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1.
Ital J Dermatol Venerol ; 159(3): 318-328, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38502535

ABSTRACT

Telomeres, the safeguarding caps at the tips of chromosomes, are pivotal in the aging process of cells and have been linked to skin ailments and inflammatory conditions. Telomeres undergo a gradual reduction in length and factors such as oxidative stress hasten this diminishing process. Skin diseases including inflammatory conditions can be correlated with the shortening of telomeres and the persistent activation of DNA damage response in skin tissues. Telomere dysfunction could disrupt the balance of the skin, impairs wound healing, and may contribute to abnormal cytokine production. Skin aging and processes related to telomeres may function as one of the triggers for skin diseases. The presence of proinflammatory cytokines and dysfunctional telomeres in conditions such as Dyskeratosis Congenita implies a possible connection between the shortening of telomeres and the onset of chronic inflammatory skin disorders. In autoinflammatory skin diseases, chronic inflammation hinders wound healing thus aggravating the progression of the disease. The NF-ĸB pathway might contribute to the initiation or progression of chronic disorders by influencing mechanisms associated with telomere biology. The intricate connections between telomeres, telomerase, telomere-associated proteins, and skin diseases are still a complex puzzle to be solved. Here, we provide an overview of the impact of telomeres on both health and disease with a specific emphasis on their role in skin, inflammation and autoinflammatory skin disorders.


Subject(s)
Telomere , Humans , Skin Diseases/genetics , Inflammation/genetics , Telomere Shortening/physiology , Telomerase/metabolism , Telomerase/genetics , Dyskeratosis Congenita/genetics , Skin Aging/genetics , Skin Aging/physiology
2.
J Cell Mol Med ; 25(3): 1583-1600, 2021 02.
Article in English | MEDLINE | ID: mdl-33462997

ABSTRACT

Protein arginine methyltransferase 5 (PRMT5) activity is dysregulated in many aggressive cancers and its enhanced levels are associated with increased tumour growth and survival. However, the role of PRMT5 in breast cancer remains underexplored. In this study, we show that PRMT5 is overexpressed in breast cancer cell lines, and that it promotes WNT/ß-CATENIN proliferative signalling through epigenetic silencing of pathway antagonists, DKK1 and DKK3, leading to enhanced expression of c-MYC, CYCLIN D1 and SURVIVIN. Through chromatin immunoprecipitation (ChIP) studies, we found that PRMT5 binds to the promoter region of WNT antagonists, DKK1 and DKK3, and induces symmetric methylation of H3R8 and H4R3 histones. Our findings also show that PRMT5 inhibition using a specific small molecule inhibitor, compound 5 (CMP5), reduces PRMT5 recruitment as well as methylation of H3R8 and H4R3 histones in the promoter regions of DKK1 and DKK3, which consequently results in reduced expression CYCLIN D1 and SURVIVIN. Furthermore, CMP5 treatment either alone or in combination with 5-Azacytidine and Trichostatin A restored expression of DKK1 and DKK3 in TNBCs. PRMT5 inhibition also altered the growth characteristics of breast cancer cells and induced their death. Collectively, these results show that PRMT5 controls breast cancer cell growth through epigenetic silencing of WNT/ß-CATENIN pathway antagonists, DKK1 and DKK3, resulting in up-regulation of WNT/ß-CATENIN proliferative signalling.


Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Epigenesis, Genetic , Gene Silencing , Intercellular Signaling Peptides and Proteins/genetics , Protein-Arginine N-Methyltransferases/metabolism , Wnt Signaling Pathway , Apoptosis/drug effects , Breast Neoplasms/genetics , Cell Line, Tumor , DNA Methylation , Decitabine/pharmacology , Female , Gene Expression Regulation, Neoplastic/drug effects , Histones/metabolism , Humans , Protein Binding , Protein-Arginine N-Methyltransferases/antagonists & inhibitors
3.
J Cell Mol Med ; 24(19): 11477-11488, 2020 10.
Article in English | MEDLINE | ID: mdl-32888398

ABSTRACT

Breast cancer (BC) is the most common malignancy and the leading cause of death in women worldwide. Only 5%-10% of mutations in BRCA genes are associated with familial breast tumours in Eastern countries, suggesting the contribution of other genes. Using a microarray gene expression profiling study of BC, we have recently identified BRIP1 (fivefold up-regulation) as a potential gene associated with BC progression in the Omani population. Although BRIP1 regulates DNA repair and cell proliferation, the precise role of BRIP1 in BC cell invasion/metastasis has not been explored yet; this prompted us to test the hypothesis that BRIP1 promotes BC cell proliferation and invasion. Using a combination of cellular and molecular approaches, our results revealed differential overexpression of BRIP1 in different BC cell lines. Functional assays validated further the physiological relevance of BRIP1 in tumour malignancy, and siRNA-mediated BRIP1 knockdown significantly reduced BC cell motility by targeting key motility-associated genes. Moreover, down-regulation of BRIP1 expression significantly attenuated cell proliferation via cell cycle arrest. Our study is the first to show the novel function of BRIP1 in promoting BC cell invasion by regulating expression of various downstream target genes. Furthermore, these findings provide us with a unique opportunity to identify BRIP1-induced pro-invasive genes that could serve as biomarkers and/or targets to guide the design of appropriate BC targeted therapies.


Subject(s)
Breast Neoplasms/genetics , Breast Neoplasms/pathology , Fanconi Anemia Complementation Group Proteins/metabolism , RNA Helicases/metabolism , Cell Cycle Checkpoints/genetics , Cell Line, Tumor , Cell Movement/genetics , Cell Proliferation/genetics , Down-Regulation/genetics , Fanconi Anemia Complementation Group Proteins/genetics , Female , Gene Expression Regulation, Neoplastic , Humans , Neoplasm Invasiveness , RNA Helicases/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Small Interfering/metabolism , Wound Healing
4.
J Biol Chem ; 295(5): 1165-1180, 2020 01 31.
Article in English | MEDLINE | ID: mdl-31822509

ABSTRACT

Protein arginine methyltransferase-5 (PRMT5) is overexpressed in aggressive B-cell non-Hodgkin's lymphomas, including mantle cell lymphoma and diffuse large B-cell lymphoma, and supports constitutive expression of CYCLIN D1 and c-MYC. Here, we combined ChIP analysis with next-generation sequencing to identify microRNA (miRNA) genes that are targeted by PRMT5 in aggressive lymphoma cell lines. We identified enrichment of histone 3 dimethylation at Arg-8 (H3(Me2)R8) in the promoter regions of miR33b, miR96, and miR503. PRMT5 knockdown de-repressed transcription of all three miRNAs, accompanied by loss of recruitment of epigenetic repressor complexes containing PRMT5 and either histone deacetylase 2 (HDAC2) or HDAC3, enhanced binding of co-activator complexes containing p300 or CREB-binding protein (CBP), and increased acetylation of specific histones, including H2BK12, H3K9, H3K14, and H4K8 at the miRNA promoters. Re-expression of individual miRNAs in B-cell lymphoma cells down-regulated expression of PRMT5, CYCLIN D1, and c-MYC, which are all predicted targets of these miRNAs, and reduced lymphoma cell survival. Luciferase reporter assays with WT and mutant 3'UTRs of CYCLIN D1 and c-MYC mRNAs revealed that binding sites for miR33b, miR96, and miR503 are critical for translational regulation of the transcripts of these two genes. Our findings link altered PRMT5 expression to transcriptional silencing of tumor-suppressing miRNAs in lymphoma cells and reinforce PRMT5's relevance for promoting lymphoma cell growth and survival.


Subject(s)
Cyclin D1/genetics , Lymphoma, B-Cell/enzymology , MicroRNAs/metabolism , Protein-Arginine N-Methyltransferases/metabolism , Proto-Oncogene Proteins c-myc/genetics , 3' Untranslated Regions , Acetylation , CREB-Binding Protein/metabolism , Chromatin Immunoprecipitation Sequencing , Cyclin D1/metabolism , Down-Regulation , E1A-Associated p300 Protein/metabolism , Gene Silencing , Genes, Tumor Suppressor , Histone Deacetylases/genetics , Histone Deacetylases/metabolism , Histones/metabolism , Humans , Lymphoma, B-Cell/genetics , Lymphoma, B-Cell/metabolism , Methylation , MicroRNAs/genetics , Promoter Regions, Genetic , Protein-Arginine N-Methyltransferases/genetics , Proto-Oncogene Proteins c-myc/metabolism
5.
J Biol Chem ; 294(19): 7692-7710, 2019 05 10.
Article in English | MEDLINE | ID: mdl-30885941

ABSTRACT

Epigenetic regulation by the type II protein arginine methyltransferase, PRMT5, plays an essential role in the control of cancer cell proliferation and tumorigenesis. In this report, we investigate the relationship between PRMT5 and WNT/ß-CATENIN as well as AKT/GSK3ß proliferative signaling in three different types of non-Hodgkin's lymphoma cell lines, clinical samples, and mouse primary lymphoma cells. We show that PRMT5 stimulates WNT/ß-CATENIN signaling through direct epigenetic silencing of pathway antagonists, AXIN2 and WIF1, and indirect activation of AKT/GSK3ß signaling. PRMT5 inhibition with either shRNA-mediated knockdown or a specific small molecule PRMT5 inhibitor, CMP-5, not only leads to derepression of WNT antagonists and decreased levels of active phospho-AKT (Thr-450 and Ser-473) and inactive phospho-GSK3ß (Ser-9) but also results in decreased transcription of WNT/ß-CATENIN target genes, CYCLIN D1, c-MYC, and SURVIVIN, and enhanced lymphoma cell death. Furthermore, PRMT5 inhibition leads to reduced recruitment of co-activators CBP, p300, and MLL1, as well as enhanced recruitment of co-repressors HDAC2 and LSD1 to the WNT/ß-CATENIN target gene promoters. These results indicate that PRMT5 governs expression of prosurvival genes by promoting WNT/ß-CATENIN and AKT/GSK3ß proliferative signaling and that its inhibition induces lymphoma cell death, which warrants further clinical evaluation.


Subject(s)
Gene Expression Regulation, Neoplastic , Glycogen Synthase Kinase 3 beta/metabolism , Lymphoma/metabolism , Protein-Arginine N-Methyltransferases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction , Wnt Signaling Pathway , Animals , Cell Line, Tumor , Cell Survival , Glycogen Synthase Kinase 3 beta/genetics , Lymphoma/genetics , Lymphoma/pathology , Mice , Protein-Arginine N-Methyltransferases/genetics , Proto-Oncogene Proteins c-akt/genetics , beta Catenin/genetics , beta Catenin/metabolism
6.
Expert Opin Ther Targets ; 22(6): 527-545, 2018 06.
Article in English | MEDLINE | ID: mdl-29781349

ABSTRACT

INTRODUCTION: Exploration in the field of epigenetics has revealed the diverse roles of the protein arginine methyltransferase (PRMT) family of proteins in multiple disease states. These findings have led to the development of specific inhibitors and discovery of several new classes of drugs with potential to treat both benign and malignant conditions. Areas covered: We provide an overview on the role of PRMT enzymes in healthy and malignant cells, highlighting the role of arginine methylation in specific pathways relevant to cancer pathogenesis. Additionally, we describe structure and catalytic activity of PRMT and discuss the mechanisms of action of novel small molecule inhibitors of specific members of the arginine methyltransferase family. Expert opinion: As the field of PRMT biology advances, it's becoming clear that this class of enzymes is highly relevant to maintaining normal physiologic processes as well and disease pathogenesis. We discuss the potential impact of PRMT inhibitors as a broad class of drugs, including the pleiotropic effects, off target effects the need for more detailed PRMT-centric interactomes, and finally, the potential for targeting this class of enzymes in clinical development of experimental therapeutics for cancer.


Subject(s)
Antineoplastic Agents/pharmacology , Neoplasms/enzymology , Protein-Arginine N-Methyltransferases/metabolism , Animals , Drug Design , Drug Discovery/methods , Enzyme Inhibitors/pharmacology , Epigenesis, Genetic , Humans , Molecular Targeted Therapy , Neoplasms/drug therapy , Protein-Arginine N-Methyltransferases/antagonists & inhibitors
7.
Oncotarget ; 9(94): 36705-36718, 2018 Nov 30.
Article in English | MEDLINE | ID: mdl-30613353

ABSTRACT

Protein arginine methyltransferases (PRMTs) are known for their ability to catalyze methylation of specific arginine residues in a wide variety of cellular proteins, which are involved in a plethora of processes including signal transduction, transcription, and more recently DNA recombination. All members of the PRMT family can be grouped into three main classes depending on the type of methylation they catalyze. Type I PRMTs induce monomethylation and asymmetric dimethylation, while type II PRMTs catalyze monomethylation and symmetric dimethylation of specific arginine residues. In contrast, type III PRMTs carry out only monomethylation of arginine residues. In this review, we will focus on PRMT5, a type II PRMT essential for viability and normal development, which has been shown to be overexpressed in a wide variety of cancer cell types, owing it to the crucial role it plays in controlling key growth regulatory pathways. Furthermore, the role of PRMT5 in regulating expression and stability of key transcription factors that control normal stem cell function as well as cancer stem cell renewal will be discussed. We will review recent work that shows that through its ability to methylate various cellular proteins, PRMT5 functions as a master epigenetic regulator essential for growth and development, and we will highlight studies that have examined its dysregulation and the effects of its inhibition on cancer cell growth.

8.
Oncotarget ; 8(43): 73757-73765, 2017 Sep 26.
Article in English | MEDLINE | ID: mdl-29088742

ABSTRACT

Hepatocellular carcinoma (HCC) is a frequent form of cancer with a poor prognosis, and environmental factors significantly contribute to the risk. Despite knowledge that a Western-style diet is a risk factor in the development of nonalcoholic steatohepatitis (NASH) and subsequent progression to HCC, diet-induced signaling changes are not well understood. Understanding molecular mechanisms altered by diet is crucial for developing preventive and therapeutic strategies. We have previously shown that diets enriched with high-fat and high-cholesterol, shown to produce NASH and HCC, induce hepatic protein kinase C beta (PKCß) expression in mice, and a systemic loss of PKCß promotes hepatic cholesterol accumulation in response to this diet. Here, we sought to determine how PKCß and diet functionally interact during the pathogenesis of NASH and how it may promote hepatic carcinogenesis. We found that diet-induced hepatic PKCß expression is accompanied by an increase in phosphorylation of Ser780 of retinoblastoma (RB) protein. Intriguingly, PKCß-/- livers exhibited reduced RB protein levels despite increased transcription of the RB gene. It is also accompanied by reduced RBL-1 with no significant effect on RBL-2 protein levels. We also found reduced expression of the PKCß in HCC compared to non-tumorous liver in human patients. These results raise an interesting possibility that diet-induced PKCß activation represents an important mediator in the functional wiring of cholesterol metabolism and tumorigenesis through modulating stability of cell cycle-associated proteins. The potential role of PKCß in the suppression of tumorigenesis is discussed.

9.
Front Biosci (Elite Ed) ; 8(3): 412-26, 2016 06 01.
Article in English | MEDLINE | ID: mdl-27100348

ABSTRACT

Autism spectrum disorder (ASD) includes a group of neurodevelopmental disorders that affect communication skills, social interaction and intellectual ability. Despite evidence suggesting a strong genetic link with ASD, the genetic determinant remains unclear. Early studies focusing on candidate genes have shown that several genes associated with neuronal synaptic function are involved in development of ASD. Linkage studies have identified several single nucleotide polymorphisms (SNPs) associated with ASD, and genome-wide association studies have implicated several loci, but failed to recognize a single specific locus with strong significance, indicating heterogeneity in ASD genetic determinants. Detection of de novo copy number variations and single nucleotide variants in several ASD probands has confirmed the genetic heterogeneity of the disease. More interestingly, next generation sequencing approaches have recently identified novel candidate genes and several point mutations in sporadic ASDs, thus increasing our knowledge of ASD etiology. The current review summarizes the findings of recent studies using genetic and genomic approaches to understand the underlying molecular mechanisms of ASD.


Subject(s)
Autism Spectrum Disorder/genetics , Autism Spectrum Disorder/therapy , DNA Copy Number Variations , Epigenesis, Genetic , Genetic Association Studies , Humans
10.
Nucleic Acids Res ; 44(11): 5133-47, 2016 06 20.
Article in English | MEDLINE | ID: mdl-26935580

ABSTRACT

PPARγ2 is a critical lineage-determining transcription factor that is essential for adipogenic differentiation. Here we report characterization of the three-dimensional structure of the PPARγ2 locus after the onset of adipogenic differentiation and the mechanisms by which it forms. We identified a differentiation-dependent loop between the PPARγ2 promoter and an enhancer sequence 10 kb upstream that forms at the onset of PPARγ2 expression. The arginine methyltransferase Prmt5 was required for loop formation, and overexpression of Prmt5 resulted in premature loop formation and earlier onset of PPARγ2 expression. Kinetic studies of regulatory factor interactions at the PPARγ2 promoter and enhancer revealed enhanced interaction of Prmt5 with the promoter that preceded stable association of Prmt5 with enhancer sequences. Prmt5 knockdown prevented binding of both MED1, a subunit of Mediator complex that facilitates enhancer-promoter interactions, and Brg1, the ATPase of the mammalian SWI/SNF chromatin remodeling enzyme required for PPARγ2 activation and adipogenic differentiation. The data indicate a dynamic association of Prmt5 with the regulatory sequences of the PPARγ2 gene that facilitates differentiation-dependent, three-dimensional organization of the locus. In addition, other differentiation-specific, long-range chromatin interactions showed Prmt5-dependence, indicating a more general role for Prmt5 in mediating higher-order chromatin connections in differentiating adipocytes.


Subject(s)
Adipogenesis/genetics , Cell Differentiation , Enhancer Elements, Genetic , Genetic Loci , PPAR gamma/genetics , Promoter Regions, Genetic , Protein-Arginine N-Methyltransferases/metabolism , 3T3-L1 Cells , Animals , CCAAT-Enhancer-Binding Proteins/metabolism , Cell Line , Chromatin Assembly and Disassembly , DNA Helicases/metabolism , Gene Expression Regulation, Developmental , Gene Knockdown Techniques , Mediator Complex Subunit 1/metabolism , Mice , Nuclear Proteins/metabolism , Protein Binding , Protein Transport , Transcription Factors/metabolism , Transcriptional Activation
11.
Nucleic Acids Res ; 43(16): 7790-804, 2015 Sep 18.
Article in English | MEDLINE | ID: mdl-26117538

ABSTRACT

Jumonji domain-containing protein 6 (JMJD6) is a nuclear protein involved in histone modification, transcription and RNA processing. Although JMJD6 is crucial for tissue development, the link between its molecular functions and its roles in any given differentiation process is unknown. We report that JMJD6 is required for adipogenic gene expression and differentiation in a manner independent of Jumonji C domain catalytic activity. JMJD6 knockdown led to a reduction of C/EBPß and C/EBPδ protein expression without affecting mRNA levels in the early phase of differentiation. However, ectopic expression of C/EBPß and C/EBPδ did not rescue differentiation. Further analysis demonstrated that JMJD6 was associated with the Pparγ2 and Cebpα loci and putative enhancers. JMJD6 was previously found associated with bromodomain and extra-terminal domain (BET) proteins, which can be targeted by the bromodomain inhibitor JQ1. JQ1 treatment prevented chromatin binding of JMJD6, Pparγ2 and Cebpα expression, and adipogenic differentiation, yet had no effect on C/EBPß and C/EBPδ expression or chromatin binding. These results indicate dual roles for JMJD6 in promoting adipogenic gene expression program by post-transcriptional regulation of C/EBPß and C/EBPδ and direct transcriptional activation of Pparγ2 and Cebpα during adipocyte differentiation.


Subject(s)
Adipocytes/metabolism , Adipogenesis/genetics , Gene Expression Regulation , Receptors, Cell Surface/metabolism , Adipose Tissue/metabolism , Animals , CCAAT-Enhancer-Binding Protein-alpha/genetics , CCAAT-Enhancer-Binding Protein-alpha/metabolism , CCAAT-Enhancer-Binding Protein-beta/metabolism , Cell Line , Chromatin/metabolism , Female , Male , Mice , PPAR gamma/genetics , Protein Structure, Tertiary , RNA Polymerase II/metabolism , Receptors, Cell Surface/antagonists & inhibitors , Receptors, Cell Surface/chemistry , Receptors, Cell Surface/physiology , Transcription, Genetic
12.
Nat Commun ; 6: 7441, 2015 Jun 17.
Article in English | MEDLINE | ID: mdl-26081415

ABSTRACT

Calcium signalling is important for differentiation-dependent gene expression, but is also involved in other cellular functions. Therefore, mechanisms must exist to distinguish calcium signalling relevant to differentiation. Calcineurin is a calcium-regulated phosphatase that is required for myogenic gene expression and skeletal muscle differentiation. Here, we demonstrate that inhibition of calcineurin blocks chromatin remodelling and that the Brg1 ATPase of the SWI/SNF chromatin remodelling enzyme, which is required for the activation of myogenic gene expression, is a calcineurin substrate. Furthermore, we identify the calcium-regulated classical protein kinase C ß (PKCß) as a repressor of myogenesis and as the enzyme that opposes calcineurin function. Replacement of endogenous Brg1 with a phosphomimetic mutant in primary myoblasts inhibits myogenesis, whereas replacement with a non-phosphorylatable mutant allows myogenesis despite inhibition of calcineurin signalling, demonstrating the functionality of calcineurin/PKC-modified residues. Thus, the Brg1 chromatin remodelling enzyme integrates two antagonistic calcium-dependent signalling pathways that control myogenic differentiation.


Subject(s)
Calcineurin/metabolism , Calcium Signaling , Chromatin Assembly and Disassembly , DNA Helicases/metabolism , Muscle Development , Nuclear Proteins/metabolism , Protein Kinase C beta/metabolism , Transcription Factors/metabolism , Amino Acid Sequence , Animals , Cell Line , Female , Male , Mice , Molecular Sequence Data , Muscle, Skeletal/cytology
13.
Blood ; 125(16): 2530-43, 2015 Apr 16.
Article in English | MEDLINE | ID: mdl-25742700

ABSTRACT

Epigenetic events that are essential drivers of lymphocyte transformation remain incompletely characterized. We used models of Epstein-Barr virus (EBV)-induced B-cell transformation to document the relevance of protein arginine methyltransferase 5 (PRMT5) to regulation of epigenetic-repressive marks during lymphomagenesis. EBV(+) lymphomas and transformed cell lines exhibited abundant expression of PRMT5, a type II PRMT enzyme that promotes transcriptional silencing of target genes by methylating arginine residues on histone tails. PRMT5 expression was limited to EBV-transformed cells, not resting or activated B lymphocytes, validating it as an ideal therapeutic target. We developed a first-in-class, small-molecule PRMT5 inhibitor that blocked EBV-driven B-lymphocyte transformation and survival while leaving normal B cells unaffected. Inhibition of PRMT5 led to lost recruitment of a PRMT5/p65/HDAC3-repressive complex on the miR96 promoter, restored miR96 expression, and PRMT5 downregulation. RNA-sequencing and chromatin immunoprecipitation experiments identified several tumor suppressor genes, including the protein tyrosine phosphatase gene PTPROt, which became silenced during EBV-driven B-cell transformation. Enhanced PTPROt expression following PRMT5 inhibition led to dephosphorylation of kinases that regulate B-cell receptor signaling. We conclude that PRMT5 is critical to EBV-driven B-cell transformation and maintenance of the malignant phenotype, and that PRMT5 inhibition shows promise as a novel therapeutic approach for B-cell lymphomas.


Subject(s)
B-Lymphocytes/drug effects , Cell Transformation, Viral/drug effects , Enzyme Inhibitors/pharmacology , Protein-Arginine N-Methyltransferases/antagonists & inhibitors , Animals , B-Lymphocytes/metabolism , B-Lymphocytes/virology , Blotting, Western , Cell Line, Transformed , Cell Transformation, Viral/genetics , Cells, Cultured , Herpesvirus 4, Human/physiology , Histone Deacetylases/genetics , Histone Deacetylases/metabolism , Host-Pathogen Interactions/drug effects , Humans , Lymphoma/genetics , Lymphoma/metabolism , Lymphoma/virology , Mice, SCID , MicroRNAs/genetics , MicroRNAs/metabolism , Microscopy, Confocal , Protein-Arginine N-Methyltransferases/genetics , Protein-Arginine N-Methyltransferases/metabolism , RNA Interference , Receptor-Like Protein Tyrosine Phosphatases, Class 3/genetics , Receptor-Like Protein Tyrosine Phosphatases, Class 3/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Small Molecule Libraries/pharmacology , Transcription Factor RelA/genetics , Transcription Factor RelA/metabolism , Transcriptome/drug effects , Transcriptome/genetics , Tumor Suppressor Proteins/genetics , Tumor Suppressor Proteins/metabolism
14.
J Biol Chem ; 289(49): 33958-70, 2014 Dec 05.
Article in English | MEDLINE | ID: mdl-25324546

ABSTRACT

The SWI/SNF chromatin remodeling complex facilitates gene transcription by remodeling chromatin using the energy of ATP hydrolysis. Recent studies have indicated an interplay between the SWI/SNF complex and protein-arginine methyltransferases (PRMTs). Little is known, however, about the role of SWI/SNF and PRMTs in vitamin D receptor (VDR)-mediated transcription. Using SWI/SNF-defective cells, we demonstrated that Brahma-related gene 1 (BRG1), an ATPase that is a component of the SWI/SNF complex, plays a fundamental role in induction by 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) of the transcription of Cyp24a1 encoding the enzyme 25-hydroxyvitamin D3 24-hydroxylase involved in the catabolism of 1,25(OH)2D3. BRG1 was found to associate with CCAAT-enhancer-binding protein (C/EBP) ß and cooperate with VDR and C/EBPß in regulating Cyp24a1 transcription. PRMT5, a type II PRMT that interacts with BRG1, repressed Cyp24a1 transcription and mRNA expression. Our findings indicate the requirement of the C/EBP site for the inhibitory effect of PRMT5 via its methylation of H3R8 and H4R3. These findings indicate that the SWI/SNF complex and PRMT5 may be key factors involved in regulation of 1,25(OH)2D3 catabolism and therefore in the maintenance of calcium homeostasis by vitamin D. These studies also define epigenetic events linked to a novel mechanism of negative regulation of VDR-mediated transcription.


Subject(s)
Calcitriol/metabolism , Calcium/metabolism , Chromosomal Proteins, Non-Histone/genetics , Epigenesis, Genetic , Protein-Arginine N-Methyltransferases/genetics , Transcription Factors/genetics , Vitamin D3 24-Hydroxylase/genetics , Animals , COS Cells , Cell Line, Tumor , Chlorocebus aethiops , Chromosomal Proteins, Non-Histone/metabolism , Epithelial Cells/cytology , Epithelial Cells/metabolism , Feedback, Physiological , Humans , Osteoblasts/cytology , Osteoblasts/metabolism , Protein-Arginine N-Methyltransferases/metabolism , Signal Transduction , Transcription Factors/metabolism , Transcription, Genetic , Vitamin D3 24-Hydroxylase/metabolism
15.
Cancer Res ; 74(6): 1752-65, 2014 Mar 15.
Article in English | MEDLINE | ID: mdl-24453002

ABSTRACT

Glioblastoma is the most common and aggressive histologic subtype of brain cancer with poor outcomes and limited treatment options. Here, we report the selective overexpression of the protein arginine methyltransferase PRMT5 as a novel candidate theranostic target in this disease. PRMT5 silences the transcription of regulatory genes by catalyzing symmetric dimethylation of arginine residues on histone tails. PRMT5 overexpression in patient-derived primary tumors and cell lines correlated with cell line growth rate and inversely with overall patient survival. Genetic attenuation of PRMT5 led to cell-cycle arrest, apoptosis, and loss of cell migratory activity. Cell death was p53-independent but caspase-dependent and enhanced with temozolomide, a chemotherapeutic agent used as a present standard of care. Global gene profiling and chromatin immunoprecipitation identified the tumor suppressor ST7 as a key gene silenced by PRMT5. Diminished ST7 expression was associated with reduced patient survival. PRMT5 attenuation limited PRMT5 recruitment to the ST7 promoter, led to restored expression of ST7 and cell growth inhibition. Finally, PRMT5 attenuation enhanced glioblastoma cell survival in a mouse xenograft model of aggressive glioblastoma. Together, our findings defined PRMT5 as a candidate prognostic factor and therapeutic target in glioblastoma, offering a preclinical justification for targeting PRMT5-driven oncogenic pathways in this deadly disease.


Subject(s)
Brain Neoplasms/enzymology , Glioblastoma/enzymology , Protein-Arginine N-Methyltransferases/genetics , Tumor Suppressor Proteins/genetics , Animals , Apoptosis , Brain Neoplasms/mortality , Brain Neoplasms/therapy , Cell Line, Tumor , Cell Proliferation , Gene Expression , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Glioblastoma/mortality , Glioblastoma/therapy , Humans , Kaplan-Meier Estimate , Mice , Mice, Knockout , Mice, Nude , Molecular Targeted Therapy , Neoplasm Transplantation , Protein-Arginine N-Methyltransferases/metabolism , RNA, Small Interfering/genetics , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Proteins/metabolism
16.
J Biol Chem ; 289(1): 326-34, 2014 Jan 03.
Article in English | MEDLINE | ID: mdl-24257758

ABSTRACT

The microphthalmia-associated transcription factor (MITF) is required for terminal osteoclast differentiation and is a signaling effector engaged by macrophage colony-stimulating factor 1 (CSF-1) and receptor activator of nuclear factor-κB ligand (RANKL). MITF exerts its regulatory functions through its association with cofactors. Discovering the identity of its various partners will provide insights into the mechanisms governing gene expression during osteoclastogenesis. Here, we demonstrate that the proto-oncogene fused in sarcoma (FUS), the chromatin remodeling ATPase BRG1, and MITF form a trimeric complex that is regulated by phosphorylation of MITF at Ser-307 by p38 MAPK during osteoclast differentiation. FUS was recruited to MITF target gene promoters Acp5 and Ctsk during osteoclast differentiation, and FUS knockdown abolished efficient transcription of Acp5 and Ctsk. Furthermore, sumoylation of MITF at Lys-316, known to negatively regulate MITF transcriptional activity, inhibited MITF interactions with FUS and BRG1 in a p38 MAPK phosphorylation-dependent manner. These results demonstrate that FUS is a coregulator of MITF activity and provide new insights into how the RANKL/p38 MAPK signaling nexus controls gene expression in osteoclasts.


Subject(s)
DNA Helicases/metabolism , Microphthalmia-Associated Transcription Factor/metabolism , Multiprotein Complexes/metabolism , Nuclear Proteins/metabolism , Osteoclasts/metabolism , Promoter Regions, Genetic/physiology , Transcription Factors/metabolism , Transcription, Genetic/physiology , Acid Phosphatase/biosynthesis , Acid Phosphatase/genetics , Animals , COS Cells , Cathepsin K/biosynthesis , Cathepsin K/genetics , Chlorocebus aethiops , DNA Helicases/genetics , Gene Expression Regulation/physiology , Humans , Isoenzymes/biosynthesis , Isoenzymes/genetics , MAP Kinase Signaling System/physiology , Mice , Microphthalmia-Associated Transcription Factor/genetics , Multiprotein Complexes/genetics , Nuclear Proteins/genetics , Osteoclasts/cytology , Phosphorylation/physiology , Proto-Oncogene Mas , RANK Ligand/genetics , RANK Ligand/metabolism , RNA-Binding Protein FUS , Tartrate-Resistant Acid Phosphatase , Transcription Factors/genetics , p38 Mitogen-Activated Protein Kinases/genetics , p38 Mitogen-Activated Protein Kinases/metabolism
17.
Diagn Pathol ; 8: 201, 2013 Dec 10.
Article in English | MEDLINE | ID: mdl-24326178

ABSTRACT

BACKGROUND: Protein arginine methyltransferase-5 (PRMT5) is a chromatin-modifying enzyme capable of methylating histone and non-histone proteins, and is involved in a wide range of cellular processes that range from transcriptional regulation to organelle biosynthesis. As such, its overexpression has been linked to tumor suppressor gene silencing, enhanced tumor cell growth and survival. MATERIAL AND METHODS: Quantitative real-time polymerase chain reaction, Western immunoblot and immunohistochemistry were used to characterize PRMT5 expression in lung cancer cell lines and human tumors. Clinicopathological findings of tissue microarray based samples from 229 patients with non-small cell lung carcinomas (NSCLC) and 133 cases with pulmonary neuroendocrine tumors (NET) were analyzed with regard to nuclear and cytoplasmic PRMT5 expression. RESULTS: There was statistically significant difference in PRMT5 messenger RNA expression between tumors and nonneoplastic lung tissues. Immunoblot experiments showed abundant expression of PRMT5 and its symmetric methylation mark H4R3 in lung carcinoma but not in non-neoplastic human pulmonary alveolar and bronchial epithelial cell lines. More than two thirds of lung tumors expressed PRMT5. High levels of cytoplasmic PRMT5 were detected in 20.5% of NSCLC and in 16.5% of NET; high levels of nuclear PRMT5 were detected in 38.0% of NSCLC and 24.0% of NET. Cytoplasmic PRMT5 was associated with high grade in both NSCLC and pulmonary NET while nuclear PRMT5 was more frequent in carcinoid tumors (p < 0.05). CONCLUSION: The observed findings support the role of PRMT5 in lung tumorigenesis and reflect its functional dichotomy in cellular compartments. VIRTUAL SLIDE: The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1611895162102528.


Subject(s)
Biomarkers, Tumor/metabolism , Carcinoma, Non-Small-Cell Lung/enzymology , Lung Neoplasms/enzymology , Neuroendocrine Tumors/enzymology , Protein-Arginine N-Methyltransferases/metabolism , Adult , Aged , Aged, 80 and over , Biomarkers, Tumor/genetics , Blotting, Western , Carcinoma, Non-Small-Cell Lung/genetics , Carcinoma, Non-Small-Cell Lung/pathology , Cell Differentiation , Cell Line, Tumor , Cell Nucleus/enzymology , Cytoplasm/enzymology , Female , Humans , Immunohistochemistry , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Male , Middle Aged , Neoplasm Grading , Neuroendocrine Tumors/genetics , Neuroendocrine Tumors/pathology , Protein-Arginine N-Methyltransferases/genetics , RNA, Messenger/metabolism , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Tissue Array Analysis , Young Adult
18.
J Biol Chem ; 288(49): 35534-47, 2013 Dec 06.
Article in English | MEDLINE | ID: mdl-24189068

ABSTRACT

Epigenetic regulation mediated by lysine- and arginine-specific enzymes plays an essential role in tumorigenesis, and enhanced expression of the type II protein arginine methyltransferase PRMT5 as well as the polycomb repressor complex PRC2 has been associated with increased cell proliferation and survival. Here, we show that PRMT5 is overexpressed in three different types of non-Hodgkin lymphoma cell lines and clinical samples as well as in mouse primary lymphoma cells and that it up-regulates PRC2 expression through inactivation of the retinoblastoma proteins RB1 and RBL2. Although PRMT5 epigenetically controls RBL2 expression, it indirectly promotes RB1 phosphorylation through enhanced cyclin D1 expression. Furthermore, we demonstrate that PRMT5 knockdown in non-Hodgkin lymphoma cell lines and mouse primary lymphoma cells leads to RBL2 derepression and RB1 reactivation, which in turn inhibit PRC2 expression and trigger derepression of its CASP10, DAP1, HOXA5, and HRK pro-apoptotic target genes. We also show that reduced PRMT5 expression leads to cyclin D1 transcriptional repression via loss of TP53K372 methylation, which results in decreased BCL3 expression and enhanced recruitment of NF-κB p52-HDAC1 repressor complexes to the cyclin D1 promoter. These findings indicate that PRMT5 is a master epigenetic regulator that governs expression of its own target genes and those regulated by PRC2 and that its inhibition could offer a promising therapeutic strategy for lymphoma patients.


Subject(s)
Lymphoma/genetics , Lymphoma/metabolism , Polycomb Repressive Complex 2/genetics , Protein Methyltransferases/antagonists & inhibitors , Protein Methyltransferases/genetics , Protein-Arginine N-Methyltransferases/antagonists & inhibitors , Protein-Arginine N-Methyltransferases/genetics , Retinoblastoma Protein/metabolism , Animals , Cell Death , Cell Line, Tumor , Cyclin D1/metabolism , Epigenesis, Genetic , Gene Knockdown Techniques , Genes, Retinoblastoma , Histone Deacetylase 2/genetics , Histone Deacetylase 2/metabolism , Humans , Lymphoma/pathology , Lymphoma, Non-Hodgkin/genetics , Lymphoma, Non-Hodgkin/metabolism , Lymphoma, Non-Hodgkin/pathology , Mice , Polycomb Repressive Complex 2/antagonists & inhibitors , Promoter Regions, Genetic , Retinoblastoma-Like Protein p130/genetics , Retinoblastoma-Like Protein p130/metabolism , Signal Transduction , Tumor Cells, Cultured
19.
PLoS One ; 8(9): e74710, 2013.
Article in English | MEDLINE | ID: mdl-24098663

ABSTRACT

Protein arginine methyltransferase-5 (PRMT5) is a Type II arginine methyltransferase that regulates various cellular functions. We hypothesized that PRMT5 plays a role in regulating the growth of human melanoma cells. Immunohistochemical analysis indicated significant upregulation of PRMT5 in human melanocytic nevi, malignant melanomas and metastatic melanomas as compared to normal epidermis. Furthermore, nuclear PRMT5 was significantly decreased in metastatic melanomas as compared to primary cutaneous melanomas. In human metastatic melanoma cell lines, PRMT5 was predominantly cytoplasmic, and associated with its enzymatic cofactor Mep50, but not STAT3 or cyclin D1. However, histologic examination of tumor xenografts from athymic mice revealed heterogeneous nuclear and cytoplasmic PRMT5 expression. Depletion of PRMT5 via siRNA inhibited proliferation in a subset of melanoma cell lines, while it accelerated growth of others. Loss of PRMT5 also led to reduced expression of MITF (microphthalmia-associated transcription factor), a melanocyte-lineage specific oncogene, and increased expression of the cell cycle regulator p27(Kip1). These results are the first to report elevated PRMT5 expression in human melanoma specimens and indicate this protein may regulate MITF and p27(Kip1) expression in human melanoma cells.


Subject(s)
Cyclin-Dependent Kinase Inhibitor p27/metabolism , Gene Expression Regulation, Neoplastic/physiology , Melanoma/metabolism , Microphthalmia-Associated Transcription Factor/metabolism , Neoplasm Metastasis/pathology , Protein-Arginine N-Methyltransferases/metabolism , Animals , Cytoplasm/metabolism , Epidermis/metabolism , Humans , Immunohistochemistry , Mice , Mice, Nude
20.
F1000Res ; 2: 279, 2013.
Article in English | MEDLINE | ID: mdl-24715966

ABSTRACT

Protein arginine methylation is a common posttranslational modification that has been implicated in numerous biological processes including gene expression. The mammalian genome encodes nine protein arginine methyltransferases (Prmts) that catalyze monomethylation, asymmetric dimethylation, and symmetric dimethylation on arginine residues. Protein arginine methyltransferase 7 (Prmt7) is categorized as a type II and type III enzyme that produces symmetric dimethylated arginine and monomethylated arginine, respectively. However, the biological role of Prmt7 is not well characterized. We previously showed that Prmt5, a type II Prmt that associates with Brg1-based SWI/SNF chromatin remodeling complex, is required for adipocyte differentiation. Since Prmt7 also associates with Brg1-based SWI/SNF complex and modifies core histones, we hypothesized that Prmt7 might play a role in transcriptional regulation of adipogenesis. In the present study, we determined that the expression of Prmt7 did not change throughout adipogenic differentiation of C3H10T1/2 mesenchymal cells. Knockdown or over-expression of Prmt7 had no effect on lipid accumulation or adipogenic gene expression in differentiating C3H10T1/2 cells or in C/EBPα-reprogrammed NIH3T3 fibroblasts. Based on these results, we conclude that Prmt7, unlike Prmt5, is dispensable for adipogenic differentiation in tissue culture models.

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