ABSTRACT
Multiple myeloma (MM) represents the malignant proliferation of terminally differentiated B cells, which, in many cases, is associated with the maintenance of high levels of the oncoprotein c-MYC. Overexpression of the histone methyltransferase MMSET (WHSC1/NSD2), due to t(4;14) chromosomal translocation, promotes the proliferation of MM cells along with global changes in chromatin; nevertheless, the precise mechanisms by which MMSET stimulates neoplasia remain incompletely understood. We found that MMSET enhances the proliferation of MM cells by stimulating the expression of c-MYC at the post-transcriptional level. A microRNA (miRNA) profiling experiment in t(4;14) MM cells identified miR-126* as an MMSET-regulated miRNA predicted to target c-MYC mRNA. We show that miR-126* specifically targets the 3'-untranslated region (3'-UTR) of c-MYC, inhibiting its translation and leading to decreased c-MYC protein levels. Moreover, the expression of this miRNA was sufficient to decrease the proliferation rate of t(4;14) MM cells. Chromatin immunoprecipitation analysis showed that MMSET binds to the miR-126* promoter along with the KAP1 corepressor and histone deacetylases, and is associated with heterochromatic modifications, characterized by increased trimethylation of H3K9 and decreased H3 acetylation, leading to miR-126* repression. Collectively, this study shows a novel mechanism that leads to increased c-MYC levels and enhanced proliferation of t(4;14) MM, and potentially other cancers with high MMSET expression.
Subject(s)
Cell Proliferation , Gene Expression Regulation, Neoplastic , Histone-Lysine N-Methyltransferase/metabolism , MicroRNAs/genetics , Multiple Myeloma/pathology , Proto-Oncogene Proteins c-myc/metabolism , Repressor Proteins/metabolism , Apoptosis , Blotting, Western , Chromatin Immunoprecipitation , Histone-Lysine N-Methyltransferase/antagonists & inhibitors , Histone-Lysine N-Methyltransferase/genetics , Humans , Immunoprecipitation , Multiple Myeloma/genetics , Multiple Myeloma/metabolism , Proto-Oncogene Proteins c-myc/genetics , RNA, Messenger/genetics , RNA, Small Interfering/genetics , Real-Time Polymerase Chain Reaction , Repressor Proteins/antagonists & inhibitors , Repressor Proteins/genetics , Reverse Transcriptase Polymerase Chain Reaction , Tumor Cells, CulturedABSTRACT
Epigenetic deregulation of gene expression has a role in the initiation and progression of prostate cancer (PCa). The histone methyltransferase MMSET/WHSC1 (Multiple Myeloma SET domain) is overexpressed in a number of metastatic tumors, but its mechanism of action has not been defined. In this work, we found that PCa cell lines expressed significantly higher levels of MMSET compared with immortalized, non-transformed prostate cells. Knockdown experiments showed that, in metastatic PCa cell lines, dimethylation of lysine 36 and trimethylation of lysine 27 on histone H3 (H3K36me2 and H3K27me3, respectively) depended on MMSET expression, whereas depletion of MMSET in benign prostatic cells did not affect chromatin modifications. Knockdown of MMSET in DU145 and PC-3 tumor cells decreased cell proliferation, colony formation in soft agar and strikingly diminished cell migration and invasion. Conversely, overexpression of MMSET in immortalized, non-transformed RWPE-1 cells promoted cell migration and invasion, accompanied by an epithelial-mesenchymal transition (EMT). Among a panel of EMT-promoting genes analyzed, TWIST1 expression was strongly activated in response to MMSET. Chromatin immunoprecipitation analysis demonstrated that MMSET binds to the TWIST1 locus and leads to an increase in H3K36me2, suggesting a direct role of MMSET in the regulation of this gene. Depletion of TWIST1 in MMSET-overexpressing RWPE-1 cells blocked cell invasion and EMT, indicating that TWIST1 was a critical target of MMSET, responsible for the acquisition of an invasive phenotype. Collectively, these data suggest that MMSET has a role in PCa pathogenesis and progression through epigenetic regulation of metastasis-related genes.
Subject(s)
Epithelial-Mesenchymal Transition , Histone-Lysine N-Methyltransferase/metabolism , Nuclear Proteins/metabolism , Prostatic Neoplasms/enzymology , Repressor Proteins/metabolism , Twist-Related Protein 1/metabolism , Cell Line, Tumor , Cell Movement , Epigenesis, Genetic , Gene Expression , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Histone-Lysine N-Methyltransferase/genetics , Histones/metabolism , Humans , Male , Methylation , Neoplasm Invasiveness , Nuclear Proteins/genetics , Prostatic Neoplasms/pathology , Protein Binding , Protein Processing, Post-Translational , RNA, Small Interfering/genetics , Repressor Proteins/genetics , Twist-Related Protein 1/geneticsABSTRACT
The frequency of the monocyte chemoattractant protein-1 (MCP-1) -2518 G-type polymorphism in Koreans is significantly higher than the frequencies reported for Caucasians and Afro-Americans. The G- vs. A-allele profile in patients with systemic autoimmune diseases is similar to that in healthy Koreans, and does not appear to contribute to elevated MCP-1 production in patients.
Subject(s)
Arthritis, Rheumatoid/genetics , Chemokine CCL2/genetics , Lupus Erythematosus, Systemic/genetics , Promoter Regions, Genetic , Still's Disease, Adult-Onset/genetics , Chemokine CCL2/blood , Chemokine CCL2/metabolism , Gene Frequency , Humans , Korea , Leukocytes, Mononuclear/metabolism , Polymorphism, GeneticABSTRACT
The behavior of the model proteins, lysozyme, myoglobin, and beta-casein, pretreated in urea and/or dithiothreitol, at air/solution interfaces was studied by surface pressure-area techniques. The data suggested that in the absence of pretreatments the globular proteins are only partially unfolded at the interfaces. The interfacial activity was enhanced by the pretreatment (lysozyme in 8 M urea with 0.2 M dithiothreitol and myoglobin in 8 M urea). The interfacial activity of casein, a random-coil type protein, was not influenced by the pretreatment (8 M urea), as it readily and completely unfolds at the interfaces. The unfolding of globular proteins at the interfaces is apparently restricted by both disulfide and noncovalent bonds. Pretreatment can relax those restrictions, resulting in more complete interfacial unfolding. Copyright 1998 Academic Press. Copyright 1998Academic Press
