Protein Arginine N-methyltransferase 1 Research Articles

PRMT1 Modulates Alternative Splicing to Enhance HPV18 mRNA Stability and Promote the Establishment of Infection.

Only persistent HPV infections lead to the development of cancer. Thus, understanding the virus-host interplay that influences the establishment of viral infection has important implications for HPV biology and human cancers. The ability of papillomaviruses to establish in cells requires the strict temporal regulation of viral gene expression in sync with cellular differentiation. This control primarily happens at the level of RNA splicing and polyadenylation. However, the details of how this spatio-temporal regulation is achieved still need to be fully understood. Until recently, it has been challenging to study the early events of the HPV lifecycle following infection. We used a single-cell genomics approach to identify cellular factors involved in viral infection and establishment. We identify protein arginine N-methyltransferase 1 (PRMT1) as an important factor in viral infection of primary human cervical cells. PRMT1 is the main cellular enzyme responsible for asymmetric dimethylation of cellular proteins. PRMT1 is an enzyme responsible for catalyzing the methylation of arginine residues on various proteins, which influences processes such as RNA processing, transcriptional regulation, and signal transduction. In this study, we show that HPV18 infection leads to increased PRMT1 levels across the viral lifecycle. PRMT1 is critical for the establishment of a persistent infection in primary cells. Mechanistically, PRMT1 inhibition leads to a highly dysregulated viral splicing pattern. Specifically, reduced PRMT1 activity leads to intron retention and a change in the E6 and E7 expression ratio. In the absence of PRMT1, viral transcripts are destabilized and subject to degradation via the nonsense-mediated decay (NMD) pathway. These findings highlight PRMT1 as a critical regulator of the HPV18 lifecycle, particularly in RNA processing, and position it as a potential therapeutic target for persistent HPV18 infections.

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.

Protein arginine N-methyltransferase 1 gene polymorphism is associated with proliferative diabetic retinopathy in a Japanese population.

To investigate the effects of single-nucleotide polymorphisms (SNPs) around the protein arginine N-methyltransferase 1 (PRMT1) gene on the incidence and severity of diabetic retinopathy (DR). A total of 310 Japanese patients with type 2 diabetes mellitus (T2DM) were investigated. Genotyping of ten tagged SNPs were performed by quantitative real-time polymerase chain reaction (qRT-PCR). The association between each SNP genotype and diabetic microangiopathy was assessed using univariate analysis in a dominant model of the minor alleles followed by multivariate logistic regression analysis with the propensity score matching (PSM) method. The effect of disease-related SNP on PRMT1 and hypoxia-inducible factor-1α (HIF-1α) mRNA levels in vivo was evaluated by qRT-PCR. In the univariate analysis, the minor A allele at rs374569 and the minor C allele at rs3745468 were associated with DR severity (P = 0.047 and P = 0.003, respectively), but not diabetic nephropathy and peripheral polyneuropathy severity. Multivariate analysis showed that the rs3745468 variant caused an increased incidence of proliferative DR (PDR) (odds ratio 9.37, 95% confidence interval 1.12-78.0, P = 0.039). In the PSM cohort, the patients carrying the rs3745468 variant had lower PRMT1 mRNA levels compared to those without the variant (P = 0.037), and there was an inverse correlation between PRMT1 and HIF-1α mRNA levels (r = -0.233, P = 0.035). The rs3745468 variant in the PRMT1 gene was associated with an increased incidence of PDR in Japanese patients with T2DM and might be involved in the HIF-1-dependent hypoxic pathway through altered PRMT1 levels.

Geranylgeranylacetone promotes human osteosarcoma cell apoptosis by inducing the degradation of PRMT1 through the E3 ubiquitin ligase CHIP.

Geranylgeranylacetone (GGA), an inducer of heat shock proteins, exerts anticancer activity in some tumours. However, the effect of GGA on human osteosarcoma (OS) has not been reported. This work is designed to evaluate the effect of GGA on the proliferation and apoptosis of human OS cells and to explore the underlying mechanisms. It was found that GGA markedly inhibited the proliferation and induced apoptosis of U‐2 OS cells in a dose‐dependent manner and also up‐regulated the expression of heat shock protein 70 (Hsp70). The degradation and ubiquitination of protein arginine N‐methyltransferase 1 (PRMT1) were obviously enhanced in U‐2 OS cells with CHIP overexpression and GGA treatment. The expression of PRMT1 was reversed in GGA‐treated cell after CHIP knockdown. The turnover of PRMT1 was obviously faster in cells overexpressing CHIP than that in control cells. The methylation and activity of STAT3 were induced by PRMT1, resulting in the inhibition of FAS transcription. Overexpression of PRMT1 reversed the effect of GGA on activation of apoptosis‐related proteins and U‐2 OS cell apoptosis. The expressions of PRMT1 were significantly up‐regulated in OS tissues compared with the adjacent normal tissues and benign bone tumours. In conclusion, GGA promotes the degradation of PRMT1 through the Hsp70‐CHIP‐mediated proteasome pathway, thereby inducing the FAS‐triggered cell apoptosis. Inhibition of PRMT1 may be a potential therapeutic strategy for OS patients.

Full-length transcriptome sequencing combined with RNA-seq analysis revealed the immune response of fat greenling (Hexagrammos otakii) to Vibrio harveyi in early infection

Fat greenling (Hexagrammos otakii) is an important commercial marine fish species cultured in northeast Asia, but its available gene sequences are limited. Vibrio harveyi is a causative agent of vibriosis in fat greenling and also causes severe losses to the aquaculture industry in China. In order to obtain more high-quality transcript information and investigate the early immune response of fat greenling against V. harveyi, the fish were artificially infected with V. harveyi, and five sampling points were set within 48 h. Iso-Seq combined with RNA-Seq were applied in the comprehensive transcriptome analysis of V. harveyi-infected fat greenling. Total 42,225 consensus isoforms were successfully extracted from the result of Iso-Seq, and more than 19,000 ORFs were predicted. In addition, total three modules were identified by WGCNA which significantly positive correlated to the infection time, and the KEGG analysis showed that the immune-related genes in these modules mainly enriched in TLR signaling pathway, NF-κB signaling pathway and Endocytosis. The activation of inflammation and endocytosis was the most significant characteristics of fat greenling immune response during the early infection. Based on the WGCNA, a series of high–degree nodes in the networks were identified as hub genes. The protein structures of cold-inducible RNA-binding protein (CIRBP), poly [ADP-ribose] polymerase 1 (PARP1) and protein arginine N-methyl transferase 1 (PRMT1) were subsequently found to be highly conserved in vertebrate, and the gene expression pattern of CIRBP, PARP1, PRMT1 and a part of TLR/NF-κB pathway-related genes indicated that these proteins might have similar biological functions in regulation of inflammatory response in teleost fish. The results of this study provided the first systematical full-length transcriptome profile of fat greenling and characterized its immune responses in early infection of V. harvey, which will serve as the foundation for further exploring the molecular mechanism of immune defense against bacterial infection in fat greenling.

Correction: PRMT1 Plays a Critical Role in Th17 Differentiation by Regulating Reciprocal Recruitment of STAT3 and STAT5.

Th17 cells are a class of Th cells that secrete IL-17 and mediate pathogenic immunity responsible for autoimmunity including experimental autoimmune encephalomyelitis, a murine model of multiple sclerosis. Retinoic acid-related orphan receptor γ t (RORγt) is the critical transcription factor that controls the differentiation of Th17 cells. However, little is known about the transcriptional cofactors for RORγt in the regulation of Th17 differentiation. In this study, we demonstrate that protein arginine N-methyltransferase 1 (PRMT1) associates with RORγt and regulates mouse Th17 differentiation. Overexpression of PRMT1 promoted Th17 differentiation, whereas inactivation or knockdown of PRMT1 decreased Th17 differentiation while expanding Foxp3+ regulatory T cells. Consistently, pharmacological inhibition of PRMT1 impaired the generation of Th17 cells and prevented induction of experimental autoimmune encephalomyelitis in mice. Mechanistically, PRMT1-dependent modification of asymmetric histone 4 arginine 3 dimethylation is required to stabilize the stimulatory STAT3 to displace the inhibitory STAT5 at IL-17 locus, resulting in the activation of IL-17 gene. Furthermore, PRMT1-facilitated recruitment of STAT3 overcame the inhibition of Th17 differentiation exerted by IL-2-induced STAT5 activation. PRMT1 thus regulates Th17 differentiation by controlling the reciprocal recruitment of STAT3 and STAT5. Our study thus reveals PRMT1 as a novel target for alleviating Th17-mediated autoimmunity by decreasing RORγt-dependent generation of pathogenic Th17 cells.

PRMT1 Plays a Critical Role in Th17 Differentiation by Regulating Reciprocal Recruitment of STAT3 and STAT5.

Th17 cells are a class of Th cells that secrete IL-17 and mediate pathogenic immunity responsible for autoimmunity including experimental autoimmune encephalomyelitis, a murine model of multiple sclerosis. Retinoic acid-related orphan receptor γ t (RORγt) is the critical transcription factor that controls the differentiation of Th17 cells. However, little is known about the transcriptional cofactors for RORγt in the regulation of Th17 differentiation. In this study, we demonstrate that protein arginine N-methyltransferase 1 (PRMT1) associates with RORγt and regulates mouse Th17 differentiation. Overexpression of PRMT1 promoted Th17 differentiation, whereas inactivation or knockdown of PRMT1 decreased Th17 differentiation while expanding Foxp3+ regulatory T cells. Consistently, pharmacological inhibition of PRMT1 impaired the generation of Th17 cells and prevented induction of experimental autoimmune encephalomyelitis in mice. Mechanistically, PRMT1-dependent modification of asymmetric histone 4 arginine 3 dimethylation is required to stabilize the stimulatory STAT3 to displace the inhibitory STAT5 at IL-17 locus, resulting in the activation of IL-17 gene. Furthermore, PRMT1-facilitated recruitment of STAT3 overcame the inhibition of Th17 differentiation exerted by IL-2-induced STAT5 activation. PRMT1 thus regulates Th17 differentiation by controlling the reciprocal recruitment of STAT3 and STAT5. Our study thus reveals PRMT1 as a novel target for alleviating Th17-mediated autoimmunity by decreasing RORγt-dependent generation of pathogenic Th17 cells.

Identifying the substrate proteins of U-box E3s E4B and CHIP by orthogonal ubiquitin transfer.

E3 ubiquitin (UB) ligases E4B and carboxyl terminus of Hsc70-interacting protein (CHIP) use a common U-box motif to transfer UB from E1 and E2 enzymes to their substrate proteins and regulate diverse cellular processes. To profile their ubiquitination targets in the cell, we used phage display to engineer E2-E4B and E2-CHIP pairs that were free of cross-reactivity with the native UB transfer cascades. We then used the engineered E2-E3 pairs to construct "orthogonal UB transfer (OUT)" cascades so that a mutant UB (xUB) could be exclusively used by the engineered E4B or CHIP to label their substrate proteins. Purification of xUB-conjugated proteins followed by proteomics analysis enabled the identification of hundreds of potential substrates of E4B and CHIP in human embryonic kidney 293 cells. Kinase MAPK3 (mitogen-activated protein kinase 3), methyltransferase PRMT1 (protein arginine N-methyltransferase 1), and phosphatase PPP3CA (protein phosphatase 3 catalytic subunit alpha) were identified as the shared substrates of the two E3s. Phosphatase PGAM5 (phosphoglycerate mutase 5) and deubiquitinase OTUB1 (ovarian tumor domain containing ubiquitin aldehyde binding protein 1) were confirmed as E4B substrates, and β-catenin and CDK4 (cyclin-dependent kinase 4) were confirmed as CHIP substrates. On the basis of the CHIP-CDK4 circuit identified by OUT, we revealed that CHIP signals CDK4 degradation in response to endoplasmic reticulum stress.

Kinetic Analysis of PRMT1 Reveals Multifactorial Processivity and a Sequential Ordered Mechanism.

Arginine methylation is a prevalent post-translational modification in eukaryotic cells. Two significant debates exist within the field: do these enzymes dimethylate their substrates in a processive or distributive manner, and do these enzymes operate using a random or sequential method of bisubstrate binding? We revealed that human protein arginine N-methyltransferase 1 (PRMT1) enzyme kinetics are dependent on substrate sequence. Further, peptides containing an Nη-hydroxyarginine generally demonstrated substrate inhibition and had improved KM values, which evoked a possible role in inhibitor design. We also revealed that the perceived degree of enzyme processivity is a function of both cofactor and enzyme concentration, suggesting that previous conclusions about PRMT sequential methyl transfer mechanisms require reassessment. Finally, we demonstrated a sequential ordered Bi-Bi kinetic mechanism for PRMT1, based on steady-state kinetic analysis. Together, our data indicate a PRMT1 mechanism of action and processivity that might also extend to other functionally and structurally conserved PRMTs.

The RNA-binding protein SERBP1 interacts selectively with the signaling protein RACK1

The RACK1 protein interacts with numerous proteins involved in signal transduction, the cytoskeleton, and mRNA splicing and translation. We used the 2-hybrid system to identify additional proteins interacting with RACK1 and isolated the RNA-binding protein SERBP1. SERPB1 shares amino acid sequence homology with HABP4 (also known as Ki-1/57), a component of the RNA spicing machinery that has been shown previously to interact with RACK1. Several different isoforms of SERBP1, generated by alternative mRNA splicing, interacted with RACK1 with indistinguishable interaction strength, as determined by a 2-hybrid beta-galactosidase assay. Analysis of deletion constructs of SERBP1 showed that the C-terminal third of the SERBP1 protein, which contains one of its two substrate sites for protein arginine N-methyltransferase 1 (PRMT1), is necessary and sufficient for it to interact with RACK1. Analysis of single amino acid substitutions in RACK1, identified in a reverse 2-hybrid screen, showed very substantial overlap with those implicated in the interaction of RACK1 with the cAMP-selective phosphodiesterase PDE4D5. These data are consistent with SERBP1 interacting selectively with RACK1, mediated by an extensive interaction surface on both proteins.

Repetitive ischemia increases myocardial dimethylarginine dimethylaminohydrolase 1 expression.

Pharmacologic inhibition of nitric oxide production inhibits growth of coronary collateral vessels. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) is the major enzyme that degrades asymmetric dimethylarginine (ADMA), a potent inhibitor of nitric oxide synthase. Here we examined regulation of the ADMA-DDAH1 pathway in a canine model of recurrent myocardial ischemia during the time when coronary collateral growth is known to occur. Under basal conditions, DDAH1 expression was non-uniform across the left ventricular (LV) wall, with expression strongest in the subepicardium. In response to ischemia, DDAH1 expression was up-regulated in the midmyocardium of the ischemic zone, and this was associated with a significant reduction in myocardial interstitial fluid (MIF) ADMA. The decrease in MIF ADMA during ischemia was likely due to increased DDAH1 because myocardial protein arginine N-methyl transferase 1 (PRMT1) and the methylated arginine protein content (the source of ADMA) were unchanged or increased, respectively, at this time. The inflammatory mediators interleukin (IL-1β) and tumor necrosis factor (TNF-α) were also elevated in the midmyocardium where DDAH1 expression was increased. Both of these factors significantly up-regulated DDAH1 expression in cultured human coronary artery endothelial cells. Taken together, these results suggest that inflammatory factors expressed in response to myocardial ischemia contributed to up-regulation of DDAH1, which was responsible for the decrease in MIF ADMA.

BTG1 potentiates apoptosis and suppresses proliferation in renal cell carcinoma by interacting with PRMT1.

B-cell translocation gene 1 (BTG1) is a member of the BTG/transducer of Erb family. BTG1 regulates cell cycle progression, inhibits proliferation, promotes apoptosis and stimulates cellular differentiation in multiple cell types. However, the functions of BTG1 in renal cell carcinoma (RCC) remain unclear. Therefore, the present study investigated the role of BTG1 in RCC tissue samples and 786-O RCC cells. RCC tissues and cells exhibited significantly weaker BTG1 protein and mRNA expression compared with para-carcinoma control tissues (P<0.05). Upregulated BTG1 expression induced significant G0/G1 cell cycle arrest, apoptosis and inhibition of cell proliferation in 786-O cells (P<0.05). Furthermore, BTG1 interacted with protein arginine N-methyltransferase 1 (PRMT1), and blocking the action of PRMT1 in 786-O cells resulted in inhibition of BTG1 function. These findings indicate that BTG1 may inhibit cell growth and promote apoptosis by interacting with PRMT1 in RCC; the identification of this mechanism may aid in the production of novel therapies for RCC.

Molecular cloning, characterization and expression analysis of the protein arginine N-methyltransferase 1 gene (As-PRMT1) from Artemia sinica

Protein arginine N-methyltransferase 1 (PRMT1) is an important epigenetic regulation factor in eukaryotic genomes. PRMT1 is involved in histone arginine loci methylation modification, changes in eukaryotic genomes' chromatin structure, and gene expression regulation. In the present paper, the full-length 1201-bp cDNA sequence of the PRMT1 homolog of Artemia sinica (As-PRMT1) was cloned for the first time. The putative As-PRMT1 protein comprises 346 amino acids with a SAM domain and a PRMT5 domain. Multiple sequence alignments revealed that the putative sequence of As-PRMT1 protein was relatively conserved across species, especially in the SAM domain. As-PRMT1 is widely expressed during embryo development of A. sinica. This is followed by a dramatic upregulation after diapause termination and then downregulation from the nauplius stage. Furthermore, As-PRMT1 transcripts are highly upregulated under conditions of high salinity and low temperature stress. These findings suggested that As-PRMT1 is a stress-related factor that might promote or inhibit the expression of certain genes, play a critical role in embryonic development and in resistance to low temperature and high salinity stress.

PRMT1-mediated arginine methylation controls ATXN2L localization

Arginine methylation is a posttranslational modification that is of importance in diverse cellular processes. Recent proteomic mass spectrometry studies reported arginine methylation of ataxin-2-like (ATXN2L), the paralog of ataxin-2, a protein that is implicated in the neurodegenerative disorder spinocerebellar ataxia type 2. Here, we investigated the methylation state of ATXN2L and its significance for ATXN2L localization. We first confirmed that ATXN2L is asymmetrically dimethylated in vivo, and observed that the nuclear localization of ATXN2L is altered under methylation inhibition. We further discovered that ATXN2L associates with the protein arginine-N-methyltransferase 1 (PRMT1). Finally, we showed that neither mutation of the arginine–glycine-rich motifs of ATXN2L nor methylation inhibition alters ATXN2L localization to stress granules, suggesting that methylation of ATXN2L is probably not mandatory.

Isoflurane Preconditioning Modulates the Expression of eNOS and eNOS‐related Genes during Myocardial Ischemia and Reperfusion

Endothelial nitric oxide synthase (eNOS) contributes to isoflurane preconditioning (IsoPC), a form of pharmacological cardioprotection against ischemia‐reperfusion injury. We investigated the effects of IsoPC on the expression of eNOS and eNOS‐related genes: GTP cyclohydrolase‐1 (GTPCH‐1), dimethylaminohydrolase‐2 (DDAH‐2), and protein arginine N‐methyltransferase‐1 (PRMT‐1) during myocardial ischemia and reperfusion. Rats were preconditioned with 1.4% isoflurane administered for 30 min followed by discontinuation for 15 min prior to occlusion of the left anterior descending coronary artery for 30 min. Gene expression in cardiac tissue was quantified by real‐time PCR at five time points: pre‐occlusion, occlusion, 30, 60 and 90 min of reperfusion. Expression of all genes decreased during occlusion and reperfusion in control animals. Isoflurane alone decreased gene expression before coronary artery occlusion, but conversely, attenuated further decreases in gene expression that were observed during occlusion and reperfusion in control rats. Expression of GTPCH‐1, DDAH‐2 and PRMT‐1 recovered to baseline values and eNOS expression was increased after 60 min of reperfusion in the IsoPC compared to the control group. This suggests that IsoPC exerts time‐dependent changes in genes expression pattern that may influence the function of eNOS during and after myocardial ischemia‐reperfusion injury.

PRMT1 mediated methylation of TAF15 is required for its positive gene regulatory function

TAF15 (formerly TAF II68) is a nuclear RNA-binding protein that is associated with a distinct population of TFIID and RNA polymerase II complexes. TAF15 harbours an N-terminal activation domain, an RNA recognition motif (RRM) and many Arg-Gly-Gly (RGG) repeats at its C-terminal end. The N-terminus of TAF15 serves as an essential transforming domain in the fusion oncoprotein created by chromosomal translocation in certain human chondrosarcomas. Post-transcriptional modifications (PTMs) of proteins are known to regulate their activity, however, nothing is known on how PTMs affect TAF15 function. Here we demonstrate that endogenous human TAF15 is methylated in vivo at its numerous RGG repeats. Furthermore, we identify protein arginine N-methyltransferase 1 (PRMT1) as a TAF15 interactor and the major PRMT responsible for its methylation. In addition, the RGG repeat-containing C-terminus of TAF15 is responsible for the shuttling between the nucleus and the cytoplasm and the methylation of RGG repeats affects the subcellular localization of TAF15. The methylation of TAF15 by PRMT1 is required for the ability of TAF15 to positively regulate the expression of the studied endogenous TAF15-target genes. Our findings demonstrate that arginine methylation of TAF15 by PRMT1 is a crucial event determining its proper localization and gene regulatory function.

Sam68 RNA binding protein is an in vivo substrate for protein arginine N-methyltransferase 1.

RNA binding proteins often contain multiple arginine glycine repeats, a sequence that is frequently methylated by protein arginine methyltransferases. The role of this posttranslational modification in the life cycle of RNA binding proteins is not well understood. Herein, we report that Sam68, a heteronuclear ribonucleoprotein K homology domain containing RNA binding protein, associates with and is methylated in vivo by the protein arginine N-methyltransferase 1 (PRMT1). Sam68 contains asymmetrical dimethylarginines near its proline motif P3 as assessed by using a novel asymmetrical dimethylarginine-specific antibody and mass spectrometry. Deletion of the methylation sites and the use of methylase inhibitors resulted in Sam68 accumulation in the cytoplasm. Sam68 was also detected in the cytoplasm of PRMT1-deficient embryonic stem cells. Although the cellular function of Sam68 is unknown, it has been shown to export unspliced human immunodeficiency virus RNAs. Cells treated with methylase inhibitors prevented the ability of Sam68 to export unspliced human immunodeficiency virus RNAs. Other K homology domain RNA binding proteins, including SLM-1, SLM-2, QKI-5, GRP33, and heteronuclear ribonucleoprotein K were also methylated in vivo. These findings demonstrate that RNA binding proteins are in vivo substrates for PRMT1, and their methylation is essential for their proper localization and function.

Identification and mapping of a novel human gene, HRMT1L1, homologous to the rat protein arginine N-methyltransferase 1 (PRMT1) gene.

Identification and mapping of a novel human gene, HRMT1L1, homologous to the rat protein arginine N-methyltransferase 1 (PRMT1) gene.