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PubMed1998

Selective binding of different p53 response elements by p53 containing complexes.

The p53 tumor suppressor protein binds two copies of a ten base pair motif that is degenerate in eight out of ten bases and conforms to the sequence, 5'PuPuPuC(A/T)(T/A)GPyPyPy-3'. As a consequence of this high degree of degeneracy, p53 response elements show a great deal of variation and it has been speculated that the variation aids in the selective activation of p53 responsive genes by specific stimuli. Here, we examined the DNA binding characteristics of several different p53 protein complexes present in nuclear extracts prepared from a cell line expressing the murine temperature sensitive p53 protein, p53val135. Interestingly, the complexes exhibited a distinct preference for binding to some p53 response elements and not others. A critical determinant of this specificity was the sequence at the center of the ten base pair motif and alteration of a single base within this region was sufficient to alter the set of complexes that associated with the oligonucleotide. In addition, thermal denaturation experiments demonstrated that some complexes could bind DNA even though the p53val135 protein had a mutant conformation. Our results are consistent with the hypothesis that p53 can distinguish between various response elements and suggest that this selectivity is manifested, in part, by the sequence of the motif and conformation of the p53 protein.

Cell Nucleus↗
PubMed1995

Hypoxic regulation of lactate dehydrogenase A. Interaction between hypoxia-inducible factor 1 and cAMP response elements.

The oxygen-regulated control system responsible for the induction of erythropoietin (Epo) by hypoxia is present in most (if not all) cells and operates on other genes, including those involved in energy metabolism. To understand the organization of cis-acting sequences that are responsible for oxygen-regulated gene expression, we have studied the 5' flanking region of the mouse gene encoding the hypoxically inducible enzyme lactate dehydrogenase A (LDH). Deletional and mutational analysis of the function of mouse LDH-reporter fusion gene constructs in transient transfection assays defined three domains, between -41 and -84 base pairs upstream of the transcription initiation site, which were crucial for oxygen-regulated expression. The most important of these, although not capable of driving hypoxic induction in isolation, had the consensus of a hypoxia-inducible factor 1 (HIF-1) site, and cross-competed for the binding of HIF-1 with functionally active Epo and phosphoglycerate kinase-1 sequences. The second domain was positioned close to the HIF-1 site, in an analogous position to one of the critical regions in the Epo 3' hypoxic enhancer. The third domain had the motif of a cAMP response element (CRE). Activation of cAMP by forskolin had no effect on the level of LDH mRNA in normoxia, but produced a magnified response to hypoxia that was dependent upon the integrity of the CRE, indicating an interaction between inducible factors binding the HIF-1 and CRE sites.

Animals↗
PubMed2001

The cAMP response element binding protein-2 (CREB-2) can interact with the C/EBP-homologous protein (CHOP).

cAMP response element binding protein-2 (CREB-2) is a basic leucine zipper (bZIP) factor that was originally described as a repressor of CRE-dependent transcription but that can also act as a transcriptional activator. Moreover, CREB-2 is able to function in association with the viral Tax protein as an activator of the human T-cell leukemia virus type I (HTLV-I) promoter. Here we show that CREB-2 is able to interact with C/EBP-homologous protein (CHOP), a bZIP transcription factor known to inhibit CAAT/enhancer-dependent transcription. Cotransfection of CHOP with CREB-2 results in decreased activation driven by the cellular CRE motif or the HTLV-I proximal Tax-responsive element, confirming that CREB-2 and CHOP can interact with each other in vivo.

Activating Transcription Factor 4↗
PubMed2005

An Sp1/KLF binding site is important for the activity of a Polycomb group response element from the Drosophila engrailed gene.

Polycomb-group response elements (PREs) are DNA elements through which the Polycomb-group (PcG) of transcriptional repressors act. Many of the PcG proteins are associated with two protein complexes that repress gene expression by modifying chromatin. Both of these protein complexes specifically associate with PREs in vivo, however, it is not known how they are recruited or held at the PRE. PREs are complex elements, made up of binding sites for many proteins. Our laboratory has been working to define all the sequences and DNA binding proteins required for the activity of a 181 bp PRE from the Drosophila engrailed gene. Here we show that one of the sites necessary for PRE activity, Site 2, can be bound by members of the Sp1/KLF family of zinc finger proteins. There are 10 Sp1/KLF family members in Drosophila, and nine of them bind to Site 2. We derive a consensus binding site for the Sp1/KLF Drosophila family members and show that this consensus sequence is present in most of the molecularly characterized PREs. These data suggest that one or more Sp1/KLF family members play a role in PRE function in Drosophila.

Amino Acid Sequence↗
PubMed2000

Polymorphism in oestrogen response element associated with variation in plasma angiotensinogen concentrations in healthy pregnant women.

OBJECTIVE: To investigate the hypothesis that the genotype at nucleotide A(-20)C in the 5' flanking region of the angiotensinogen gene, which lies within a sequence with high homology to an oestrogen response element, affects plasma angiotensinogen levels in pregnancy. DESIGN: Prospective observational study METHODS: Seventy-two healthy pregnant women were recruited in the second half of pregnancy from hospital and primary care antenatal clinics in Nottingham, UK. Plasma angiotensinogen concentrations were measured by radioimmunoassay of angiotensin I generated from endogenous angiotensinogen in the presence of excess human renin. DNA was extracted from peripheral venous blood, and angiotensinogen genotype determined at A(-20)C, G(-6)A and Met235Thr. Associations between genotype and plasma angiotensinogen concentration were assessed by analysis of variance. RESULTS: Women homozygous for the -20C allele had the lowest mean plasma angiotensinogen concentration of 1.7 +/- 0.3micromol/l. Women homozygous for -20A had significantly higher plasma angiotensinogen concentrations (2.6 +/- 0.1 micromol/l), and intermediate levels (2.0 +/- 0.1 micromol/l) were observed in women heterozygous for A(-20)C (P = 0.002, ANOVA). The polymorphisms at nucleotide -6 and codon 235 were in almost complete linkage disequilibrium, and nucleotide -20C was found only in a subset of -6A/235Thr alleles. Conclusion The low plasma angiotensinogen levels associated with the -20C/-6A/235Thr haplotype in pregnant women contrast with the high concentrations associated with the 235Thr allele in the non-pregnant state. A possible explanation lies in the presence of a motif with high homology to an oestrogen response element between the TATA box and transcription initiation site. Previous in vitro studies of reporter gene constructs have demonstrated thatthe A(-20)C polymorphism affects oestrogen responsiveness. The results of this study support the hypothesis that the oestrogen response element of the angiotensinogen gene is of functional importance in pregnancy, and that oestrogen responsiveness in pregnancy is influenced by the genotype at nucleotide - 20.

Alleles↗
PubMed2002

Regulation of steroidogenesis and the steroidogenic acute regulatory protein by a member of the cAMP response-element binding protein family.

The mitochondrial phosphoprotein, the steroidogenic acute regulatory (StAR) protein, is an essential component in the regulation of steroid biosynthesis in adrenal and gonadal cells through cAMP-dependent pathways. In many cases transcriptional induction by cAMP is mediated through the interaction of a cAMP response-element binding protein (CREB) family member with a consensus cAMP response element (CRE; 5'-TGACGTCA-3') found in the promoter of target genes. The present investigation was carried out to determine whether a CRE-binding protein (CREB) family member [CREB/CRE modulator (CREM) family] was involved in the regulation of steroidogenesis and StAR protein expression. Transient expression of wild- type CREB in MA-10 mouse Leydig tumor cells further increased the levels of (Bu)2cAMP-induced progesterone synthesis, StAR promoter activity, StAR mRNA, and StAR protein. These responses were significantly inhibited by transfection with a dominant-negative CREB (A-CREB), or with a CREB mutant that cannot be phosphorylated (CREB-M1), the latter observation indicating the importance of phosphorylation of a CREB/CREM family member in steroidogenesis and StAR expression. The CREB/CREM-responsive region in the mouse StAR gene was located between -110 and -67 bp upstream of the transcriptional start site. An oligonucleotide probe (-96/-67 bp) containing three putative half-sites for 5'-canonical CRE sequences (TGAC) demonstrated the formation of protein-DNA complexes in EMSAs with recombinant CREB protein as well as with nuclear extracts from MA-10 or Y-1 mouse adrenal tumor cells. The predominant binding factor observed with EMSA was found to be the CREM protein as demonstrated using specific antibodies and RT-PCR analyses. The CRE elements identified within the -96/-67 bp region were tested for cAMP responsiveness by generating mutations in each of the CRE half-sites either alone or in combination. Although each of the CRE sites contribute in part to the CREM response, the CRE2 appears to be the most important site as determined by EMSA and by reporter gene analyses. Binding specificity was further assessed using specific antibodies to CREB/CREM family members, cold competitors, and mutations in the target sites that resulted in either supershift and/or inhibition of these complexes. We also demonstrate that the inducible cAMP early repressor markedly diminished the endogenous effects of CREM on cAMP-induced StAR promoter activity and on StAR mRNA expression. These are the first observations to provide evidence for the functional involvement of a CREB/CREM family member in the acute regulation of trophic hormone-stimulated steroidogenesis and StAR gene expression.

5' Flanking Region↗
PubMed1998

Additional protein factors play a role in the formation of VDR/RXR complexes on vitamin D response elements.

The vitamin D receptor (VDR) elicits a transcriptional response to 1,25-dihydroxyvitamin D3 by binding to specific response elements (VDRE) in the promoter of target genes. Retinoic X receptor (RXR) is required for formation of the VDR-VDRE complex when VDR is supplied at physiologic concentrations. When porcine intestinal nuclear extract is used as a source of VDR, two distinct complexes are always observed with native gel electrophoresis. Both complexes contain VDR and RXR. We now show that the faster-migrating complex requires another heretofore unknown nuclear factor for its formation. In addition, we provide evidence that the formation of the slower-migrating complex is enhanced by transcription factor IIB (TFIIB). Using ligand binding assays, we determined that both complexes contain the same ratio of VDR to VDRE. Using RXR subtype-specific antibodies in gel shift assays, we show that the complexes contain more than one RXR subtype. Therefore, the present results demonstrate VDR-RXR-VDRE complexes formed with pig intestinal nuclear extracts contain other proteins and that the complexes formed between VDR and VDRE are not simply heterodimers of VDR and RXR.

Cytochrome P-450 Enzyme System↗
PubMed2004

Gonadotropin-releasing hormone (GnRH) agonist triptorelin inhibits estradiol-induced serum response element (SRE) activation and c-fos expression in human endometrial, ovarian and breast cancer cells.

BACKGROUND AND METHODS: The majority of human endometrial (>80%), ovarian (>80%) and breast (>50%) cancers express GnRH receptors. Their spontaneous and epidermal growth-factor-induced proliferation is dose- and time-dependently reduced by treatment with GnRH and its agonists. In this study, we demonstrate that the GnRH agonist triptorelin inhibits estradiol (E2)-induced cancer cell proliferation. RESULTS: The proliferation of quiescent estrogen receptor alpha (ER alpha)-/ER beta-positive, but not of ER alpha-negative/ER beta-positive endometrial, ovarian and breast cancer cell lines, was significantly stimulated (P<0.001) (ANOVA) after treatment with E2 (10(-8) M). This effect was time- and dose-dependently antagonized by simultaneous treatment with triptorelin. The inhibitory effect was maximal at 10(-5) M concentration of triptorelin (P<0.001). In addition, we could show that, in ER alpha-/ER beta-positive cell lines, E2 induces activation of serum response element (SRE) and expression of the immediate early-response gene c-fos. These effects were blocked by triptorelin (P<0.001). E2-induced activation of estrogen-response element (ERE) was not affected by triptorelin. CONCLUSIONS: The transcriptional activation of SRE by E2 is due to ER alpha activation of the mitogen-activated protein kinase (MAPK) pathway. This pathway is impeded by GnRH, resulting in a reduction of E2-induced SRE activation and, in consequence, a reduction of E2-induced c-fos expression. This causes downregulation of E2-induced cancer cell proliferation.

Antineoplastic Agents, Hormonal↗
PubMed1998

Thyroid hormone response element architecture affects corepressor release from thyroid hormone receptor dimers.

Thyroid hormone receptors are ligand-modulated transcription factors that can repress or activate transcription depending upon the absence or presence of thyroid hormone and the nature of the hormone response element to which the receptors are bound. The ability of thyroid hormone receptors to repress transcription in the absence of ligand is thought to be due to associations with nuclear hormone receptor corepressors. Ligand binding by the thyroid hormone receptor is believed to dissociate these corepressors and recruit coactivators to promote transcription from target promoters. We hypothesize that variations in response element architecture may influence both the association and dissociation of corepressors from DNA-bound thyroid hormone receptors. Using a chimeric corepressor, we find that ligand alone does not fully relieve corepressor-mediated repression, particularly in the presence of thyroid hormone receptor and its heterodimerization partner, the retinoid X receptor. Interestingly, the steroid receptor coactivator 1 together with ligand is able to mediate full release of corepression, but this relief is dependent upon the architecture of the response element to which the nuclear receptor dimer-corepressor complex is bound. These studies suggest that other cellular factors in addition to ligand may be required for the release of corepressors from thyroid hormone receptor dimers.

Dimerization↗
PubMed2006

Solution structures and characterization of human immunodeficiency virus Rev responsive element IIB RNA targeting zinc finger proteins.

The Rev responsive element (RRE), a part of unspliced human immunodeficiency virus (HIV) RNA, serves a crucial role in the production of infectious HIV virions. The viral protein Rev binds to RRE and facilitates transport of mRNA to the cytoplasm. Inhibition of the Rev-RRE interaction disrupts the viral life cycle. Using a phage display protocol, dual zinc finger proteins (ZNFs) were generated that bind specifically to RREIIB at the high affinity Rev binding site. These proteins were further shortened and simplified, and they still retained their RNA binding affinity. The solution structures of ZNF29 and a mutant, ZNF29G29R, have been determined by nuclear magnetic resonance (NMR) spectroscopy. Both proteins form C(2)H(2)-type zinc fingers with essentially identical structures. RNA protein interactions were evaluated quantitatively by isothermal titration calorimetry, which revealed dissociation constants (K(d)'s) in the nanomolar range. The interaction with the RNA is dependent upon the zinc finger structure; in the presence of EDTA, RNA binding is abolished. For both proteins, RNA binding is mediated by the alpha-helical portion of the zinc fingers and target the bulge region of RREIIB-TR. However, ZNF29G29R exhibits significantly stronger binding to the RNA target than ZNF29; this illustrates that the binding of the zinc finger scaffold is amenable to further improvements.

Binding Sites↗
PubMed2006

Luman/CREB3 induces transcription of the endoplasmic reticulum (ER) stress response protein Herp through an ER stress response element.

Luman/CREB3 (also called LZIP) is an endoplasmic reticulum (ER) membrane-bound transcription factor which is believed to undergo regulated intramembrane proteolysis in response to cellular cues. We previously found that Luman activates transcription from the unfolded protein response element. Here we report the identification of Herp, a gene involved in ER stress-associated protein degradation (ERAD), as a direct target of Luman. We found that Luman was transcriptionally induced and proteolytically activated by the ER stress inducer thaspsigargin. Overexpression of Luman activated transcription of cellular Herp via ER stress response element II (ERSE-II; ATTGG-N-CCACG) in the promoter region. Mutagenesis studies and chromatin immunoprecipitation assays showed that Luman physically associates with the Herp promoter, specifically the second half-site (CCACG) of ERSE-II. Luman was also necessary for the full activation of Herp during the ER stress response, since Luman small interfering RNA knockdown or functional repression by a dominant negative mutant attenuated Herp gene expression. Like Herp, overexpression of Luman protected cells against ER stress-induced apoptosis. With Luman structurally similar to ATF6 but resembling XBP1 in DNA-binding specificities, we propose that Luman is a novel factor that plays a role in ERAD and a converging point for various signaling pathways channeling through the ER.

Animals↗
PubMed2004

Testosterone activates mitogen-activated protein kinase and the cAMP response element binding protein transcription factor in Sertoli cells.

The androgen testosterone is essential for the Sertoli cell to support the maturation of male germ cells and the production of spermatozoa (spermatogenesis). In the classical view of androgen action, binding of androgen to the intracellular androgen receptor (AR) produces a conformational change in AR such that the receptor-steroid complex has high affinity for specific DNA regulatory elements and is able to stimulate gene transcription. Here, we demonstrate that testosterone can act by means of an alternative, rapid, and sustainable mechanism in Sertoli cells that is independent of AR-DNA interactions. Specifically, the addition of physiological levels of testosterone to Sertoli cells stimulates the mitogen-activated protein kinase signaling pathway and causes phosphorylation of the cAMP response element binding protein transcription factor on serine 133, a modification known to be required for Sertoli cells to support spermatogenesis. Androgen-mediated activation of mitogen-activated protein kinase and cAMP response element binding protein occurs within 1 min, extends for at least 12 h and requires AR. Furthermore, androgen induces endogenous cAMP response element binding protein-mediated transcription in Sertoli cells. These newly identified mechanisms of androgen action in Sertoli cells suggest new targets for developing male contraceptive agents.

Animals↗
PubMed1990

The inhibition of the iron responsive element RNA-protein interaction by heme does not mimic in vivo iron regulation.

Hemin at greater than 1 microM concentrations inhibits the interaction of the iron responsive element (IRE) and the iron responsive element binding protein (IRE-BP) as measured by gel retardation and UV cross-linking. Heme has recently been proposed to inhibit the repression of translation of an IRE-containing mRNA (Lin, J. J., Daniels-McQueen, S., Patino, M. M., Gaffield, L., Walden, W. E., and Thach, R. E., (1990) Science 247, 74-76). Our binding inhibition provides structural support for these observations. The action of hemin, however, does not mimic the physiologically demonstrated inhibition of high affinity binding of the IRE to IRE-BP by the oxidation of a sulfhydryl of the IRE-BP. In addition to this effect, hemin also inhibits a wide variety of RNA and DNA binding proteins, restriction endonucleases, and nucleases. Therefore, in vitro, the inhibitory effects of hemin are not limited to the interaction of the IRE-BP and the IRE, but are nonspecific and affect a wide variety of nucleic acid-protein interactions. Any hypothesis on the effects on protein-nucleic acid interactions employing greater than 1 microM concentrations of hemin should be interpreted with caution.

Base Sequence↗
PubMed2004

Transcriptional activation of phosphodiesterase 7B1 by dopamine D1 receptor stimulation through the cyclic AMP/cyclic AMP-dependent protein kinase/cyclic AMP-response element binding protein pathway in primary striatal neurons.

Phosphodiesterase (PDE) 7B, a cAMP-specific PDE which is dominantly expressed in striatum, is expected to be involved in dopaminergic signaling in striatal neurons. Here we show, for the first time, the involvement of the dopaminergic signaling pathway in transcriptional activation of rat PDE7B in primary striatal culture. RT-PCR analysis revealed that dopamine, D1 agonist, forskolin and 8-Br-cAMP stimulation potentiated PDE7B transcription in striatal neurons, while D2 agonist failed to activate the PDE7B transcription. Pre-treatment with D1 antagonist abolished the dopamine- or D1 agonist-induced transcriptional activation of PDE7B. The activation of PDE7B transcription by these stimulators was completely ablated by pre-treatment of the cells with a cAMP-dependent protein kinase inhibitor, H-89. RT-PCR using splice variant-specific primers revealed that transcription of PDE7B1, but not of other splice variants, was activated by D1 agonist. We determined the putative transcription start site of PDE7B1, a brain-specific splice variant of PDE7B, by 5'-RACE and identified a promoter region of PDE7B1. Sequence analysis of the PDE7B1 promoter revealed the presence of a canonical cAMP-response element at 166 bp upstream of the putative transcription start site. The cAMP-responsiveness of the PDE7B1 promoter was demonstrated by functional promoter analysis using the luciferase reporter system. Deletion and mutation of the cAMP-response element site in the PDE7B1 promoter abolished the forskolin-induced activation of the PDE7B1 promoter activity. Electrophoretic mobility shift assay showed the binding of cAMP-response element binding protein to the PDE7B1 promoter. These data demonstrate the dopamine D1 receptor-mediated transcriptional activation of PDE7B through the cAMP/cAMP-dependent protein kinase/cAMP-response element binding protein pathway in striatal neurons.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1994

The cyclic AMP response element plays an essential role in the expression of the human prostaglandin-endoperoxide synthase 2 gene in differentiated U937 monocytic cells.

The promoter activity of 1432 bp upstream of the human prostaglandin-endoperoxide synthase 2 gene (PTGS2) was examined in differentiated U937 monocytic cells expressing prostaglandin-endoperoxide synthase 2 mRNA. Transient transfection experiments were performed using these cells and reporter vectors containing the upstream region of the gene with deletions or site-specific mutations and the luciferase gene. The deletion or destruction of the cyclic AMP response element (nucleotides -59 to -53) markedly reduced the promoter activity of this gene. Electrophoretic mobility shift assays showed that a nuclear protein(s) binding to the cyclic AMP response element was induced during monocytic differentiation of U937 cells. These results indicate that expression of the human prostaglandin-endoperoxide synthase 2 gene in differentiated U937 monocytic cells is regulated by the cyclic AMP response element.

Base Sequence↗
PubMed1993

High affinity binding of the estrogen receptor to a DNA response element does not require homodimer formation or estrogen.

We have developed an antibody-based DNA binding assay to study the effects of the absence or presence of an estrogen receptor agonist and two antagonists on the thermodynamic binding parameters for estrogen receptor binding to a consensus estrogen response element in vitro. We first demonstrate that antibodies raised against a region of the estrogen receptor directly adjacent to the DNA-binding domain do not interfere with the receptor's ability to preferentially bind to the vitellogenin estrogen response element in plasmid DNA. Exploiting this property to develop a quantitative DNA binding assay, we demonstrate that estrogen is not required for high affinity binding of the receptor for an oligonucleotide containing this element, nor do antiestrogens alter this interaction. In addition, we find that 1 mol of estrogen receptor is complexed with high affinity to 1 mol of vitellogenin estrogen response element, instead of two estrogen receptors/response element as would be predicted if estrogen receptor homodimer formation was required for high affinity DNA binding. Our data best fit a model in which the active estrogen receptor form is a monomer or heterodimer, but not a homodimer, and the regulatory role of estrogen on the estrogen receptor is the induction of protein-protein, but not protein-DNA, interactions.

Animals↗
PubMed1997

U5 region of the human immunodeficiency virus type 1 long terminal repeat contains TRE-like cAMP-responsive elements that bind both AP-1 and CREB/ATF proteins.

Activating protein-1 (AP-1) binding phorbol ester responsive elements (TRE) are located downstream of the transcription initiation site in the U5 region of the human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR). These downstream sequence elements, termed DSE, can bind cFos and junD and transmit protein kinase C (PKC) activation signals to the LTR. Further studies suggested the DSE might also bind AP-1-related proteins of the CREB/ATF family. Since enhanced HIV-1 expression is associated with activation of the cAMP-dependent protein kinase A (PKA) signaling pathway, we determined whether binding of CREB/ATF proteins to the DSE mediate cAMP/PKA activation of the HIV-1 LTR. In the present study. DSE binding complexes in nuclear protein extracta from colonic epithelial cells are shown to contain ATF-1, ATF-2, and CREB and transfection of either an ATF-2 or PKA expressing plasmid transactivated the DSE. Cholera toxin (Ctx), a potent activator of the cAMP/PKA pathway. Increased HIV-1 virus production from a latently infected promonocytic cell line, U1. Ctx increased LTR promoter activity and increased the CREB content of DSE binding complexes. Transfection of U1 cells with a series of mutant LTR reporter constructs demonstrated that the Ctx response was in large part mediated by the DSE. The Ctx response was also mediated by a heterologous promoter containing multiple TRE sites. Nuclear protein extracts from a T-cell line infected by HIV-1 contained higher levels of CREB/ATF proteins and manifested increased CREB/ATF binding activity. Collectively, these results indicate the DSE are TRE-like cAMP responsive elements that bind both AP-1 and CREB/ATF permitting induction of the HIV-1 LTR by both PKC and PKA activation signals.

Activating Transcription Factor 1↗
PubMed1998

Transforming growth factor-beta1 and protein kinase C synergistically activate the c-fos serum response element in myocardial cells.

We previously reported that transforming growth factor-beta1 (TGF-beta1) potentiated alpha1-adrenergic and stretch-induced c-fos mRNA expression and norepinephrine (NE)-induced amino acid incorporation in rat cultured myocardial cells (MCs). In the present study, we attempted to explore the mode of TGF-beta1 action for c-fos gene expression in MCs. In the transient transfection assay, TGF-beta1 potentiated NE- or 12-O-tetradecanoylphorbol-13-acetate (TPA)-activated c-fos promoter/enhancer, but not forskolin-activated c-fos promoter/enhancer. The c-fos serum response element (SRE) and the TPA response element (TRE) were responsible for TGF-beta1-induced potentiation of the NE or TPA action. Although TGF-beta1 activated not only the wild-type c-fos SRE, but also the mutated c-fos SRE, which contains an intact binding site for the serum response factor (SRF) but lacks the ternary complex factor (TCF) binding site, TPA activated the wild-type c-fos SRE but not the mutated c-fos SRE. TGF-beta1 did not potentiate the effects of TPA on the activation of mitogen-activated protein kinase (MAPK) and the phosphorylation of Elk-1 and SAP-1a, which belong to TCF at the c-fos SRE. These results indicate that TGF-betaf potentiates the c-fos SRE activated by PKC through the SRF binding site. TGF-beta1 is involved in the regulation of c-fos gene expression through the c-fos SRE and is subsequently involved in the regulation of the gene which has the TRE in the promoter/enhancer region.

Animals↗