Significant association of PRMT6 hypomethylation with colorectal cancer

Hypermethylation of BMPR2 and TGF-β Promoter Regions in Tibetan Patients with High-Altitude Polycythemia at Extreme Altitude

Although the expression of many genes is associated with adaptation to high-altitude hypoxic environments, the role of epigenetics in the response to this harsh environmental stress is currently unclear. We explored whether abnormal DNA promoter methylation levels of six genes, namely, ABCA1, SOD2, AKT1, VEGFR2, TGF-β, and BMPR2, affect the occurrence and development of high-altitude polycythemia (HAPC) in Tibetans. The methylation levels of HAPC and the control group of 130 Tibetans from very high altitudes (> 4500 m) were examined using quantitative methylation-specific real-time PCR (QMSP). Depending on the type of data, the Pearson chi-square test, Wilcoxon rank-sum test, and Fisher exact test were used to assess the differences between the two groups. The correlation between the methylation levels of each gene and the hemoglobin content was explored using a linear mixed model. Our experiment revealed that the methylation levels of the TGF-β and BMPR2 genes differed significantly in the two groups (p < 0.05) and linear mixed model analysis showed that the correlation between the hemoglobin and methylation of ABCA1, TGF-β, and BMPR2 was statistically significant (p < 0.05). Our study suggests that levels of TGF-β and BMPR2 methylation are associated with the occurrence of HAPC in extreme-altitude Tibetan populations among 6 selected genes. Epigenetics may be involved in the pathogenesis of HAPC, and future experiments could combine gene and protein levels to verify the diagnostic value of TGF-β and BMPR2 methylation levels in HAPC.

Arginine methylation of ALKBH5 by PRMT6 promotes breast tumorigenesis via LDHA-mediated glycolysis

ALKBH5 is a master regulator of N6-methyladenosine (m6A) modification, which plays a crucial role in many biological processes. Here, we show that ALKBH5 is required for breast tumor growth. Interestingly, PRMT6 directly methylates ALKBH5 at R283, which subsequently promotes breast tumor growth. Furthermore, arginine methylation of ALKBH5 by PRMT6 increases LDHA RNA stability via m6A demethylation, leading to increased aerobic glycolysis. Moreover, PRMT6-mediated ALKBH5 arginine methylation is confirmed in PRMT6-knockout mice. Collectively, these findings identify a PRMT6-ALKBH5-LDHA signaling axis as a novel target for the treatment of breast cancer.

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.

Discovery of cysteine-targeting covalent histone methyltransferase inhibitors

Post-translational methylation of histone lysine or arginine residues by histone methyltransferases (HMTs) plays crucial roles in gene regulation and diverse physiological processes and is implicated in a plethora of human diseases, especially cancer. Therefore, histone methyltransferases have been increasingly recognized as potential therapeutic targets. Consequently, the discovery and development of histone methyltransferase inhibitors have been pursued with steadily increasing interest over the past decade. However, the disadvantages of limited clinical efficacy, moderate selectivity, and propensity for acquired resistance have hindered the development of HMTs inhibitors. Targeted covalent modification represents a proven strategy for kinase drug development and has gained increasing attention in HMTs drug discovery. In this review, we focus on the discovery, characterization, and biological applications of covalent inhibitors for HMTs with emphasis on advancements in the field. In addition, we identify the challenges and future directions in this fast-growing research area of drug discovery.

PRMT6 functionally associates with PRMT5 to promote colorectal cancer progression through epigenetically repressing the expression of CDKN2B and CCNG1

BACKGROUND

Protein arginine methyltransferase 6 (PRMT6) is a type I arginine methyltransferase that asymmetrically dimethylates histone H3 arginine 2 (H3R2me2a). However, the biological roles and underlying molecular mechanisms of PRMT6 in colorectal cancer (CRC) remain unclear.

METHODS

PRMT6 expression in CRC tissue was examined using immunohistochemistry. The effect of PRMT6 on CRC cells was investigated in vitro and in vivo. Mass spectrometry, co-immunoprecipitation and GST pulldown assays were performed to identify interaction partners of PRMT6. RNA-seq, chromatin immunoprecipitation, Western blot and qRT-PCR assays were used to investigate the mechanism of PRMT6 in gene regulation.

RESULTS

PRMT6 is significantly upregulated in CRC tissues and facilitates cell proliferation of CRC cells in vitro and in vivo. Through RNA-seq analysis, CDKN2B (p15^INK4b) and CCNG1 were identified as new transcriptional targets of PRMT6. PRMT6-dependent H3R2me2a mark was predominantly deposited at the promoters of CDKN2B and CCNG1 in CRC cells. Furthermore, PRMT5 was firstly characterized as an interaction partner of PRMT6. Notably, H3R2me2a coincides with PRMT5-mediated H4R3me2s and H3R8me2s marks at the promoters of CDKN2B and CCNG1 genes, thus leading to transcriptional repression of these genes.

CONCLUSIONS

PRMT6 functionally associates with PRMT5 to promote CRC progression through epigenetically repressing the expression of CDKN2B and CCNG1. These insights raise the possibility that combinational intervention of PRMT6 and PRMT5 may be a promising strategy for CRC therapy.

Structure, Activity and Function of the Protein Arginine Methyltransferase 6

Members of the protein arginine methyltransferase (PRMT) family methylate the arginine residue(s) of several proteins and regulate a broad spectrum of cellular functions. Protein arginine methyltransferase 6 (PRMT6) is a type I PRMT that asymmetrically dimethylates the arginine residues of numerous substrate proteins. PRMT6 introduces asymmetric dimethylation modification in the histone 3 at arginine 2 (H3R2me2a) and facilitates epigenetic regulation of global gene expression. In addition to histones, PRMT6 methylates a wide range of cellular proteins and regulates their functions. Here, we discuss (i) the biochemical aspects of enzyme kinetics, (ii) the structural features of PRMT6 and (iii) the diverse functional outcomes of PRMT6 mediated arginine methylation. Finally, we highlight how dysregulation of PRMT6 is implicated in various types of cancers and response to viral infections.

Discovery of a First-in-Class Protein Arginine Methyltransferase 6 (PRMT6) Covalent Inhibitor

Protein arginine methyltransferase 6 (PRMT6) plays important roles in several biological processes associated with multiple cancers. Well-characterized potent, selective, and cell-active PRMT6 inhibitors are invaluable tools for testing biological and therapeutic hypotheses. Although there are several known reversible PRMT6 inhibitors, covalent PRMT6 inhibitors have not been reported. Based on a cocrystal structure of PRMT6-MS023 (a type I PRMT inhibitor), we discovered the first potent and cell-active irreversible PRMT6 inhibitor, 4 (MS117). The covalent binding mode of compound 4 to PRMT6 was confirmed by mass spectrometry and kinetic studies and by a cocrystal structure. Compound 4 did not covalently modify other closely related PRMTs, potently inhibited PRMT6 in cells, and was selective for PRMT6 over other methyltransferases. We also developed two structurally similar control compounds, 5 (MS167) and 7 (MS168). We provide these valuable chemical tools to the scientific community for further studying PRMT6 physiological and pathophysiological functions.

Chemical probes for protein arginine methyltransferases

Protein arginine methyltransferases (PRMTs) catalyze the transfer of methyl groups to specific arginine residues of their substrates using S-adenosylmethionine as a methyl donor, contributing to regulation of many biological processes including transcription, and DNA damage repair. Dysregulation of PRMT expression is often associated with various diseases including cancers. Different methods have been used to characterize the activities of PRMTs and determine their kinetic parameters including mass spectrometry, radiometric, and antibody-based assays. Here, we present kinetic characterization of PRMTs using a radioactivity-based assay for better comparison along with previously reported values. We also report on full characterization of PRMT9 activity with SAP145 peptide as substrate. We further review the potent, selective and cell-active PRMT inhibitors discovered in recent years to provide a better understanding of available tools to investigate the roles these proteins play in health and disease.

Cellular consequences of arginine methylation

Arginine methylation is a ubiquitous post-translational modification. Three predominant types of arginine-guanidino methylation occur in Eukarya: mono (Rme1/MMA), symmetric (Rme2s/SDMA), and asymmetric (Rme2a/ADMA). Arginine methylation frequently occurs at sites of protein-protein and protein-nucleic acid interactions, providing specificity for binding partners and stabilization of important biological interactions in diverse cellular processes. Each methylarginine isoform-catalyzed by members of the protein arginine methyltransferase family, Type I (PRMT1-4,6,8) and Type II (PRMT5,9)-has unique downstream consequences. Methylarginines are found in ordered domains, domains of low complexity, and in intrinsically disordered regions of proteins-the latter two of which are intimately connected with biological liquid-liquid phase separation. This review highlights discoveries illuminating how arginine methylation affects genome integrity, gene transcription, mRNA splicing and mRNP biology, protein translation and stability, and phase separation. As more proteins and processes are found to be regulated by arginine methylation, its importance for understanding cellular physiology will continue to grow.

Serine hydroxymethyltransferase 1 promoter hypermethylation increases the risk of essential hypertension

BACKGROUND

Serine hydroxymethyltransferase 1 (SHMT1) is an enzyme involved in folic acid metabolism and is known to contribute to the development of hypertension. We evaluated the relationship between SHMT1 promoter methylation and essential hypertension (EH).

METHODS

Quantitative methylation-specific polymerase chain reaction was used to measure the SHMT1 promoter methylation level in 241 EH patients and 288 age- and gender-matched healthy individuals. The diagnostic value of SHMT1 promoter hypermethylation was analyzed using a receiver operating characteristic (ROC) curve. The Gene Expression Omnibus (GEO) database and dual-luciferase reporter assay were used to validate our findings.

RESULTS

Compared with the control group, significant differences in SHMT1 promoter methylation were found in both EH and hyperhomocysteinemia groups (P < 0.001 and P = 0.029, respectively). The area under the curve of the diagnosis of SHMT1 promoter hypermethylation for EH was 0.808, with a sensitivity and specificity of 73.9% and 77.8%, respectively. The risk of SHMT1 promoter hypermethylation was significantly higher in the >65-year group than in the ≤65-year group (odds ratio = 3.925; 95% confidence interval = 2.141-7.196). In addition, GEO database analysis showed that 5-aza-deoxycytidine increased gene expression in several carotid endothelial cell lines. A dual-luciferase reporter assay revealed that the target sequence in the SHMT1 promoter upregulated gene expression.

CONCLUSION

Our findings indicate that SHMT1 promoter hypermethylation increases the risk of EH and may be a promising biomarker for EH.

Significant association of PRMT6 hypomethylation with colorectal cancer

BACKGROUND

Protein arginine N-methyltransferase 6 (PRMT6) was deemed to be indispensable in the variety of biological processes. Upregulated PRMT6 was found in various human diseases including cancer. Herein, we investigated the performance of PRMT6 methylation in the diagnosis for CRC.

METHODS

A quantitative methylation-specific polymerase chain reaction (qMSP) method was used to measure PRMT6 promoter methylation. The percentage of methylated reference (PMR) was applied to represent gene methylation level.

RESULTS

Our data indicated that PRMT6 promoter methylation levels were significantly lower in CRC tissues than those in paired nontumor tissues (median PMR: 36.93% vs 63.12%, P = 1E-6) and normal intestinal tissues (median PMR: 36.93% vs 506.55%, P = 8E-12). We further examined the potential role of PRMT6 hypomethylation by the receiver operating characteristic (ROC) curve. Our results showed that the area under the curve (AUC) was 0.644 (95% CI = 0.596-0.733) between CRC tissues and paired nontumor tissues, 0.958 (95% CI = 0.919-0.998) between CRC tissues and normal intestinal tissues, and 0.899 (95% CI = 0.825-0.972) between paired nontumor tissues and normal intestinal tissues.

CONCLUSION

Our study firstly indicated that the hypomethylation of PRMT6 promoter could be a novel diagnostic biomarker for CRC.