scholarly journals Liver X Receptor Ligands Suppress Ubiquitination and Degradation of LXRα by Displacing BARD1/BRCA1

2009 ◽  
Vol 23 (4) ◽  
pp. 466-474 ◽  
Author(s):  
Kang Ho Kim ◽  
Jeong Min Yoon ◽  
A Hyun Choi ◽  
Woo Sik Kim ◽  
Gha Young Lee ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Target Gene ◽  
Target Genes ◽  
Cancer Susceptibility ◽  
Liver X Receptor ◽  
Lipid Homeostasis ◽  
Gene Promoters ◽  
Receptor Ligands ◽  
Ubiquitin E3 Ligase ◽  
Ligand Free

Abstract Liver X receptor (LXR) is a ligand-activated transcription factor that plays important roles in cholesterol and lipid homeostasis. However, ligand-induced posttranslational modification of LXR is largely unknown. Here, we show that ligand-free LXRα is rapidly degraded by ubiquitination. Without ligand, LXRα interacts with an ubiquitin E3-ligase protein complex containing breast and ovarian cancer susceptibility 1 (BRCA1)-associated RING domain 1 (BARD1). Interestingly, LXR ligand represses ubiquitination and degradation of LXRα, and the interaction between LXRα and BARD1 is inhibited by LXR ligand. Consistently, T0901317, a synthetic LXR ligand, increased the level of LXRα protein in liver. Moreover, overexpression of BARD1/BRCA1 promoted the ubiquitination of LXRα and reduced the recruitment of LXRα to the target gene promoters, whereas BARD1 knockdown reversed such effects. Taken together, these data suggest that LXR ligand prevents LXRα from ubiquitination and degradation by detaching BARD1/BRCA1, which might be critical for the early step of transcriptional activation of ligand-stimulated LXRα through a stable binding of LXRα to the promoters of target genes.

scholarly journals Target Gene Specificity of E2F and Pocket Protein Family Members in Living Cells

2000 ◽  
Vol 20 (16) ◽  
pp. 5797-5807 ◽  
Author(s):  
Julie Wells ◽  
Kathryn E. Boyd ◽  
Christopher J. Fry ◽  
Stephanie M. Bartley ◽  
Peggy J. Farnham
Keyword(s):  
Cell Cycle ◽  
Target Gene ◽  
Target Genes ◽  
Protein Complexes ◽  
Current Model ◽  
Family Members ◽  
Living Cells ◽  
Gene Promoters ◽  
Pocket Protein ◽  
Protein Dna Interactions

ABSTRACT E2F-mediated transcription is thought to involve binding of an E2F-pocket protein complex to promoters in the G0 phase of the cell cycle and release of the pocket protein in late G1, followed by release of E2F in S phase. We have tested this model by monitoring protein-DNA interactions in living cells using a formaldehyde cross-linking and immunoprecipitation assay. We find that E2F target genes are bound by distinct E2F-pocket protein complexes which change as cells progress through the cell cycle. We also find that certain E2F target gene promoters are bound by pocket proteins when such promoters are transcriptionally active. Our data indicate that the current model applies only to certain E2F target genes and suggest that Rb family members may regulate transcription in both G0 and S phases. Finally, we find that a given promoter can be bound by one of several different E2F-pocket protein complexes at a given time in the cell cycle, suggesting that cell cycle-regulated transcription is a stochastic, not a predetermined, process.

scholarly journals Regulation of Poly(ADP-ribose) Polymerase-1-dependent Gene Expression through Promoter-directed Recruitment of a Nuclear NAD+ Synthase

2012 ◽  
Vol 287 (15) ◽  
pp. 12405-12416 ◽  
Author(s):  
Tong Zhang ◽  
Jhoanna G. Berrocal ◽  
Jie Yao ◽  
Michelle E. DuMond ◽  
Raga Krishnakumar ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Target Gene ◽  
Target Genes ◽  
Enzymatic Activities ◽  
Gene Promoters ◽  
Protein Coding ◽  
Photon Excitation ◽  
Gene Sets ◽  
Cellular Compartments ◽  
Parp 1

NMNAT-1 and PARP-1, two key enzymes in the NAD+ metabolic pathway, localize to the nucleus where integration of their enzymatic activities has the potential to control a variety of nuclear processes. Using a variety of biochemical, molecular, cell-based, and genomic assays, we show that NMNAT-1 and PARP-1 physically and functionally interact at target gene promoters in MCF-7 cells. Specifically, we show that PARP-1 recruits NMNAT-1 to promoters where it produces NAD+ to support PARP-1 catalytic activity, but also enhances the enzymatic activity of PARP-1 independently of NAD+ production. Furthermore, using two-photon excitation microscopy, we show that NMNAT-1 catalyzes the production of NAD+ in a nuclear pool that may be distinct from other cellular compartments. In expression microarray experiments, depletion of NMNAT-1 or PARP-1 alters the expression of about 200 protein-coding genes each, with about 10% overlap between the two gene sets. NMNAT-1 enzymatic activity is required for PARP-1-dependent poly(ADP-ribosyl)ation at the promoters of commonly regulated target genes, as well as the expression of those target genes. Collectively, our studies link the enzymatic activities of NMNAT-1 and PARP-1 to the regulation of a set of common target genes through functional interactions at target gene promoters.

scholarly journals Transcriptional Inhibitors Identified in a 160,000-Compound Small-Molecule DUX4 Viability Screen

2016 ◽  
Vol 21 (7) ◽  
pp. 680-688 ◽  
Author(s):  
Si Ho Choi ◽  
Darko Bosnakovski ◽  
Jessica M. Strasser ◽  
Erik A. Toso ◽  
Michael A. Walters ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Muscular Dystrophy ◽  
Transcriptional Activation ◽  
Target Gene ◽  
Target Genes ◽  
Facioscapulohumeral Muscular Dystrophy ◽  
Oxidative Stress Pathway ◽  
Nonspecific Effects ◽  
Stress Pathway ◽  
Mouse Myoblast

Facioscapulohumeral muscular dystrophy is a genetically dominant, currently untreatable muscular dystrophy. It is caused by mutations that enable expression of the normally silent DUX4 gene, which encodes a pathogenic transcription factor. A screen based on Tet-on DUX4-induced mouse myoblast death previously uncovered compounds from a 44,000-compound library that protect against DUX4 toxicity. Many of those compounds acted downstream of DUX4 in an oxidative stress pathway. Here, we extend this screen to an additional 160,000 compounds and, using greater stringency, identify a new set of DUX4-protective compounds. From 640 hits, we performed secondary screens, repurchased 46 of the most desirable, confirmed activity, and tested each for activity against other cell death–inducing insults. The majority of these compounds also protected against oxidative stress. Of the 100 repurchased compounds identified through both screens, only SHC40, 75, and 98 inhibited DUX4 target genes, but they also inhibited dox-mediated DUX4 expression. Using a target gene readout on the 640-compound hit set, we discovered three overlooked compounds, SHC351, 540, and 572, that inhibit DUX4 target gene upregulation without nonspecific effects on the Tet-on system. These novel inhibitors of DUX4 transcriptional activity may thus act on pathways or cofactors needed by DUX4 for transcriptional activation in these cells.

scholarly journals Coactivation of Estrogen Receptor β by Gonadotropin-Induced Cofactor GIOT-4

2008 ◽  
Vol 29 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Madoka Kouzu-Fujita ◽  
Yoshihiro Mezaki ◽  
Shun Sawatsubashi ◽  
Takahiro Matsumoto ◽  
Ikuko Yamaoka ◽  
...  
Keyword(s):  
Target Gene ◽  
Target Genes ◽  
Gene Promoters ◽  
Ovulatory Cycle ◽  
Independent Manner ◽  
Ovarian Granulosa Cell ◽  
Transcriptional Regulatory Mechanism ◽  
Transcriptional Regulatory ◽  
Specific Stage ◽  
Regulatory Convergence

ABSTRACT Estrogen exerts its diverse effects through two subtypes of estrogen receptors (ER), ERα and ERβ. Each subtype has its own distinct function and expression pattern in its target tissues. Little, however, is known about the transcriptional regulatory mechanism of ERβ in the major ERβ-expressing tissues. Using biochemical methods, we identified and described a novel ERβ coactivator. This protein, designated GIOT-4, was biochemically purified from 293F cells. It coactivated ERβ in ovarian granulosa cells. GIOT-4 expression was induced by stimulation with follicle-stimulating hormone (FSH). GIOT-4 recruited an SWI/SNF-type complex in a ligand-independent manner to ERβ as an ER subtype-specific physical bridging factor and induced subsequent histone modifications in the ERβ target gene promoters in a human ovarian granulosa cell line (KGN). Indeed, two ERβ-specific target genes were upregulated by FSH at a specific stage of a normal ovulatory cycle in intact mice. These findings imply the presence of a novel regulatory convergence between the gonadotropin signaling cascade and ERβ-mediated transcription in the ovary.

scholarly journals Enhancer-bound LDB1 regulates a corticotrope promoter-pausing repression program

2015 ◽  
Vol 112 (5) ◽  
pp. 1380-1385 ◽  
Author(s):  
Feng Zhang ◽  
Bogdan Tanasa ◽  
Daria Merkurjev ◽  
Chijen Lin ◽  
Xiaoyuan Song ◽  
...  
Keyword(s):  
Target Gene ◽  
Target Genes ◽  
Binding Protein ◽  
Homeodomain Protein ◽  
Gene Promoters ◽  
Cell Type ◽  
Lim Domain ◽  
Transcriptional Initiation ◽  
Nucleosome Remodeling ◽  
Enhancer Binding Protein

Substantial evidence supports the hypothesis that enhancers are critical regulators of cell-type determination, orchestrating both positive and negative transcriptional programs; however, the basic mechanisms by which enhancers orchestrate interactions with cognate promoters during activation and repression events remain incompletely understood. Here we report the required actions of LIM domain-binding protein 1 (LDB1)/cofactor of LIM homeodomain protein 2/nuclear LIM interactor, interacting with the enhancer-binding protein achaete-scute complex homolog 1, to mediate looping to target gene promoters and target gene regulation in corticotrope cells. LDB1-mediated enhancer:promoter looping appears to be required for both activation and repression of these target genes. Although LDB1-dependent activated genes are regulated at the level of transcriptional initiation, the LDB1-dependent repressed transcription units appear to be regulated primarily at the level of promoter pausing, with LDB1 regulating recruitment of metastasis-associated 1 family, member 2, a component of the nucleosome remodeling deacetylase complex, on these negative enhancers, required for the repressive enhancer function. These results indicate that LDB1-dependent looping events can deliver repressive cargo to cognate promoters to mediate promoter pausing events in a pituitary cell type.

scholarly journals Phosphorylation of Liver X Receptor α Selectively Regulates Target Gene Expression in Macrophages

2008 ◽  
Vol 28 (8) ◽  
pp. 2626-2636 ◽  
Author(s):  
Inés Pineda Torra ◽  
Naima Ismaili ◽  
Jonathan E. Feig ◽  
Chong-Feng Xu ◽  
Claudio Cavasotto ◽  
...  
Keyword(s):  
Target Gene ◽  
Target Genes ◽  
Metabolic Diseases ◽  
Liver X Receptor ◽  
Raw 264.7 Cells ◽  
Raw 264.7 ◽  
Deficient Mutant ◽  
Liver X Receptor Α ◽  
Ck2 Inhibitors ◽  
Ck2 Inhibitor

ABSTRACT Dysregulation of liver X receptor α (LXRα) activity has been linked to cardiovascular and metabolic diseases. Here, we show that LXRα target gene selectivity is achieved by modulation of LXRα phosphorylation. Under basal conditions, LXRα is phosphorylated at S198; phosphorylation is enhanced by LXR ligands and reduced both by casein kinase 2 (CK2) inhibitors and by activation of its heterodimeric partner RXR with 9-cis-retinoic acid (9cRA). Expression of some (AIM and LPL), but not other (ABCA1 or SREBPc1) established LXR target genes is increased in RAW 264.7 cells expressing the LXRα S198A phosphorylation-deficient mutant compared to those with WT receptors. Surprisingly, a gene normally not expressed in macrophages, the chemokine CCL24, is activated specifically in cells expressing LXRα S198A. Furthermore, inhibition of S198 phosphorylation by 9cRA or by a CK2 inhibitor similarly promotes CCL24 expression, thereby phenocopying the S198A mutation. Thus, our findings reveal a previously unrecognized role for phosphorylation in restricting the repertoire of LXRα-responsive genes.

scholarly journals Peroxisome Proliferator-Activated Receptor γ Target Gene Encoding a Novel Angiopoietin-Related Protein Associated with Adipose Differentiation

2000 ◽  
Vol 20 (14) ◽  
pp. 5343-5349 ◽  
Author(s):  
J. Cliff Yoon ◽  
Troy W. Chickering ◽  
Evan D. Rosen ◽  
Barry Dussault ◽  
Yubin Qin ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Time Course ◽  
Target Gene ◽  
Target Genes ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Isolation And Characterization ◽  
Adipose Differentiation ◽  
Novel Target

ABSTRACT The nuclear receptor peroxisome proliferator-activated receptor γ regulates adipose differentiation and systemic insulin signaling via ligand-dependent transcriptional activation of target genes. However, the identities of the biologically relevant target genes are largely unknown. Here we describe the isolation and characterization of a novel target gene induced by PPARγ ligands, termed PGAR (for PPARγ angiopoietin related), which encodes a novel member of the angiopoietin family of secreted proteins. The transcriptional induction of PGAR follows a rapid time course typical of immediate-early genes and occurs in the absence of protein synthesis. The expression of PGAR is predominantly localized to adipose tissues and placenta and is consistently elevated in genetic models of obesity. Hormone-dependent adipocyte differentiation coincides with a dramatic early induction of the PGAR transcript. Alterations in nutrition and leptin administration are found to modulate the PGAR expression in vivo. Taken together, these data suggest a possible role for PGAR in the regulation of systemic lipid metabolism or glucose homeostasis.

scholarly journals Direct Protein Interactions Are Responsible for Ikaros-GATA and Ikaros-Cdk9 Cooperativeness in Hematopoietic Cells

2013 ◽  
Vol 33 (16) ◽  
pp. 3064-3076 ◽  
Author(s):  
Stefania Bottardi ◽  
Lionel Mavoungou ◽  
Vincent Bourgoin ◽  
Nazar Mashtalir ◽  
El Bachir Affar ◽  
...  
Keyword(s):  
Zinc Finger ◽  
Protein Interactions ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Transcription Elongation ◽  
Hematopoietic Cells ◽  
Elongation Factor ◽  
Gene Promoters ◽  
Zinc Finger Domain

Ikaros (Ik) is a critical regulator of hematopoietic gene expression. Here, we established that the Ik interactions with GATA transcription factors and cyclin-dependent kinase 9 (Cdk9), a component of the positive transcription elongation factor b (P-TEFb), are required for transcriptional activation of Ik target genes. A detailed dissection of Ik-GATA and Ik-Cdk9 protein interactions indicated that the C-terminal zinc finger domain of Ik interacts directly with the C-terminal zinc fingers of GATA1, GATA2, and GATA3, whereas the N-terminal zinc finger domain of Ik is required for interaction with the kinase and T-loop domains of Cdk9. The relevance of these interactions was demonstratedin vivoin COS-7 and primary hematopoietic cells, in which Ik facilitated Cdk9 and GATA protein recruitment to gene promoters and transcriptional activation. Moreover, the oncogenic isoform Ik6 did not efficiently interact with Cdk9 or GATA proteinsin vivoand perturbed Cdk9/P-TEFb recruitment to Ik target genes, thereby affecting transcription elongation. Finally, characterization of a novel nuclear Ik isoform revealed that Ik exon 6 is dispensable for interactions with Mi2 and GATA proteins but is essential for the Cdk9 interaction. Thus, Ik is central to the Ik-GATA-Cdk9 regulatory network, which is broadly utilized for gene regulation in hematopoietic cells.

scholarly journals Unusual DNA-binding properties of the Arabidopsis thaliana WRKY50 transcription factor at target gene promoters

2020 ◽  
Author(s):  
Konstantin Kanofsky ◽  
Jendrik Rusche ◽  
Lea Eilert ◽  
Fabian Machens ◽  
Reinhard Hehl
Keyword(s):  
Dna Binding ◽  
Binding Site ◽  
Target Gene ◽  
Target Genes ◽  
Specific Binding ◽  
Gene Promoters ◽  
Molecular Pattern ◽  
High Flexibility ◽  
Site Recognition

Abstract Key message WRKY50 from A. thaliana requires WT-boxes at target gene promoters for activation and binding. Abstract Based on the genome-wide prediction of WRKY50 target genes and the similarity of a WRKY50 binding site to WT-boxes in microbe-associated molecular pattern (MAMP)-responsive cis-regulatory modules (CRM), four WT-box containing CRMs from the promoter region of three WRKY50 target genes were investigated for their interaction with WRKY50. These target genes are DJ1E, WRKY30 and ATBBE4. Two of the four CRMs, one from DJ1E and one from WRKY30, were able to activate reporter gene expression in the presence of WRKY50. Activation requires the WT-boxes GGACTTTT, GGACTTTG from DJ1E and GGACTTTC from WRKY30. WRKY50 does not activate a second CRM from WRKY30 and the CRM from ATBBE4, both containing the WT-box TGACTTTT. In vitro gel-shift assays demonstrate WT-box-specific binding of the WRKY50 DNA-binding domain to all four CRMs. This work shows a high flexibility of WRKY50 binding site recognition beyond the classic W-box TTGACC/T.

scholarly journals Physiological Significance of Reactive Cysteine Residues of Keap1 in Determining Nrf2 Activity

2008 ◽  
Vol 28 (8) ◽  
pp. 2758-2770 ◽  
Author(s):  
Tae Yamamoto ◽  
Takafumi Suzuki ◽  
Akira Kobayashi ◽  
Junko Wakabayashi ◽  
Jon Maher ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Target Genes ◽  
Cysteine Residue ◽  
Cysteine Residues ◽  
Transgenic Expression ◽  
Ubiquitin E3 Ligase ◽  
Nrf2 Activation ◽  
Before And After

ABSTRACT Keap1 and Cul3 constitute a unique ubiquitin E3 ligase that degrades Nrf2, a key activator of cytoprotective genes. Upon exposure to oxidants/electrophiles, the enzymatic activity of this ligase complex is inhibited and the complex fails to degrade Nrf2, resulting in the transcriptional activation of Nrf2 target genes. Keap1 possesses several reactive cysteine residues that covalently bond with electrophiles in vitro. To clarify the functional significance of each Keap1 cysteine residue under physiological conditions, we established a transgenic complementation rescue model. The transgenic expression of mutant Keap1(C273A) and/or Keap1(C288A) protein in Keap1 null mice failed to reverse constitutive Nrf2 activation, indicating that cysteine residues at positions 273 and 288 are essential for Keap1 to repress Nrf2 activity in vivo. In contrast, Keap1(C151S) retained repressor activity and mice expressing this molecule were viable. Mouse embryonic fibroblasts from Keap1(C151S) transgenic mice displayed decreased expression of Nrf2 target genes both before and after an electrophilic challenge, suggesting that Cys151 is important in facilitating Nrf2 activation. These results demonstrate critical roles of the cysteine residues in vivo in maintaining Keap1 function, such that Nrf2 is repressed under quiescent conditions and active in response to oxidants/electrophiles.

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