Protein arginine methylation in mammals: who, what, and why. Mol Cell. 2009;33:1-13. [PMID: 19150423 DOI: 10.1016/j.molcel.2008.12.013]

Drug discovery targeting protein arginine methyltransferase 5 (PRMT5): an update

Protein arginine methyltransferase 5 (PRMT5) plays an important role in regulating gene expression, cell differentiation and development, and chromatin structure by catalyzing the methylation of histones and non-histone proteins. The aberrant expression of PRMT5 is closely associated with the occurrence and progression of various diseases, particularly malignant tumors. Accordingly, developing potent and specific PRMT5 inhibitors may provide a potential novel therapeutic approach. In this Perspective, we highlight the structures, the biological functions, regulatory mechanisms, relevant signaling pathways, and associations with cancer development of PRMT5, as well as the recent advances in drug discovery strategies targeting PRMT5. The challenges, opportunities, and future directions for developing PRMT5 inhibitors and degraders are also discussed.

Serine phosphorylation of protein arginine methyltransferase Hmt1 is critical for controlling its protein levels

In eukaryotes, protein arginine methylation is a prevalent post-translational modification found in a multitude of proteins responsible for key biological processes, ranging from transcription to signaling. One model suggests that phosphorylation of serine 9 (S9) in the Saccharomyces cerevisiae major protein arginine methyltransferase Hmt1 is critical for its oligomerization and activity. In this study, we used classic biochemical approaches to demonstrate that neither the S9 phosphomimetic nor the non-phosphorylatable substitution mutants of Hmt1 affect its oligomerization. These mutants remain active in vivo, retaining their ability to methylate the SR-/hnRNP-like protein Npl3 and displaying a monomethylarginine and asymmetric dimethylarginine banding profile similar to that of the wild-type. In cells lacking Dbf2, the proposed kinase responsible for phosphorylating Hmt1 at S9, Npl3 remains methylated. Additionally, monomethylarginine and asymmetric dimethylarginine banding profiles in cells lacking Dbf2 mostly resemble those observed in the wild-type rather than in hmt1Δ cells. Synchronized yeast cells expressing either S9 substitution exhibit entry into the M phase of the cell cycle at a rate similar to that of both wild-type and hmt1Δ cells. Our results suggest that the C-terminal epitope tagging of Hmt1 is responsible for the previously observed loss of enzymatic activities, rather than the S9 phosphorylation status of Hmt1. Finally, we demonstrate that S9 phosphorylation plays a role in maintaining Hmt1 protein levels in vivo. Overall, our finding demonstrates a novel role for Hmt1 S9 phosphorylation in tuning its in vivo protein levels.

Arginine methylation modulates tumor fate and prognosis in clear cell renal cell carcinoma

BACKGROUND

Arginine methylation, a key post-translational modification, plays a pivotal role in regulating various cellular processes and has been implicated in cancer progression. However, the potential of arginine methylation-related genes as prognostic markers in clear cell renal cell carcinoma (ccRCC) remains underexplored.

METHODS

We utilized public transcriptomic datasets from TCGA, E-MTAB-1980 and ICGC, for model construction and validation. Single-cell RNA sequencing datasets were employed to evaluate gene expression patterns at the cellular level. Consensus clustering, KM survival analysis, and GSVA were applied to identify molecular subtypes and related pathways. Univariate and multivariate Cox regression analyses were applied to develop an arginine methylation-related signature (AMS). Immune profiling, mutation landscape, and drug sensitivity prediction were also employed to explore the model's association with clinical features, immune infiltration, mutation burden, and therapeutic responses.

RESULTS

The AMS demonstrated robust prognostic performance, with consistent validation across external cohorts. High-risk patients exhibited significantly worse survival, elevated TMB, and an immunosuppressive tumor microenvironment characterized by increased infiltration of regulatory immune cells. Single-cell RNA sequencing revealed key prognostic genes expressed predominantly in cancer and immune cells, supporting their role in tumor progression and immune interactions.

CONCLUSION

The arginine methylation-based prognostic model provides a reliable framework for survival risk stratification in ccRCC and holds promise for guiding personalized therapeutic strategies. Future research should emphasize clinical validation of this model and explore its potential role in optimizing immunotherapy and targeted treatment strategies for ccRCC.

Decoding stress granules dynamics: Implications for neurodegenerative disease

Stress granules (SGs) are membrane-less cytoplasmic structures formed by cells in response to external stress, primarily composed of mRNA and proteins. The dynamic properties of their assembly, maintenance, and disassembly play crucial roles in cellular homeostasis. Recent studies have increasingly revealed that aberrations in SGs dynamics are closely related to the pathogenesis of various neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This review summarizes the latest research progress on SGs dynamics in neurodegenerative diseases. It begins with an overview of the basic biological characteristics of SGs and their functions in neurons, followed by an in-depth exploration of the mechanisms and regulatory pathways of SGs dynamics. The review then summarizes potential therapeutic strategies targeting SGs dynamics abnormalities, particularly through small molecule drugs to modulate SGs formation and disassembly, aiming to delay or halt the progression of neurodegenerative diseases. The review also highlights the application prospects of these interventions in treating neurodegenerative diseases. Finally, the review introduces current techniques used to study SGs dynamics, discussing their advantages, limitations, and future development possibilities. This review aims to provide researchers with a comprehensive perspective to advance the understanding and clinical application of SGs dynamics in the field of neurodegenerative diseases.

The E3 Ligase NEDD4L Prevents Colorectal Cancer Liver Metastasis via Degradation of PRMT5 to Inhibit the AKT/mTOR Signaling Pathway

Colorectal cancer is the second most common cause of cancer mortality worldwide, and liver metastasis is the major cause of death of patients with colorectal cancer. Dysfunctional E3 ligase activity has recently been shown to be associated with colorectal cancer. However, the key E3 ligases affecting colorectal cancer liver metastasis remain unknown. Therefore, an shRNA library targeting 156 E3 ubiquitin ligases has been used to perform an in vivo loss-of-function screen of a human colorectal cancer cell line in a mouse model of liver metastasis. The screen reveals that neural precursor cell expressed developmentally down-regulated gene 4-like (NEDD4L) knockdown promotes colorectal cancer liver metastasis. Mechanistic studies reveal that NEDD4L binds to the PPNAY motif in protein arginine methyltransferase 5 (PRMT5) and ubiquitinates PRMT5 to promote its degradation. PRMT5 degradation attenuates the arginine methylation of AKT1 to inhibit the AKT/mTOR signaling pathway. The effect of NEDD4L decreases colorectal cancer cell proliferation to suppress colonization. This study is the first to show that PRMT5 is a substrate of NEDD4L and reveals not only the metastasis-inhibiting function of NEDD4L but also a novel mechanism by which NEDD4L prevents colorectal cancer liver metastasis. These findings may provide a new preventive strategy for liver metastasis.

BRD9 functions as a methylarginine reader to regulate AKT-EZH2 signaling

Recognition of methylarginine marks by effector proteins ("readers") is a critical link between arginine methylation and various cellular processes. Recently, we identified methylation of AKT1 at arginine-391 (R391), but the reader for this methylation has yet to be characterized. Here, we show that bromodomain-containing protein 9 (BRD9), a reader of acetylated lysine, unexpectedly recognizes methylated R391 of AKT1 through an aromatic cage in its bromodomain. Disrupting the methylarginine reader function of BRD9 suppresses AKT activation and tumorigenesis. RNA sequencing data show that BRD9 and AKT coregulate a hallmark transcriptional program in part through enhancer of zeste homolog 2 (EZH2)-mediated methylation of histone-3 lysine-27. We also find that inhibitors of BRD9 and EZH2 display synergistic effects on suppression of cell proliferation and tumor growth. Collectively, our study reveals a previously unknown function of BRD9 and a potential therapeutic strategy for cancer treatment by combining BRD9 and EZH2 inhibitors.

Regulation of protein arginine methyltransferase in osteoporosis: a narrative review

Osteoporosis (OP), a systemic bone disease characterised by increased bone fragility and susceptibility to fracture, is mainly caused by a decline in bone mineral density (BMD) and quality caused by an imbalance between bone formation and resorption. Protein arginine methyltransferases (PRMTs) are epigenetic factors and post-translational modification (PTM) enzymes participating in various biological processes, including mRNA splicing, DNA damage repair, transcriptional regulation, and cell signalling. They act by catalysing the transfer and modification of arginine residues and, thus, have become therapeutic targets for OP. In-depth studies have found that these enzymes also play key roles in bone matrix protein metabolism, skeletal cell proliferation and differentiation, and signal pathway regulation to regulate bone formation, bone resorption balance, or both and jointly maintain bone health and stability. However, the expression changes and mechanisms of action of multiple members of the PRMT family differ in OP. Therefore, this paper discusses the biological functions, mechanisms of action, and influencing factors of PRMTs in OP, which is expected to provide a new understanding of the pathogenesis of OP. Furthermore, we present theoretical support for the development of more precise and effective treatment strategies as well as for further study of the molecular mechanisms of PRMTs.

The mRNA export pathway licenses viral mimicry response and antitumor immunity by actively exporting nuclear retroelement transcripts

Nuclear retroelement transcripts (RTs), which can be elicited both transcriptionally and posttranscriptionally, form double-stranded RNA (dsRNA) in cytosol to trigger the viral mimicry response (VMR) and antitumor immunity. However, the strength of the induced VMR varies tremendously across tumor types, and the underlying mechanisms remain poorly understood. Here, we demonstrate that the mRNA export pathway modulates the VMR through actively exporting nuclear RTs for cytosolic dsRNA formation after their induction. Tumor cells hijack this process for immune evasion through aberrant coactivator-associated arginine methyltransferase 1 (CARM1) expression. Mechanistically, we show that the cytoplasmic transportation of RTs by the mRNA export pathway is counteracted by the RNA exosome, which cleaves multiple transcripts within this pathway, including those encoding the essential DExD-box helicase 39A (DDX39A) and the adaptor protein ALYREF. CARM1 enhances the RNA exosome activity to attenuate the nuclear export of RTs by the mRNA export pathway through two synergistic mechanisms: (i) transcriptionally activating several RNA exosome components and (ii) posttranslationally methylating arginine 6 of the RNA exosome subunit EXOSC1, which protects it from proteasome-mediated degradation. Collectively, our study highlights the critical active regulatory role of the mRNA export pathway in transporting nuclear RTs into the cytosol for triggering the VMR and tumor immunity. Furthermore, we propose that enhancing the mRNA export pathway activity, either through CARM1 inhibition or RNA exosome modulation, could reinforce the therapeutic agent-induced VMR, thus holding the promise for overcoming tumor immune evasion and immunotherapy resistance.

PRMT5 deficiency in myeloid cells reprograms macrophages to enhance antitumor immunity and synergizes with anti-PD-L1 therapy

BACKGROUND

Arginine methyltransferase protein arginine methyltransferase 5 (PRMT5) plays a significant role in immune regulation, particularly within the tumor microenvironment (TME). Macrophages are crucial modulators of both innate and adaptive immune responses, and their differentiation into tumor-associated macrophages is critical in shaping the TME. Despite ongoing clinical trials of small molecule inhibitors of PRMT5 for cancer therapy, their effects on macrophages, a key component of the immune system, remain poorly understood.

METHODS

A pan-cancer single-cell transcriptional analysis was initially conducted to investigate the expression of PRMT5 in tumor-infiltrating myeloid cells. Myeloid-specific deletion of Prmt5 in mice, as well as the use of a PRMT5-specific inhibitor, was performed to evaluate the impact of PRMT5 on macrophage polarization and tumor progression. Bulk and single-cell transcriptomics were employed to explore the mechanistic roles of PRMT5 in regulating lipid metabolism and macrophage polarization. Additionally, the therapeutic potential of combining Prmt5 deletion with anti-programmed death-ligand 1 (PD-L1) therapy was assessed to study its effects on antitumor immunity in vivo.

RESULTS

The pan-cancer single-cell transcriptional analysis revealed that PRMT5 is highly expressed in the PPARG-macrophage subset, which correlates with poor patient survival. Myeloid-specific deletion of Prmt5 reprogrammed macrophages towards an antitumor phenotype, effectively inhibiting tumor progression. Mechanistically, PRMT5 was found to regulate lipid metabolism and drive macrophage polarization toward an anti-inflammatory state via the STAT6-PPARγ pathway, fostering an immunosuppressive TME conducive to tumor growth. Notably, Prmt5 deletion induced PD-L1 expression on myeloid cells. Combining Prmt5 deletion with anti-PD-L1 therapy significantly enhanced antitumor efficacy, demonstrating a synergistic therapeutic effect.

CONCLUSIONS

These findings uncover a crucial role for PRMT5 in macrophage biology and suggest that targeting PRMT5 in myeloid cells offers a promising new approach for cancer immunotherapy. The combination of PRMT5 inhibition with anti-PD-L1 therapy may provide a potent strategy to reprogram the TME and enhance antitumor immune responses.

Fructose-induced progression of steatohepatitis involves disrupting aldolase B-AMPK signaling in methionine adenosyltransferase 1A deficient mice

OBJECTIVE

Aldolases (ALDO) are sensors that regulate AMPK via binding to fructose 1,6-biphosphate (FBP), an intermediate of glucose and fructose metabolism. Fructose consumption is linked to metabolic dysfunction-associated steatotic liver disease (MASLD) progression but whether ALDO-AMPK signaling is involved is unknown. Methionine adenosyltransferase alpha 1 (Mat1a) knockout (KO) mice have low hepatic S-adenosylmethionine (SAMe) level and spontaneously develop steatohepatitis. ALDOB methylation has not been reported and here we investigated whether SAMe level regulates ALDOB and ALDOB-AMPK signaling and whether fructose feeding accelerates MASLD progression by disrupting ALDOB-AMPK signaling.

METHODS

Mass spectrometry identified ALDOB methylation sites and recombinant in vitro approaches assessed how methylation at those sites affects ALDOB oligomerization and activity. Primary hepatocytes cultured with high/low glucose and/or fructose and wild type (WT) and Mat1a KO mice fed with a high-fructose diet examined AMPK-ALDOB signaling and MASLD progression.

RESULTS

In Mat1a KO livers ALDOB R173 is hypomethylated while ALDOB activity is enhanced. Recombinant ALDOB is methylated at R173 and R304 by protein arginine methyltransferase 1. Low hepatic SAMe level results in hypomethylated ALDOB, which favors the tetrameric form that has higher enzymatic activity, and higher capacity to signal to activate AMPK. Fructose, independently of glucose levels, inhibited AMPK activity and induced lipid accumulation in hepatocytes. Mat1a KO mice have hyperactivated AMPK and fructose feeding inhibits it, enhancing the accumulation of fat in the liver and the progression of MASLD.

CONCLUSION

Hepatic SAMe levels regulate ALDOB oligomeric state and enzymatic activity impacting on AMPK signaling and fructose-induced MASLD progression.

Analysis of Metabolomic Reprogramming Induced by Infection with Kaposi's Sarcoma-Associated Herpesvirus Using Untargeted Metabolomic Profiling

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus. There are no vaccines or antiviral therapies for KSHV. Identifying the cellular metabolic pathways that KSHV manipulates can broaden the knowledge of how these pathways contribute to sustaining lytic infection, which can be targeted in future therapies to prevent viral spread. In this study, we performed an untargeted metabolomic analysis of KSHV infected telomerase-immortalized gingival keratinocytes (TIGK) cells at 4 h post-infection compared to mock-infected cells. We found that the metabolomic landscape of KSHV-infected TIGK differed from that of the mock. Specifically, a total of 804 differential metabolic features were detected in the two groups, with 741 metabolites that were significantly upregulated, and 63 that were significantly downregulated in KSHV-infected TIGK cells. The differential metabolites included ornithine, arginine, putrescine, dimethylarginine, orotate, glutamate, and glutamine, and were associated with pathways, such as the urea cycle, polyamine synthesis, dimethylarginine synthesis, and de novo pyrimidine synthesis. Overall, our untargeted metabolomics analysis revealed that KSHV infection results in marked rapid alterations in the metabolic profile of the oral epithelial cells. We envision that a subset of these rapid metabolic changes might result in altered cellular functions that can promote viral lytic replication and transmission in the oral cavity.

L-arginine dependence of breast cancer - molecular subtypes matter

L-arginine limits proliferation in highly proliferative tissues. It is a substrate for nitric oxide synthases, arginases; its methylation by protein-L-arginine methyltransferases (PRMTs) leads to asymmetric (ADMA) and symmetric dimethylarginine (SDMA). We measured L-arginine and its metabolites L-ornithine, L-citrulline, ADMA, and SDMA in a prospective cohort of 243 women with primary breast cancer (BC) and their associations with mortality and disease recurrence during 88 (IQR, 82-93) months of follow-up. We quantified these metabolites and expression of genes involved in L-arginine metabolic pathways in MCF-7, BT-474, SK-BR-3, MDA-MB-231, and MDA-MB-468 cells representing ER-positive, HER2-positive, and triple-negative BC compared to MCF-12 A cells. Plasma L-arginine and ADMA concentrations were elevated in 47 patients with recurrent disease and in 34 non-survivors. ADMA was significantly associated with mortality and recurrent disease in Luminal A patients; low L-citrulline was significantly associated with survival in triple-negative BC. In all BC cells except MCF-7, DDAH1 and DDAH2 expression was higher than in MCF-12 A (DDAH1: 32-44 fold, DDAH2: 1.7-4.2 fold; p < 0.05). By contrast, MCF-7 cells showed low DDAH1 and DDAH2, but high PRMT4 and PRMT6 expression and high L-arginine content. BT-474 and MDA-MB-468 cells showed high ARG2 expression and high L-ornithine concentrations, and MDA-MB-468 cells had the highest L-citrulline/L-arginine ratio. In conclusion, regulation of L-arginine metabolic pathways shows a complex and differential pattern between BC subtypes. ADMA is a prognostic biomarker in Luminal A patients; its metabolizing enzyme, DDAH, is highly overexpressed in BC cells. Thus, fingerprinting of L-arginine metabolism may offer novel personalized treatment options within BC subtypes.

PRMT7-Mediated PTEN Activation Enhances Bone Regeneration in Female Mice

Epigenetic regulation provides new insights into the mechanisms of osteogenic differentiation and identifies potential targets for treating bone-related diseases. However, the specific regulatory networks and mechanisms involved still need further investigation. In this study, we identify PRMT7 as a novel epigenetic regulator of mesenchymal stem cells (MSCs) osteogenic commitment. Conditional knockout of Prmt7 in mice reveals a significant impairment in osteogenesis and bone regeneration, specifically in females, affecting both femurs and mandibles, with no noticeable effect in males. Mechanistically, PRMT7 modulates MSCs osteogenic differentiation by activating PTEN. Specifically, PRMT7 enhances PTEN transcription by increasing H3R2me1 levels at the PTEN promoter. Additionally, PRMT7 interacts with the PTEN protein and stabilizes nuclear PTEN, revealing an unprecedented pathway. Notably, overexpression of PTEN alleviates the osteogenic deficits observed in Prmt7-deficient mice. This research establishes PRMT7 as a potential therapeutic target for promoting bone formation/regeneration and offers novel molecular insights into the PRMT7-PTEN regulatory axis, underscoring its significance in bone biology and regenerative medicine.

High PRMT5 levels, maintained by KEAP1 inhibition, drive chemoresistance in high-grade serous ovarian cancer

Protein arginine methyl transferases (PRMTs) are generally upregulated in cancers. However, the mechanisms leading to this upregulation and its biological consequences are poorly understood. Here, we identify PRMT5, the main symmetric arginine methyltransferase, as a critical driver of chemoresistance in high-grade serous ovarian cancer (HGSOC). PRMT5 levels and its enzymatic activity are induced in a platinum-resistant (Pt-resistant) state at the protein level. To reveal potential regulators of high PRMT5 protein levels, we optimized intracellular immunostaining conditions and performed unbiased CRISPR screening. We identified Kelch-like ECH-associated protein 1 (KEAP1) as a top-scoring negative regulator of PRMT5. Our mechanistic studies show that KEAP1 directly interacted with PRMT5, leading to its ubiquitin-dependent degradation under normal physiological conditions. At the genomic level, ChIP studies showed that elevated PRMT5 directly interacted with the promoters of stress response genes and positively regulated their transcription. Combined PRMT5 inhibition with Pt resulted in synergistic cellular cytotoxicity in vitro and reduced tumor growth in vivo in Pt-resistant patient-derived xenograft tumors. Overall, the findings from this study identify PRMT5 as a critical therapeutic target in Pt-resistant HGSOC cells and reveal the molecular mechanisms that lead to high PRMT5 levels in Pt-treated and chemo-resistant tumors.

Specific sDMA modifications on the RGG/RG motif of METTL14 regulate its function in AML

BACKGROUND

Protein arginine methylations are crucial post-translational modifications (PTMs) in eukaryotes, playing a significant regulatory role in diverse biological processes. Here, we present our investigation into the detailed arginine methylation pattern of the C-terminal RG-rich region of METTL14, a key component of the m6A RNA methylation machinery, and its functional implications in biology and disease.

METHODS

Using ETD-based mass spectrometry and in vitro enzyme reactions, we uncover a specific arginine methylation pattern on METTL14. RNA methyltransferase activity assays were used to assess the impact of sDMA on METTL3:METTL14 complex activity. RNA immunoprecipitation was used to evaluate mRNA-m6A reader interactions. MeRIP-seq analysis was used to study the genome-wide effect of METTL14 sDMA on m6A modification in acute myeloid leukemia cells.

RESULTS

We demonstrate that PRMT5 catalyzes the site-specific symmetric dimethylation at R425 and R445 within the extensively methylated RGG/RG motifs of METTL14. We show a positive regulatory role of symmetric dimethylarginines (sDMA) in the catalytic efficiency of the METTL3:METTL14 complex and m6A-specific gene expression in HEK293T and acute myeloid leukemia cells, potentially through the action of m6A reader protein YTHDF1. In addition, the combined inhibition of METTL3 and PRMT5 further reduces the expression of several m6A substrate genes essential for AML proliferation, suggesting a potential therapeutic strategy for AML treatment.

CONCLUSIONS

The study confirms the coexistence of sDMA and aDMA modifications on METTL14's RGG/RG motifs, with sDMA at R425 and R445 enhancing METTL3:METTL14's catalytic efficacy and regulating gene expression through m6A deposition in cancer cells.

CARM1 regulates tubulin autoregulation through PI3KC2α R175 methylation

Tubulin is crucial in several cellular processes, including intracellular organization, organelle transport, motility, and chromosome segregation. Intracellular tubulin concentration is tightly regulated by an autoregulation mechanism, in which excess free tubulin promotes tubulin mRNA degradation. However, the details of how changes in free tubulin levels initiate this autoregulation remain unclear. In this study, we identified coactivator-associated arginine methyltransferase 1 (CARM1)-phosphatidylinositol 3-kinase class 2α (PI3KC2α) axis as a novel regulator of tubulin autoregulation. CARM1 stabilizes PI3KC2α by methylating its R175 residue. Once PI3KC2α is not methylated, it becomes unstable, leading to decreased cellular levels. Loss of PI3KC2α results in the release of tetratricopeptide repeat domain 5 (TTC5), which initiates tubulin autoregulation. Thus, PI3KC2α, along with its CARM1-mediated arginine methylation, regulates the initiation of tubulin autoregulation. Additionally, disruption of the CARM1-PI3KC2α axis decreases intracellular tubulin levels, leading to a synergistic increase in the cytotoxicity of microtubule-targeting agents (MTAs). Taken together, our study demonstrates that the CARM1-PI3KC2α axis is a key regulator of TTC5-mediated tubulin autoregulation and that disrupting this axis enhances the anti-cancer activity of MTAs.

The l-Arginine pathway may act as a mediator in the association between impaired one-carbon metabolism and hypertension

Elevated fasting plasma total homocysteine (tHcy) and the methylenetetrahydrofolate reductase C677T polymorphism (rs1801133) have been associated with hypertension. Whether the l-Arginine pathway is involved, is unclear. We aimed to investigate whether the association between tHcy, the rs1801133 polymorphism and hypertension involves the l-Arginine pathway. THcy, plasma folate and cobalamin, erythrocyte glutathionine reductase activation coefficient, rs1801133 genotype, plasma l-Arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) were determined in a cross-sectional study of 788 adults (aged 18 to 75), randomly selected from 2 town population registers. Participants participated in a medical checkup and provided a fasting blood sample. Associations between tHcy, rs1801133 genotype and l-Arginine pathway metabolites were assessed by multiple linear regression analysis and whether the tHcy and rs1801133 genotype are associated with hypertension via the l-Arginine pathway was investigated using mediation analysis. tHcy was positively associated with ADMA (B = 0.003; SE = 0.001; P < 0.001) and SDMA (B = 0.007; SE = 0.002; P < 0.001) and negatively associated with the l-Arginine/ADMA (B = -1.140; SE = 0.451; P < 0.05) and ADMA/SDMA (B = -0.006; SE = 0.003; P < 0.05) ratios. The MTHFR 677 CT vs CC genotype was negatively associated with ADMA (B = -0.013; SE = 0.007; P < 0.05) and with SDMA (B = -0.029; SE = 0.013; P < 0.05) in participants under 50 years. Each standard deviation increase (37.6) in the l-Arginine/ADMA ratio was associated with reduced hypertension risk (OR [95%CI], 0.6 [0.5, 0.8]). Mediation analysis showed that tHcy and ADMA were mediators in the association between the rs1801133 TT vs CC genotypes and hypertension. Our results support the l-Arginine pathway as a mediator in the association of impaired One-Carbon metabolism and hypertension.

A Retrospective Evaluation of Serum Symmetric Dimethylarginine Concentration in Dogs With Protein-Losing Enteropathy

BACKGROUND

Serum symmetric dimethylarginine (SDMA) is abnormally increased in people with inflammatory bowel disease (IBD). Changes in dogs with gastrointestinal disease, such as protein-losing enteropathy (PLE), have not been assessed.

OBJECTIVES

Evaluate SDMA concentration in non-azotemic dogs with PLE.

ANIMALS

A total of 127 client-owned dogs, 17 with PLE, 34 controls matched for age, breed, sex, and neuter status, and 76 additional controls for multiple linear regression modeling.

METHODS

Retrospective case-control study. The clinical records of a United Kingdom referral hospital were reviewed. Dogs with azotemia or prior glucocorticoid or immunosuppressive treatment were excluded. Dogs diagnosed with PLE that had serum symmetric dimethylarginine (SDMA) concentrations measured were compared with the matched controls. Signalment, clinical presentation, clinicopathological abnormalities, treatment, and SDMA concentration pre- (PLE-T0) and post- (PLE-T1) treatment were recorded.

RESULTS

At baseline, SDMA concentration was higher in PLE (T0, 15.2 ± 2.02 μg/dL) than in control (11.0 ± 3.13 μg/dL) dogs (p < 0.001; Hedge's G, 1.48), but decreased with treatment (PLE-T1: 10.3 ± 2.78 μg/dL; T0 vs. T1: p = 0.01, Hedge's G, 1.31). Serum creatinine concentration was similar in PLE (T0, 0.81 ± 0.24 μg/dL) and control (0.85 ± 0.26 μg/dL) dogs at baseline (p = 0.57; Hedge's G, 0.18). Serum albumin concentration was lower in PLE (1.60 ± 0.51 g/dL) than in control (2.96 ± 0.49 g/dL) dogs (p < 0.001; Hedge's G, 2.68) before treatment, but increased with treatment (PLE-T1: 2.29 ± 0.65 g/dL; T0 vs. T1: p = 0.003; Hedge's G, 1.14), although it remained lower than the concentration in controls (p = 0.002; Hedge's G, 1.23). No other clinicopathological differences were evident.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum SDMA concentration is increased in dogs with PLE; the clinical relevance of this finding requires further investigation.

Metformin inhibits the histone methyltransferase CARM1 and attenuates H3 histone methylation during gluconeogenesis

Hyperglycemia is a hallmark of metabolic disorders, yet the precise mechanisms linking epigenetic regulation to glucose metabolism remain underexplored. Coactivator-associated arginine methyltransferase 1 (CARM1), a type I histone methyltransferase, promotes transcriptional activation through the methylation of histone H3 at arginine residues H3R17 and H3R26. Here, we identify a novel mechanism by which metformin, a widely prescribed antidiabetic drug, inhibits CARM1 activity. Using biochemical and biophysical assays, we show that metformin binds to the substrate-binding site of CARM1, reducing histone H3 methylation levels in CARM1-overexpressing hepatic cells and liver tissues from metformin-fed mice. This epigenetic modulation suppresses the expression of gluconeogenic enzymes (G6Pase, FBPase, and PCK1), thereby reversing CARM1-induced glycolytic suppression and regulating gluconeogenesis. Importantly, metformin does not alter CARM1 protein levels and its recruitment to gluconeogenic gene promoters but diminishes H3R17me2a marks at these loci. Our findings reveal a previously unrecognized epigenetic mechanism of metformin action, offering new therapeutic insights for hyperglycemia management.

PRMT5 Maintains Homeostasis of the Intestinal Epithelium by Modulating Cell Proliferation and Survival

Intestinal homeostasis is sustained by self-renewal of intestinal stem cells, which continuously divide and produce proliferative transit-amplifying (TA) and progenitor cells. Protein arginine methyltransferases 5 (PRMT5) plays a crucial role in regulating homeostasis of various mammalian tissues. However, its function in intestinal homeostasis remains elusive. In this study, conditional knockout of Prmt5 in the mouse intestinal epithelium leads to a reduction in stem cell population, suppression of cell proliferation, and increased cell apoptosis within the intestinal crypts, accompanied with shortened gut length, decreased mouse body weight, and eventual animal mortality. Additionally, Prmt5 deletion or its enzymatic inhibition in intestinal organoids in vitro also shows resembling cellular phenotypes. Methylome profiling identifies 90 potential Prmt5 substrates, which are involved in RNA-related biological processes and cell division. Consistently, Prmt5 depletion in intestinal organoids leads to aberrant alternative splicing in a subset of genes related to the mitotic cell cycle. Furthermore, Prmt5 loss triggers p53-mediated apoptosis in the intestinal epithelium. Collectively, the findings uncover an indispensable role of PRMT5 in promoting cell proliferation and survival, as well as maintaining stem cells in the gut epithelium.

Mina53 catalyzes arginine demethylation of p53 to promote tumor growth

Arginine methylation is a common post-translational modification that plays critical roles in many biological processes. However, the existence of arginine demethylases that remove the modification has not been fully established. Here, we report that Myc-induced nuclear antigen 53 (Mina53), a member of the jumonji C (JmjC) protein family, is an arginine demethylase. Mina53 catalyzes the removal of asymmetric dimethylation at arginine 337 of p53. Mina53-mediated demethylation reduces p53 stability and oligomerization and alters chromatin modifications at the gene promoter, thereby suppressing p53-mediated transcriptional activation and cell-cycle arrest. Mina53 represses p53-dependent tumor suppression both in mouse xenografts and spontaneous tumor models. Moreover, downregulation of p53-mediated gene expression is observed in several types of cancer with elevated expression of Mina53. Thus, our study reveals a regulatory mechanism of p53 homeostasis and activity and, more broadly, defines a paradigm for dynamic arginine methylation in controlling important biological functions.

PRMT1 Promotes the Self-renewal of Leukemia Stem Cells by Regulating Protein Synthesis

The application of tyrosine kinase inhibitors (TKIs) has revolutionized the management of chronic myeloid leukemia (CML). However, disease relapse and progression particularly due to persistent leukemia stem cells (LSCs) remain a big challenge in the clinic. Therefore, validation of the therapeutic vulnerability in LSCs is urgently needed. This study verifies the critical role of protein arginine methyltransferase 1 (PRMT1) in the maintenance of CML LSCs. It is found that PRMT1 promotes the survival and serially plating abilities of human primary CML LSCs. Genetic deletion of Prmt1 significantly delays the leukemogenesis and impairs the self-renewal of LSCs in BCR-ABL-driven CML mice. PRMT1 regulates LSCs and leukemia development depending on its methyltransferase activity. Pharmacological inhibition of PRMT1 activity by MS023 remarkably eliminates LSCs and prolongs the survival of CML mice. Mechanistical studies reveal that PRMT1 promotes transcriptional activation of ribosomal protein L29 (RPL29) via catalyzing asymmetric dimethylation of histone H4R3 (H4R3me2a) at its gene promoter region. PRMT1 augments the global protein synthesis via RPL29 in CML LSCs. Taken together, the findings provide new evidence that histone arginine methylation modification regulates protein synthesis in LSCs and highlight PRMT1 as a valuable druggable target for patients with CML.

Protein arginine methyltransferases as regulators of cellular stress

Arginine modification can be a "switch" to regulate DNA transcription and a post-translational modification via methylation of a variety of cellular targets involved in signal transduction, gene transcription, DNA repair, and mRNA alterations. This consequently can turn downstream biological effectors "on" and "off". Arginine methylation is catalyzed by protein arginine methyltransferases (PRMTs 1-9) in both the nucleus and cytoplasm, and is thought to be involved in many disease processes. However, PRMTs have not been well-documented in the brain and their function as it relates to metabolism, circulation, functional learning and memory are understudied. In this review, we provide a comprehensive overview of PRMTs relevant to cellular stress, and future directions into PRMTs as therapeutic regulators in brain pathologies.

Protein Arginine Methyltransferase 1: A Multi-Purpose Player in the Development of Cancer and Metabolic Disease

Protein arginine methyltransferase 1 (PRMT1) is the main PRMT family member involved in the formation of monomethylarginine and asymmetric dimethylarginine on its protein substrates. Many protein substrates of PRMT1 are key mediators of cell proliferation and oncogenesis. As such, the function of PRMT1 has been most prominently investigated in the context of cancer development. However, recent in vitro and in vivo studies have highlighted that PRMT1 may also promote metabolic disorders. With the current review, we aim to present an in-depth overview of how PRMT1 influences epigenetic modulation, transcriptional regulation, DNA damage repair, and signal transduction in cancer. Furthermore, we summarize the current knowledge regarding the role of PRMT1 in metabolic reprogramming, lipid metabolism, and glucose metabolism and describe the association of PRMT1 with numerous metabolic pathologies such as obesity, liver disease, and type 2 diabetes. It has become apparent that inhibiting the function of PRMT1 will likely serve as the most beneficial therapeutic approach, since several PRMT1 inhibitors have already been shown to exert positive effects on both cancer and metabolic disease in preclinical settings. However, pharmacological PRMT1 inhibition has not yet been shown to be therapeutically effective in clinical studies.

Discovery of Potent, Highly Selective, and Orally Bioavailable MTA Cooperative PRMT5 Inhibitors with Robust In Vivo Antitumor Activity

Protein arginine methyltransferase 5 (PRMT5), which catalyzes the symmetric dimethylation of arginine residues on target proteins, plays a critical role in gene expression regulation, RNA processing, and signal transduction. Aberrant PRMT5 activity has been implicated in cancers and other diseases, making it a potential therapeutic target. Here, we report the discovery of a methylthioadenosine (MTA) cooperative PRMT5 inhibitor. Compound 20 exhibited strong antiproliferation activity in multiple MTAP-deleted cancer cell lines, excellent selectivity over MTAP wild-type cell lines, as well as satisfactory oral pharmacokinetic properties over various preclinical species. Notably, compound 20 demonstrated a dose-dependent reduction of symmetric dimethylarginine (SDMA) expression in the LU99 cell line and robust in vivo antitumor activity in the LU99 subcutaneous model.

Discovery of novel PRMT1 inhibitors: a combined approach using AI classification model and traditional virtual screening

Protein arginine methyltransferases (PRMTs) play crucial roles in gene regulation, signal transduction, mRNA splicing, DNA repair, cell differentiation, and embryonic development. Due to its significant impact, PRMTs is a target for the prevention and treatment of various diseases. Among the PRMT family, PRMT1 is the most abundant and ubiquitously expressed in the human body. Although extensive research has been conducted on PRMT1, the reported inhibitors have not successfully passed clinical trials. In this study, deep learning was employed to analyze the characteristics of existing PRMTs inhibitors and to construct a classification model for PRMT1 inhibitors. Through a classification model and molecular docking, a series of potential PRMT1 inhibitors were identified. The representative compound (compound 156) demonstrates stable binding to the PRMT1 protein by molecular hybridization, molecular dynamics simulations, and binding free energy analyses. The study discovered novel scaffolds for potential PRMT1 inhibitors.

Arginine demethylation of Serine/Arginine-rich splicing factor 1 enhances miRNA enrichment in small extracellular vesicles derived from pancreatic ductal adenocarcinoma cells

Small extracellular vesicles (sEVs) are enriched in certain miRNAs, impacting the progression of pancreatic ductal adenocarcinoma (PDAC). The mechanisms involved in the selective sEV miRNA enrichment remain to be elucidated. We recently reported that Serine/Arginine-rich splicing factor 1 (SRSF1) regulates selective sEV miRNA enrichment in PDAC cells. SRSF1 is an onco-protein that is overexpressed in PDAC, and its function is dictated by posttranslational modifications such as phosphorylation and arginine methylation. The objective of this study was to examine the role of phosphorylation and arginine methylation in SRSF1-mediated sEV miRNA enrichment in PDAC cells. Treatment of PDAC cells with the protein arginine methyltransferase inhibitors AMI-5 and EPZ015666, but not with the phosphorylation inhibitor SRPIN340, selectively enhanced the level of sEV miR-1246, a miRNA known to be highly enriched in PDAC sEVs. Consistently, overexpression of the mutant SRSF1 with the three arginine residues R93, R97, and R109 being replaced with lysinaugmented sEV miR-1246 levels in both wild-type and SRSF1-knockdown PANC-1 cells. Interestingly, the binding of SRSF1 to miR-1246 was significantly reduced in PDAC cells overexpressing the mutant SRSF1, which was further confirmed using purified wild-type and the mutant SRSF1 proteins. We demonstrate that arginine demethylation of SRSF1 reduces SRSF1-miRNA binding in PDAC cells and enhances selective sEV miRNA enrichment, providing novel insight into SRSF1-mediated sEV miRNA enrichment in PDAC cells and opening up new avenues of investigation on the biology and function of extracellular vesicles in PDAC.

PRMT1-mediated BRD4 arginine methylation and phosphorylation promote partial epithelial-mesenchymal transformation and renal fibrosis

Bromodomain-containing protein 4 (BRD4) plays a vital role in fibrosis of various organs. However, the underlying mechanism of BRD4 in renal fibrosis remains unclear. To construct in vitro and in vivo models of renal fibrosis, TCMK-1 cells were subjected to TGF-β1 treatment and mice were subjected to UUO surgery and adenine induction. IP assay was used for arginine asymmetric dimethylation (ADMA) level, ubiquitination degradation of Snail, and acetylation level of Snail test. Co-IP was used to validate the interactions of BRD4, protein arginine methyltransferase-1 (PRMT1), and Snail. HE staining and Masson staining were used for morphological examination of renal tissue. BRD4 was abnormally overexpressed during renal fibrosis. TGF-β1-induced fibrosis and partial epithelial-mesenchymal transition (pEMT) could be inhibited by BRD4 silencing. PRMT1 mediated ADMA level of BRD4 to enhance BRD4 phosphorylation and its protein stability. Snail protein degradation was attenuated by BRD4 overexpression in an acetylation-dependent manner in TCMK-1 cells. Furthermore, PRMT1 inhibitor abolished BRD4 overexpression-induced fibrosis and pEMT in TGF-β1-treated TCMK-1 cells and Snail overexpression reversed BRD4 silencing-induced inhibition of fibrosis and pEMT. What's more, the reduction of BRD4 arginine methylation inhibited BRD4 phosphorylation and Snail expression to alleviate renal fibrosis in UUO surgery and adenine induction mice. Collectively, PRMT1-mediated BRD4 arginine methylation and phosphorylation promoted pEMT and renal fibrosis through regulation of Snail expression.

Design, Synthesis, and Biological Evaluation of 3,4-Dihydroisoquinolin-1(2H)-one Derivatives as Protein Arginine Methyltransferase 5 Inhibitors for the Treatment of Non-Hodgkin's Lymphoma

Through catalyzing the transfer of methyl groups onto the guanidinium of arginine, protein arginine methyltransferase 5 (PRMT5) was essential to the cell growth of cancer cells. By utilizing a scaffold hopping strategy, a novel series of 3,4-dihydroisoquinolin-1(2H)-one derivatives were designed and synthesized. Through a systematic SAR study, D3 demonstrated excellent PRMT5 inhibitory activity, potent antiproliferative activity against Z-138, favorable pharmacokinetic profiles, and low hERG toxicity. Molecular docking, molecular dynamic (MD) simulation, and surface plasmon resonance (SPR) study indicated that D3 was tightly interacted with PRMT5. Meanwhile, D3 exhibited high selectivity against PRMT5, which could inhibit the growth of various cancer cells, induce apoptosis, and arrest the cell cycle in the G0/G1 phase. Additionally, D3 possessed excellent antitumor efficacy in Z-138 xenograft models, low toxicity in vivo, and acceptable drug metabolism and pharmacokinetics (DMPK) profiles in vitro. Therefore, D3 can be developed as a promising candidate for the treatment of non-Hodgkin's lymphoma (NHL).

PRMT5-Mediated ALKBH5 Methylation Promotes Colorectal Cancer Immune Evasion via Increasing CD276 Expression

Numerous diseases have been connected to protein arginine methylations mediated by protein arginine methyltransferase 5 (PRMT5). Clinical investigations of the PRMT5-specific inhibitor GSK3326595 are currently being conducted, and the results are promising for preventing cancers. However, the detailed mechanism of PRMT5 promoting colorectal cancer (CRC) malignant progression remains unclear. Here, we found that PRMT5 directly catalyzes AlkB homologue 5 (ALKBH5) symmetric dimethylation at the R316 residue (meR316-ALKBH5), which enhances TRIM28-mediated ALKBH5 ubiquitination degradation. Then, an ALKBH5 decrease attenuates ALKBH5-mediated m6A demethylation on the CD276 transcript 3' untranslated region, which increases CD276 messenger RNA stability and its expression in CRC cells. Furthermore, a CD276 expression increase facilitates CRC immune evasion by inhibiting cytotoxic T-cell functions. Moreover, we revealed that PRMT5-mediated meR316-ALKBH5 activates CD276 transcription by increasing its messenger RNA m6A modification to increase CRC immune evasion in vitro and in vivo. Furthermore, we consistently showed a strong association between meR316-ALKBH5 and poor outcomes in patients with CRC. Finally, we demonstrated that combining an anti-PD1 antibody with the PRMT5 inhibitor GSK3326595 markedly halts the progression of CRC. Our findings could serve as a basis for the development of a PRMT5-meR316-ALKBH5-CD276 axis-targeting treatment approach for CRC.

One stone two birds: Introducing piperazine into a series of nucleoside derivatives as potent and selective PRMT5 inhibitors

The protein arginine methyltransferase 5 (PRMT5) has emerged as potential target for the treatment of cancer. Many efforts have been made to develop potent and selective PRMT5 inhibitors targeting either S-adenosyl methionine (SAM) pocket or substrate binding pocket. Here, we rationally designed a series of nucleoside derivatives incorporated with piperazine as novel PRMT5 inhibitors occupying both pockets. The representative compound 36 exhibited highly potent PRMT5 inhibition activity as well as good selectivity over other methyltransferases. Further cellular experiments revealed that compound 36 potently reduced the level of symmetric dimethylarginines (sDMA) and inhibited the proliferation of MOLM-13 cell lines by inducing apoptosis and cell cycle arrest. Moreover, compound 36 had more favorable metabolic stability and aqueous solubility than JNJ64619178 (9). Meanwhile, it obviously suppressed the tumor growth in a MOLM-13 tumor xenograft model. These results clearly indicate that 36 is a highly potent and selective PRMT5 inhibitor worthy for further development.

Emergent properties of the lysine methylome reveal regulatory roles via protein interactions and histone mimicry

AIMS

Epigenomics has significantly advanced through the incorporation of Systems Biology approaches. This study aims to investigate the human lysine methylome as a system, using a data-science approach to reveal its emergent properties, particularly focusing on histone mimicry and the broader implications of lysine methylation across the proteome.

METHODS

We employed a data-science-driven OMICS approach, leveraging high-dimensional proteomic data to study the lysine methylome. The analysis focused on identifying sequence-based recognition motifs of lysine methyltransferases and evaluating the prevalence and distribution of lysine methylation across the human proteome.

RESULTS

Our analysis revealed that lysine methylation impacts 15% of the known proteome, with a notable bias toward mono-methylation. We identified sequence-based recognition motifs of 13 lysine methyltransferases, highlighting candidates for histone mimicry. These findings suggest that the selective inhibition of individual lysine methyltransferases could have systemic effects rather than merely targeting histone methylation.

CONCLUSIONS

The lysine methylome has significant mechanistic value and should be considered in the design and testing of therapeutic strategies, particularly in precision oncology. The study underscores the importance of considering non-histone proteins involved in DNA damage and repair, cell signaling, metabolism, and cell cycle pathways when targeting lysine methyltransferases.

A new pathway for ferroptosis regulation: The PRMTs

Protein arginine methyltransferases (PRMTs) play an essential role in the regulation of ferroptosis, a form of programmed cell death characterized by abnormal iron ion metabolism, lipid peroxidation, and DNA damage. Through methylation, PRMTs modify specific proteins, thereby altering their activity, localizations, or interactions with other molecules to control the ferroptosis process. This study was conducted to provide a comprehensive overview of the relationship between PRMTs and ferroptosis, with a focus on the mechanisms by which PRMTs regulate ferroptosis and their effect on this cell death pathway. Currently, only a few studies have been conducted on the regulation of ferroptosis by PRMTs. However, this review provides insights into the effects of PRMTs on ferroptosis regulators, suggesting that the regulation of ferroptosis by PRMTs holds potential as a new therapeutic target for related diseases.

Basic Epigenetic Mechanisms

The human genome consists of 23 chromosome pairs (22 autosomes and one pair of sex chromosomes), with 46 chromosomes in a normal cell. In the interphase nucleus, the 2 m long nuclear DNA is assembled with proteins forming chromatin. The typical mammalian cell nucleus has a diameter between 5 and 15 μm in which the DNA is packaged into an assortment of chromatin assemblies. The human brain has over 3000 cell types, including neurons, glial cells, oligodendrocytes, microglial, and many others. Epigenetic processes are involved in directing the organization and function of the genome of each one of the 3000 brain cell types. We refer to epigenetics as the study of changes in gene function that do not involve changes in DNA sequence. These epigenetic processes include histone modifications, DNA modifications, nuclear RNA, and transcription factors. In the interphase nucleus, the nuclear DNA is organized into different structures that are permissive or a hindrance to gene expression. In this chapter, we will review the epigenetic mechanisms that give rise to cell type-specific gene expression patterns.

The Association of Plasma Asymmetric Dimethylarginine Concentrations and Inflammation Markers in Non-small Cell Lung Cancer

Objectives

Nonsmall cell lung cancer (NSCLC) accounts for about 85% of all lung cancers. Asymmetric dimethylarginine (ADMA) is an emerging molecule that is highlighted in carcinogenesis and tumor progression in lung cancer. Since elevated concentrations of ADMA are observed in lung cancer patients, we aimed to explore its associations with inflammation markers and established prognostic indices.

Methods

78 newly diagnosed non-small cell lung cancer patients who were presented with brain metastases at the initial admission and 41 Stage 1 patients with NSCLC were included in the study. ADMA concentrations among the groups were correlated. Further, the relationship between ADMA levels and the other inflammatory markers was analyzed.

Results

ADMA levels were significantly higher in the group of NSCLC patients with brain metastases than in the Stage 1 patients control group (p<0.001). A significant negative correlation was found between ADMA levels and BMI, albumin and hemoglobin (p<0.001), whereas it was positively correlated with platelet, WBC, neutrophil-to-lymphocyte ratio, RDW, RDW/albumin ratio, LDH, CRP, fibrinogen, platelet, and CRP/albumin ratio (p<0.001).

Conclusion

Increased circulating concentrations of ADMA were significantly correlated with higher NLR, CRP and LDH; which were accepted as indicators of poor prognosis in NSCLC patients. ADMA might contribute to tumor growth and dissemination via systemic inflammatory pathways.

Key Regulators of Parasite Biology Viewed Through a Post-Translational Modification Repertoire

Parasites are the leading causes of morbidity and mortality in both humans and animals, imposing substantial socioeconomic burdens worldwide. Controlling parasitic diseases has become one of the key issues in achieving "One Health". Most parasites have sophisticated life cycles exhibiting progressive developmental stages, morphologies, and host-switching, which are controlled by various regulatory machineries including protein post-translational modifications (PTMs). PTMs have emerged as a key mechanism by which parasites modulate their virulence, developmental transitions, and environmental adaptations. PTMs are enzyme-mediated additions or removals of chemical groups that dynamically regulate the stability and functions of proteins and confer novel properties, playing vital roles in a variety of biological processes and cellular functions. In this review, we circumscribe how parasites utilize various PTMs to regulate their intricate lives, with a focus on the biological role of PTMs in parasite biology and pathogenesis.

Covalent inhibitors meet epigenetics: New opportunities

Epigenetic intervention has become an important therapeutic strategy for a variety of diseases, such as cancer. Although a small number of epigenetic drugs have been marketed, most of these inhibitors are limited by their poor efficacy, dose-dependent toxicity, poor selectivity, and drug resistance. The development of covalent inhibitors has progressed from questioning to resurgence. Its slow dissociation is expected to inject new vitality into epigenetic drugs. In this review, more than 40 covalent inhibitors of 29 epigenetic targets were collated, focusing on their design strategies, reaction mechanisms, covalent warheads and targeted amino acids, and covalent verification methods. Furthermore, this review presented new opportunities based on the current development of covalent inhibitors targeting epigenetic regulators. It is believed that epigenetic covalent inhibitors will lead to more breakthroughs.

Therapeutic targeting potential of the protein lysine and arginine methyltransferases to reverse cancer chemoresistance

Cancer treatments have continued to improve tremendously over the past decade, but therapy resistance is still a common, major factor encountered by patients diagnosed with cancer. Chemoresistance arises due to various circumstances and among these causes, increasing evidence has shown that enzymes referred to as protein methyltransferases (PMTs) play a significant role in the development of chemoresistance in various cancers. These enzymes are responsible for the methylation of different amino acids, particularly lysine and arginine, via protein lysine methyltransferases (PKMTs) and protein arginine methyltransferases (PRMTs), respectively. Various PMTs have been identified to be dysregulated in the development of cancer and chemoresistance. Nonetheless, the functional role of these PMTs in the development of chemoresistance is poorly characterised. This advocates the need for innovative approaches and technologies suitable for better characterisation of these PMTs and their potential clinical inhibitors. In the case of a handful of PMTs, inhibitory small molecules which can function as anticancer drugs have been developed and have also entered clinical trials. Considering all this, PMTs have become a promising and valuable target in cancer chemoresistance related research. This review will give a small introduction on the different PKMTs and PRMTs families which are dysregulated in different cancers and the known proteins targeted by the respective enzymes. The focus will then shift towards PMTs known to be involved in chemoresistance development and the inhibitors developed against these, together with their mode of action. Lastly, the current obstacles and future perspectives of PMT inhibitors in cancer chemoresistance will be discussed.

Metabolites and metabolism in vascular calcification: links between adenosine signaling and the methionine cycle

The global population of individuals with cardiovascular disease is expanding, and a key risk factor for major adverse cardiovascular events is vascular calcification. The pathogenesis of cardiovascular calcification is complex and multifaceted, with external cues driving epigenetic, transcriptional, and metabolic changes that promote vascular calcification. This review provides an overview of some of the lesser understood molecular processes involved in vascular calcification and discusses the links between calcification pathogenesis and aspects of adenosine signaling and the methionine pathway; the latter of which salvages the essential amino acid methionine, but also provides the substrate critical for methylation, a modification that regulates the function and activity of DNA and proteins. We explore the complex and dynamic nature of osteogenic reprogramming underlying intimal atherosclerotic calcification and medial arterial calcification (MAC). Atherosclerotic calcification is more widely studied; however, emerging studies now show that MAC is a significant pathology independent from atherosclerosis. Furthermore, we emphasize metabolite and metabolic-modulating factors that influence vascular calcification pathogenesis. Although the contributions of these mechanisms are more well-define in relation to atherosclerotic intimal calcification, understanding these pathways may provide crucial mechanistic insights into MAC and inform future therapeutic approaches. Herein, we highlight the significance of adenosine and methyltransferase pathways as key regulators of vascular calcification pathogenesis.

Tumor suppressors RBL1 and PTEN are epigenetically silenced in IPF mesenchymal progenitor cells by a CD44/Brg1/PRMT5 regulatory complex

The idiopathic pulmonary fibrosis (IPF) lung contains mesenchymal progenitor cells (MPCs) that display durable activation of oncogenic signaling and cell-autonomous fibrogenicity in vivo. Prior work identified a CD44/Brg1/PRMT5 nuclear regulatory module in IPF MPCs that increased the expression of genes positively regulating pluripotency and self-renewal. Left unanswered is how IPF MPCs evade negative regulation of self-renewal. Here we sought to identify mechanisms disabling negative regulation of self-renewal in IPF MPCs. We demonstrate that expression of the tumor suppressor genes rbl1 and pten is decreased in IPF MPCs. The mechanism involves the CD44-facilitated association of the chromatin remodeler Brg1 with the histone-modifying methyltransferase PRMT5. Brg1 enhances chromatin accessibility leading to PRMT5-mediated methylation of H3R8 and H4R3 on the rbl1 and pten genes, repressing their expression. Genetic knockdown or pharmacological inhibition of either Brg1 or PRMT5 restored RBL1 and PTEN expression reduced IPF MPC self-renewal in vitro and inhibited IPF MPC-mediated pulmonary fibrosis in vivo. Our studies indicate that the CD44/Brg1/PRMT5 regulatory module not only functions to activate positive regulators of pluripotency and self-renewal but also functions to repress tumor suppressor genes rbl1 and pten. This confers IPF MPCs with the cancer-like property of cell-autonomous self-renewal providing a molecular mechanism for relentless fibrosis progression in IPF.NEW & NOTEWORTHY Here we demonstrate that a CD44/Brg1/PRMT5 epigenetic regulatory module represses the tumor suppressor genes RBL1 and PTEN in IPF mesenchymal progenitor cells, thereby promoting their self-renewal and maintenance of a critical pool of fibrogenic mesenchymal progenitor cells.

Mina53 demethylates histone H4 arginine 3 asymmetric dimethylation to regulate neural stem/progenitor cell identity

Arginine methylation of histones plays a critical role in regulating gene expression. The writers (methyltransferases) and readers of methylarginine marks are well-known, but the erasers-arginine demethylases-remain mysterious. Here we identify Myc-induced nuclear antigen 53 (Mina53), a jumonji C domain containing protein, as an arginine demethylase for removing asymmetric di-methylation at arginine 3 of histone H4 (H4R3me2a). Using a photoaffinity capture method, we first identify Mina53 as an interactor of H4R3me2a. Biochemical assays in vitro and in cells characterize the arginine demethylation activity of Mina53. Molecular dynamics simulations provide further atomic-level evidence that Mina53 acts on H4R3me2a. In a transgenic mouse model, specific Mina53 deletion in neural stem/progenitor cells prevents H4R3me2a demethylation at distinct genes clusters, dysregulating genes important for neural stem/progenitor cell proliferation and differentiation, and consequently impairing the cognitive function of mice. Collectively, we identify Mina53 as a bona fide H4R3me2a eraser, expanding the understanding of epigenetic gene regulation.

Ferroptosis in Cancer: Epigenetic Control and Therapeutic Opportunities

Ferroptosis, an iron-dependent form of regulated cell death driven by lipid peroxidation, has emerged as a critical pathway in cancer biology. This review delves into the epigenetic mechanisms that modulate ferroptosis in cancer cells, focusing on how DNA methylation, histone modifications, and non-coding RNAs influence the expression and function of essential genes involved in this process. By unraveling the complex interplay between these epigenetic mechanisms and ferroptosis, the article sheds light on novel gene targets and functional insights that could pave the way for innovative cancer treatments to enhance therapeutic efficacy and overcome resistance in cancer therapy.

Oligomerization of protein arginine methyltransferase 1 and its functional impact on substrate arginine methylation

Protein arginine methyltransferases (PRMTs) are important posttranslational modifying enzymes in eukaryotic proteins and regulate diverse pathways from gene transcription, RNA splicing, and signal transduction to metabolism. Increasing evidence supports that PRMTs exhibit the capacity to form higher-order oligomeric structures, but the structural basis of PRMT oligomerization and its functional consequence are elusive. Herein, we revealed for the first time different oligomeric structural forms of the predominant arginine methyltransferase PRMT1 using cryo-EM, which included tetramer (dimer of dimers), hexamer (trimer of dimers), octamer (tetramer of dimers), decamer (pentamer of dimers), and also helical filaments. Through a host of biochemical assays, we showed that PRMT1 methyltransferase activity was substantially enhanced as a result of the high-ordered oligomerization. High-ordered oligomerization increased the catalytic turnover and the multimethylation processivity of PRMT1. Presence of a catalytically dead PRMT1 mutant also enhanced the activity of WT PRMT1, pointing out a noncatalytic role of oligomerization. Structural modeling demonstrates that oligomerization enhances substrate retention at the PRMT1 surface through electrostatic force. Our studies offered key insights into PRMT1 oligomerization and established that oligomerization constitutes a novel molecular mechanism that positively regulates the enzymatic activity of PRMTs in biology.

Pancreatic ductal adenocarcinoma cells reshape the immune microenvironment: Molecular mechanisms and therapeutic targets

Pancreatic ductal adenocarcinoma (PDAC) is a digestive system malignancy characterized by challenging early detection, limited treatment alternatives, and generally poor prognosis. Although there have been significant advancements in immunotherapy for hematological malignancies and various solid tumors in recent decades, with impressive outcomes in recent preclinical and clinical trials, the effectiveness of these therapies in treating PDAC continues to be modest. The unique immunological microenvironment of PDAC, especially the abnormal distribution, complex composition, and variable activation states of tumor-infiltrating immune cells, greatly restricts the effectiveness of immunotherapy. Undoubtedly, integrating data from both preclinical models and human studies helps accelerate the identification of reliable molecules and pathways responsive to targeted biological therapies and immunotherapies, thereby continuously optimizing therapeutic combinations. In this review, we delve deeply into how PDAC cells regulate the immune microenvironment through complex signaling networks, affecting the quantity and functional status of immune cells to promote immune escape and tumor progression. Furthermore, we explore the multi-modal immunotherapeutic strategies currently under development, emphasizing the transformation of the immunosuppressive environment into an anti-tumor milieu by targeting specific molecular and cellular pathways, providing insights for the development of novel treatment strategies.

The PRMT6/STAT1/ACSL1 axis promotes ferroptosis in diabetic nephropathy

Hyperglycaemia-induced ferroptosis is a significant contributor to kidney dysfunction in diabetic nephropathy (DN) patients. In addition, targeting ferroptosis has clinical implications for the treatment of DN. However, effective therapeutic targets for ferroptosis have not been identified. In this study, we aimed to explore the precise role of protein arginine methyltransferase 6 (PRMT6) in regulating ferroptosis in DN. In the present study, we utilized a mouse DN model consisting of both wild-type and PRMT6-knockout (PRMT6-/-) mice. Transcriptomic and lipidomic analyses, along with various molecular biological methodologies, were used to determine the potential mechanism by which PRMT6 regulates ferroptosis in DN. Our results indicate that PRMT6 downregulation participates in kidney dysfunction and renal cell death via the modulation of ferroptosis in DN. Moreover, PRMT6 reduction induced lipid peroxidation by upregulating acyl-CoA synthetase long-chain family member 1 (ACSL1) expression, ultimately contributing to ferroptosis. Furthermore, we investigated the molecular mechanism by which PRMT6 interacts with signal transducer and activator of transcription 1 (STAT1) to jointly regulate ACSL1 transcription. Additionally, treatment with the STAT1-specific inhibitor fludarabine delayed DN progression. Furthermore, we observed that PRMT6 and STAT1 synergistically regulate ACSL1 transcription to mediate ferroptosis in hyperglycaemic cells. Our study demonstrated that PRMT6 and STAT1 comodulate ACSL1 transcription to induce the production of phospholipid-polyunsaturated fatty acids (PL-PUFAs), thus participating in ferroptosis in DN. These findings suggest that the PRMT6/STAT1/ACSL1 axis is a new therapeutic target for the prevention and treatment of DN.

Deciphering adipose development: Function, differentiation and regulation

The overdevelopment of adipose tissues, accompanied by excess lipid accumulation and energy storage, leads to adipose deposition and obesity. With the increasing incidence of obesity in recent years, obesity is becoming a major risk factor for human health, causing various relevant diseases (including hypertension, diabetes, osteoarthritis and cancers). Therefore, it is of significance to antagonize obesity to reduce the risk of obesity-related diseases. Excess lipid accumulation in adipose tissues is mediated by adipocyte hypertrophy (expansion of pre-existing adipocytes) or hyperplasia (increase of newly-formed adipocytes). It is necessary to prevent excessive accumulation of adipose tissues by controlling adipose development. Adipogenesis is exquisitely regulated by many factors in vivo and in vitro, including hormones, cytokines, gender and dietary components. The present review has concluded a comprehensive understanding of adipose development including its origin, classification, distribution, function, differentiation and molecular mechanisms underlying adipogenesis, which may provide potential therapeutic strategies for harnessing obesity without impairing adipose tissue function.

Hetero-oligomeric interaction as a new regulatory mechanism for protein arginine methyltransferases

Protein arginine methylation is a versatile post-translational protein modification that has notable cellular roles such as transcriptional activation or repression, cell signaling, cell cycle regulation, and DNA damage response. However, in spite of their extensive significance in the biological system, there is still a significant gap in understanding of the entire function of the protein arginine methyltransferases (PRMTs). It has been well-established that PRMTs form homo-oligomeric complexes to be catalytically active, but in recent years, several studies have showcased evidence that different members of PRMTs can have cross-talk with one another to form hetero-oligomeric complexes. Additionally, these heteromeric complexes have distinct roles separate from their homomeric counterparts. Here, we review and highlight the discovery of the heterodimerization of PRMTs and discuss the biological implications of these hetero-oligomeric interactions.

An Adenosine Analogue Library Reveals Insights into Active Sites of Protein Arginine Methyltransferases and Enables the Discovery of a Selective PRMT4 Inhibitor

Protein arginine methyltransferases (PRMTs) represent promising drug targets. However, the lack of isoform-selective chemical probes poses a significant hurdle in deciphering their biological roles. To address this issue, we devised a library of 100 diverse adenosine analogues, enabling a detailed exploration of the active site of PRMTs. Despite their close homology, our analysis unveiled specific chemical trends unique to the individual members. Notably, compound YD1130 demonstrated over 1000-fold selectivity for PRMT4 (IC50 < 0.5 nM) over a panel of 38 methyltransferases, including the other PRMTs. Its prodrug YD1342 exhibited potent inhibition on cellular substrate methylation, breast cancer cell colony formation, and tumor growth in the animal model, surpassing or matching known PRMT4-specific inhibitors. In summary, our focused library not only illuminates the intricate active sites of PRMTs to facilitate the discovery of highly potent and isoform-selective probes but also offers a versatile blueprint for identifying chemical probes for other methyltransferases.

Deciphering the potential role of post-translational modifications of histones in gastrointestinal cancers: a proteomics-based review with therapeutic challenges and opportunities

Oncogenesis is a complex and multi-step process, controlled by several factors including epigenetic modifications. It is considered that histone modifications are critical components in the regulation of gene expression, protein functions, and molecular interactions. Dysregulated post-translationally modified histones and the related enzymatic systems are key players in the control of cell proliferation and differentiation, which are associated with the onset and progression of cancers. The most of traditional investigations on cancer have focused on mutations of oncogenes and tumor suppressor genes. However, increasing evidence indicates that epigenetics, especially histone post-translational modifications (PTMs) play important roles in various cancer types. Mass spectrometry-based proteomic approaches have demonstrated tremendous potential in PTMs profiling and quantitation in different biological systems. In this paper, we have made a proteomics-based review on the role of histone modifications involved in gastrointestinal cancers (GCs) tumorigenesis processes. These alterations function not only as diagnostic or prognostic biomarkers for GCs, but a deeper comprehension of the epigenetic regulation of GCs could facilitate the treatment of this prevalent malignancy through the creation of more effective targeted therapies.

Methylarginine targeting chimeras for lysosomal degradation of intracellular proteins

A paradigm shift in drug development is the discovery of small molecules that harness the ubiquitin-proteasomal pathway to eliminate pathogenic proteins. Here we provide a modality for targeted protein degradation in lysosomes. We exploit an endogenous lysosomal pathway whereby protein arginine methyltransferases (PRMTs) initiate substrate degradation via arginine methylation. We developed a heterobifunctional small molecule, methylarginine targeting chimera (MrTAC), that recruits PRMT1 to a target protein for induced degradation in lysosomes. MrTAC compounds degraded substrates across cell lines, timescales and doses. MrTAC degradation required target protein methylation for subsequent lysosomal delivery via microautophagy. A library of MrTAC molecules exemplified the generality of MrTAC to degrade known targets and neo-substrates-glycogen synthase kinase 3β, MYC, bromodomain-containing protein 4 and histone deacetylase 6. MrTAC selectively degraded target proteins and drove biological loss-of-function phenotypes in survival, transcription and proliferation. Collectively, MrTAC demonstrates the utility of endogenous lysosomal proteolysis in the generation of a new class of small molecule degraders.