity for both compounds with LD50 value in the range of 500-700 mg/kg. MD simulation reveals the stable formation of the complex for both the compounds and their average trajectory values were found to be lower than the control inhibitor and protein alone. MMGBSA analysis corroborates the MD simulation result and showed the lowest energy for the compounds 2734589 and 138968421. The DFT and MEP analysis also predicts the better reactivity and stability of both the hit compounds. Overall, both andrographolide derivatives exhibit good potential as potent inhibitors for both nsp14 and nsp16 proteins, however, in-vitro and in vivo assessment would be required to prove their efficacy and safety in clinical settings. Moreover, the drug discovery strategy aiming at the dual target approach might serve as a useful model for inventing novel drug molecules for various other diseases.

Targeting cap1 RNA methyltransferases as an antiviral strategy.

Methylation is one of the critical modifications that regulates numerous biological processes. Guanine capping and methylation at the 7th position (m7G) have been shown to mature mRNA for increased RNA stability and translational efficiency. The m7G capped cap0 RNA remains immature and requires additional methylation at the first nucleotide (N1-2'-O-Me), designated as cap1, to achieve full maturation. This cap1 RNA with N1-2'-O-Me prevents its recognition by innate immune sensors as non-self. Viruses have also evolved various strategies to produce self-like capped RNAs with the N1-2'-O-Me that potentially evades the antiviral response and establishes an efficient replication. In this review, we focus on the importance of the presence of N1-2'-O-Me in viral RNAs and discuss the potential for drug development by targeting host and viral N1-2'-O-methyltransferases.

Chemical Proteomic Discovery of Isotype-Selective Covalent Inhibitors of the RNA Methyltransferase NSUN2.

5-Methylcytosine (m5 C) is an RNA modification prevalent on tRNAs, where it can protect tRNAs from endonucleolytic cleavage to maintain protein synthesis. The NSUN family (NSUN1-7 in humans) of RNA methyltransferases are capable of installing the methyl group onto the C5 position of cytosines in RNA. NSUNs are implicated in a wide range of (patho)physiological processes, but selective and cell-active inhibitors of these enzymes are lacking. Here, we use cysteine-directed activity-based protein profiling (ABPP) to discover azetidine acrylamides that act as stereoselective covalent inhibitors of human NSUN2. Despite targeting a conserved catalytic cysteine in the NSUN family, the NSUN2 inhibitors show negligible cross-reactivity with other human NSUNs and exhibit good proteome-wide selectivity. We verify that the azetidine acrylamides inhibit the catalytic activity of recombinant NSUN2, but not NSUN6, and demonstrate that these compounds stereoselectively disrupt NSUN2-tRNA interactions in cancer cells, leading to a global reduction in tRNA m5 C content. Our findings thus highlight the potential to create isotype-selective and cell-active inhibitors of NSUN2 with covalent chemistry targeting a conserved catalytic cysteine.

[METTL3 inhibitor STM2457 improves metabolic dysfunction-associated fatty liver disease by regulating mitochondrial function in mice].

OBJECTIVE: To investigate the effect of methyltransferase-like 3 (METTL3) inhibitor STM2457 in metabolic dysfunction-associated fatty liver disease (MAFLD). METHODS: C57BL/6J mouse models of MAFLD induced by high-fat diet feeding for 16 weeks were treated with intraperitoneal injections of STM2457 (50 mg/kg) for 2 weeks. The changes in m6A modification level in the liver tissue of the mice were determined with dot-blot hybridization, and the hepatic levels of triglyceride (TG), alanine aminotransferase (ALT) and glutathione aminotransferase (AST) were detected. The histological changes of the liver and changes in insulin resistance and metabolic profile of the mice were evaluated using HE staining, insulin tolerance tests and metabolic cages; transmission electron microscopy (TEM) was employed to examine the changes in mitochondrial morphology. In a HepG2 cell model of steatosis induced by treatment with sodium oleate/sodium palmitate for 48 h, the protective effect of STM2457 (1 µmol/L) on mitochondrial function was assessed by measuring mitochondrial membrane potential using a fluorescence probe (JC-1). RESULTS: The mouse models of MAFLD showed significant elevation of m6A modification level in the liver tissues and obviously upregulated mRNA expression of METT3 (P<0.05). Treatment with STM2457 significantly reduced body weight and liver lipid deposition and m6A modification levels, increased glucose tolerance and insulin sensitivity, lowered hepatic TG and serum ALT and AST levels, and increased respiratory entropy (RQ) in the mouse models (all P<0.05). HepG2 cells with steatosis exhibited obvious mitochondrial swelling with decreased mitochondrial membrane potential, but the STM2457-treated cells maintained a normal mitochondrial morphology with a higher membrane potential (P<0.05). CONCLUSION: The METTL3 inhibitor STM2457 improves MAFLD by reducing high-fat diet-induced mitochondrial damage in mice.

Methyltransferase Inhibition Enables Tgfß Driven Induction of CDKN2A and B in Cancer Cells.

CDKN2A/B deletion or silencing is common across human cancer, reinforcing the general importance of bypassing its tumor suppression in cancer formation or progression. In rhabdomyosarcoma (RMS) and neuroblastoma, two common childhood cancers, the three CDKN2A/B transcripts are independently expressed to varying degrees, but one, ARF, is uniformly silenced. Although TGFß induces certain CDKN2A/B transcripts in HeLa cells, it was unable to do so in five tested RMS lines unless the cells were pretreated with a broadly acting methyltransferase inhibitor, DZNep, or one targeting EZH2. CDKN2A/B induction by TGFß correlated with de novo appearance of three H3K27Ac peaks within a 20 kb cis element ∼150 kb proximal to CDKN2A/B. Deleting that segment prevented their induction by TGFß but not a basal increase driven by methyltransferase inhibition alone. Expression of two CDKN2A/B transcripts was enhanced by dCas9/CRISPR activation targeting either the relevant promoter or the 20 kb cis elements, and this "precise" manipulation diminished RMS cell propagation in vitro. Our findings show crosstalk between methyltransferase inhibition and TGFß-dependent activation of a remote enhancer to reverse CDKN2A/B silencing. Though focused on CDKN2A/B here, such crosstalk may apply to other TGFß-responsive genes and perhaps govern this signaling protein's complex effects promoting or blocking cancer.

Inhibition of cellular RNA methyltransferase abrogates influenza virus capping and replication.

Orthomyxo- and bunyaviruses steal the 5' cap portion of host RNAs to prime their own transcription in a process called "cap snatching." We report that RNA modification of the cap portion by host 2'-O-ribose methyltransferase 1 (MTr1) is essential for the initiation of influenza A and B virus replication, but not for other cap-snatching viruses. We identified with in silico compound screening and functional analysis a derivative of a natural product from Streptomyces, called trifluoromethyl-tubercidin (TFMT), that inhibits MTr1 through interaction at its S-adenosyl-l-methionine binding pocket to restrict influenza virus replication. Mechanistically, TFMT impairs the association of host cap RNAs with the viral polymerase basic protein 2 subunit in human lung explants and in vivo in mice. TFMT acts synergistically with approved anti-influenza drugs.

Structural basis of regulated m7G tRNA modification by METTL1-WDR4.

Chemical modifications of RNA have key roles in many biological processes1-3. N7-methylguanosine (m7G) is required for integrity and stability of a large subset of tRNAs4-7. The methyltransferase 1-WD repeat-containing protein 4 (METTL1-WDR4) complex is the methyltransferase that modifies G46 in the variable loop of certain tRNAs, and its dysregulation drives tumorigenesis in numerous cancer types8-14. Mutations in WDR4 cause human developmental phenotypes including microcephaly15-17. How METTL1-WDR4 modifies tRNA substrates and is regulated remains elusive18. Here we show,  through structural, biochemical and cellular studies of human METTL1-WDR4, that WDR4 serves as a scaffold for METTL1 and the tRNA T-arm. Upon tRNA binding, the αC region of METTL1 transforms into a helix, which together with the α6 helix secures both ends of the tRNA variable loop. Unexpectedly, we find that the predicted disordered N-terminal region of METTL1 is part of the catalytic pocket and essential for methyltransferase activity. Furthermore, we reveal that S27 phosphorylation in the METTL1 N-terminal region inhibits methyltransferase activity by locally disrupting the catalytic centre. Our results provide a molecular understanding of tRNA substrate recognition and phosphorylation-mediated regulation of METTL1-WDR4, and reveal the presumed disordered N-terminal region of METTL1 as a nexus of methyltransferase activity.

3-(Adenosylthio)benzoic Acid Derivatives as SARS-CoV-2 Nsp14 Methyltransferase Inhibitors.

SARS-CoV-2 nsp14 guanine-N7-methyltransferase plays an important role in the viral RNA translation process by catalyzing the transfer of a methyl group from S-adenosyl-methionine (SAM) to viral mRNA cap. We report a structure-guided design and synthesis of 3-(adenosylthio)benzoic acid derivatives as nsp14 methyltransferase inhibitors resulting in compound 5p with subnanomolar inhibitory activity and improved cell membrane permeability in comparison with the parent inhibitor. Compound 5p acts as a bisubstrate inhibitor targeting both SAM and mRNA-binding pockets of nsp14. While the selectivity of 3-(adenosylthio)benzoic acid derivatives against human glycine N-methyltransferase was not improved, the discovery of phenyl-substituted analogs 5p,t may contribute to further development of SARS-CoV-2 nsp14 bisubstrate inhibitors.

Mycobacterial MenG: Partial Purification, Characterization, and Inhibition.

Menaquinone (MK) is an essential component of the electron transport chain (ETC) in the gram-variable Mycobacterium tuberculosis and many Gram-positive pathogens. Three genes in the M. tuberculosis genome were annotated as methyltransferases involved in lipoquinone synthesis in mycobacteria. Heterologous expression of Rv0558 complemented an ubiE (the quinone C-methyltransferase involved in ubiquinone and menaquinone synthesis) deletion in Escherichia coli, and expression in a wild-type E. coli strain increased quinone C-methyltransferase specific activity by threefold. Rv0558 encodes a canonical C-methyltransferase or, more specifically, a S-adenosylmethionine/demethylmenaquinol methyltransferase. Partially purified recombinant protein catalyzed the formation of MK from demethylmenaquinone (DMK), although the activity of the recombinant protein was low and appeared to require a cofactor or intact membrane structure for activity. Membrane preparations from irradiated M. tuberculosis also showed poor activity; however, membrane preparations from wild-type Mycobacterium smegmatis showed robust, substrate-dependent activity. The apparent Km values for demethylmenaquinone and SAM were 14 ± 5.0 and 17 ± 7.0 µM, respectively. Interestingly, addition of dithiothreitol, dithionite, NADH, or other substrates of primary dehydrogenases to reaction mixtures containing membrane preparations stimulated the activity. Thus, these observations strongly suggest that demethylmenaquinol is the actual substrate of MenG. Ro 48-8071, previously reported to inhibit mycobacterial MK synthesis and growth, inhibited Rv0558 activity with an IC50 value of 5.1 ± 0.5 µM, and DG70 (GSK1733953A), first described as a respiration inhibitor in M. tuberculosis, inhibits MenG activity with an IC50 value of 2.6 ± 0.6 µM.

METTL3 inhibition reduces N6 -methyladenosine levels and prevents allogeneic CD4+ T-cell responses.

Alloreactive CD4+ T cells play a central role in allograft rejection. However, the post-transcriptional regulation of the effector program in alloreactive CD4+ T cells remains unclear. N6 -methyladenosine (m6 A) RNA modification is involved in various physiological and pathological processes. Herein, we investigated whether m6 A methylation plays a role in the allogeneic T-cell effector program. m6 A levels of CD4+ T cells from spleens, draining lymph nodes and skin allografts were determined in a skin transplantation model. The effects of a METTL3 inhibitor (STM2457) on CD4+ T-cell characteristics including proliferation, cell cycle, cell apoptosis and effector differentiation were determined after stimulation of polyclonal and alloantigen-specific (TEa; CD4+ T cells specific for I-Eα52-68 ) CD4+ T cells with α-CD3/α-CD28 monoclonal antibodies and cognate CB6F1 alloantigen, respectively. We found that graft-infiltrating CD4+ T cells expressed high m6 A levels. Administration of STM2457 reduced m6 A levels, inhibited T-cell proliferation and suppressed effector differentiation of polyclonal CD4+ T cells. Alloreactive TEa cells challenged with 40 µm STM2457 exhibited deficits in T-cell proliferation and T helper type 1 cell differentiation, a cell cycle arrest in the G0 phase and elevated cell apoptosis. Moreover, these impaired T-cell responses were associated with the diminished expression levels of transcription factors Ki-67, c-Myc and T-bet. Therefore, METTL3 inhibition reduces the expression of several key transcriptional factors for the T-cell effector program and suppresses alloreactive CD4+ T-cell effector function and differentiation. Targeting m6 A-related enzymes and molecular machinery in CD4+ T cells represents an attractive therapeutic approach to prevent allograft rejection.

Kinetic Characterization of SARS-CoV-2 nsp13 ATPase Activity and Discovery of Small-Molecule Inhibitors.

SARS-CoV-2 non-structural protein 13 (nsp13) is a highly conserved helicase and RNA 5'-triphosphatase. It uses the energy derived from the hydrolysis of nucleoside triphosphates for directional movement along the nucleic acids and promotes the unwinding of double-stranded nucleic acids. Nsp13 is essential for replication and propagation of all human and non-human coronaviruses. Combined with its defined nucleotide binding site and druggability, nsp13 is one of the most promising candidates for the development of pan-coronavirus therapeutics. Here, we report the development and optimization of bioluminescence assays for kinetic characterization of nsp13 ATPase activity in the presence and absence of single-stranded DNA. Screening of a library of 5000 small molecules in the presence of single-stranded DNA resulted in the discovery of six nsp13 small-molecule inhibitors with IC50 values ranging from 6 ± 0.5 to 50 ± 6 µM. In addition to providing validated methods for high-throughput screening of nsp13 in drug discovery campaigns, the reproducible screening hits we present here could potentially be chemistry starting points toward the development of more potent and selective nsp13 inhibitors, enabling the discovery of antiviral therapeutics.

CD8+T cell responsiveness to anti-PD-1 is epigenetically regulated by Suv39h1 in melanomas.

Tumor-infiltrating CD8 + T cells progressively lose functionality and fail to reject tumors. The underlying mechanism and re-programing induced by checkpoint blockers are incompletely understood. We show here that genetic ablation or pharmacological inhibition of histone lysine methyltransferase Suv39h1 delays tumor growth and potentiates tumor rejection by anti-PD-1. In the absence of Suv39h1, anti-PD-1 induces alternative activation pathways allowing survival and differentiation of IFNγ and Granzyme B producing effector cells that express negative checkpoint molecules, but do not reach final exhaustion. Their transcriptional program correlates with that of melanoma patients responding to immune-checkpoint blockade and identifies the emergence of cytolytic-effector tumor-infiltrating lymphocytes as a biomarker of clinical response. Anti-PD-1 favors chromatin opening in loci linked to T-cell activation, memory and pluripotency, but in the absence of Suv39h1, cells acquire accessibility in cytolytic effector loci. Overall, Suv39h1 inhibition enhances anti-tumor immune responses, alone or combined with anti-PD-1, suggesting that Suv39h1 is an "epigenetic checkpoint" for tumor immunity.

Mitochondrial RNA modifications shape metabolic plasticity in metastasis.

Aggressive and metastatic cancers show enhanced metabolic plasticity1, but the precise underlying mechanisms of this remain unclear. Here we show how two NOP2/Sun RNA methyltransferase 3 (NSUN3)-dependent RNA modifications-5-methylcytosine (m5C) and its derivative 5-formylcytosine (f5C) (refs.2-4)-drive the translation of mitochondrial mRNA to power metastasis. Translation of mitochondrially encoded subunits of the oxidative phosphorylation complex depends on the formation of m5C at position 34 in mitochondrial tRNAMet. m5C-deficient human oral cancer cells exhibit increased levels of glycolysis and changes in their mitochondrial function that do not affect cell viability or primary tumour growth in vivo; however, metabolic plasticity is severely impaired as mitochondrial m5C-deficient tumours do not metastasize efficiently. We discovered that CD36-dependent non-dividing, metastasis-initiating tumour cells require mitochondrial m5C to activate invasion and dissemination. Moreover, a mitochondria-driven gene signature in patients with head and neck cancer is predictive for metastasis and disease progression. Finally, we confirm that this metabolic switch that allows the metastasis of tumour cells can be pharmacologically targeted through the inhibition of mitochondrial mRNA translation in vivo. Together, our results reveal that site-specific mitochondrial RNA modifications could be therapeutic targets to combat metastasis.

Chemical biology and medicinal chemistry of RNA methyltransferases.

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.

Ligand and Structure-Based In Silico Determination of the Most Promising SARS-CoV-2 nsp16-nsp10 2'-o-Methyltransferase Complex Inhibitors among 3009 FDA Approved Drugs.

As a continuation of our earlier work against SARS-CoV-2, seven FDA-approved drugs were designated as the best SARS-CoV-2 nsp16-nsp10 2'-o-methyltransferase (2'OMTase) inhibitors through 3009 compounds. The in silico inhibitory potential of the examined compounds against SARS-CoV-2 nsp16-nsp10 2'-o-methyltransferase (PDB ID: (6W4H) was conducted through a multi-step screening approach. At the beginning, molecular fingerprints experiment with SAM (S-Adenosylmethionine), the co-crystallized ligand of the targeted enzyme, unveiled the resemblance of 147 drugs. Then, a structural similarity experiment recommended 26 compounds. Therefore, the 26 compounds were docked against 2'OMTase to reveal the potential inhibitory effect of seven promising compounds (Protirelin, (1187), Calcium folinate (1913), Raltegravir (1995), Regadenoson (2176), Ertapenem (2396), Methylergometrine (2532), and Thiamine pyrophosphate hydrochloride (2612)). Out of the docked ligands, Ertapenem (2396) showed an ideal binding mode like that of the co-crystallized ligand (SAM). It occupied all sub-pockets of the active site and bound the crucial amino acids. Accordingly, some MD simulation experiments (RMSD, RMSF, Rg, SASA, and H-bonding) have been conducted for the 2'OMTase-Ertapenem complex over 100 ns. The performed MD experiments verified the correct binding mode of Ertapenem against 2'OMTase exhibiting low energy and optimal dynamics. Finally, MM-PBSA studies indicated that Ertapenem bonded advantageously to the targeted protein with a free energy value of -43 KJ/mol. Furthermore, the binding free energy analysis revealed the essential amino acids of 2'OMTase that served positively to the binding. The achieved results bring hope to find a treatment for COVID-19 via in vitro and in vivo studies for the pointed compounds.

Improved Cell-Potent and Selective Peptidomimetic Inhibitors of Protein N-Terminal Methyltransferase 1.

Protein N-terminal methyltransferase 1 (NTMT1) recognizes a unique N-terminal X-P-K/R motif (X represents any amino acid other than D/E) and transfers 1-3 methyl groups to the N-terminal region of its substrates. Guided by the co-crystal structures of NTMT1 in complex with the previously reported peptidomimetic inhibitor DC113, we designed and synthesized a series of new peptidomimetic inhibitors. Through a focused optimization of DC113, we discovered a new cell-potent peptidomimetic inhibitor GD562 (IC50 = 0.93 ± 0.04 µM). GD562 exhibited improved inhibition of the cellular N-terminal methylation levels of both the regulator of chromosome condensation 1 and the oncoprotein SET with an IC50 value of ~50 µM in human colorectal cancer HCT116 cells. Notably, the inhibitory activity of GD562 for the SET protein increased over 6-fold compared with the previously reported cell-potent inhibitor DC541. Furthermore, GD562 also exhibited over 100-fold selectivity for NTMT1 against several other methyltransferases. Thus, this study provides a valuable probe to investigate the biological functions of NTMT1.

16S rRNA Methyltransferases as Novel Drug Targets Against Tuberculosis.

Tuberculosis (TB) is an airborne infectious disease caused by Mycobacterium tuberculosis (M.tb) whose natural history traces back to 70,000 years. TB remains a major global health burden. Methylation is a type of post-replication, post-transcriptional and post-translational epi-genetic modification involved in transcription, translation, replication, tissue specific expression, embryonic development, genomic imprinting, genome stability and chromatin structure, protein protein interactions and signal transduction indicating its indispensable role in survival of a pathogen like M.tb. The pathogens use this epigenetic mechanism to develop resistance against certain drug molecules and survive the lethality. Drug resistance has become a major challenge to tackle and also a major concern raised by WHO. Methyltransferases are enzymes that catalyze the methylation of various substrates. None of the current TB targets belong to methyltransferases which provides therapeutic opportunities to develop novel drugs through studying methyltransferases as potential novel targets against TB. Targeting 16S rRNA methyltransferases serves two purposes simultaneously: a) translation inhibition and b) simultaneous elimination of the ability to methylate its substrates hence stopping the emergence of drug resistance strains. There are ~ 40 different rRNA methyltransferases and 13 different 16S rRNA specific methyltransferases which are unexplored and provide a huge opportunity for treatment of TB.

Roles and drug development of METTL3 (methyltransferase-like 3) in anti-tumor therapy.

Methyltransferase complex, such as METTL3/METTL14/WTP, catalyze N6-methyladenosine (m6A), which is the most abundant mRNA modification in mammals. Besides acting as a m6A methyltransferase, METTL3 also regulates mRNA translation and other biological processes. Studies have identified numerous roles and molecular mechanisms associated with METTL3 in multiple biological processes especially in tumors in recent years. Furthermore, targeting METTL3 as an efficient therapeutic way for the treatment of different kinds of tumors has gained a lot of attention. However, these findings and researches have not been summarized. In this review, the most recent important roles of METTL3 in various tumors including acute myeloid leukemia, lung cancer, breast cancer, liver cancer, gastric cancer, pancreatic cancer, colorectal cancer, bladder cancer, prostate cancer and glioblastoma were systematically summarized. In addition, disclosed METTL3 inhibitors recently were also summarized and discussed for medicinal chemists investigating METTL3 inhibitors with different skeleton structures for the application of human cancer therapy.