Transcriptional activation of the cholesterol 7alpha-hydroxylase gene (CYP7A) by nuclear hormone receptors.
Animals; Rats; Transcription Factors/metabolism; Base Sequence; Molecular Sequence Data; DNA/metabolism; Cholesterol 7-alpha-Hydroxylase/*genetics; Hepatocyte Nuclear Factor 4; Mutagenesis; Luciferases/genetics; Retinoid X Receptors; Phosphoproteins/metabolism; COUP Transcription Factor II; COUP Transcription Factors; *Transcriptional Activation; Bile Acids and Salts/biosynthesis; DNA-Binding Proteins/metabolism; Hormones/*physiology; Oligonucleotide Probes/metabolism; Genes; Cultured; Receptors; Genetic; Cytoplasmic and Nuclear/*physiology; Tumor Cells; Reporter; Retinoic Acid/metabolism; Promoter Regions; Nucleic Acid; Site-Directed; *Receptors; Repetitive Sequences; Steroid
The gene encoding cholesterol 7alpha-hydroxylase (CYP7A), the rate-limiting enzyme in bile acid synthesis, is transcriptionally regulated by bile acids and hormones. Previously, we have identified two bile acid response elements (BARE) in the promoter of the CYP7A gene. The BARE II is located in nt -149/-118 region and contains three hormone response element (HRE)-like sequences that form two overlapping nuclear receptor binding sites. One is a direct repeat separated by one nucleotide DR1 (-146- TGGACTtAGTTCA-134) and the other is a direct repeat separated by five nucleotides DR5 (-139-AGTTCAaggccGGG TAA-123). Mutagenesis of these HRE sequences resulted in lower transcriptional activity of the CYP7A promoter/reporter genes in transient transfection assay in HepG2 cells. The orphan nuclear receptor, hepatocyte nuclear factor 4 (HNF-4)1, binds to the DR1 sequence as assessed by electrophoretic mobility shift assay, and activates the CYP7A promoter/reporter activity by about 9-fold. Cotransfection of HNF-4 plasmid with another orphan nuclear receptor, chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), synergistically activated the CYP7A transcription by 80-fold. The DR5 binds the RXR/RAR heterodimer. A hepatocyte nuclear factor-3 (HNF-3) binding site (-175-TGTTTGTTCT-166) was identified. HNF-3 was required for both basal transcriptional activity and stimulation of the rat CYP7A promoter activity by retinoic acid. Combinatorial interactions and binding of these transcription factors to BAREs may modulate the promoter activity and also mediate bile acid repression of CYP7A gene transcription.
Crestani M; Sadeghpour A; Stroup D; Galli G; Chiang J Y
Journal of lipid research
1998
1998-11
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Multiple signals induce endoplasmic reticulum stress in both primary and immortalized chondrocytes resulting in loss of differentiation, impaired cell growth, and apoptosis.
Animals; Annexin A5/metabolism; Anti-Bacterial Agents/metabolism; Apoptosis/*physiology; Biomarkers; Caspase 12; Caspases/metabolism; CCAAT-Enhancer-Binding Proteins/metabolism; Cell Differentiation/*physiology; Cells; Chondrocytes/cytology/*physiology; Collagen Type II/metabolism; Cultured; DNA Fragmentation; Endoplasmic Reticulum/*metabolism; Extracellular Matrix/metabolism; Gene Expression Regulation; Glucose/metabolism; Proliferating Cell Nuclear Antigen/metabolism; Rats; Signal Transduction/*physiology; Thapsigargin/metabolism; Transcription Factor CHOP; Transcription Factors/metabolism; Tunicamycin/metabolism
The endoplasmic reticulum is the site of synthesis and folding of secretory proteins and is sensitive to changes in the internal and external environment of the cell. Both physiological and pathological conditions may perturb the function of the endoplasmic reticulum, resulting in endoplasmic reticulum stress. The chondrocyte is the only resident cell found in cartilage and is responsible for synthesis and turnover of the abundant extracellular matrix and may be sensitive to endoplasmic reticulum stress. Here we report that glucose withdrawal, tunicamycin, and thapsigargin induce up-regulation of GADD153 and caspase-12, two markers of endoplasmic reticulum stress, in both primary chondrocytes and a chondrocyte cell line. Other agents such as interleukin-1beta or tumor necrosis factor alpha induced a minimal or no induction of GADD153, respectively. The endoplasmic reticulum stress resulted in decreased chondrocyte growth based on cell counts, up-regulation of p21, and decreased PCNA expression. In addition, perturbation of endoplasmic reticulum function resulted in decreased accumulation of an Alcian Blue positive matrix by chondrocytes and decreased expression of type II collagen at the protein level. Further, quantitative real-time PCR was used to demonstrate a down-regulation of steady state mRNA levels coding for aggrecan, collagen II, and link protein in chondrocytes exposed to endoplasmic reticulum stress-inducing conditions. Ultimately, endoplasmic reticulum stress resulted in chondrocyte apoptosis, as evidenced by DNA fragmentation and annexin V staining. These findings have potentially important implications regarding consequences of endoplasmic reticulum stress in cartilage biology.
Yang Ling; Carlson Sara G; McBurney Denise; Horton Walter E Jr
The Journal of biological chemistry
2005
2005-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1074/jbc.M501069200" target="_blank" rel="noreferrer noopener">10.1074/jbc.M501069200</a>
Valproate increases dopamine transporter expression through histone acetylation and enhanced promoter binding of Nurr1.
Acetylation/drug effects; Animals; Butyrates/pharmacology; Cell Line; Cell Survival/drug effects; Dopamine Plasma Membrane Transport Proteins/*metabolism; Dopamine transporter; Dopaminergic Neurons/cytology/drug effects/metabolism; Dose-Response Relationship; Drug; Epigenesis; Epigenetics; Genetic; Genetic/drug effects; Group A; HDAC; Histone deacetylase; Histone Deacetylase Inhibitors/*pharmacology; Histone Deacetylases/metabolism; Histones/*drug effects/metabolism; Homeodomain Proteins/metabolism; Hydroxamic Acids/pharmacology; Member 2/*metabolism; Messenger/metabolism; Nuclear Receptor Subfamily 4; Nurr1; Pitx3; Promoter Regions; Rats; RNA; Transcription Factors/metabolism; Valproate; Valproic Acid/*pharmacology
The dopamine transporter (DAT) is the key regulator of dopaminergic transmission and is a target of several xenobiotics, including pesticides and pharmacological agents. Previously, we identified a prominent role for histone deacetylases in the regulation of DAT expression. Here, we utilized a rat dopaminergic cell line (N27) to probe the responsiveness of DAT mRNA expression to inhibitors of histone acetylation. Inhibition of histone deacetylases (HDACs) by valproate, butyrate and Trichostatin A led to a 3-10-fold increase in DAT mRNA expression, a 50% increase in protein levels, which were accompanied by increased H3 acetylation levels. To confirm the mechanism of valproate-mediated increase in DAT mRNA, chromatin immunoprecipitation (ChIP) assays were used and demonstrated a significant increase in enrichment of acetylation of histone 3 on lysines 9 and 14 (H3K9/K14ac) in the DAT promoter. Expression of Nurr1 and Pitx3, key regulators of DAT expression, were increased following valproate treatment and Nurr1 binding was enriched in the DAT promoter. Together, these results indicate that histone acetylation and subsequent enhancement of transcription factor binding are plausible mechanisms for DAT regulation by valproate and, perhaps, by other xenobiotics.
Green Ashley L; Zhan Le; Eid Aseel; Zarbl Helmut; Guo Grace L; Richardson Jason R
Neuropharmacology
2017
2017-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.neuropharm.2017.07.020" target="_blank" rel="noreferrer noopener">10.1016/j.neuropharm.2017.07.020</a>
Promoter activity and regulation of the CYP4F2 leukotriene B(4) omega-hydroxylase gene by peroxisomal proliferators and retinoic acid in HepG2 cells.
*Gene Expression Regulation; *Promoter Regions; Amino Acid Sequence; Base Sequence; Cell Line; Cloning; Cytochrome P-450 CYP4A; Cytochrome P-450 Enzyme System/*genetics/metabolism; Cytochrome P450 Family 4; Cytoplasmic and Nuclear/metabolism; DNA; DNA Footprinting; Enzymologic; Exons; Genes; Genetic; Genetic/drug effects; Humans; Introns; Leukotriene B4/metabolism; Mixed Function Oxygenases/metabolism; Models; Molecular; Molecular Sequence Data; Peroxisome Proliferators/*metabolism; Receptors; Reporter; Retinoic Acid Receptor alpha; Retinoic Acid/metabolism; Sequence Analysis; Transcription; Transcription Factors/metabolism; Transfection; Tretinoin/*metabolism
The human liver CYP4F2 gene (Accession No. AF221943) encodes a leukotriene B(4) omega-hydroxylase that metabolizes leukotriene B(4) (LTB(4)) to a less potent proinflammatory eicosanoid, 20-OH-LTB(4). We sequenced a 6.7-kb genomic fragment of the human CYP4F2 gene that has the first five exons and 500 bp of the 5'-flanking region. The major transcription start site was found to be 49 bp upstream of the 3' end of exon 1 and the ATG translation initiation codon was located in exon 2. Besides the TATA box at -39 bp and basal transcription factor binding sites, the promoter region and 412-bp intron 1 have several putative binding sites for nuclear factors that may mediate the inflammatory response and lipid homeostasis. We found two DR1 elements in the 5' promoter, a DR2 element in intron 1, and RXR/RAR binding sites in both intron 1 and the 5' promoter. DNase I footprinting revealed three protected sequences, with the region containing two CAATT boxes at -71 and -111 bp important in CYP4F2 gene expression. Luciferase reporter assays showed that the 500-bp upstream sequence has strong promoter activity. Transient transfection experiments identified two sites in the 5' promoter and intron 1 that cooperate in gene transcription while exon 1 and a
Zhang X; Chen L; Hardwick J P
Archives of biochemistry and biophysics
2000
2000-06
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1006/abbi.2000.1836" target="_blank" rel="noreferrer noopener">10.1006/abbi.2000.1836</a>
Bile acids activate fibroblast growth factor 19 signaling in human hepatocytes to inhibit cholesterol 7alpha-hydroxylase gene expression.
Butadienes/pharmacology; Carcinoma; Cell Line; Chenodeoxycholic Acid/*pharmacology; Cholesterol 7-alpha-Hydroxylase/*biosynthesis; Cytoplasmic and Nuclear/metabolism/physiology; DNA-Binding Proteins/metabolism; Fibroblast Growth Factor; Fibroblast Growth Factors/drug effects/*physiology; Gene Expression/drug effects; Hepatocellular/metabolism; Hepatocytes/metabolism; Humans; Isoxazoles/pharmacology; Mitogen-Activated Protein Kinase 1/metabolism; Mitogen-Activated Protein Kinase 3/metabolism; Nitriles/pharmacology; Receptor; Receptors; Signal Transduction/drug effects; Transcription Factors/metabolism; Tumor; Type 4/antagonists & inhibitors
UNLABELLED: Mouse fibroblast growth factor 15 (FGF15) and human ortholog FGF19 have been identified as the bile acid-induced intestinal factors that mediate bile acid feedback inhibition of cholesterol 7alpha-hydroxylase gene (C YP7A1) transcription in mouse liver. The mechanism underlying FGF15/FGF19 inhibition of bile acid synthesis in hepatocytes remains unclear. Chenodeoxycholic acid (CDCA) and the farnesoid X receptor (FXR)-specific agonist GW4064 strongly induced FGF19 but inhibited CYP7A1 messenger RNA (mRNA) levels in primary human hepatocytes. FGF19 strongly and rapidly repressed CYP7A1 but not small heterodimer partner (SHP) mRNA levels. Kinase inhibition and phosphorylation assays revealed that the mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 (MAPK/Erk1/2) pathway played a major role in mediating FGF19 inhibition of CYP7A1. However, small interfering RNA (siRNA) knockdown of SHP did not affect FGF19 inhibition of CYP7A1. Interestingly, CDCA stimulated tyrosine phosphorylation of the FGF receptor 4 (FGFR4) in hepatocytes. FGF19 antibody and siRNA specific to FGFR4 abrogated GW4064 inhibition of CYP7A1. These results suggest that bile acid-activated FXR is able to induce FGF19 in hepatocytes to inhibit CYP7A1 by an autocrine/paracrine mechanism. CONCLUSION: The hepatic FGF19/FGFR4/Erk1/2 pathway may inhibit CYP7A1 independent of SHP. In addition to inducing FGF19 in the intestine, bile acids in hepatocytes may activate the liver FGF19/FGFR4 signaling pathway to inhibit bile acid synthesis and prevent accumulation of toxic bile acid in human livers.
Song Kwang-Hoon; Li Tiangang; Owsley Erika; Strom Stephen; Chiang John Y L
Hepatology (Baltimore, Md.)
2009
2009-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/hep.22627" target="_blank" rel="noreferrer noopener">10.1002/hep.22627</a>