Down-regulation of hepatic nuclear factor 4α on expression of human hepatic stimulator substance via its action on the proximal promoter in HepG2 cells

2008 ◽  
Vol 415 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Duo Guo ◽  
Ling-yue Dong ◽  
Yuan Wu ◽  
Lin Yang ◽  
Wei An

hHSS (human hepatic stimulator substance) stimulates hepatocyte growth. To understand the mechanism controlling hHSS expression, we analysed the proximal promoter activity and identified two regulatory regions (−212/−192 and −152/−132) that were important for transcription in HepG2 cells. Using the luciferase reporter assay, gel-shift experiments and ChIP (chromatin immunoprecipitation), we found that the transcription factors HNF4α (hepatocyte nuclear factor 4α) and Sp1 (stimulating protein-1) were essential for hHSS promoter activity and could directly bind to regions −209/−204 and −152/−145 respectively. We also confirmed that activation and repression of hHSS transcription induced by Sp1 and HNF4α resulted from binding of these factors to these two cis-elements respectively. Overexpression of HNF4α led to a dramatic repression of the promoter activity and, in contrast, the activity was markedly elevated by overexpression of Sp1. Furthermore, overexpression of HNF4α1, one of the HNF4α isoforms, resulted in a dramatic suppression of the promoter activity. Moreover, repression of HNF4α expression by siRNA (small interfering RNA) remarkably enhanced the hHSS mRNA level. It has been reported previously that expression of HNF4α is functionally regulated by dexamethasone. To further confirm the transcriptional control of HNF4α on hHSS, we tested the effect of dexamethasone on hHSS transcription in HepG2 cells. In the present study we have demonstrated that the expression of the hHSS gene was down-regulated at the transcriptional level by dexamethasone in HepG2 cells. A deletion and decoy assay revealed that binding of HNF4α to nucleotides −209/−204 was responsible for the suppression of hHSS promoter activity by dexamethasone. Increases in the HNF4α-binding activity and expression were simultaneously observed in an electrophoretic mobility-shift assay and Western blot analysis. These results suggested that Sp1 activates hHSS basal expression, but HNF4α inhibits hHSS gene expression.

2002 ◽  
Vol 283 (1) ◽  
pp. E50-E57 ◽  
Author(s):  
Quan He ◽  
Mariela Mendez ◽  
Margot C. LaPointe

Brain natriuretic peptide (BNP) is a cardiac hormone constitutively expressed in the adult heart. We previously showed that the human BNP (hBNP) proximal promoter region from −127 to −40 confers myocyte-specific expression. The proximal hBNP promoter contains several putative cis elements. Here we tested whether the proximal GATA element plays a role in basal and inducible regulation of the hBNP promoter. The hBNP promoter was coupled to a luciferase reporter gene (1818hBNPLuc) and transferred into neonatal ventricular myocytes (NVM), and luciferase activity was measured as an index of hBNP promoter activity. Mutation of the putative GATA element at −85 of the hBNP promoter [1818(mGATA)hBNPLuc] reduced activity by 97%. To study transactivation of the hBNP promoter, we co-transfected 1818hBNPLuc with the GATA-4 expression vector. GATA-4 activated 1818hBNPLuc, and this effect was eliminated by mutation of the proximal GATA element. Electrophoretic mobility shift assay showed that an oligonucleotide containing the hBNP GATA motif bound to cardiomyocyte nuclear protein, which was competed for by a consensus GATA oligonucleotide but not a mutated hBNP GATA element. The β-adrenergic agonist isoproterenol and its second messenger cAMP stimulated hBNP promoter activity and binding of nuclear protein to the proximal GATA element. Thus the GATA element in the proximal hBNP promoter is involved in both basal and inducible transcriptional regulation in cardiac myocytes.


2014 ◽  
Vol 104 (6) ◽  
pp. 801-808 ◽  
Author(s):  
F. Li ◽  
X.N. Liu ◽  
Y. Zhu ◽  
J. Ma ◽  
N. Liu ◽  
...  

AbstractEukaryote transcription is controlled by regulatory DNA sequences and transcription factors, so transcriptional control of gene plays a pivotal role in gene expression. In this study, we identified the region of the CYP6B6 gene promoter of Helicoverpa armigera which responds to the plant secondary toxicant 2-tridecanone. Transient transfection assay results from five of stepwise deletion fragments linked to the luciferase reporter gene revealed that the promoter activity of each CYP6B6 fragment was significantly higher than that of their basal activity after the Sf9 cells were treated with 2-tridecanone. Among all, the fragment spanning −373 to +405 bp of the CYP6B6 promoter showed an obviously 2-tridecanone inducibility (P<0.0001), which might have the 2-tridecanone responsive element based on promoter activity. Electrophoretic mobility shift assays revealed that the nuclear protein extracted from midgut of the 6th instar larva of H. armigera, reared on 10 mg 2-tridecanone per gram artificial diet for 48 h, could specifically bind to the active region from −373 to 21 bp of the CYP6B6 promoter. The combination feature also appeared when using a shorter fragment from −292 to −154 bp of the CYP6B6 promoter. Taken together, we found a 2-tridecanone core responsive region between −292 and −154 bp of the CYP6B6 promoter. This may lead us to a better understanding of transcriptional mechanism of P450 gene and provide very useful information for the pest control.


2005 ◽  
Vol 387 (3) ◽  
pp. 763-772 ◽  
Author(s):  
Francisco M. REIMUNDE ◽  
Cristina CASTAÑARES ◽  
Mariano REDONDO-HORCAJO ◽  
Santiago LAMAS ◽  
Fernando RODRÍGUEZ-PASCUAL

The regulation of the synthesis of the endothelial-derived vasoconstrictor ET-1 (endothelin-1) is a complex process that occurs mainly at the mRNA level. Transcription of the gene accounts for an important part of the regulation of expression, as already described for different modulators such as the cytokine TGF-β (transforming growth factor-β). However, very little is known about mechanisms governing ET-1 expression at the post-transcriptional level. The aim of the present study was to investigate the regulation of the ET-1 expression at this level. Since the 3′-UTR (3′-untranslated region) of mRNAs commonly contains genetic determinants for the post-transcriptional control of gene expression, we focused on the potential role of the 3′-UTR of ET-1 mRNA. Experiments performed with luciferase reporter constructs containing the 3′-UTR showed that this region exerts a potent destabilizing effect. Deletional analyses allowed us to locate this activity within a region at positions 924–1127. Some (but not all) of the AREs (AU-rich elements) present in this region were found to be essential for this mRNA-destabilizing activity. We also present evidence that cytosolic proteins from endothelial cells interact specifically with these RNA elements, and that a close correlation exists between the ability of the AREs to destabilize ET-1 mRNA and the binding of proteins to these elements. Our results are compatible with the existence of a strong repressional control of ET-1 expression mediated by destabilization of the mRNA exerted through the interaction of specific cytosolic proteins with AREs present in the 3′-UTR of the gene.


2004 ◽  
Vol 380 (2) ◽  
pp. 455-463 ◽  
Author(s):  
Hsueh-Hsiao WANG ◽  
An-Na CHIANG

β2-Glycoprotein I (β2-GPI) is a plasma glycoprotein primarily synthesized in the liver. The interindividual variability of β2-GPI expression in subjects with various metabolic syndromes and disease states suggests that it may have clinical importance. However, the regulation of β2-GPI gene expression has not been clarified. To gain more insight into the control of β2-GPI gene expression, we cloned the 4.1-kb 5´-flanking region and characterized the proximal promoter of the β2-GPI gene in this study. Cis-acting elements required for β2-GPI promoter activity were identified with transient transfection assays in the hepatoma cell lines HepG2 and Huh7 and in non-hepatic HeLa cells. Serial deletion analyses of the β2-GPI 5´-flanking sequence revealed that the region from −197 to +7 had strong promoter activity in hepatoma cells but not in HeLa cells. Truncation and site-directed mutagenesis of putative cis-elements within this region showing an atypical TATA box and a HNF-1 (hepatic nuclear factor-1) element were both essential for the β2-GPI promoter activity. Subsequent gel mobility shift assays confirmed the interaction of HNF-1α with the HNF-1 site residing downstream of the TATA box. Co-transfection of β2-GPI promoter-luciferase vector with HNF-1α expression vector in Huh7 and HNF-1-deficient HeLa cells demonstrated the transactivation effect of HNF-1α on β2-GPI promoter activity. In addition, overexpression of HNF-1α enhanced the endogenous β2-GPI expression. These results suggest that the atypical TATA box and HNF-1 cis-element are critical for β2-GPI transcription and HNF-1α may play an important role in cell-specific regulation of β2-GPI gene expression.


1999 ◽  
Vol 276 (3) ◽  
pp. G728-G736 ◽  
Author(s):  
E. Scott Swenson ◽  
Elizabeth A. Mann ◽  
M. Lynn Jump ◽  
Ralph A. Giannella

We have investigated the regulation of gene transcription in the intestine using the guanylyl cyclase C (GCC) gene as a model. GCC is expressed in crypts and villi in the small intestine and in crypts and surface epithelium of the colon. DNase I footprint, electrophoretic mobility shift assay (EMSA), transient transfection assays, and mutagenesis experiments demonstrated that GCC transcription is regulated by a critical hepatocyte nuclear factor-4 (HNF-4) binding site between bp −46 and −29 and that bp −38 to −36 were essential for binding. Binding of HNF-4 to the GCC promoter was confirmed by competition EMSA and by supershift EMSA. In Caco-2 and T84 cells, which express both GCC and HNF-4, the activity of GCC promoter and/or luciferase reporter plasmids containing 128 or 1973 bp of 5′-flanking sequence was dependent on the HNF-4 binding site in the proximal promoter. In COLO-DM cells, which express neither GCC nor HNF-4, cotransfection of GCC promoter/luciferase reporter plasmids with an HNF-4 expression vector resulted in 23-fold stimulation of the GCC promoter. Mutation of the HNF-4 binding site abolished this transactivation. Transfection of COLO-DM cells with the HNF-4 expression vector stimulated transcription of the endogenous GCC gene as well. These results indicate that HNF-4 is a key regulator of GCC expression in the intestine.


2000 ◽  
Vol 348 (3) ◽  
pp. 675-686 ◽  
Author(s):  
Isabelle VAN SEUNINGEN ◽  
Michaël PERRAIS ◽  
Pascal PIGNY ◽  
Nicole PORCHET ◽  
Jean-Pierre AUBERT

Control of gene expression in intestinal cells is poorly understood. Molecular mechanisms that regulate transcription of cellular genes are the foundation for understanding developmental and differentiation events. Mucin gene expression has been shown to be altered in many intestinal diseases and especially cancers of the gastrointestinal tract. Towards understanding the transcriptional regulation of a member of the 11p15.5 human mucin gene cluster, we have characterized 3.55 kb of the 5ʹ-flanking region of the human mucin gene MUC5B, including the promoter, the first two exons and the first intron. We report here the promoter activity of successively 5ʹ-truncated sections of 956 bases of this region by fusing it to the coding region of a luciferase reporter gene. The transcription start site was determined by primer-extension analysis. The region upstream of the transcription start site is characterized by the presence of a TATA box at bases -32/-26, DNA-binding elements for transcription factors c-Myc, N-Myc, Sp1 and nuclear factor ĸB as well as putative activator protein (AP)-1-, cAMP-response-element-binding protein (CREB)-, hepatocyte nuclear factor (HNF)-1-, HNF-3-, TGT3-, gut-enriched Krüppel factor (GKLF)-, thyroid transcription factor (TTF)-1- and glucocorticoid receptor element (GRE)-binding sites. Intron 1 of MUC5B was also characterized, it is 2511 nucleotides long and contains a DNA segment of 259 bp in which are clustered eight tandemly repeated GA boxes and a CACCC box that bind Sp1. AP-2α and GATA-1 nuclear factors were also shown to bind to their respective cognate elements in intron 1. In transfection studies the MUC5B promoter showed a cell-specific activity as it is very active in mucus-secreting LS174T cells, whereas it is inactive in Caco-2 enterocytes and HT-29 STD (standard) undifferentiated cells. Within the promoter, maximal transcription activity was found in a segment covering the first 223 bp upstream of the transcription start site. Finally, in co-transfection experiments a transactivating effect of Sp1 on to MUC5B promoter was seen in LS174T and Caco-2 cells.


2005 ◽  
Vol 34 (1) ◽  
pp. 177-197 ◽  
Author(s):  
A Cote-Vélez ◽  
L Pérez-Martínez ◽  
M Y Díaz-Gallardo ◽  
C Pérez-Monter ◽  
A Carreón-Rodríguez ◽  
...  

Hypothalamic proTRH mRNA levels are rapidly increased (at 1 h) in vivo by cold exposure or suckling, and in vitro by 8Br-cAMP or glucocorticoids. The aim of this work was to study whether these effects occurred at the transcriptional level. Hypothalamic cells transfected with rat TRH promoter (− 776/+85) linked to the luciferase reporter showed increased transcription by protein kinase (PK) A and PKC activators, or by dexamethasone (dex), but co-incubation with dex and 8Br-cAMP decreased their stimulatory effect (as observed for proTRH mRNA levels). These effects were also observed in NIH-3T3-transfected cells supporting a characteristic of TRH promoter and not of hypothalamic cells. Transcriptional regulation by 8Br-cAMP was mimicked by noradrenaline which increased proTRH mRNA levels, but not in the presence of dex. PKA inhibition by H89 avoided 8Br-cAMP or noradrenaline stimulation. TRH promoter sequences, cAMP response element (CRE)-like (− 101/− 94 and − 59/− 52) and glucocorticoid response element (GRE) half-site (− 210/− 205), were analyzed by electrophoretic mobility shift assays with nuclear extracts from hypothalamic or neuroblastoma cultures. PKA stimulation increased binding to CRE (− 101/− 94) but not to CRE (− 59/− 52); dex or 12-O-tetradecanoylphorbol-13-acetate (TPA) increased binding to GRE, a composite site flanked by a perfect and an imperfect activator protein (AP-1) site in the complementary strand. Interference was observed in the binding of CRE or GRE with nuclear extracts from cells co-incubated for 3 h with 8Br-cAMP and dex; from cells incubated for 1 h, only the binding to GRE showed interference. Rapid cross-talk of glucocorticoids with PKA signaling pathways regulating TRH transcription constitutes another example of neuroendocrine integration.


2018 ◽  
Vol 314 (1) ◽  
pp. G14-G21 ◽  
Author(s):  
Saminathan Muthusamy ◽  
Jong Jin Jeong ◽  
Ming Cheng ◽  
Jessica A. Bonzo ◽  
Anoop Kumar ◽  
...  

Na+/H+ exchanger isoform 3 (NHE3) plays a key role in coupled electroneutral NaCl absorption in the mammalian intestine. Reduced NHE3 expression or function has been implicated in the pathogenesis of diarrhea associated with inflammatory bowel disease (IBD) or enteric infections. Our previous studies revealed transcriptional regulation of NHE3 by various agents such as TNF-α, IFN-γ, and butyrate involving transcription factors Sp1 and Sp3. In silico analysis revealed that the NHE3 core promoter also contains a hepatocyte nuclear factor 4α (HNF-4α) binding site that is evolutionarily conserved in several species suggesting that HNF-4α has a role in NHE3 regulation. Nhe3 mRNA levels were reduced in intestine-specific Hnf4α-null mice. However, detailed mechanisms of NHE3 regulation by HNF-4α are not known. We investigated the regulation of NHE3 gene expression by HNF-4α in vitro in the human intestinal epithelial cell line C2BBe1 and in vivo in intestine-specific Hnf4α-null ( Hnf4αΔIEpC) and control ( Hnf4αfl/fl) mice. HNF-4α knockdown by short interfering RNA in C2BBe1 cells significantly decreased NHE3 mRNA and NHE3 protein levels. Gel mobility shift and chromatin immunoprecipitation assays revealed that HNF-4α directly interacts with the HNF-4α motif in the NHE3 core promoter. Site-specific mutagenesis on the HNF-4α motif decreased, whereas ectopic overexpression of HNF-4α increased, NHE3 promoter activity. Furthermore, loss of HNF-4α in Hnf4αΔIEpC mice decreased colonic Nhe3 mRNA and NHE3 protein levels. Our results demonstrate a novel role for HNF-4α in basal regulation of NHE3 expression. These studies represent an important and novel target for therapeutic intervention in IBD-associated diarrhea. NEW & NOTEWORTHY Our studies for the first time show that hepatocyte nuclear factor 4α directly regulates NHE3 promoter activity and its basal expression in the intestine.


1999 ◽  
Vol 338 (2) ◽  
pp. 241-249 ◽  
Author(s):  
Chin-Hui HSIANG ◽  
Norman W. MARTEN ◽  
Daniel S. STRAUS

Transcription of the serum albumin gene occurs almost exclusively in the liver and is controlled in part by a strong liver-specific promoter. The upstream region of the serum albumin gene promoter is highly conserved among species and is footprinted in vitro by a number of nuclear proteins. However, the role of the upstream promoter region in regulating transcription and the identity of the transcription factors that bind to this region have not been established. In the present study, deletion analysis of the rat serum albumin promoter in transiently transfected HepG2 cells demonstrated that elimination of the region between -207 and -153 bp caused a two-fold decrease in promoter activity (P< 0.05). Additional analysis of the -207 to -124 bp promoter interval led to the identification of two potential binding sites for hepatocyte nuclear factor-3 (HNF-3) located at -168 to -157 bp (site X) and -145 to -134 bp (site Y). Electrophoretic mobility-shift assays performed with the HNF-3 X and Y sites demonstrated that both sites are capable of binding HNF-3α and HNF-3β. Placement of a single copy of the HNF-3 X site upstream from a minimal promoter increased promoter activity by about four-fold in HepG2 cells, and the reporter construct containing this site could be transactivated if co-transfected with an HNF-3 expression construct. Furthermore, inactivation of the HNF-3 X site by site-directed mutagenesis within the context of the -261 bp albumin promoter construct resulted in a 40% decrease in transcription (P< 0.05). These results indicate that the positive effect of the -207 to -153 bp promoter interval is attributable to the presence of the HNF-3 X site within this interval. Additional results obtained with transfected HepG2 cells suggest that the HNF-3 Y site plays a lesser role in activation of transcription than the X site.


2012 ◽  
Vol 33 (1) ◽  
Author(s):  
Lidia A. Daimiel ◽  
María E. Fernández-Suárez ◽  
Sara Rodríguez-Acebes ◽  
Lorena Crespo ◽  
Miguel A. Lasunción ◽  
...  

DHCR24 (3β-hydroxysterol Δ24-reductase) catalyses the reduction of the C-24 double bond of sterol intermediates during cholesterol biosynthesis. DHCR24 has also been involved in cell growth, senescence and cellular response to oncogenic and oxidative stress. Despite its important roles, little is known about the transcriptional mechanisms controlling DHCR24 gene expression. We analysed the proximal promoter region and the cholesterol-mediated regulation of DHCR24. A putative SRE (sterol-regulatory element) at −98/−90 bp of the transcription start site was identified. Other putative regulatory elements commonly found in SREBP (SRE-binding protein)-targeted genes were also identified. Sterol responsiveness was analysed by luciferase reporter assays of approximately 1 kb 5′-flanking region of the human DHCR24 gene in HepG2 and SK-N-MC cells. EMSAs (electrophoretic mobility-shift assays) and ChIP (chromatin immunoprecipitation) assays demonstrated cholesterol-dependent recruitment and binding of SREBPs to the putative SRE. Given the presence of several CACCC-boxes in the DHCR24 proximal promoter, we assessed the role of KLF5 (Krüppel-like factor 5) in androgen-regulated DHCR24 expression. DHT (dihydrotestosterone) increased DHCR24 expression synergistically with lovastatin. However, DHT was unable to activate the DHCR24 proximal promoter, whereas KLF5 did, indicating that this mechanism is not involved in the androgen-induced stimulation of DHCR24 expression. The results of the present study allow the elucidation of the mechanism of regulation of the DHCR24 gene by cholesterol availability and identification of other putative cis-acting elements which may be relevant for the regulation of DHCR24 expression.


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