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The Journal of Comparative Neurology Sep 2020The ability to rapidly change gene expression patterns is essential for differentiation, development, and functioning of the brain. Throughout development, or in...
The ability to rapidly change gene expression patterns is essential for differentiation, development, and functioning of the brain. Throughout development, or in response to environmental stimuli, gene expression patterns are tightly regulated by the dynamic interplay between transcription activators and repressors. Nuclear receptor corepressor 1 (NCoR1) and silencing mediator for retinoid or thyroid-hormone receptors (SMRT) are the best characterized transcriptional co-repressors from a molecular point of view. They mediate epigenetic silencing of gene expression in a wide range of developmental and homeostatic processes in many tissues, including the brain. For instance, NCoR1 and SMRT regulate neuronal stem cell proliferation and differentiation during brain development and they have been implicated in learning and memory. However, we still have a limited understanding of their regional and cell type-specific expression in the brain. In this study, we used fluorescent immunohistochemistry to map their expression patterns throughout the adult mouse brain. Our findings reveal that NCoR1 and SMRT share an overall neuroanatomical distribution, and are detected in both excitatory and inhibitory neurons. However, we observed striking differences in their cell type-specific expression in glial cells. Specifically, all oligodendrocytes express NCoR1, but only a subset express SMRT. In addition, NCoR1, but not SMRT, was detected in a subset of astrocytes and in the microglia. These novel observations are corroborated by single cell transcriptomics and emphasize how NCoR1 and SMRT may contribute to distinct biological functions, suggesting an exclusive role of NCoR1 in innate immune responses in the brain.
Topics: Animals; Brain; Female; Gene Expression Profiling; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nuclear Receptor Co-Repressor 1; Nuclear Receptor Co-Repressor 2; Transcription, Genetic
PubMed: 32072640
DOI: 10.1002/cne.24886 -
The Journal of Cell Biology Oct 2008Silencing mediator for retinoic acid and thyroid hormone receptor (SMRT) is a transcriptional corepressor that participates in diverse signaling pathways and human...
Silencing mediator for retinoic acid and thyroid hormone receptor (SMRT) is a transcriptional corepressor that participates in diverse signaling pathways and human diseases. However, regulation of SMRT stability remains largely unexplored. We show that the peptidyl-prolyl isomerase Pin1 interacts with SMRT both in vitro and in mammalian cells. This interaction requires the WW domain of Pin1 and SMRT phosphorylation. Pin1 regulates SMRT protein stability, thereby affecting SMRT-dependent transcriptional repression. SMRT phosphorylation at multiple sites is required for Pin1 interaction, and these sites can be phosphorylated by Cdk2, which interacts with SMRT. Cdk2-mediated phosphorylation of SMRT is required for Pin1 binding and decreases SMRT stability, whereas mutation of these phosphorylation sites abrogates Pin1 binding and stabilizes SMRT. Finally, decreases in SMRT stability occur in response to the activation of Her2/Neu/ErbB2, and this receptor functions upstream of both Pin1 and Cdk2 in the signaling cascade that regulates SMRT stability and cellular response to tamoxifen.
Topics: Animals; Benzothiazoles; Cell Line; Cell Proliferation; Chlorocebus aethiops; Cyclin-Dependent Kinase 2; Cyclins; DNA-Binding Proteins; Gene Expression; Genes, myc; Humans; Mice; Models, Biological; Mutation; NIMA-Interacting Peptidylprolyl Isomerase; Neuregulin-1; Nuclear Receptor Co-Repressor 2; Peptide Fragments; Peptidylprolyl Isomerase; Phosphorylation; Protein Binding; Protein Kinase Inhibitors; Receptor, ErbB-2; Receptors, Progesterone; Repressor Proteins; Signal Transduction; Tamoxifen; Two-Hybrid System Techniques; Tyrphostins
PubMed: 18838553
DOI: 10.1083/jcb.200806172 -
Nucleic Acids Research Feb 2023The Th2 cytokine interleukin 4 (IL4) promotes macrophage differentiation into alternative subtypes and plays important roles in physiology, in metabolic and inflammatory...
The Th2 cytokine interleukin 4 (IL4) promotes macrophage differentiation into alternative subtypes and plays important roles in physiology, in metabolic and inflammatory diseases, in cancer and in tissue regeneration. While the regulatory transcription factor networks governing IL4 signaling are already well-characterized, it is currently less understood which transcriptional coregulators are involved and how they operate mechanistically. In this study, we discover that G protein pathway suppressor 2 (GPS2), a core subunit of the HDAC3 corepressor complex assembled by SMRT and NCOR, represses IL4-dependent enhancer activation in mouse macrophages. Our genome-wide and gene-specific characterization revealed that, instead of directly repressing STAT6, chromatin-bound GPS2 cooperates with SMRT and NCOR to antagonize enhancer activation by lysine demethylase 1A (KDM1A, LSD1). Mechanistically, corepressor depletion increased KDM1A recruitment to enhancers linked to IL4-induced genes, accompanied by demethylation of the repressive histone marks H3K9me2/3 without affecting H3K4me1/2, the classic KDM1A substrates for demethylation in other cellular contexts. This in turn caused enhancer and gene activation already in the absence of IL4/STAT6 and sensitized the STAT6-dependent IL4 responsiveness of macrophages. Thus, our work identified with the antagonistic action of a GPS2-containing corepressor complex and the lysine demethylase KDM1A a hitherto unknown epigenetic corepressor-coactivator switching mechanism that governs alternative macrophage activation.
Topics: Animals; Mice; Co-Repressor Proteins; Histone Demethylases; Interleukin-4; Intracellular Signaling Peptides and Proteins; Lysine; Macrophage Activation
PubMed: 36610795
DOI: 10.1093/nar/gkac1230 -
PloS One 2019Silencing Mediator of Retinoid and Thyroid Hormone Receptors (SMRT) and the nuclear receptor co-repressor1 (NCoR1) are paralogs and regulate nuclear receptor (NR)...
Silencing Mediator of Retinoid and Thyroid Hormone Receptors (SMRT) and the nuclear receptor co-repressor1 (NCoR1) are paralogs and regulate nuclear receptor (NR) function through the recruitment of a multiprotein complex that includes histone deacetylase activity. Previous genetic strategies which deleted SMRT in a specific tissue or which altered the interaction between SMRT and NRs have suggested that it may regulate adiposity and insulin sensitivity. However, the full role of SMRT in adult mice has been difficult to establish because its complete deletion during embryogenesis is lethal. To elucidate the specific roles of SMRT in mouse target tissues especially in the context of thyroid hormone (TH) signaling, we used a tamoxifen-inducible post-natal disruption strategy. We found that global SMRT deletion causes dramatic obesity even though mice were fed a standard chow diet and exhibited normal food intake. This weight gain was associated with a decrease in energy expenditure. Interestingly, the deletion of SMRT had no effect on TH action in any tissue but did regulate retinoic acid receptor (RAR) function in the liver. We also demonstrate that the deletion of SMRT leads to profound hepatic steatosis in the setting of obesity. This is unlike NCoR1 deletion, which results in hepatic steatosis due to the upregulation of lipogenic gene expression. Taken together, our data demonstrate that SMRT plays a unique and CoR specific role in the regulation of body weight and has no role in TH action. This raises the possibility that additional role of CoRs besides NCoR1 and SMRT may exist to regulate TH action.
Topics: Animals; Blotting, Western; Body Weight; Cholesterol; Echocardiography; Energy Metabolism; Glucose Tolerance Test; Lipids; Liver; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nuclear Receptor Co-Repressor 2; Real-Time Polymerase Chain Reaction; Thyroid Hormones; Thyrotropin; Thyroxine; Triglycerides; Weight Gain
PubMed: 31404087
DOI: 10.1371/journal.pone.0220717 -
Oncology Letters Jan 2011Nordihydroguaiaretic acid (NDGA) and its derivatives possess anti-cancer effects on various types of cancer via the induction of apoptosis or cell cycle arrest. This...
Nordihydroguaiaretic acid (NDGA) and its derivatives possess anti-cancer effects on various types of cancer via the induction of apoptosis or cell cycle arrest. This study proved that NDGA inhibited cervical cancer SiHa cell growth and induced cell cycle arrest at the G(1) phase, which may be a consequence of cell cycle kinase inhibitor p21 induction. NDGA promoted acetylation of histone H3 in total and p21 gene-associated chromatin. This effect is gene selective, since NDGA has no impact on the p27 gene. NDGA also inhibited HPV-16 E6 gene transcription, which in turn resulted in the restoration of p53 protein levels. The silencing mediator for retinoid and thyroid hormone receptors (SMRT) is a key component of the HDAC3-HDAC4-N-CoR/SMRT complex. We found that NDGA significantly inhibited the transcription of SMRT, which, together with p53, may aid in the detection of the increase of histone H3 acetylation within the p21 gene. Our results suggest that NDGA induces p21 transcription by selectively elevating histone H3 acetylation associated with p21 gene and p53 protein levels via the inhibition of HPV-16 E6 expression.
PubMed: 22870140
DOI: 10.3892/ol.2010.205 -
Molecular Endocrinology (Baltimore, Md.) Feb 2009To repress the expression of target genes, the unliganded nuclear receptor generally recruits the silencing mediator of retinoid and thyroid hormone receptor...
To repress the expression of target genes, the unliganded nuclear receptor generally recruits the silencing mediator of retinoid and thyroid hormone receptor (SMRT)/nuclear receptor corepressor via its direct association with the conserved motif within bipartite nuclear receptor-interaction domains (IDs) of the corepressor. Here, we investigated the involvement of the SMRT corepressor in transcriptional repression by the unliganded vitamin D receptor (VDR). Using small interference RNA against SMRT in human embryonic kidney 293 cells, we demonstrated that SMRT is involved in the repression of the VDR-target genes, osteocalcin and vitamin D(3) 24-hydroxylase in vivo. Consistent with this, VDR and SMRT are recruited to the vitamin D response element of the endogenous osteocalcin promoter in the absence of 1alpha,25-(OH)(2)D(3) in chromatin immunoprecipitation assays. To address the involvement of the VDR-specific interaction of SMRT in this repression, we identified the molecular determinants of the interaction between VDR and SMRT. Interestingly, VDR specifically interacts with ID1 of the SMRT/nuclear receptor corepressor and that ID1 is required for their stable interaction. We also identified specific residues in the SMRT-ID1 that are required for VDR binding, using the one- plus two-hybrid system, a novel genetic selection method for specific missense mutations that disrupt protein-protein interactions. These mutational studies revealed that VDR interaction requires a wide range of the residues within and outside the extended helix motif of SMRT-ID1. Notably, SMRT mutants defective in the VDR interaction were also defective in the repression of endogenous VDR-target genes, indicating that the SMRT corepressor is directly involved in the VDR-mediated repression in vivo via an ID1-specific interaction with the VDR.
Topics: Amino Acid Sequence; Cell Line; DNA-Binding Proteins; Gene Expression Regulation; Humans; Inhibitor of Differentiation Protein 1; Molecular Sequence Data; Mutagenesis, Site-Directed; Nuclear Receptor Co-Repressor 2; Osteocalcin; RNA, Small Interfering; Receptors, Calcitriol; Repressor Proteins; Sequence Alignment; Steroid Hydroxylases; Transcription, Genetic; Two-Hybrid System Techniques; Vitamin D3 24-Hydroxylase
PubMed: 19098224
DOI: 10.1210/me.2008-0426 -
Molecular and Cellular Biology May 2005The expression of the glutathione S-transferase gene (GST), whose induction accounts for cancer chemoprevention, is regulated by activation of CCAAT/enhancer binding...
The expression of the glutathione S-transferase gene (GST), whose induction accounts for cancer chemoprevention, is regulated by activation of CCAAT/enhancer binding protein beta (C/EBPbeta) and NF-E2-related factor 2 (Nrf2). The present study investigated the repressing effects of activating glucocorticoid receptor (GR) on C/EBPbeta- and Nrf2-mediated GSTA2 gene induction and the mechanism. Dexamethasone that activates GR inhibited constitutive and oltipraz- or tert-butylhydroquinone (t-BHQ)-inducible GSTA2 expression in H4IIE cells. Also, dexamethasone repressed GSTA2 promoter-luciferase gene activity. Dexamethasone-GR activation did not inhibit nuclear translocation of C/EBPbeta or Nrf2 nor their DNA binding activities induced by oltipraz or t-BHQ. Deletion of the glucocorticoid response element (GRE) in the GSTA2 promoter abolished dexamethasone inhibition of the gene induction. Immunoprecipitation-immunoblotting, chromatin immunoprecipitation, and GST pull-down assays revealed that silencing mediator for retinoid and thyroid hormone receptors (SMRT), a corepressor recruited to steroid-GR complex for histone deacetylation, bound to TAD domain of C/EBPbeta and Neh4/5 domain of Nrf2. The GSTA2 promoter-luciferase activities were decreased by SMRT but not by truncated SMRTs. The small interference RNA (siRNA) against SMRT abolished SMRT repression of the gene induction by C/EBPbeta or Nrf2. The plasmid transfection and siRNA experiments directly evidenced the functional role of SMRT in GSTA2 repression. In conclusion, dexamethasone antagonizes C/EBPbeta- and Nrf2-mediated GSTA2 gene induction via ligand-GR binding to the GRE, and steroid-mediated GSTA2 repression involves inactivation of C/EBPbeta and Nrf2 by SMRT recruited to steroid-GR complex.
Topics: Acetylation; Animals; Binding Sites; CCAAT-Enhancer-Binding Protein-beta; Cell Line; DNA-Binding Proteins; Dexamethasone; Down-Regulation; Glutathione Transferase; Histones; Isoenzymes; Mice; NF-E2-Related Factor 2; Nuclear Receptor Co-Repressor 2; Promoter Regions, Genetic; Protein Binding; Rats; Receptors, Glucocorticoid; Repressor Proteins; Response Elements; Trans-Activators
PubMed: 15870285
DOI: 10.1128/MCB.25.10.4150-4165.2005 -
Proceedings of the National Academy of... Oct 2018Nuclear hormone receptors (NRs), such as retinoic acid receptors (RARs), play critical roles in vertebrate development and homeostasis by regulating target gene...
Nuclear hormone receptors (NRs), such as retinoic acid receptors (RARs), play critical roles in vertebrate development and homeostasis by regulating target gene transcription. Their activity is controlled by ligand-dependent release of corepressors and subsequent recruitment of coactivators, but how these individual receptor modes contribute to development are unknown. Here, we show that mice carrying targeted knockin mutations in the corepressor Silencing Mediator of Retinoid and Thyroid hormone receptor (SMRT) that specifically disable SMRT function in NR signaling (SMRT), display defects in cranial neural crest cell-derived structures and posterior homeotic transformations of axial vertebrae. SMRT embryos show enhanced transcription of RAR targets including Hox loci, resulting in respecification of vertebral identities. Up-regulated histone acetylation and decreased H3K27 methylation are evident in the Hox loci whose somitic expression boundaries are rostrally shifted. Furthermore, enhanced recruitment of super elongation complex is evident in rapidly induced non-Pol II-paused targets in SMRT embryonic stem cells. These results demonstrate that SMRT-dependent repression of RAR is critical to establish and maintain the somitic Hox code and segmental identity during fetal development via epigenetic marking of target loci.
Topics: Animals; Antineoplastic Agents; Gene Expression Regulation; Genes, Homeobox; Mice; Mice, Inbred C57BL; Neural Crest; Nuclear Receptor Co-Repressor 2; Somites; Transcription, Genetic; Tretinoin
PubMed: 30254164
DOI: 10.1073/pnas.1809480115 -
Lab on a Chip Jun 2013Recent developments on various lab-on-a-chip techniques allow miniaturized and integrated devices to perform on-chip single-molecule studies. Fluidic-based platforms...
Recent developments on various lab-on-a-chip techniques allow miniaturized and integrated devices to perform on-chip single-molecule studies. Fluidic-based platforms that utilize unique microscale fluidic behavior are capable of conducting single-molecule experiments with high sensitivities and throughputs, while biomolecular systems can be studied on-chip using techniques such as DNA curtains, magnetic tweezers, and solid-state nanopores. The advances of these on-chip single-molecule techniques lead to next-generation lab-on-a-chip devices, such as DNA transistors, and single-molecule real-time (SMRT) technology for rapid and low-cost whole genome DNA sequencing. In this Focus article, we will discuss some recent successes in the development of lab-on-a-chip techniques for single-molecule studies and expound our thoughts on the near future of on-chip single-molecule studies.
Topics: DNA; DNA Helicases; Lab-On-A-Chip Devices; Magnetics; Microfluidic Analytical Techniques; Miniaturization; Nanopores; Polymerase Chain Reaction; Protein Binding
PubMed: 23670195
DOI: 10.1039/c3lc90042h -
Proceedings of the National Academy of... Feb 2011The ligand-dependent competing actions of nuclear receptor (NR)-associated transcriptional corepressor and coactivator complexes allow for the precise regulation of...
The ligand-dependent competing actions of nuclear receptor (NR)-associated transcriptional corepressor and coactivator complexes allow for the precise regulation of NR-dependent gene expression in response to both temporal and environmental cues. Here we report the mouse model termed silencing mediator of retinoid and thyroid hormone receptors (SMRT)(mRID1) in which targeted disruption of the first receptor interaction domain (RID) of the nuclear corepressor SMRT disrupts interactions with a subset of NRs and leads to diet-induced superobesity associated with a depressed respiratory exchange ratio, decreased ambulatory activity, and insulin resistance. Although apparently normal when chow fed, SMRT(mRID1) mice develop multiple metabolic dysfunctions when challenged by a high-fat diet, manifested by marked lipid accumulation in white and brown adipose tissue and the liver. The increased weight gain of SMRT(mRID1) mice on a high-fat diet occurs predominantly in fat with adipocyte hypertrophy evident in both visceral and s.c. depots. Importantly, increased inflammatory gene expression was detected only in the visceral depots. SMRT(mRID1) mice are both insulin-insensitive and refractory to the glucose-lowering effects of TZD and AICAR. Increased serum cholesterol and triglyceride levels were observed, accompanied by increased leptin and decreased adiponectin levels. Aberrant storage of lipids in the liver occurred as triglycerides and cholesterol significantly compromised hepatic function. Lipid accumulation in brown adipose tissue was associated with reduced thermogenic capacity and mitochondrial biogenesis. Collectively, these studies highlight the essential role of NR corepressors in maintaining metabolic homeostasis and describe an essential role for SMRT in regulating the progression, severity, and therapeutic outcome of metabolic diseases.
Topics: Adipose Tissue; Animals; Diet; Homeostasis; Insulin Resistance; Lipid Metabolism; Liver; Mice; Nuclear Receptor Co-Repressor 2; Obesity; Oxidative Phosphorylation
PubMed: 21300871
DOI: 10.1073/pnas.1017707108