PRMTs and Arginine Methylation: Cancer's Best-Kept Secret?

Tumor antigen presentation and the associated signal transduction during carcinogenesis

Numerous developments have been achieved in the study and treatment of cancer throughout the decades that it has been common. After decades of research, about 100 different kinds of cancer have been found, each with unique subgroups within certain organs. This has significantly expanded our understanding of the illness. A mix of genetic, environmental, and behavioral variables contribute to the complicated and diverse process of cancer formation. Mutations, or changes in the DNA sequence, are crucial to the development of cancer. These mutations have the ability to downregulate the expression and function of Major Histocompatibility Complex class I (MHC I) and MHCII receptors, as well as activate oncogenes and inactivate tumor suppressor genes. Cancer cells use this tactic to avoid being recognized by cytotoxic CD8+T lymphocytes, which causes issues with antigen presentation and processing. This review goes into great length into the PI3K pathway, changes to MHC I, and positive impacts of tsMHC-II on disease-free survival and overall survival and the involvement of dendritic cells (DCs) in different tumor microenvironments. The vital functions that the PI3K pathway and its link to the mTOR pathway are highlighted and difficulties in developing effective cancer targeted therapies and feedback systems has also been mentioned, where resistance mechanisms include RAS-mediated oncogenic changes and active PI3K signalling.

A Chemoenzymatic Method Enables Global Enrichment and Characterization of Protein Arginine Methylation

Arginine methylation is one of the most important post-translational modifications involved in the regulation of numerous biological processes. To better understand the biological significance of arginine methylation, enrichment methods need to be developed to analyze the methylated proteome at large-scale. Unfortunately, the prevailing enrichment method based on immunoaffinity purification can only enrich a subset of them due to the lack of pan-specific antibodies. Therefore, it is crucial to develop a stable and efficient antibody-free approach for the global analysis of arginine methylation. In this study, we developed a chemoenzymatic method for the simultaneous identification of mono- and dimethylated arginine. Totally, we identified 1006 arginine methylation events in Jurkat T cells, corresponding to 645 dimethylated sites and 361 monomethylated sites. We further applied the developed approach to global identification of the substrate proteins regulated by type I protein arginine methyltransferases (PRMTs) and identified 49 substrate proteins of type I PRMTs, which will facilitate a better understanding of PRMTs-regulated biological processes. Given the robust performance of this method, it would have broad application in methylproteomics analysis.

Oligomerization of protein arginine methyltransferase 1 and its effect on methyltransferase activity and substrate specificity

Proper protein arginine methylation by protein arginine methyltransferase 1 (PRMT1) is critical for maintaining cellular health, while dysregulation is often associated with disease. How the activity of PRMT1 is regulated is therefore paramount, but is not clearly understood. Several studies have observed higher order oligomeric species of PRMT1, but it is unclear if these exist at physiological concentrations and there is confusion in the literature about how oligomerization affects activity. We therefore sought to determine which oligomeric species of PRMT1 are physiologically relevant, and quantitatively correlate activity with specific oligomer forms. Through quantitative western blotting, we determined that concentrations of PRMT1 available in a variety of human cell lines are in the sub-micromolar to low micromolar range. Isothermal spectral shift binding data were modeled to a monomer/dimer/tetramer equilibrium with an EC50 for tetramer dissociation of ~20 nM. A combination of sedimentation velocity and Native polyacrylamide gel electrophoresis experiments directly confirmed that the major oligomeric species of PRMT1 at physiological concentrations would be dimers and tetramers. Surprisingly, the methyltransferase activity of a dimeric PRMT1 variant is similar to wild type, tetrameric PRMT1 with some purified substrates, but dimer and tetramer forms of PRMT1 show differences in catalytic efficiencies and substrate specificity for other substrates. Our results define an oligomerization paradigm for PRMT1, show that the biophysical characteristics of PRMT1 are poised to support a monomer/dimer/tetramer equilibrium in vivo, and suggest that the oligomeric state of PRMT1 could be used to regulate substrate specificity.

Targeting PRMT5 enhances the radiosensitivity of tumor cells grown in vitro and in vivo

PRMT5 is a widely expressed arginine methyltransferase that regulates processes involved in tumor cell proliferation and survival. In the study described here, we investigated whether PRMT5 provides a target for tumor radiosensitization. Knockdown of PRMT5 using siRNA enhanced the radiosensitivity of a panel of cell lines corresponding to tumor types typically treated with radiotherapy. To extend these studies to an experimental therapeutic setting, the PRMT5 inhibitor LLY-283 was used. Exposure of the tumor cell lines to LLY-283 decreased PRMT5 activity and enhanced their radiosensitivity. This increase in radiosensitivity was accompanied by an inhibition of DNA double-strand break repair as determined by γH2AX foci and neutral comet analyses. For a normal fibroblast cell line, although LLY-283 reduced PRMT5 activity, it had no effect on their radiosensitivity. Transcriptome analysis of U251 cells showed that LLY-283 treatment reduced the expression of genes and altered the mRNA splicing pattern of genes involved in the DNA damage response. Subcutaneous xenografts were then used to evaluate the in vivo response to LLY-283 and radiation. Treatment of mice with LLY-283 decreased tumor PRMT5 activity and significantly enhanced the radiation-induced growth delay. These results suggest that PRMT5 is a tumor selective target for radiosensitization.

Sustained cancer-relevant alternative RNA splicing events driven by PRMT5 in high-risk neuroblastoma

Protein arginine methyltransferase 5 (PRMT5) is over-expressed in a wide variety of cancers and is implicated as having a key oncogenic role, achieved in part through its control of the master transcription regulator E2F1. We investigated the relevance of PRMT5 and E2F1 in neuroblastoma (NB) and found that elevated expression of PRMT5 and E2F1 occurs in poor prognosis high-risk disease and correlates with an amplified Myelocytomatosis viral-related oncogene, neuroblastoma-derived (MYCN) gene. Our results show that MYCN drives the expression of splicing factor genes that, together with PRMT5 and E2F1, lead to a deregulated alternative RNA splicing programme that impedes apoptosis. Pharmacological inhibition of PRMT5 or inactivation of E2F1 restores normal splicing and renders NB cells sensitive to apoptosis. Our findings suggest that a sustained cancer-relevant alternative RNA splicing programme desensitises NB cells to apoptosis, and identify PRMT5 as a potential therapeutic target for high-risk disease.

Strategy of combining CDK4/6 inhibitors with other therapies and mechanisms of resistance

Cell cycle-dependent protein kinase 4/6 (CDK4/6) is a crucial kinase that regulates the cell cycle, essential for cell division and proliferation. Hence, combining CDK4/6 inhibitors with other anti-tumor drugs is a pivotal clinical strategy. This strategy can efficiently inhibit the growth and division of tumor cells, reduce the side effects, and improve the quality of life of patients by reducing the dosage of combined anticancer drugs. Furthermore, the combination therapy strategy of CDK4/6 inhibitors could ameliorate the drug resistance of combined drugs and overcome the CDK4/6 resistance caused by CDK4/6 inhibitors. Various tumor treatment strategies combined with CDK4/6 inhibitors have entered the clinical trial stage, demonstrating their substantial clinical potential. This study reviews the research progress of CDK4/6 inhibitors from 2018 to 2022, the related resistance mechanism of CDK4/6 inhibitors, and the strategy of combination medication.

Intricate effects of post-translational modifications in liver cancer: mechanisms to clinical applications

Liver cancer is a significant global health challenge, with hepatocellular carcinoma (HCC) being the most prevalent form, characterized by high incidence and mortality rates. Despite advances in targeted therapies and immunotherapies, the prognosis for advanced liver cancer remains poor. This underscores the urgent need for a deeper understanding of the molecular mechanisms underlying HCC to enable early detection and the development of novel therapeutic strategies. Post-translational modifications (PTMs) are crucial regulatory mechanisms in cellular biology, affecting protein functionality, interactions, and localization. These modifications, including phosphorylation, acetylation, methylation, ubiquitination, and glycosylation, occur after protein synthesis and play vital roles in various cellular processes. Recent advances in proteomics and molecular biology have highlighted the complex networks of PTMs, emphasizing their critical role in maintaining cellular homeostasis and disease pathogenesis. Dysregulation of PTMs has been associated with several malignant cellular processes in HCC, such as altered cell proliferation, migration, immune evasion, and metabolic reprogramming, contributing to tumor growth and metastasis. This review aims to provide a comprehensive understanding of the pathological mechanisms and clinical implications of various PTMs in liver cancer. By exploring the multifaceted interactions of PTMs and their impact on liver cancer progression, we highlight the potential of PTMs as biomarkers and therapeutic targets. The significance of this review lies in its potential to inform the development of novel therapeutic approaches and improve prognostic tools for early intervention in the fight against liver cancer.

Protein Arginine Methyltransferases: Emerging Targets in Cardiovascular and Metabolic Disease

Cardiovascular diseases (CVDs) and metabolic disorders stand as formidable challenges that significantly impact the clinical outcomes and living quality for afflicted individuals. An intricate comprehension of the underlying mechanisms is paramount for the development of efficacious therapeutic strategies. Protein arginine methyltransferases (PRMTs), a class of enzymes responsible for the precise regulation of protein methylation, have ascended to pivotal roles and emerged as crucial regulators within the intrinsic pathophysiology of these diseases. Herein, we review recent advancements in research elucidating on the multifaceted involvements of PRMTs in cardiovascular system and metabolic diseases, contributing significantly to deepen our understanding of the pathogenesis and progression of these maladies. In addition, this review provides a comprehensive analysis to unveil the distinctive roles of PRMTs across diverse cell types implicated in cardiovascular and metabolic disorders, which holds great potential to reveal novel therapeutic interventions targeting PRMTs, thus presenting promising perspectives to effectively address the substantial global burden imposed by CVDs and metabolic disorders.

A PRMT5-ZNF326 axis mediates innate immune activation upon replication stress

DNA replication stress (RS) is a widespread phenomenon in carcinogenesis, causing genomic instability and extensive chromatin alterations. DNA damage leads to activation of innate immune signaling, but little is known about transcriptional regulators mediating such signaling upon RS. Using a chemical screen, we identified protein arginine methyltransferase 5 (PRMT5) as a key mediator of RS-dependent induction of interferon-stimulated genes (ISGs). This response is also associated with reactivation of endogenous retroviruses (ERVs). Using quantitative mass spectrometry, we identify proteins with PRMT5-dependent symmetric dimethylarginine (SDMA) modification induced upon RS. Among these, we show that PRMT5 targets and modulates the activity of ZNF326, a zinc finger protein essential for ISG response. Our data demonstrate a role for PRMT5-mediated SDMA in the context of RS-induced transcriptional induction, affecting physiological homeostasis and cancer therapy.

Epigenetic regulation of androgen dependent and independent prostate cancer

Prostate cancer is one of the most common malignancies among men worldwide. Besides genetic alterations, epigenetic modulations including DNA methylation, histone modifications and miRNA mediated alteration of gene expression are the key driving forces for the prostate tumor development and cancer progression. Aberrant expression and/or the activity of the epigenetic modifiers/enzymes, results in aberrant expression of genes involved in DNA repair, cell cycle regulation, cell adhesion, apoptosis, autophagy, tumor suppression and hormone response and thereby disease progression. Altered epigenome is associated with prostate cancer recurrence, progression, aggressiveness and transition from androgen-dependent to androgen-independent phenotype. These epigenetic modifications are reversible and various compounds/drugs targeting the epigenetic enzymes have been developed that are effective in cancer treatment. This chapter focuses on the epigenetic alterations in prostate cancer initiation and progression, listing different epigenetic biomarkers for diagnosis and prognosis of the disease and their potential as therapeutic targets. This chapter also summarizes different epigenetic drugs approved for prostate cancer therapy and the drugs available for clinical trials.

FBXO7 ubiquitinates PRMT1 to suppress serine synthesis and tumor growth in hepatocellular carcinoma

Cancer cells are often addicted to serine synthesis to support growth. How serine synthesis is regulated in cancer is not well understood. We recently demonstrated protein arginine methyltransferase 1 (PRMT1) is upregulated in hepatocellular carcinoma (HCC) to methylate and activate phosphoglycerate dehydrogenase (PHGDH), thereby promoting serine synthesis. However, the mechanisms underlying PRMT1 upregulation and regulation of PRMT1-PHGDH axis remain unclear. Here, we show the E3 ubiquitin ligase F-box-only protein 7 (FBXO7) inhibits serine synthesis in HCC by binding PRMT1, inducing lysine 37 ubiquitination, and promoting proteosomal degradation of PRMT1. FBXO7-mediated PRMT1 downregulation cripples PHGDH arginine methylation and activation, resulting in impaired serine synthesis, accumulation of reactive oxygen species (ROS), and inhibition of HCC cell growth. Notably, FBXO7 is significantly downregulated in human HCC tissues, and inversely associated with PRMT1 protein and PHGDH methylation level. Overall, our study provides mechanistic insights into the regulation of cancer serine synthesis by FBXO7-PRMT1-PHGDH axis, and will facilitate the development of serine-targeting strategies for cancer therapy.

Tumor Necrosis Factor α-Induced Protein 8-Like 1 Binds to Protein Arginine Methyltransferase 1 to Suppress the Methylation of Signal Transducer and Activator of Transcription 3 and Cell Growth in Oral Squamous Cell Carcinoma

The tumor necrosis factor α-induced protein 8 (TIPE, also TNFAIP8 or OXi-α) family is a newly discovered series of proteins involved in immune regulation and tumorigenesis. TIPE1, a member of the TIPE/TNFAIP8/OXi-α family, has emerged as an anticancer-drug target, as it promotes cancer cell apoptosis and inhibits cell proliferation. The current study aimed to systematically reveal that TIPE1 regulates the activity of protein arginine methyltransferase (PRMT)-1 and the subsequent methylation of signal transducer and activator of transcription (STAT)-3 to suppress oral squamous cell carcinoma (OSCC) growth. TIPE1 was down-regulated in the OSCC cell lines (Tca8113, SCC25, Cal27, SCC15, and HSC27). TIPE1 overexpression significantly inhibited cell proliferation, colony formation, in vivo tumorgenicity, and Ki-67 expression in OSCC. TIPE1 interacted with the catalytic region of PRMT1 and inhibited STAT3 methylation. The effects of TIPE1 on OSCC cells were alleviated after PRMT1 overexpression, confirming the importance of this interaction to the tumor-suppressive effects of TIPE1. Together, these findings confirmed that TIPE1 mediated PRMT1 suppression through direct binding to its catalytic domain and subsequently inhibited the methylation and expression of STAT3 in OSCC cells, thereby inhibiting cell growth and tumorgenicity.

A CARM1 Inhibitor Potently Suppresses Breast Cancer Both In Vitro and In Vivo

CARM1, belonging to the protein arginine methyltransferase (PRMT) family, is intricately associated with the progression of cancer and is viewed as a promising target for both cancer diagnosis and therapy. However, the number of specific and potent CARM1 inhibitors is limited. We herein discovered a CARM1 inhibitor, iCARM1, that showed better specificity and activity toward CARM1 compared to the known CARM1 inhibitors, EZM2302 and TP-064. Similar to CARM1 knockdown, iCARM1 suppressed the expression of oncogenic estrogen/ERα-target genes, whereas activated type I interferon (IFN) and IFN-induced genes (ISGs) in breast cancer cells. Consequently, iCARM1 potently suppressed breast cancer cell growth both in vitro and in vivo. The combination of iCARM1 with either endocrine therapy drugs or etoposide demonstrated synergistic effects in inhibiting the growth of breast tumors. In summary, targeting CARM1 by iCARM1 effectively suppresses breast tumor growth, offering a promising therapeutic approach for managing breast cancers in clinical settings.

Repression of PRMT activities sensitize homologous recombination-proficient ovarian and breast cancer cells to PARP inhibitor treatment

An "induced PARP inhibitor (PARPi) sensitivity by epigenetic modulation" strategy is being evaluated in the clinic to sensitize homologous recombination (HR)-proficient tumors to PARPi treatments. To expand its clinical applications and identify more efficient combinations, we performed a drug screen by combining PARPi with 74 well-characterized epigenetic modulators that target five major classes of epigenetic enzymes. Both type I PRMT inhibitor and PRMT5 inhibitor exhibit high combination and clinical priority scores in our screen. PRMT inhibition significantly enhances PARPi treatment-induced DNA damage in HR-proficient ovarian and breast cancer cells. Mechanistically, PRMTs maintain the expression of genes associated with DNA damage repair and BRCAness and regulate intrinsic innate immune pathways in cancer cells. Analyzing large-scale genomic and functional profiles from TCGA and DepMap further confirms that PRMT1, PRMT4, and PRMT5 are potential therapeutic targets in oncology. Finally, PRMT1 and PRMT5 inhibition act synergistically to enhance PARPi sensitivity. Our studies provide a strong rationale for the clinical application of a combination of PRMT and PARP inhibitors in patients with HR-proficient ovarian or breast cancer.

Discovery of a first-in-class degrader for the protein arginine methyltransferase 6 (PRMT6)

PRMT6 is a member of the protein arginine methyltransferase family, which participates in a variety of physical processes and plays an important role in the occurrence and development of tumors. Using small molecules to design and synthesize targeted protein degraders is a new strategy for drug development. Here, we report the first-in-class degrader SKLB-0124 for PRMT6 based on the hydrophobic tagging (HyT) method.Importantly, SKLB-0124 induced proteasome dependent degradation of PRMT6 and significantly inhibited the proliferation of HCC827 and MDA-MB-435 cells. Moreover, SKLB-0124 effectively induced apoptosis and cell cycle arrest in these two cell lines. Our data clarified that SKLB-0124 is a promising selective PRMT6 degrader for cancer therapy which is worthy of further evaluation.

SMYD4 monomethylates PRMT5 and forms a positive feedback loop to promote hepatocellular carcinoma progression

Both lysine and arginine methyltransferases are thought to be promising therapeutic targets for malignant tumors, yet how these methyltransferases function in malignant tumors, especially hepatocellular carcinoma (HCC), has not been fully elucidated. Here, we reported that SMYD4, a lysine methyltransferase, acts as an oncogene in HCC. SMYD4 was highly upregulated in HCC and promoted HCC cell proliferation and metastasis. Mechanistically, PRMT5, a well-known arginine methyltransferase, was identified as a SMYD4-binding protein. SMYD4 monomethylated PRMT5 and enhanced the interaction between PRMT5 and MEP50, thereby promoting the symmetrical dimethylation of H3R2 and H4R3 on the PRMT5 target gene promoter and subsequently activating DVL3 expression and inhibiting expression of E-cadherin, RBL2, and miR-29b-1-5p. Moreover, miR-29b-1-5p was found to inversely regulate SMYD4 expression in HCC cells, thus forming a positive feedback loop. Furthermore, we found that the oncogenic effect of SMYD4 could be effectively suppressed by PRMT5 inhibitor in vitro and in vivo. Clinically, high coexpression of SMYD4 and PRMT5 was associated with poor prognosis of HCC patients. In summary, our study provides a model of crosstalk between lysine and arginine methyltransferases in HCC and highlights the SMYD4-PRMT5 axis as a potential therapeutic target for the treatment of HCC.

NEAT1 repression by MED12 creates chemosensitivity in p53 wild-type breast cancer cells

Breast cancer is often treated with chemotherapy. However, the development of chemoresistance results in treatment failure. Long non-coding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) has been shown to contribute to chemoresistance in breast cancer cells. In studying the transcriptional regulation of NEAT1 using multi-omics approaches, we showed that NEAT1 is up-regulated by 5-fluorouracil in breast cancer cells with wild-type cellular tumor antigen p53 but not in mutant-p53-expressing breast cancer cells. The regulation of NEAT1 involves mediator complex subunit 12 (MED12)-mediated repression of histone acetylation marks at the promoter region of NEAT1. Knockdown of MED12 but not coactivator-associated arginine methyltransferase 1 (CARM1) induced histone acetylation at the NEAT1 promoter, leading to elevated NEAT1 mRNAs, resulting in a chemoresistant phenotype. The MED12-dependent regulation of NEAT1 differs between wild-type and mutant p53-expressing cells. MED12 depletion led to increased expression of NEAT1 in a wild-type p53 cell line, but decreased expression in a mutant p53 cell line. Chemoresistance caused by MED12 depletion can be partially rescued by NEAT1 knockdown in p53 wild-type cells. Collectively, our study reveals a novel mechanism of chemoresistance dependent on MED12 transcriptional regulation of NEAT1 in p53 wild-type breast cancer cells.

Type-I protein arginine methyltransferase inhibition primes anti-programmed cell death protein 1 immunotherapy in triple-negative breast cancer

BACKGROUND

Immune-checkpoint blockade (ICB) therapy shows promise for treating aggressive triple-negative breast cancer (TNBC). However, only some patients benefit from ICB, revealing an urgent need for identifying novel strategies for sensitizing patients to ICB. Previously, the authors demonstrated that type-I protein arginine methyltransferases (PRMTs) regulated antiviral innate-immune responses in TNBC by altering RNA splicing. This study aimed to explore the effects of targeting type-I PRMTs on the tumor microenvironment (TME) and the efficacy of ICB therapy against TNBC.

METHODS

Single-cell transcriptomic analysis was performed to investigate the effects of type-I PRMT inhibition on the TME, especially T-cell subsets. Single-cell T-cell receptor sequencing was performed to analyze the diversity and dynamics of the T-cell repertoire. A syngeneic murine model of TNBC was used to evaluate the therapeutic efficacy and immune memory effect of combining a type-I PRMT inhibitor (MS023) with an anti-programmed cell death protein 1 (PD-1) antibody.

RESULTS

Type-I PRMT inhibition combined with anti-PD-1 therapy reduced tumor growth. Mechanistically, type-I PRMT inhibition reshaped the TME. Increased CD8 T-cell infiltration was verified using flow cytometry. Increased clonotypes and clonal diversity were also observed after MS023 treatment, which contributed to immune memory following combination treatment.

CONCLUSIONS

Targeting type-I PRMT can potentially improve immunotherapeutic efficacies in patients with TNBC. By enhancing the tumor immunogenicity and promoting a more favorable immune microenvironment, this combined approach may enable more patients with TNBC to benefit from immunotherapies.

Protein Arginine Methyltransferases in Pancreatic Ductal Adenocarcinoma: New Molecular Targets for Therapy

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignant disease with a low 5-year overall survival rate. It is the third-leading cause of cancer-related deaths in the United States. The lack of robust therapeutics, absence of effective biomarkers for early detection, and aggressive nature of the tumor contribute to the high mortality rate of PDAC. Notably, the outcomes of recent immunotherapy and targeted therapy against PDAC remain unsatisfactory, indicating the need for novel therapeutic strategies. One of the newly described molecular features of PDAC is the altered expression of protein arginine methyltransferases (PRMTs). PRMTs are a group of enzymes known to methylate arginine residues in both histone and non-histone proteins, thereby mediating cellular homeostasis in biological systems. Some of the PRMT enzymes are known to be overexpressed in PDAC that promotes tumor progression and chemo-resistance via regulating gene transcription, cellular metabolic processes, RNA metabolism, and epithelial mesenchymal transition (EMT). Small-molecule inhibitors of PRMTs are currently under clinical trials and can potentially become a new generation of anti-cancer drugs. This review aims to provide an overview of the current understanding of PRMTs in PDAC, focusing on their pathological roles and their potential as new therapeutic targets.

Fibroblast-specific PRMT5 deficiency suppresses cardiac fibrosis and left ventricular dysfunction in male mice

Protein arginine methyltransferase 5 (PRMT5) is a well-known epigenetic regulatory enzyme. However, the role of PRMT5-mediated arginine methylation in gene transcription related to cardiac fibrosis is unknown. Here we show that fibroblast-specific deletion of PRMT5 significantly reduces pressure overload-induced cardiac fibrosis and improves cardiac dysfunction in male mice. Both the PRMT5-selective inhibitor EPZ015666 and knockdown of PRMT5 suppress α-smooth muscle actin (α-SMA) expression induced by transforming growth factor-β (TGF-β) in cultured cardiac fibroblasts. TGF-β stimulation promotes the recruitment of the PRMT5/Smad3 complex to the promoter site of α-SMA. It also increases PRMT5-mediated H3R2 symmetric dimethylation, and this increase is inhibited by Smad3 knockdown. TGF-β stimulation increases H3K4 tri-methylation mediated by the WDR5/MLL1 methyltransferase complex, which recognizes H3R2 dimethylation. Finally, treatment with EPZ015666 significantly improves pressure overload-induced cardiac fibrosis and dysfunction. These findings suggest that PRMT5 regulates TGF-β/Smad3-dependent fibrotic gene transcription, possibly through histone methylation crosstalk, and plays a critical role in cardiac fibrosis and dysfunction.

Investigating Protein Binding with the Isothermal Ligand-induced Resolubilization Assay

Target engagement assays typically detect and quantify the direct physical interaction of a protein of interest and its ligand through stability changes upon ligand binding. Commonly used target engagement methods detect ligand-induced stability by subjecting samples to thermal or proteolytic stress. Here we describe a new variation to these approaches called Isothermal Ligand-induced Resolubilization Assay (ILIRA), which utilizes lyotropic solubility stress to measure ligand binding through changes in target protein solubility. We identified distinct buffer systems and salt concentrations that compromised protein solubility for four diverse proteins: dihydrofolate reductase (DHFR), nucleoside diphosphate-linked moiety X motif 5 (NUDT5), poly [ADP-ribose] polymerase 1 (PARP1), and protein arginine N-methyltransferase 1 (PRMT1). Ligand-induced solubility rescue was demonstrated for these proteins, suggesting that ILIRA can be used as an additional target engagement technique. Differences in ligand-induced protein solubility were assessed by Coomassie blue staining for SDS-PAGE and dot blot, as well as by NanoOrange, Thioflavin T, and Proteostat fluorescence, thus offering flexibility for readout and assay throughput.

PRMT5 is an actionable therapeutic target in CDK4/6 inhibitor-resistant ER+/RB-deficient breast cancer

CDK4/6 inhibitors (CDK4/6i) have improved survival of patients with estrogen receptor-positive (ER+) breast cancer. However, patients treated with CDK4/6i eventually develop drug resistance and progress. RB1 loss-of-function alterations confer resistance to CDK4/6i, but the optimal therapy for these patients is unclear. Through a genome-wide CRISPR screen, we identify protein arginine methyltransferase 5 (PRMT5) as a molecular vulnerability in ER+/RB1-knockout breast cancer cells. Inhibition of PRMT5 blocks the G1-to-S transition in the cell cycle independent of RB, leading to growth arrest in RB1-knockout cells. Proteomics analysis uncovers fused in sarcoma (FUS) as a downstream effector of PRMT5. Inhibition of PRMT5 results in dissociation of FUS from RNA polymerase II, leading to hyperphosphorylation of serine 2 in RNA polymerase II, intron retention, and subsequent downregulation of proteins involved in DNA synthesis. Furthermore, treatment with the PRMT5 inhibitor pemrametostat and a selective ER degrader fulvestrant synergistically inhibits growth of ER+/RB-deficient cell-derived and patient-derived xenografts. These findings highlight dual ER and PRMT5 blockade as a potential therapeutic strategy to overcome resistance to CDK4/6i in ER+/RB-deficient breast cancer.

Arginine methylation and respiratory disease

Arginine methylation, a vital post-translational modification, plays a pivotal role in numerous cellular functions such as signal transduction, DNA damage response and repair, regulation of gene transcription, mRNA splicing, and protein interactions. Central to this modification is the role of protein arginine methyltransferases (PRMTs), which have been increasingly recognized for their involvement in the pathogenesis of various respiratory diseases. This review begins with an exploration of the biochemical underpinnings of arginine methylation, shedding light on the intricate molecular regulatory mechanisms governed by PRMTs. It then delves into the impact of arginine methylation and the dysregulation of arginine methyltransferases in diverse pulmonary disorders. Concluding with a focus on the therapeutic potential and recent advancements in PRMT inhibitors, this article aims to offer novel perspectives and therapeutic avenues for the management and treatment of respiratory diseases.

Overview of the development of protein arginine methyltransferase modulators: Achievements and future directions

Protein methylation is a post-translational modification (PTM) that organisms undergo. This process is considered a part of epigenetics research. In recent years, there has been an increasing interest in protein methylation, particularly histone methylation, as research has advanced. Methylation of histones is a dynamic process that is subject to fine control by histone methyltransferases and demethylases. In addition, many non-histone proteins also undergo methylation, and these modifications collectively regulate physiological phenomena, including RNA transcription, translation, signal transduction, DNA damage response, and cell cycle. Protein arginine methylation is a crucial aspect of protein methylation, which plays a significant role in regulating the cell cycle and repairing DNA. It is also linked to various diseases. Therefore, protein arginine methyltransferases (PRMTs) that are involved in this process have gained considerable attention as a potential therapeutic target for treating diseases. Several PRMT inhibitors are in phase I/II clinical trials. This paper aims to introduce the structure, biochemical functions, and bioactivity assays of PRMTs. Additionally, we will review the structure-function of currently popular PRMT inhibitors. Through the analysis of various data on known PRMT inhibitors, we hope to provide valuable assistance for future drug design and development.

Genetically encoded fluorescent sensor to monitor intracellular arginine methylation

Arginine methylation (ArgMet), as a post-translational modification, plays crucial roles in RNA processing, transcriptional regulation, signal transduction, DNA repair, apoptosis and liquid-liquid phase separation (LLPS). Since arginine methylation is associated with cancer pathogenesis and progression, protein arginine methyltransferases have gained interest as targets for anti-cancer therapy. Despite considerable process made to elucidate (patho)physiological mechanisms regulated by arginine methylation, there remains a lack of tools to visualize arginine methylation with high spatiotemporal resolution in live cells. To address this unmet need, we generated an ArgMet-sensitive genetically encoded, Förster resonance energy transfer-(FRET) based biosensor, called GEMS, capable of quantitative real-time monitoring of ArgMet dynamics. We optimized these biosensors by using different ArgMet-binding domains, arginine-glycine-rich regions and adjusting the linkers within the biosensors to improve their performance. Using a set of mammalian cell lines and modulators, we demonstrated the applicability of GEMS for monitoring changes in arginine methylation with single-cell and temporal resolution. The GEMS can facilitate the in vitro screening to find potential protein arginine methyltransferase inhibitors and will contribute to a better understanding of the regulation of ArgMet related to differentiation, development and disease.

ETD-Based Proteomic Profiling Improves Arginine Methylation Identification and Reveals Novel PRMT5 Substrates

Protein arginine methylations are important post-translational modifications (PTMs) in eukaryotes, regulating many biological processes. However, traditional collision-based mass spectrometry methods inevitably cause neutral losses of methylarginines, preventing the deep mining of biologically important sites. Herein we developed an optimized mass spectrometry workflow based on electron-transfer dissociation (ETD) with supplemental activation for proteomic profiling of arginine methylation in human cells. Using symmetric dimethylarginine (sDMA) as an example, we show that the ETD-based optimized workflow significantly improved the identification and site localization of sDMA. Quantitative proteomics identified 138 novel sDMA sites as potential PRMT5 substrates in HeLa cells. Further biochemical studies on SERBP1, a newly identified PRMT5 substrate, confirmed the coexistence of sDMA and asymmetric dimethylarginine in the central RGG/RG motif, and loss of either methylation caused increased the recruitment of SERBP1 to stress granules under oxidative stress. Overall, our optimized workflow not only enabled the identification and localization of extensive, nonoverlapping sDMA sites in human cells but also revealed novel PRMT5 substrates whose sDMA may play potentially important biological functions.

CRISPR-Cas9-mediated chicken prmt5 gene knockout and its critical role in interferon regulation

Protein arginine methyltransferase 5 (PRMT5), a type II arginine methyltransferase, controls arginine dimethylation of a variety of substrates. While many papers have reported the function of mammalian PRMT5, it remains unclear how PRMT5 functions in chicken cells. In this study, we found that chicken (ch) PRMT5 is widely expressed in a variety of chicken tissues and is distributed in both the cytoplasm and the nucleus. Ectopic expression of chPRMT5 significantly suppresses chIFN-β activation induced by chMDA5. In addition, a prmt5 gene-deficient DF-1 cell line was constructed using CRISPR/Cas9. In comparison with the wild-type cells, the prmt5-/- DF-1 cells displays normal morphology and maintain proliferative capacity. Luciferase reporter assay and overexpression showed that prmt5-/- DF-1 cells had increased IFN-β production. With identified chicken PRMT5 and CRISPR/Cas9 knockout performed in DF-1 cells, we uncovered a functional link of chPRMT5 in suppression of IFN-β production and interferon-stimulated gene expression.

Protein arginine methyltransferases (PRMTs): Orchestrators of cancer pathogenesis, immunotherapy dynamics, and drug resistance

Protein Arginine Methyltransferases (PRMTs) are a family of enzymes regulating protein arginine methylation, which is a post-translational modification crucial for various cellular processes. Recent studies have highlighted the mechanistic role of PRMTs in cancer pathogenesis, immunotherapy, and drug resistance. PRMTs are involved in diverse oncogenic processes, including cell proliferation, apoptosis, and metastasis. They exert their effects by methylation of histones, transcription factors, and other regulatory proteins, resulting in altered gene expression patterns. PRMT-mediated histone methylation can lead to aberrant chromatin remodeling and epigenetic changes that drive oncogenesis. Additionally, PRMTs can directly interact with key signaling pathways involved in cancer progression, such as the PI3K/Akt and MAPK pathways, thereby modulating cell survival and proliferation. In the context of cancer immunotherapy, PRMTs have emerged as critical regulators of immune responses. They modulate immune checkpoint molecules, including programmed cell death protein 1 (PD-1), through arginine methylation. Drug resistance is a significant challenge in cancer treatment, and PRMTs have been implicated in this phenomenon. PRMTs can contribute to drug resistance through multiple mechanisms, including the epigenetic regulation of drug efflux pumps, altered DNA damage repair, and modulation of cell survival pathways. In conclusion, PRMTs play critical roles in cancer pathogenesis, immunotherapy, and drug resistance. In this overview, we have endeavored to illuminate the mechanistic intricacies of PRMT-mediated processes. Shedding light on these aspects will offer valuable insights into the fundamental biology of cancer and establish PRMTs as promising therapeutic targets.

GlPRMT5 inhibits GlPP2C1 via symmetric dimethylation and regulates the biosynthesis of secondary metabolites in Ganoderma lucidum

PRMT5, a type II arginine methyltransferase, is involved in transcriptional regulation, RNA processing and other biological processes and signal transduction. Secondary metabolites are vital pharmacological compounds in Ganoderma lucidum, and their content is an important indicator for evaluating the quality of G. lucidum. Here, we found that GlPRMT5 negatively regulates the biosynthesis of secondary metabolites. In further in-depth research, GlPP2C1 (a type 2C protein phosphatase) was identified out as an interacting protein of GlPRMT5 by immunoprecipitation-mass spectrometry (IP-MS). Further mass spectrometry detection revealed that GlPRMT5 symmetrically dimethylates the arginine 99 (R99) and arginine 493 (R493) residues of GlPP2C1 to weaken its activity. The symmetrical dimethylation modification of the R99 residue is the key to affecting GlPP2C1 activity. Symmetrical demethylation-modified GlPP2C1 does not affect the interaction with GlPRMT5. In addition, silencing GlPP2C1 clearly reduced GA content, indicating that GlPP2C1 positively regulates the biosynthesis of secondary metabolites in G. lucidum. In summary, this study reveals the molecular mechanism by which GlPRMT5 regulates secondary metabolites, and these studies provide further insights into the target proteins of GlPRMT5 and symmetric dimethylation sites. Furthermore, these studies provide a basis for the mutual regulation between different epigenetic modifications.

Impact of Histone Lysine Methyltransferase SUV4-20H2 on Cancer Onset and Progression with Therapeutic Potential

Histone lysine methyltransferase SUV4-20H2, a member of the suppressor of variegation 4-20 homolog (SUV4-20) family, has a critical impact on the regulation of chromatin structure and gene expression. This methyltransferase establishes the trimethylation of histone H4 lysine 20 (H4K20me3), a repressive histone mark that affects several cellular processes. Deregulated SUV4-20H2 activity has been associated with altered chromatin dynamics, leading to the misregulation of key genes involved in cell cycle control, apoptosis and DNA repair. Emerging research evidence indicates that SUV4-20H2 acts as a potential epigenetic modifier, contributing to the development and progression of several malignancies, including breast, colon and lung cancer, as well as renal, hepatocellular and pancreatic cancer. Understanding the molecular mechanisms that underlie SUV4-20H2-mediated effects on chromatin structure and gene expression may provide valuable insights into novel therapeutic strategies for targeting epigenetic alterations in cancer. Herein, we discuss structural and functional aspects of SUV4-20H2 in cancer onset, progression and prognosis, along with current targeting options.

Cooperation between PRMT1 and PRMT6 drives lung cancer health disparities among Black/African American men

Lung cancer is the third most common cancer with Black/AA men showing higher risk and poorer outcomes than NHW men. Lung cancer disparities are multifactorial, driven by tobacco exposure, inequities in care access, upstream health determinants, and molecular determinants including biological and genetic factors. Elevated expressions of protein arginine methyltransferases (PRMTs) correlating with poorer prognosis have been observed in many cancers. Most importantly, our study shows that PRMT6 displays higher expression in lung cancer tissues of Black/AA men compared to NHW men. In this study, we investigated the underlying mechanism of PRMT6 and its cooperation with PRMT1 to form a heteromer as a driver of lung cancer. Disrupting PRMT1/PRMT6 heteromer by a competitive peptide reduced proliferation in non-small cell lung cancer cell lines and patient-derived organoids, therefore, giving rise to a more strategic approach in the treatment of Black/AA men with lung cancer and to eliminate cancer health disparities.

The role of protein arginine N-methyltransferases in inflammation

Protein arginine methyltransferases (PRMTs) promote the methylation of numerous proteins at their arginine residues. An increasing number of publications have suggested that dysregulation of PRMTs participates in various human diseases, such as cardiovascular diseases, cancer, diabetes and neurodegenerative disorders. Inflammation is one normal response to infection or injury by immune system, which can keep body homeostasis. Emerging data reveal that inflammation is associated with the development of numerous diseases. Moreover, accumulated evidence proves that PRMTs have been characterized to regulate inflammation in various diseases. In this review article, we delineate the function and molecular mechanism of PRMTs in regulation of inflammation in current literature. Moreover, we discuss that targeting PRMTs by its inhibitors and compounds could have therapeutic potential.

Role of deubiquitinase JOSD2 in the pathogenesis of esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a deadly malignancy with limited treatment options. Deubiquitinases (DUBs) have been confirmed to play a crucial role in the development of malignant tumors. JOSD2 is a DUB involved in controlling protein deubiquitination and influencing critical cellular processes in cancer.

AIM

To investigate the impact of JOSD2 on the progression of ESCC.

METHODS

Bioinformatic analyses were employed to explore the expression, prognosis, and enriched pathways associated with JOSD2 in ESCC. Lentiviral transduction was utilized to manipulate JOSD2 expression in ESCC cell lines (KYSE30 and KYSE150). Functional assays, including cell proliferation, colony formation, drug sensitivity, migration, and invasion, were performed, revealing the impact of JOSD2 on ESCC cell lines. JOSD2's role in xenograft tumor growth and drug sensitivity in vivo was also assessed. The proteins that interacted with JOSD2 were identified using mass spectrometry.

RESULTS

Preliminary research indicated that JOSD2 was highly expressed in ESCC tissues, which was associated with poor prognosis. Further analysis demonstrated that JOSD2 was upregulated in ESCC cell lines compared to normal esophageal cells. JOSD2 knockdown inhibited ESCC cell activity, including proliferation and colony-forming ability. Moreover, JOSD2 knockdown decreased the drug resistance and migration of ESCC cells, while JOSD2 overexpression enhanced these phenotypes. In vivo xenograft assays further confirmed that JOSD2 promoted tumor proliferation and drug resistance in ESCC. Mechanistically, JOSD2 appears to activate the MAPK/ERK and PI3K/AKT signaling pathways. Mass spectrometry was used to identify crucial substrate proteins that interact with JOSD2, which identified the four primary proteins that bind to JOSD2, namely USP47, IGKV2D-29, HSP90AB1, and PRMT5.

CONCLUSION

JOSD2 plays a crucial role in enhancing the proliferation, migration, and drug resistance of ESCC, suggesting that JOSD2 is a potential therapeutic target in ESCC.

PRMT1 Inhibition Activates the Interferon Pathway to Potentiate Antitumor Immunity and Enhance Checkpoint Blockade Efficacy in Melanoma

Despite the immense success of immune checkpoint blockade (ICB) in cancer treatment, many tumors, including melanoma, exhibit innate or adaptive resistance. Tumor-intrinsic T-cell deficiency and T-cell dysfunction have been identified as essential factors in the emergence of ICB resistance. Here, we found that protein arginine methyltransferase 1 (PRMT1) expression was inversely correlated with the number and activity of CD8+ T cells within melanoma specimen. PRMT1 deficiency or inhibition with DCPT1061 significantly restrained refractory melanoma growth and increased intratumoral CD8+ T cells in vivo. Moreover, PRMT1 deletion in melanoma cells facilitated formation of double-stranded RNA derived from endogenous retroviral elements (ERV) and stimulated an intracellular interferon response. Mechanistically, PRMT1 deficiency repressed the expression of DNA methyltransferase 1 (DNMT1) by attenuating modification of H4R3me2a and H3K27ac at enhancer regions of Dnmt1, and DNMT1 downregulation consequently activated ERV transcription and the interferon signaling. Importantly, PRMT1 inhibition with DCPT1061 synergized with PD-1 blockade to suppress tumor progression and increase the proportion of CD8+ T cells as well as IFNγ+CD8+ T cells in vivo. Together, these results reveal an unrecognized role and mechanism of PRMT1 in regulating antitumor T-cell immunity, suggesting PRMT1 inhibition as a potent strategy to increase the efficacy of ICB.

SIGNIFICANCE

Targeting PRMT1 stimulates interferon signaling by increasing expression of endogenous retroviral elements and double-stranded RNA through repression of DNMT1, which induces antitumor immunity and synergizes with immunotherapy to suppress tumor progression.

Overview of epigenetic degraders based on PROTAC, molecular glue, and hydrophobic tagging technologies

Epigenetic pathways play a critical role in the initiation, progression, and metastasis of cancer. Over the past few decades, significant progress has been made in the development of targeted epigenetic modulators (e.g., inhibitors). However, epigenetic inhibitors have faced multiple challenges, including limited clinical efficacy, toxicities, lack of subtype selectivity, and drug resistance. As a result, the design of new epigenetic modulators (e.g., degraders) such as PROTACs, molecular glue, and hydrophobic tagging (HyT) degraders has garnered significant attention from both academia and pharmaceutical industry, and numerous epigenetic degraders have been discovered in the past decade. In this review, we aim to provide an in-depth illustration of new degrading strategies (2017-2023) targeting epigenetic proteins for cancer therapy, focusing on the rational design, pharmacodynamics, pharmacokinetics, clinical status, and crystal structure information of these degraders. Importantly, we also provide deep insights into the potential challenges and corresponding remedies of this approach to drug design and development. Overall, we hope this review will offer a better mechanistic understanding and serve as a useful guide for the development of emerging epigenetic-targeting degraders.

Approaching the catalytic mechanism of protein lysine methyltransferases by biochemical and simulation techniques

Protein lysine methyltransferases (PKMTs) transfer up to three methyl groups to the side chains of lysine residues in proteins and fulfill important regulatory functions by controlling protein stability, localization and protein/protein interactions. The methylation reactions are highly regulated, and aberrant methylation of proteins is associated with several types of diseases including neurologic disorders, cardiovascular diseases, and various types of cancer. This review describes novel insights into the catalytic machinery of various PKMTs achieved by the combined application of biochemical experiments and simulation approaches during the last years, focusing on clinically relevant and well-studied enzymes of this group like DOT1L, SMYD1-3, SET7/9, G9a/GLP, SETD2, SUV420H2, NSD1/2, different MLLs and EZH2. Biochemical experiments have unraveled many mechanistic features of PKMTs concerning their substrate and product specificity, processivity and the effects of somatic mutations observed in PKMTs in cancer cells. Structural data additionally provided information about the substrate recognition, enzyme-substrate complex formation, and allowed for simulations of the substrate peptide interaction and mechanism of PKMTs with atomistic resolution by molecular dynamics and hybrid quantum mechanics/molecular mechanics methods. These simulation technologies uncovered important mechanistic details of the PKMT reaction mechanism including the processes responsible for the deprotonation of the target lysine residue, essential conformational changes of the PKMT upon substrate binding, but also rationalized regulatory principles like PKMT autoinhibition. Further developments are discussed that could bring us closer to a mechanistic understanding of catalysis of this important class of enzymes in the near future. The results described here illustrate the power of the investigation of enzyme mechanisms by the combined application of biochemical experiments and simulation technologies.

PRMT1 Integrates Immune Microenvironment and Fatty Acid Metabolism Response in Progression of Hepatocellular Carcinoma

Background

Protein arginine methyltransferase (PRMT) family members have important roles in cancer processes. However, its functions in the regulation of cancer immunotherapy of hepatocellular carcinoma (HCC) are incompletely understood. This study aimed to investigate the roles of PRMT1 in HCC.

Methods

Single-cell RNA sequencing (scRNA-seq) and clinicopathological data were obtained and used to explore the diagnostic and prognostic value, cellular functions and roles in immune microenvironment regulation of PRMT1 in HCC. The functions of PRMT1 were explored using Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO), as well as gene set enrichment analysis (GSEA). TIMER and CIBERSORT were used to analyze the relationships between PRMT1 expression and immune cell infiltration. The STRING database was used to construct a protein-protein interaction (PPI) network.

Results

PRMT1 was aberrantly expressed in HCC, which high expression was associated with tumor progression, worse overall survival (OS) and disease-free survival (DFS) of patients with HCC. PRMT1 was also associated with immune cell infiltration. Moreover, it was specifically expressed in immune cells, including exhausted CD8 T cells, B cells, and mono/macro cells in patients with immunotherapy. The expression of immune checkpoints was significantly increased in the high-PRMT1 expression groups of HCC patients. Regarding biological mechanisms, cell viability, migration and invasion, and the expression of genes related to fatty acid metabolism were suppressed in PRMT1 knockdown HCC cells. Moreover, genes co-expressed with PRMT1 were involved in the fatty acid metabolic process and enriched in fatty and drug-induced liver disease.

Conclusion

Taken together, these results indicate that PRMT1 might exert its oncogenic effects via immune microenvironment regulation and fatty acid metabolism in HCC. Our finding will provide a foundation for further studies and indicate a potential clinical therapeutic target for liver cancer.

Combined inhibition of MTAP and MAT2a mimics synthetic lethality in tumor models via PRMT5 inhibition

Homozygous 5'-methylthioadenosine phosphorylase (MTAP) deletions occur in approximately 15% of human cancers. Co-deletion of MTAP and methionine adenosyltransferase 2 alpha (MAT2a) induces a synthetic lethal phenotype involving protein arginine methyltransferase 5 (PRMT5) inhibition. MAT2a inhibitors are now in clinical trials for genotypic MTAP-/- cancers, however the MTAP-/- genotype represents fewer than 2% of human colorectal cancers (CRCs), limiting the utility of MAT2a inhibitors in these and other MTAP+/+ cancers. Methylthio-DADMe-immucillin-A (MTDIA) is a picomolar transition state analog inhibitor of MTAP that renders cells enzymatically MTAP-deficient to induce the MTAP-/- phenotype. Here, we demonstrate that MTDIA and MAT2a inhibitor AG-270 combination therapy mimics synthetic lethality in MTAP+/+ CRC cell lines with similar effects in mouse xenografts and without adverse histology on normal tissues. Combination treatment is synergistic with a 104-fold increase in drug potency for inhibition of CRC cell growth in culture. Combined MTDIA and AG-270 decreases S-adenosyl-L-methionine and increases 5'-methylthioadenosine in cells. The increased intracellular methylthioadenosine:S-adenosyl-L-methionine ratio inhibits PRMT5 activity, leading to cellular arrest and apoptotic cell death by causing MDM4 alternative splicing and p53 activation. Combination MTDIA and AG-270 treatment differs from direct inhibition of PRMT5 by GSK3326595 by avoiding toxicity caused by cell death in the normal gut epithelium induced by the PRMT5 inhibitor. The combination of MTAP and MAT2a inhibitors expands this synthetic lethal approach to include MTAP+/+ cancers, especially the remaining 98% of CRCs without the MTAP-/- genotype.

Promising role of protein arginine methyltransferases in overcoming anti-cancer drug resistance

Drug resistance remains a major challenge in cancer treatment, necessitating the development of novel strategies to overcome it. Protein arginine methyltransferases (PRMTs) are enzymes responsible for epigenetic arginine methylation, which regulates various biological and pathological processes, as a result, they are attractive therapeutic targets for overcoming anti-cancer drug resistance. The ongoing development of small molecules targeting PRMTs has resulted in the generation of chemical probes for modulating most PRMTs and facilitated clinical treatment for the most advanced oncology targets, including PRMT1 and PRMT5. In this review, we summarize various mechanisms underlying protein arginine methylation and the roles of specific PRMTs in driving cancer drug resistance. Furthermore, we highlight the potential clinical implications of PRMT inhibitors in decreasing cancer drug resistance. PRMTs promote the formation and maintenance of drug-tolerant cells via several mechanisms, including altered drug efflux transporters, autophagy, DNA damage repair, cancer stem cell-related function, epithelial-mesenchymal transition, and disordered tumor microenvironment. Multiple preclinical and ongoing clinical trials have demonstrated that PRMT inhibitors, particularly PRMT5 inhibitors, can sensitize cancer cells to various anti-cancer drugs, including chemotherapeutic, targeted therapeutic, and immunotherapeutic agents. Combining PRMT inhibitors with existing anti-cancer strategies will be a promising approach for overcoming anti-cancer drug resistance. Furthermore, enhanced knowledge of the complex functions of arginine methylation and PRMTs in drug resistance will guide the future development of PRMT inhibitors and may help identify new clinical indications.

The functions and mechanisms of post-translational modification in protein regulators of RNA methylation: Current status and future perspectives

RNA methylation, an epigenetic modification that does not alter gene sequence, may be important to diverse biological processes. Protein regulators of RNA methylation include "writers," "erasers," and "readers," which respectively deposit, remove, and recognize methylated RNA. RNA methylation, particularly N6-methyladenosine (m6A), 5-methylcytosine (m5C), N3-methylcytosine (m3C), N1-methyladenosine (m1A) and N7-methylguanosine (m7G), has been suggested as disease therapeutic targets. Despite advances in the structure and pharmacology of RNA methylation regulators that have improved drug discovery, regulating these proteins by various post-translational modifications (PTMs) has received little attention. PTM modifies protein structure and function, affecting all aspects of normal biology and pathogenesis, including immunology, cell differentiation, DNA damage repair, and tumors. It is becoming evident that RNA methylation regulators are also regulated by diverse PTMs. PTM of RNA methylation regulators induces their covalent linkage to new functional groups, hence modifying their activity and function. Mass spectrometry has identified many PTMs on protein regulators of RNA methylation. In this review, we describe the functions and PTM of protein regulators of RNA methylation and summarize the recent advances in the regulatory mode of human disease and its underlying mechanisms.

Protein post-translational modifications: A key factor in colorectal cancer resistance mechanisms

Colorectal cancer (CRC) is one of the leading causes of cancer-related death. Despite advances in treatment, drug resistance remains a critical impediment. Post-translational modifications (PTMs) regulate protein stability, localization, and activity, impacting vital cellular processes. Recent research has highlighted the essential role of PTMs in the development of CRC resistance. This review summarizes recent advancements in understanding PTMs' roles in CRC resistance, focusing on the latest discoveries. We discuss the functional impact of PTMs on signaling pathways and molecules involved in CRC resistance, progress in drug development, and potential therapeutic targets. We also summarize the primary enrichment methods for PTMs. Finally, we discuss current challenges and future directions, including the need for more comprehensive PTM analysis methods and PTM-targeted therapies. This review identifies potential therapeutic interventions for addressing medication resistance in CRC, proposes prospective therapeutic options, and gives an overview of the function of PTMs in CRC resistance.

PRMT3-Mediated Arginine Methylation of METTL14 Promotes Malignant Progression and Treatment Resistance in Endometrial Carcinoma

Protein arginine methyltransferase (PRMT) plays essential roles in tumor initiation and progression, but its underlying mechanisms in the treatment sensitivity of endometrial cancer (EC) remain unclear and warrant further investigation. Here, a comprehensive analysis of the Cancer Genome Atlas database and Clinical Proteomic Tumor Analysis Consortium database identifies that PRMT3 plays an important role in EC. Specifically, further experiments show that PRMT3 inhibition enhances the susceptibility of EC cells to ferroptosis. Mechanistically, PRMT3 interacts with Methyltransferase 14 (METTL14) and is involved in its arginine methylation. In addition, PRMT3 inhibition-mediated METTL14 overexpression promotes methylation modification via an m6 A-YTHDF2-dependent mechanism, reducing Glutathione peroxidase 4 (GPX4) mRNA stability, increasing lipid peroxidation levels, and accelerating ferroptosis. Notably, combined PRMT3 blockade and anti-PD-1 therapy display more potent antitumor effects by accelerating ferroptosis in cell-derived xenograft models. The specific PRMT3 inhibitor SGC707 exerts the same immunotherapeutic sensitizing effect in a patient-derived xenograft model. Notably, blocking PRMT3 improves tumor suppression in response to cisplatin and radiation therapy. Altogether, this work demonstrates that PRMT3 depletion is a promising target for EC.

Protein arginine N-methyltransferase 2 plays a noncatalytic role in the histone methylation activity of PRMT1

Protein arginine N-methyltransferases are a family of epigenetic enzymes responsible for monomethylation or dimethylation of arginine residues on histones. Dysregulation of protein arginine N-methyltransferase activity can lead to aberrant gene expression and cancer. Recent studies have shown that PRMT2 expression and histone H3 methylation at arginine 8 are correlated with disease severity in glioblastoma multiforme, hepatocellular carcinoma, and renal cell carcinoma. In this study, we explore a noncatalytic mechanistic role for PRMT2 in histone methylation by investigating interactions between PRMT2, histone peptides and proteins, and other PRMTs using analytical and enzymatic approaches. We quantify interactions between PRMT2, peptide ligands, and PRMT1 in a cofactor- and domain-dependent manner using differential scanning fluorimetry. We found that PRMT2 modulates the substrate specificity of PRMT1. Using calf thymus histones as substrates, we saw that a 10-fold excess of PRMT2 promotes PRMT1 methylation of both histone H4 and histone H2A. We found equimolar or a 10-fold excess of PRMT2 to PRMT1 can improve the catalytic efficiency of PRMT1 towards individual histone substrates H2A, H3, and H4. We further evaluated the effects of PRMT2 towards PRMT1 on unmodified histone octamers and mononucleosomes and found marginal PRMT1 activity improvements in histone octamers but significantly greater methylation of mononucleosomes in the presence of 10-fold excess of PRMT2. This work reveals the ability of PRMT2 to serve a noncatalytic role through its SH3 domain in driving site-specific histone methylation marks.

Arginine Methylation Regulates Self-Assembly of Peptides

Bio-inspired design of peptides represents one facile strategy for development of supramolecular monomers for self-assembly into well-defined nanostructures. Inspired by methylation of arginine during post-translational modification for manipulating protein functions, herein, the controllable self-assembly of peptides via rational incorporation of methylated arginine residues into bola-amphiphilic peptides is reported. A series of bola-amphiphilic peptides are designed and synthesized either containing natural arginine or methylated arginine and investigate the influence of arginine methylation on peptide assembly. This study finds that incorporation of symmetrically di-methylated arginine into oppositely charged hexapeptide hex-SDMAE leads to distinct assembling performance compare to natural peptide hex-RE. The findings demonstrate that the methylation of rationally designed peptide sequences allows for regulation of self-assembly of peptides, thus implying the great potential of arginine methylation in establishing controllable peptide assembling systems and creating in situ formulation of biomedical materials in the future.

Loss of the methylarginine reader function of SND1 confers resistance to hepatocellular carcinoma

Staphylococcal nuclease Tudor domain containing 1 (SND1) protein is an oncogene that 'reads' methylarginine marks through its Tudor domain. Specifically, it recognizes methylation marks deposited by protein arginine methyltransferase 5 (PRMT5), which is also known to promote tumorigenesis. Although SND1 can drive hepatocellular carcinoma (HCC), it is unclear whether the SND1 Tudor domain is needed to promote HCC. We sought to identify the biological role of the SND1 Tudor domain in normal and tumorigenic settings by developing two genetically engineered SND1 mouse models, an Snd1 knockout (Snd1 KO) and an Snd1 Tudor domain-mutated (Snd1 KI) mouse, whose mutant SND1 can no longer recognize PRMT5-catalyzed methylarginine marks. Quantitative PCR analysis of normal, KO, and KI liver samples revealed a role for the SND1 Tudor domain in regulating the expression of genes encoding major acute phase proteins, which could provide mechanistic insight into SND1 function in a tumor setting. Prior studies indicated that ectopic overexpression of SND1 in the mouse liver dramatically accelerates the development of diethylnitrosamine (DEN)-induced HCC. Thus, we tested the combined effects of DEN and SND1 loss or mutation on the development of HCC. We found that both Snd1 KO and Snd1 KI mice were partially protected against malignant tumor development following exposure to DEN. These results support the development of small molecule inhibitors that target the SND1 Tudor domain or the use of upstream PRMT5 inhibitors, as novel treatments for HCC.

Targeting PRMT1-mediated SRSF1 methylation to suppress oncogenic exon inclusion events and breast tumorigenesis

PRMT1 plays a vital role in breast tumorigenesis; however, the underlying molecular mechanisms remain incompletely understood. Herein, we show that PRMT1 plays a critical role in RNA alternative splicing, with a preference for exon inclusion. PRMT1 methylome profiling identifies that PRMT1 methylates the splicing factor SRSF1, which is critical for SRSF1 phosphorylation, SRSF1 binding with RNA, and exon inclusion. In breast tumors, PRMT1 overexpression is associated with increased SRSF1 arginine methylation and aberrant exon inclusion, which are critical for breast cancer cell growth. In addition, we identify a selective PRMT1 inhibitor, iPRMT1, which potently inhibits PRMT1-mediated SRSF1 methylation, exon inclusion, and breast cancer cell growth. Combination treatment with iPRMT1 and inhibitors targeting SRSF1 phosphorylation exhibits an additive effect of suppressing breast cancer cell growth. In conclusion, our study dissects a mechanism underlying PRMT1-mediated RNA alternative splicing. Thus, PRMT1 has great potential as a therapeutic target in breast cancer treatment.

Therapeutic Advantage of Targeting PRMT5 in Combination with Chemotherapies or EGFR/HER2 Inhibitors in Triple-Negative Breast Cancers

Purpose

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subgroup characterized by a high risk of resistance to chemotherapies and high relapse potential. TNBC shows inter-and intra-tumoral heterogeneity; more than half expresses high EGFR levels and about 30% are classified as HER2-low breast cancers. High PRMT5 mRNA levels are associated with poor prognosis in TNBC and inhibiting PRMT5 impairs the viability of subsets of TNBC cell lines and delays tumor growth in TNBC mice models. TNBC patients may therefore benefit from a treatment targeting PRMT5. The aim of this study was to assess the therapeutic benefit of combining a PRMT5 inhibitor with different chemotherapies used in the clinics to treat TNBC patients, or with FDA-approved inhibitors targeting the HER family members.

Methods

The drug combinations were performed using proliferation and colony formation assays on TNBC cell lines that were sensitive or resistant to EPZ015938, a PRMT5 inhibitor that has been evaluated in clinical trials. The chemotherapies analyzed were cisplatin, doxorubicin, camptothecin, and paclitaxel. The targeted therapies tested were erlotinib (EGFR inhibitor), neratinib (EGFR/HER2/HER4 inhibitor) and tucatinib (HER2 inhibitor).

Results

We found that PRMT5 inhibition synergized mostly with cisplatin, and to a lesser extent with doxorubicin or camptothecin, but not with paclitaxel, to impair TNBC cell proliferation. PRMT5 inhibition also synergized with erlotinib and neratinib in TNBC cell lines, especially in those overexpressing EGFR. Additionally, a synergistic interaction was observed with neratinib and tucatinib in a HER2-low TNBC cell line as well as in a HER2-positive breast cancer cell line. We noticed that synergy can be obtained in TNBC cell lines that were resistant to PRMT5 inhibition alone.

Conclusion

Altogether, our data highlight the therapeutic potential of targeting PRMT5 using combinatorial strategies for the treatment of subsets of TNBC patients.

PRMT1 promotes the proliferation and metastasis of gastric cancer cells by recruiting MLXIP for the transcriptional activation of the β-catenin pathway

Protein arginine methyltransferase 1 (PRMT1), a type I PRMT, is overexpressed in gastric cancer (GC) cells. To elucidate the function of PRMT1 in GC, PRMT1 expression in HGC-27 and MKN-45 cells was knocked down by short hairpin RNA (shRNA) or inhibited by PRMT1 inhibitors (AMI-1 or DCLX069), which resulted in inhibition of GC cell proliferation, migration, invasion, and tumorigenesis in vitro and in vivo. MLX-interacting protein (MLXIP) and Kinectin 1 (KTN1) were identified as PRMT1-binding proteins. PRMT1 recruited MLXIP to the promoter of β-catenin, which induced β-catenin transcription and activated the β-catenin signaling pathway, promoting GC cell migration and metastasis. Furthermore, KTN1 inhibited the K48-linked ubiquitination of PRMT1 by decreasing the interaction between TRIM48 and PRMT1. Collectively, our findings reveal a mechanism by which PRMT1 promotes cell proliferation and metastasis mediated by the β-catenin signaling pathway.

The protein arginine methyltransferase family (PRMTs) regulates metastases in various tumors: From experimental study to clinical application

Tumor metastasis is the leading cause of mortality among advanced cancer patients. Understanding its mechanisms and treatment strategies is vital for clinical application. Arginine methylation, a post-translational modification catalyzed by protein arginine methyltransferases (PRMTs), is implicated in diverse physiological processes and disease progressions. Previous research has demonstrated PRMTs' involvement in tumor occurrence, progression, and metastasis. This review offers a comprehensive summary of the relationship between PRMTs, prognosis, and metastasis in various cancers. Our focus centers on elucidating the molecular mechanisms through which PRMTs regulate tumor metastasis. We also discuss relevant clinical trials and effective PRMT inhibitors, including chemical compounds, long non-coding RNA (lncRNA), micro-RNA (miRNA), and nanomaterials, for treating tumor metastasis. While a few studies present conflicting results, the overall trajectory suggests that inhibiting arginine methylation exhibits promise in curtailing tumor metastasis across various cancers. Nonetheless, the underlying mechanisms and molecular interactions are diverse. The development of inhibitors targeting arginine methylation, along with the progression of clinical trials, holds substantial potential in the field of tumor metastasis, meriting sustained attention.