An extract from date palm fruit (Phoenix dactylifera) acts as a co-agonist ligand for the nuclear receptor FXR and differentially modulates FXR target-gene expression in vitro

Hedgehog (HH) is an important morphogen involved in pattern formation during Drosophila embryogenesis and disc development. cubitus interruptus (ci) encodes a transcription factor responsible for transducing the hh signal in the nucleus and activating hh target gene expression. Previous studies have shown that CI exists in two forms: a 75 kDa proteolytic repressor form and a 155 kDa activator form. The ratio of these forms, which is regulated positively by hh signaling and negatively by PKA activity, determines the on/off status of hh target gene expression. In this paper, we demonstrate that the exogenous expression of CI that is mutant for four consensus PKA sites [CI(m1-4)], causes ectopic expression of wingless (wg) in vivo and a phenotype consistent with wg overexpression. Expression of CI(m1-4), but not CI(wt), can rescue the hh mutant phenotype and restore wg expression in hh mutant embryos. When PKA activity is suppressed by expressing a dominant negative PKA mutant, the exogenous expression of CI(wt) results in overexpression of wg and lethality in embryogenesis, defects that are similar to those caused by the exogenous expression of CI(m1-4). In addition, we demonstrate that, in cell culture, the mutation of any one of the three serine-containing PKA sites abolishes the proteolytic processing of CI. We also show that PKA directly phosphorylates the four consensus phosphorylation sites in vitro. Taken together, our results suggest that positive hh and negative PKA regulation of wg gene expression converge on the regulation of CI phosphorylation.

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MicroRNA Mediated Changes in Drug Metabolism and Target Gene Expression by Efavirenz and Rifampicin In Vitro: Clinical Implications

OMICS A Journal of Integrative Biology ◽

10.1089/omi.2019.0122 ◽

2019 ◽

Vol 23 (10) ◽

pp. 496-507 ◽

Cited By ~ 3

Author(s):

Marelize Swart ◽

Collet Dandara

Keyword(s):

Gene Expression ◽

Drug Metabolism ◽

Target Gene ◽

Clinical Implications ◽

Target Gene Expression

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487 Correlations of in vitro chemosensitivity of solid tumors to Pemetrexed (P, ALIMTA®) and target gene expression

European Journal of Cancer Supplements ◽

10.1016/s1359-6349(04)80495-6 ◽

2004 ◽

Vol 2 (8) ◽

pp. 148-149

Author(s):

O. Oberschmidt ◽

U. Eismann ◽

M. Ehnert ◽

S. Struck ◽

J. Blatter ◽

...

Keyword(s):

Gene Expression ◽

Solid Tumors ◽

Target Gene ◽

Target Gene Expression ◽

In Vitro Chemosensitivity

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SAT-726 Estrogen Receptor Alpha as a Potential Target for Bisphenol A-Mediated Epigenetic Reprogramming: An in Vitro Analysis

Journal of the Endocrine Society ◽

10.1210/jendso/bvaa046.043 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

Author(s):

Morgan Gallo ◽

Lindsey S Treviño ◽

Tiffany A Katz

Keyword(s):

Gene Expression ◽

Target Gene ◽

Target Genes ◽

Hepatic Cell ◽

Time Points ◽

Target Gene Expression ◽

Er Alpha ◽

Hepatic Cell Lines ◽

Gene Expression Levels

Abstract Perinatal exposure to bisphenol A (BPA) has been shown to reprogram the hepatic epigenome of rodents and may promote the development of various metabolic diseases later in life, such as nonalcoholic fatty liver disease (NAFLD). This developmental reprogramming is characterized by the creation of “super promoters” at target genes implicated in metabolic pathways. While it is unclear how these “super promoters” are created, their creation is potentially mediated through BPA and estrogen receptor (ER) interaction. In order to test this potential mechanism, in vitro methods were used to examine ER target gene expression via RT-qPCR in 2 human hepatic cell lines transiently transfected with the ER isoform, ER alpha, prior to BPA exposure for various lengths of time. Within individual time points, there were no significant differences in target gene expression levels between cells that had been transfected with ER alpha and the vector control. Gene expression levels in the target genes were visibly increased at the 24-hour exposure mark in both transfection groups in comparison to the 0- and 6-hour time points, however only a fraction of these increases were found to be statistically significant. These gene expression patterns are not only consistent with previous studies examining target gene expression in BPA-treated hepatic cell lines, but more importantly, suggest BPA does not act via ER alpha to orchestrate the epigenetic changes seen in vitro. BPA may interact with a different ER isoform or an unknown target to create the observed “super promoters” at target genes, reinforcing the promiscuity of BPA and other xenoestrogens in facilitating epigenetic modifications, and ultimately, disease phenotypes.

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Pbx-Hox Heterodimers Recruit Coactivator-Corepressor Complexes in an Isoform-Specific Manner

Molecular and Cellular Biology ◽

10.1128/mcb.19.12.8219 ◽

1999 ◽

Vol 19 (12) ◽

pp. 8219-8225 ◽

Cited By ~ 101

Author(s):

Hiroshi Asahara ◽

Sanjoy Dutta ◽

Hung-Ying Kao ◽

Ronald M. Evans ◽

Marc Montminy

Keyword(s):

Gene Expression ◽

Dna Binding ◽

Cell Fate ◽

Target Gene ◽

Biological Action ◽

Binding Activity ◽

Creb Binding Protein ◽

Target Gene Expression

ABSTRACT Homeobox (hox) proteins have been shown to regulate cell fate and segment identity by promoting the expression of specific genetic programs. In contrast to their restricted biological action in vivo, however, most homeodomain factors exhibit promiscuous DNA binding properties in vitro, suggesting a requirement for additional cofactors that enhance target site selectivity. In this regard, thepbx family of homeobox genes has been found to heterodimerize with and thereby augment the DNA binding activity of certain hox proteins on a subset of potential target sites. Here we examine the transcriptional properties of a forcedhox-pbx heterodimer containing the pancreas-specific orphan homeobox factor pdx fused to pbx-1a. Compared to the pdx monomer, the forced pdx-pbx1a dimer, displayed 10- to 20-fold-higher affinity for a consensushox-pbx binding site but was completely unable to bind ahox monomer recognition site. The pdx-pbx dimer stimulated target gene expression via an N-terminaltrans-activation domain in pdx that interacts with the coactivator CREB binding protein. The pdx-pbxdimer was also found to repress transcription via a C-terminal domain in pbx-1a that associates with the corepressors SMRT and NCoR. The transcriptional properties of the pdx-pbx1complex appear to be regulated at the level of alternative splicing; apdx-pbx polypeptide containing the pbx1bisoform, which lacks the C-terminal extension in pbx1a, was unable to repress target gene expression via NCoR-SMRT. Sincepbx1a and pbx1b are differentially expressed in endocrine versus exocrine compartments of the adult pancreas, our results illustrate a novel mechanism by which pbx proteins may modulate the expression of specific genetic programs, either positively or negatively, during development.

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Alternative Mechanisms by Which Mediator Subunit MED1/TRAP220 Regulates Peroxisome Proliferator-Activated Receptor γ-Stimulated Adipogenesis and Target Gene Expression

Molecular and Cellular Biology ◽

10.1128/mcb.00967-07 ◽

2007 ◽

Vol 28 (3) ◽

pp. 1081-1091 ◽

Cited By ~ 65

Author(s):

Kai Ge ◽

Young-Wook Cho ◽

Hong Guo ◽

Teresa B. Hong ◽

Mohamed Guermah ◽

...

Keyword(s):

Gene Expression ◽

Rna Polymerase Ii ◽

Nuclear Receptor ◽

Transcriptional Activity ◽

Target Gene ◽

Molecular Mechanisms ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Cultured Fibroblasts ◽

Target Gene Expression

ABSTRACT Mediator is a general coactivator complex connecting transcription activators and RNA polymerase II. Recent work has shown that the nuclear receptor-interacting MED1/TRAP220 subunit of Mediator is required for peroxisome proliferator-activated receptor γ (PPARγ)-stimulated adipogenesis of mouse embryonic fibroblasts (MEFs). However, the molecular mechanisms remain undefined. Here, we show an intracellular PPARγ-Mediator interaction that requires the two LXXLL nuclear receptor recognition motifs on MED1/TRAP220 and, furthermore, we show that the intact LXXLL motifs are essential for optimal PPARγ function in a reconstituted cell-free transcription system. Surprisingly, a conserved N-terminal region of MED1/TRAP220 that lacks the LXXLL motifs but gets incorporated into Mediator fully supports PPARγ-stimulated adipogenesis. Moreover, in undifferentiated MEFs, MED1/TRAP220 is dispensable both for PPARγ-mediated target gene activation and for recruitment of Mediator to a PPAR response element on the aP2 target gene promoter. However, PPARγ shows significantly reduced transcriptional activity in cells deficient for a subunit (MED24/TRAP100) important for the integrity of the Mediator complex, indicating a general Mediator requirement for PPARγ function. These results indicate that there is a conditional requirement for MED1/TRAP220 and that a direct interaction between PPARγ and Mediator through MED1/TRAP220 is not essential either for PPARγ-stimulated adipogenesis or for PPARγ target gene expression in cultured fibroblasts. As Mediator is apparently essential for PPARγ transcriptional activity, our data indicate the presence of alternative mechanisms for Mediator recruitment, possibly through intermediate cofactors or other cofactors that are functionally redundant with MED1/TRAP220.

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Liver X Receptors Interact with Corepressors to Regulate Gene Expression

Molecular Endocrinology ◽

10.1210/me.2002-0399 ◽

2003 ◽

Vol 17 (6) ◽

pp. 1019-1026 ◽

Cited By ~ 99

Author(s):

Xiao Hu ◽

Suzhen Li ◽

Jun Wu ◽

Chunsheng Xia ◽

Deepak S. Lala

Keyword(s):

Gene Expression ◽

Nuclear Receptor ◽

Target Gene ◽

Critical Role ◽

Cholesterol Homeostasis ◽

Liver X Receptors ◽

Regulate Gene Expression ◽

Target Gene Expression ◽

X Receptors ◽

Regulate Gene

Abstract Liver X receptors (LXRs) are members of the nuclear receptor superfamily that regulate gene expression in response to oxysterols and play a critical role in cholesterol homeostasis by regulating genes that are involved in cholesterol transport, catabolism, and triglyceride synthesis. Oxysterols and synthetic agonists bind LXRs and activate transcription by recruiting coactivator proteins. The role of LXRs in regulating target gene expression in the absence of ligand is unknown. Here we show that LXRs interact with corepressors, N-CoR (nuclear receptor corepressor) and SMRT (silent mediator of retinoic acid receptor and thyroid receptor), which are released upon binding agonists. The LXR-corepressor interaction is isoform selective, wherein LXRα has a very strong interaction with corepressors and LXRβ only shows weak interaction. LXRs also exhibit a preference for interacting with N-CoR vs. SMRT. Similar to other nuclear receptors, mutations in the LXR helix 3 and 4 region abolish corepressor interaction. Using a transient transfection assay, we demonstrate that LXR represses transcription that can be further increased by cotransfecting N-CoR into cells. Chromatin immunoprecipitation experiments further indicated that N-CoR is recruited onto endogenous LXR target genes, and addition of LXR agonists releases N-CoR from their promoters. Collectively, these results suggest that corepressors play an important role in regulating LXR target gene expression.

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Dfrizzled-3, a new Drosophila Wnt receptor, acting as an attenuator of Wingless signaling in wingless hypomorphic mutants

Development ◽

10.1242/dev.126.20.4421 ◽

1999 ◽

Vol 126 (20) ◽

pp. 4421-4430 ◽

Cited By ~ 8

Author(s):

A. Sato ◽

T. Kojima ◽

K. Ui-Tei ◽

Y. Miyata ◽

K. Saigo

Keyword(s):

Gene Expression ◽

Target Gene ◽

Beta Catenin ◽

Immunochemical Analysis ◽

Target Gene Expression ◽

The Third ◽

Wingless Signaling ◽

Morphological Defects ◽

Drosophila Cells

In Drosophila, two Frizzled proteins, Frizzled and Dfrizzled-2, have been reported to serve as receptors of Wingless. Here, we identified the third member of the Drosophila Frizzled family (Dfrizzled-3). In contrast to Dfrizzled-2, Dfrizzled-3 was transcriptionally upregulated by Wingless signaling. Although Dfrizzled-3 was capable of binding to Wingless in vitro, Wingless-dependent Armadillo/beta -catenin stabilization occurred much less effectively in Drosophila cells transfected with Dfrizzled-3 than in those with Dfrizzled-2. Flies lacking Dfrizzled-3 activity were viable and fertile, with few morphological defects. Genetic and immunochemical analysis indicated that the absence of Dfrizzled-3 activity suppresses the effects of hypomorphic wingless mutations such as failure of wing and antenna formation and restores target gene expression to the normal levels without change in wingless expression. Wingless signaling may thus be attenuated by Dfrizzled-3 at least in wingless hypomorphic mutants.

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