Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Response Elements”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed1993

Membrane depolarization and calcium influx induce glucagon gene transcription in pancreatic islet cells through the cyclic AMP-responsive element.

Glucagon-producing pancreatic islet cells generate calcium-dependent action potentials. By the control of calcium influx through voltage-gated calcium channels, calcium is a tightly regulated second messenger in these cells. It is unknown whether calcium is a signal for glucagon gene transcription. Therefore, rat glucagon reporter fusion genes were transiently transfected into pancreatic islet cell lines. High potassium-induced membrane depolarization activated glucagon gene transcription. The effects of a calcium chelator, calcium channel blockers, calmodulin antagonists, and an inhibitor of calcium/calmodulin-dependent protein kinase II (CaM kinase II) indicate that depolarization-induced glucagon gene transcription depends on calcium influx and CaM kinase II. The depolarization-responsive element was mapped to the glucagon cAMP-responsive element (CRE). The CRE-binding protein CREB was shown, by using GAL4-CREB fusion proteins, to function as a depolarization-regulated transcription factor in pancreatic islet cells. Membrane depolarization and cAMP had synergistic effects on glucagon gene transcription. These results suggest that rat glucagon gene transcription is regulated by membrane electrical activity and calcium influx in pancreatic islet cells. This signal may be transmitted via CaM kinase II and CREB to the glucagon CRE.

Calcium↗
PubMed1991

A new cAMP response element in the transcribed region of the human c-fos gene.

In NIH 3T3 cells the c-fos gene is induced rapidly and transiently by cAMP. As shown by the analysis of 3T3 cells stably transfected with promoter mutants of the human c-fos gene this induction does not depend on the dyad symmetry element (position -320 to -300), but involves at least two other non-related sites: an element located around position -60 resembling the cAMP response element of the fibronectin and somatostatin genes (which has been described before), and an element located between positions +18 and +38. Destruction of one or the other element in the c-fos gene reduces cAMP inducibility. The cAMP response of c-fos promoter CAT gene constructs also depends on these elements in transient transfection assays. When cloned in front of the albumin TATA box, both elements independently mediate cAMP inducibility. These elements do not bind the same protein as shown in gel retardation analyses, suggesting that two different cAMP inducible factors mediate the activation of the c-fos gene by cAMP.

Animals↗
PubMed1998

Hypoglycemia-induced seizures reduce cyclic AMP response element binding protein levels in the rat hippocampus.

Cyclic AMP response element binding protein (CREB) is a transcription factor that has been implicated in the activation of protein synthesis required for long-term memory. Since memory deficits are manifest following seizure, we undertook the present study to investigate the effects of hypoglycemia-induced seizure on CREB-immunoreactive neurons in several brain regions. We induced generalized seizures in male Long Evans rats (n=5) by injecting them with insulin (30 IU/kg, i.p). Animals were recovered by administration of 3 ml of 30% glucose within 5 min of the occurrence of seizure. Control animals (n=3) were injected with saline instead of insulin. All animals were perfused 90 min after recovery and the brains processed for CREB immunohistochemistry. Cell counts were determined for CREB-positive neurons using a computer-assisted program. When compared to control animals there was a 50% decrease (P<0.0001) in CREB-positive neurons in the CA1 region of the experimental animals. In the CA3 and dentate gyrus there was a 36% (P<0.001) and 25% decrease (P<0.001), respectively. Given the importance of hippocampus in memory-related processes and evidence that CREB is critical for memory formation, it is possible that seizures interfere with memory by disrupting CREB-dependent transcription.

Animals↗
PubMed1996

Integration of growth factor signals at the c-fos serum response element.

A transcription factor ternary complex composed of serum response factor (SRF) and a second factor, ternary complex factor (TCF), mediates the response of the c-fos Serum Response Element to growth factors and mitogens. In NIH3T3 fibroblasts, TCF binding is required for transcriptional activation by the SRE in response to activation of the Ras-Raf-ERK pathway. We compared the properties of three members of the TCF family, Elk-1, SAP-1 and SAP-2 (ERP/NET). Although all the proteins contain sequences required for ternary complex formation with SRF, only Elk-1 and SAP-1 appear to interact with the c-fos SRE efficiently in vivo. Each TCF contains a C-terminal activation domain capable of transcriptional activation in response to activation of the Ras-Raf-ERK pathway, and this is dependent on the integrity of S/T-P motifs conserved between all the TCF family members. In contrast, activation of the SRE by whole serum and the mitogenic phospholipid LPA requires SRF binding alone. Constitutively activated members of the Rho subfamily of Ras-like GTPases are also capable of inducing activation of the SRE in the absence of TCF; unlike activated Ras itself, these proteins do not activate the TCFs in NIH3T3 cells. At the SRE, SRF- and TCF-linked signalling pathways act synergistically to potentiate transcription.

3T3 Cells↗
PubMed2000

Characterization of a retinoic acid responsive element in the human ets-1 promoter.

The vitamin A metabolite retinoic acid (RA) is a powerful regulator of cellular proliferation and differentiation. The effects of RA on target gene expression are mediated by a family of ligand dependent nuclear transcription factors known as retinoic acid receptors (RAR). RARs have functional domains for retinoic acid binding, dimerization, and transactivation. RA response elements (RARE) found in the promoters of many genes consist of variable direct repeats of the sequence PuGGTCA spaced by five nucleotides (DR5). We have identified a novel DR5 element in the human ets-1 promoter. Mutational analysis of this site indicates that it is necessary for RA- and RAR-dependent activation of the ets-1 promoter. RARalpha can bind specifically to this site as determined by electrophoretic mobility shift analysis. Finally, RA mediates induction of the human ets-1 gene at the mRNA and protein levels. These data suggest that induction of ets-1 expression by RA is mediated by a novel retinoic acid response element in the promoter region of this gene.

Cells, Cultured↗
PubMed2001

The basis for IL-2-induced IL-2 receptor alpha chain gene regulation: importance of two widely separated IL-2 response elements.

The interleukin-2 receptor alpha (IL-2Ralpha) chain is an essential component of high-affinity IL-2 receptors. Accordingly, IL-2Ralpha expression helps to regulate T cell growth and other lymphoid functions. Lineage-restricted and activation-dependent IL-2Ralpha transcription is controlled by three upstream positive regulatory regions (PRRs). We now describe an additional IL-2 response element, PRRIV, within intron 1, in humans and mice. PRRIV activity requires GAS motifs that bind Stat5 proteins and additional upstream HMG-I(Y) binding sites. Moreover, IL-2 induces the binding of HMG-I(Y), Stat5a, and Stat5b in vivo to PRRIV and PRRIII, which also functions as an IL-2 response element. Thus, the IL-2 inducibility of the IL-2Ralpha gene is unexpectedly mediated by two widely separated regulatory Stat5-dependent elements, located both upstream and downstream of the transcription initiation sites.

Amino Acid Motifs↗
PubMed2000

Identification of phosphorylated form of cAMP/calcium response element binding protein expression in the brain stem nuclei at early stage of vestibular compensation in rats.

The present study was aimed at evaluating the time-dependent expressions of phosphorylated forms in the cAMP/calcium response element binding protein (pCREB) known to be one of transcription factors for immediate early genes in the brain stem nuclei of Sprague-Dalwey rats. Animals received surgical ablation of right peripheral vestibular labyrinth through a ventral approach. Immunohistochemical staining and digital image analysis systems were used to observe pCREB expressions in neuronal cells of the brain stem nuclei. The number of pCREB labeling neurons were increased with time, and peaked in the vestibular nuclear complex (VNC) bilaterally 1 h after unilateral labyrinthectomy (UL). In addition, high levels of phosphorylated CREB-like immunoreactivity (pCREB-LI) were also observed in bilateral cerebellum, olivary nuclear complex, and medullary nuclei. There was a rapid reduction of pCREB-LI in contralateral VNC but a slow reduction in the ipsilateral side 2 h after UL, causing an asymmetric number of pCREB labeling neurons between bilateral VNC (P<0.05). Thereafter pCREB-LI in bilateral VNC decreased to a very low level and returned to basal level 24 h after UL. These results suggest that the activation of the cAMP/calcium response element binding protein plays a role in the initial events of vestibular compensation in rats.

Animals↗
PubMed1990

Synergistic activation of transcription by the human estrogen receptor bound to tandem responsive elements.

The synergistic action of the human estrogen receptor (hER) has been investigated using minimal promoters containing a TATA region and one or two estrogen responsive elements (EREs). We find that paired perfectly palindromic EREs act additively and independently of their relative spacing when positioned close to the TATA box. However, when moved 175 bp further upstream, perfectly palindromic EREs act synergistically and in a stereoalignment-dependent manner. Less efficient imperfectly palindromic EREs display a stereoalignment-dependent synergism even when positioned close to the TATA box. Analysis of binding in vitro of the hER to perfectly or imperfectly palindromic EREs by gel retardation and nitrocellulose filter binding assays does not provide any evidence for cooperative DNA binding. Conversely, the human progesterone receptor (hPR) clearly shows cooperative binding to paired responsive elements (PREs) under similar conditions in vitro. Thus, hER molecules bound to adjacent EREs must be properly stereoaligned to activate transcription synergistically in vivo. However, our data suggest that this synergism is not primarily due to cooperative binding to the EREs.

Adenoviruses, Human↗
PubMed2000

Self-assembly of an oligodeoxyribonucleotide harboring the estrogen response element in the presence of polyamines: ionic, structural, and DNA sequence specificity effects.

Estrogenic regulation of gene expression is mediated by the binding of the hormone to its specific receptor, estrogen receptor (ER), which undergoes structural and conformational alterations to recognize specific DNA sequences, estrogen response elements (ERE), in responsive genes to trigger a series of events culminating in the transcription of these genes. Polyamines are ubiquitous cellular cations that are important for cell growth and differentiation, and have been shown to participate in estrogenic regulation of gene expression. Polyamine-mediated DNA condensation/aggregation has been studied to understand the ionic and structural requirements for the compaction of DNA. DNA condensation/decondensation may also play a role in transcription and replication. We studied the aggregation of a 38-mer oligonucleotide duplex (ODN) in the presence of natural and synthetic polyamines under different ionic conditions (NaCl, KCl, and K glutamate). Our results showed that an ODN harboring the consensus ERE (ODN1) was 2-fold more susceptible to precipitation by spermine compared to ODN2 containing scrambled sequences, or a mutant ODN (ODN3). The nature of the monovalent cations (Na+ vs K+), and anions (Cl- vs glutamate) also played an important role in the efficacy of a polyamine to precipitate ODNs: potassium glutamate being the least effective in suppressing the ability of spermine to precipitate ODNs. The concentration of polyamines required for precipitating the ODNs increased with monovalent ion concentration in the buffer. With ODN1, a plot of log[spermine4+] at the 50% precipitation concentrations against log[Na+/K+] yielded a straight line, with a slope of 1.8 +/- 0.18, a value comparable to that predicted by the counterion condensation theory (1.85). We also observed significant structural specificity effects of spermine and its analogues [NH2(CH2)3NH(CH2)nNH(CH2)3NH2, where n = 2-9; n = 4 for spermine] on aggregating the ODN1. These results demonstrate DNA sequence and polyamine structural specificity effects on the aggregation of ODNs, and suggest that the gene regulatory function of ERE may be linked to its ability to undergo facile condensation/decondensation in the presence of biological cations, such as polyamines.

Base Sequence↗
PubMed1988

Characterization of the cAMP responsive elements from the genes for the alpha-subunit of glycoprotein hormones and phosphoenolpyruvate carboxykinase (GTP). Conserved features of nuclear protein binding between tissues and species.

Cyclic AMP responsive elements (CRE) have been identified in several genes, including those encoding the alpha-subunit of glycoprotein hormones and the cytosolic form of phosphoenolpyruvate carboxykinase (PEPCK) from the rat. Common to the CRE in these genes is the palindromic sequence T(G/T)ACGTCA. Based upon the strong conservation of this element, we hypothesize that the CRE functions by binding a protein that has been conserved across tissue and species lines. Scatchard analysis of gel mobility shift assays indicate that a nuclear protein in extracts prepared from rat liver and from a human choriocarcinoma cell line binds with high affinity to the cAMP responsive element from either gene (Kd approximately 10(-10) M). In order to identify the critical nucleotides within the CRE from these two genes, a series of oligodeoxynucleotides containing systematic mutations was synthesized and tested for protein binding and transcriptional function. Mutations within the palindromic core of either CRE resulted in a marked loss of binding to the nuclear proteins. Sequences outside the 8-base pair element were less important for nuclear protein binding to the PEPCK CRE and were not important for the alpha-subunit CRE. The relative binding, as determined by gel shift assays, correlated with the ability to confer cAMP responsive transcription to a viral promoter in transfected choriocarcinoma cells. DNase I protection assays suggest that binding of the nuclear factor from rat liver to the PEPCK CRE is more efficient when the core sequence is present in the intact PEPCK promoter regulatory region as compared to the isolated CRE oligodeoxynucleotide. Collectively, these results indicate that the nuclear factors necessary for cAMP induction of transcription of the alpha-subunit and PEPCK genes are conserved between tissues and species. In addition to the conserved features of these cis- and trans-active elements, nonconserved sequences and other elements of the promoter regulatory region influence the affinity of the protein-DNA interaction.

Animals↗
PubMed2006

Nuclear receptor binding to the retinoic acid response elements of the phosphoenolpyruvate carboxykinase gene in vivo: effects of vitamin A deficiency.

Vitamin A deficiency decreases hepatic phosphoenolpyruvate carboxykinase (PEPCK) gene expression in mice and expression is restored with retinoic acid treatment in vivo. This report examines further the mechanism of retinoid regulation of the PEPCK gene in vivo. We have identified nuclear receptors that bind to retinoic acid response elements (RAREs) in the PEPCK promoter by electrophoretic mobility shift assay and have verified these in vivo using chromatin immunoprecipitation (ChIP) in mouse liver. Based on the results of our ChIP assay, hepatic nuclear factor (HNF)-4alpha, retinoid X receptor (RXR) alpha, retinoic acid receptor (RAR) alpha, peroxisome proliferator-activated receptor (PPAR) alpha and chicken ovalbumin upstream promoter transcription factor (COUP-TF) II bind to the downstream retinoic acid response unit RARE1/RARE2, and PPARalpha and RXRalpha bind to the upstream RARE3 of the PEPCK gene. HNF-4alpha, RXRalpha, RARalpha, PPARalpha and COUP-TFII bind PEPCK RAREs in a specific pattern that, with the exception of PPARalpha, does not change significantly with vitamin A deficiency. PPARalpha binding to the upstream retinoic acid response element is decreased in the vitamin A-deficient liver, when compared to the vitamin A-sufficient state. These results provide the first in vivo measures of nuclear receptor binding to the upstream and downstream RAREs of the PEPCK gene under conditions where the nucleosomal structure of the chromatin is maintained and the nuclear receptors are physically cross-linked in situ to the PEPCK DNA in intact liver.

Animals↗
PubMed1994

Transcriptional regulation of a rat liver glutathione S-transferase Ya subunit gene. Analysis of the antioxidant response element and its activation by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate.

Using transfection and gel retardation assays, we have characterized further the antioxidant response element (ARE) found in the 5'-flanking region of the rat glutathione S-transferase Ya subunit gene. The ARE core sequence (5'-GTGACAAAGC-3') is sufficient for transcriptional activation of the Ya subunit gene by metabolizable planar aromatic compounds, phenolic antioxidants, and hydrogen peroxide. When the ARE sequence is ligated to a chloramphenicol acetyltransferase reporter gene and transfected into HepG2 cells, chloramphenicol acetyltransferase activity is modestly inducible by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Since the ARE is responsive to TPA and shows some sequence similarity to an AP-1-binding site (Jun/Fos recognition motif), we have explored whether members of the Jun/Fos family of transcription factors might bind to the ARE. Using in vitro synthesized Jun and Fos, binding to the ARE could not be detected, whereas Jun/Fos binding to a classical AP-1-binding site, a TPA response element (TRE) from the human collagenase gene, could be demonstrated by gel retardation assays. If the 2 A nucleotides underlined in the ARE core sequence (5'-GTGACAAAGC-3') are changed to TC, the ARE sequence (ARE-TRE) becomes a high-affinity AP-1-binding site and retains xenobiotic inducibility. Removal of the -GC- dinucleotide at the 3'-end of the ARE or the ARE-TRE eliminates xenobiotic inducibility. However, the ARE-TRE construct without the -GC- dinucleotide is still a high-affinity AP-1 site and responsive to TPA. Taken together, our data suggest that the ARE is not a high-affinity binding site for the Jun/Fos heterodimer. Functionally, however, an AP-1-binding site can resemble an ARE in its response to various xenobiotics if a 3'-GC- dinucleotide is present.

Animals↗
PubMed2001

Identification of negative and positive estrogen response elements in human GnRH upstream promoter in the placental JEG-3 cells.

Results from our previous studies have demonstrated regulatory effects of estradiol on human gonadotropin-releasing hormone (GnRH) gene expression in human placental cells. The present study was designed to determine the molecular mechanisms whereby estrogens regulate the human GnRH gene expression in the placenta. The effects of estradiol on human GnRH upstream promoter activity in JEG-3 cells depends on the amounts of estrogen receptor (ER) alpha expression vector co-transfected, with the maximal effect obtained at the amount of 1.0 microg of ER expression vector cotransfected. Estriol, an isoform of estradiol, also possesses a regulatory effect on the upstream promoter activity, while estrone, another isoform, does not. Serial deletion studies revealed two estrogen responsive elements in the GnRH upstream promoter region. One element (-987 to -968 bp, E4 element) confers a negative estradiol response, while another one (-827 to -730 bp) is responsible for a positive estradiol effect. Replacement of these two elements with unrelated DNA sequences could abolish the responsiveness to estradiol treatment. Furthermore, footprinting and gel shift assays demonstrated that nuclear protein from estradiol-treated JEG-3 cells, but not from control cells, could bind to a 41 bp DNA fragment (-824 to -784 bp) within the estrogen positive responsive element. Results of gel-shift assay demonstrated that other protein(s) might also be involved in interacting the E4 element to mediate the negative effect of estradiol on the hGnRH upstream promoter activity in JEG-3 cells.

Dose-Response Relationship, Drug↗
PubMed2003

Transcriptional analysis of the orphan nuclear receptor constitutive androstane receptor (NR1I3) gene promoter: identification of a distal glucocorticoid response element.

The constitutive androstane receptor (CAR, NR1I3) transcriptionally activates cytochrome P450 2B6, 2C9, and 3A4 when activated by xenobiotics, such as phenobarbital. Information on the human CAR promoter was obtained by searching the NCBI human genome database. A contig (NT026945) corresponding to a fragment of chromosome 1q21 was found to contain the complete CAR gene. These data were confirmed using chromosomal in situ hybridization. Both primer extension and 5'-rapid amplification of the cDNA end PCR analysis were carried out to determine the transcriptional start site of human CAR, which was found to be 32 nucleotides downstream of a potential TATA box (CATAAAA). In addition, we found that the 5'-untranslated region of CAR mRNA is 110 nucleotides shorter than previously reported. Using genomic PCR, we amplified and cloned approximately 4.9 kb (-4711/+144) of the CAR gene promoter. The activity of this promoter was measured by transient transfection. Deletion analysis suggested the presence of a glucocorticoid responsive element in its distal region (-4477/-4410). From cotransfection experiments, mutagenesis, and gel shift assays, we identified a glucocorticoid response element at -4447/-4432 that was recognized and transactivated by the human glucocorticoid receptor. Finally, using the chromatin immunoprecipitation assay, we demonstrated that the glucocorticoid receptor binds to the distal region of CAR promoter in cultured hepatocytes only in the presence of dexamethasone. Identification of this functional element provides a rational mechanistic basis for CAR induction by glucocorticoids. CAR appears to be a primary glucocorticoid receptor-response gene.

Cells, Cultured↗
PubMed2006

An IFNG SNP with an estrogen-like response element selectively enhances promoter expression in peripheral but not lamina propria T cells.

This study examines mucosa-specific regulatory pathways involved in modulation of interferon-gamma (IFN-gamma) in lamina propria T cells. Previous studies identified mucosa-specific CD2 cis-elements within the -204 to -108 bp IFNG promoter. Within this region, a single-site nucleotide polymorphism, -179G/T, imparts tumor necrosis factor-alpha stimulation of IFNG in peripheral blood lymphocytes, and is linked with accelerated AIDS progression. We discovered a putative estrogen response element (ERE) introduced by the -179T, which displays selective activation in peripheral blood mononuclear cells (PBMC) vs lamina propria mononuclear cells (LPMC). Transfection of PBMC with constructs containing the -179G or -179T site revealed CD2-mediated enhancement of the -179T compared to -179G allele, although, in LPMC, a similar level of expression was detected. Electrophoretic mobility shift assay (EMSA) analysis demonstrated CD2-mediated nucleoprotein binding to the -179T but not the -179G in PBMC. In LPMC, binding is constitutive to both -179G and -179T regions. Sequence and EMSA analysis suggests that the -179T allele creates an ERE-like binding site capable of binding recombinant estrogen receptor. Estrogen response element transactivation is enhanced by CD2 signaling, but inhibited by estrogen in PBMC but not in LPMC, although expression of estrogen receptor was similar. This is the first report to describe a potential molecular mechanism responsible for selectively controlling IFN-gamma production in LPMC.

Base Sequence↗
PubMed1997

A novel lipopolysaccharide-response element contributes to induction of nitric oxide synthase.

The gene encoding the high output isoform of nitric oxide synthase represents a large class of alarm and defense genes transcriptionally induced in response to bacterial lipopolysaccharide (LPS). The promoters of most of these genes contain at least two LPS-response elements, one of which commonly binds transcription factors of the NF-kappaB/Rel family. Here a novel LPS-response element is identified in the inducible nitric oxide synthase promoter, termed LREAA, which contains critical adenosine residues lying 19-20 base pairs downstream of the proximal NF-kappaB binding element (NFkappaBd). Both NFkappaBd and LREAA are required for LPS-induced promoter activity. A protein partially recognized by antibody against transcription factor Oct-1 binds to the LREAA element constitutively in untreated macrophages while contributing to a DNA-protein complex that includes NF-kappaB p50 in macrophages treated with LPS. NF-kappaB p50 and the LREAA-binding proteins may together recruit an LPS-triggered transactivator of transcription.

Animals↗
PubMed1992

Gibberellin-responsive elements in the promoter of a barley high-pI alpha-amylase gene.

Deletion analysis has previously shown that the major gibberellic acid (GA)- and abscisic acid (ABA)-responsive elements in the promoter of a high-pI alpha-amylase gene of barley are located downstream of -174 (Jacobsen and Close, 1991). We have used transient expression assays in barley aleurone protoplasts to identify sequences between -174 and +53 that confer GA and ABA responsiveness on expression of a beta-glucuronidase reporter gene. Using alpha-amylase promoter fragments and synthetic oligonucleotides fused to minimal promoters, we have shown that the hormone-responsive region is located between -174 and -108. A single copy of this region fused to a minimal alpha-amylase promoter (-41) conferred both GA- and ABA-responsive expression on the reporter gene comparable to the positive control, Am(-174)IGN. Multiple copies of this region were able to activate even greater levels of expression. Site-directed mutagenesis was used to determine the functional importance of the conserved motifs (-169pyrimidine box, -143TAACAAA box, and -124TATCCAC box) and nonconserved intervening sequences within the region between -174 and -108. Our results showed that both the TAACAAA and TATCCAC boxes play an important role in GA-regulated expression. We propose that the TAACAAA box is a gibberellin response element, that the TATCCAC box acts cooperatively with the TAACAAA box to give a high level of GA-regulated expression, and that together these motifs form important components of a gibberellin response complex in high-pI alpha-amylase genes. The TAACAAA box also appears to be the site of action of ABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed2001

Hormonal regulation of multiple promoters of the rat mitochondrial glycerol-3-phosphate dehydrogenase gene: identification of a complex hormone-response element in the ubiquitous promoter B.

Rat mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) is regulated by multiple promoters in a tissue-specific manner. Here, we demonstrate that thyroid hormone (3,5,3'-tri-iodo-L-thyronine) and steroid hormone but not the peroxisome proliferator clofibrate and retinoic acid stimulate the activation of the ubiquitous promoter B in a receptor-dependent manner, whereas the more tissue-restricted promoters A and C are not inducible by these hormones. Thyroid hormone action is mediated by a direct repeat +4 (DR+4) hormone-response element as identified by deletion and mutation analyses of promoter B in transient transfection analyses. The DR+4 element was able to bind to an in vitro translated thyroid hormone receptor in band-shift and supershift experiments. The hormone-response element comaps with a recognition site for the transcription factor Sp1, suggesting complex regulation of this sequence element. Mutation of this Sp1-recognition site reduces the basal promoter B activity dramatically in HepG2 and HEK293 cells in transient transfection and abolishes the binding of Sp1 in band-shift experiments. As demonstrated by Western-blot experiments, administration of tri-iodothyronine to euthyroid rats increases hepatic mGPDH protein concentrations in vivo. As it has recently been reported that human mGPDH promoter B is not regulated by tri-iodothyronine, this is the first example of a differentially tri-iodothyronine-regulated orthologous gene promoter in man and rat.

Animals↗