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PubMed2000

Murine hoxd4 expression in the CNS requires multiple elements including a retinoic acid response element.

We have identified a retinoic acid response element (RARE) within a neural enhancer located 3' to the Hoxd4 gene. This RARE is required for the initiation and maintenance of Hoxd4 transgene expression in neurectoderm, and for full anteriorized expression upon retinoic acid (RA) treatment. Mutations within the sequence TTTTCTG, located 2 bp downstream of the RARE, posteriorized transgene activity. However, the onset of transgene expression and its response to RA were indistinguishable from wild type. While the TTTTCTG motif resembles a CDX binding site, human CDX1 protein did not interact with this element in vitro. Three additional regions were also shown to control transgene expression in neurectoderm, establishing that multiple elements constitute the Hoxd4 neural enhancer.

Animals↗
PubMed1991

A common ancestor DNA motif for invertebrate and vertebrate hormone response elements.

The ecdysone-responsive DNA sequence of the Drosophila hsp27 gene promoter contains four direct and inverted repeats reminiscent of those that compose the vertebrate palindromic estrogen response element (ERE) and the thyroid hormone/retinoic acid response element (TRE/RRE). Interestingly, a 3 bp substitution in the wild-type Hsp27 ecdysone response element (EcdRE) increases both its similarity with the vertebrate ERE and TRE/RRE and its capacity to confer ecdysone responsiveness to a heterologous promoter. Remarkably, increasing the spacing between the inverted repeats of this strong EcdRE by two nucleotides converts it into an ERE. Inversely, decreasing the spacing between the two inverted repeats of the vertebrate consensus palindromic ERE, from three to one nucleotide, converts it into a functional EcdRE. Thus, the only difference between an invertebrate EcdRE and a vertebrate palindromic ERE or TRE/RRE is in the spacing between the conserved inverted repeated motifs forming these palindromic HREs. The finding that the sequence motif 5'-GGTCA-3' present in the vertebrate ERE and TRE/RRE is also a functionally important characteristic of an invertebrate HRE, suggests that a common ancestor regulatory DNA sequence gave rise to all HREs known so far. We discuss the possibility that this progenitor motif is the GGTCA sequence.

Animals↗
PubMed1999

Cadmium-mediated activation of the metal response element in human neuroblastoma cells lacking functional metal response element-binding transcription factor-1.

Metal response element-binding transcription factor-1 (MTF-1) binds specifically to metal response elements (MREs) and transactivates metallothionein (MT) gene expression in response to zinc and cadmium. This investigation contrasts the mechanism of mouse MT gene (mMT-I) promoter activation by cadmium and zinc in IMR-32 human neuroblastoma cells to determine whether MTF-1 binding to the MRE is necessary for activation by these metals. Cadmium activated a mMT-1 promoter (-150 base pairs) luciferase reporter 20-25-fold through a MRE-dependent mechanism. In contrast, zinc had little effect on the mMT-1 luciferase reporter. IMR-32 cells lacked MRE binding activity, and treatment with zinc in vitro or in vivo did not generate a MTF-1. MRE complex, suggesting that IMR-32 cells lack functional MTF-1. Overexpression of mMTF-1 regenerated a zinc-mediated induction of the MRE without affecting cadmium activation. Because no other transition metals tested activated the MRE, this effect appeared to be cadmium-specific. These data demonstrate that in IMR-32 human neuroblastoma cells, zinc and cadmium can use independent mechanisms for activation of the mMT-I promoter and cadmium-mediated MRE activation is independent of MTF-1 and zinc.

Base Sequence↗
PubMed2001

The cAMP responsive element and CREB partially mediate the response of the tyrosine hydroxylase gene to phorbol ester.

Tyrosine hydroxylase (TH) gene promoter activity is increased in PC12 cells that are treated with the phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA). Mutagenesis of either the cAMP responsive element (CRE) or the activator protein-1 element (AP1) within the TH gene proximal promoter leads to a dramatic inhibition of the TPA response. The TH CRE and TH AP1 sites are also independently responsive to TPA in minimal promoter constructs. TPA treatment results in phosphorylation of cAMP responsive element binding protein (CREB) and activation of cAMP-dependent protein kinase (PKA) in PC12 cells; hence, we tested whether CREB and/or PKA are essential for the TPA response. In CREB-deficient cells, the response of the full TH gene proximal promoter or the independent response of the TH CRE by itself to TPA is inhibited. The TPA-inducibility of TH mRNA is also blocked in CREB-deficient cells. Expression of the PKA inhibitor protein, PKI, also inhibits the independent response of the TH CRE to TPA. Our results support the hypothesis that TPA stimulates the TH gene promoter via signaling pathways that activate either the TH AP1 or TH CRE sites. Both signaling pathways are dependent on CREB and the TH CRE-mediated pathway is dependent on PKA.

Animals↗
PubMed1997

Expression of maspin in prostate cells is regulated by a positive ets element and a negative hormonal responsive element site recognized by androgen receptor.

Prostate cancer is the most common cancer in men. The molecular mechanisms leading to its development are poorly understood. Maspin is a tumor-suppressing serpin expressed in normal breast and prostate epithelium. We have found that expression of maspin in normal and carcinoma-derived prostate epithelial cells is differentially regulated at the transcriptional level. We have identified two different kinds of cis elements, Ets and hormonal responsive element (HRE), in the maspin promoter. The Ets element is active in regulating maspin expression in normal prostate epithelial cells but inactive in tumor cells. The HRE site is a negative element that is active in both cell types. This negative DNA sequence can repress a heterologous promoter recognized by the androgen receptor. We conclude that expression of maspin is under the influence of both a positive Ets and a negative HRE element. Loss of maspin expression during tumor progression apparently results from both the absence of transactivation through the Ets element and the presence of transcription repression through the negative HRE element recognized by androgen receptor.

Base Sequence↗
PubMed1996

DEAF-1, a novel protein that binds an essential region in a Deformed response element.

A 120 bp homeotic response element that is regulated specifically by Deformed in Drosophila embryos contains a single binding site for Deformed protein. However, a 24 bp sub-element containing this site does not constitute a Deformed response element. Specific activation requires a second region in the 120 bp element, which presumably contains one or more binding sites for Deformed cofactors. We have isolated a novel protein from Drosophila nuclear extracts which binds specifically to a site in this second region. This protein, which we call DEAF-1 (Deformed epidermal autoregulatory factor-1), contains three conserved domains. One of these includes a cysteine repeat motif that is similar to a motif found in Drosophila Nervy and the human MTG8 proto-oncoprotein, and another matches a region of Drosophila Trithorax. Mutations in the response element designed to improve binding to DEAF-1 in vitro resulted in increased embryonic expression. Conversely, small mutations designed to diminish binding to DEAF-1 resulted in reduced expression of the element. Thus, DEAF-1 is likely to contribute to the functional activity, and perhaps to the homeotic specificity, of this response element. Consistent with this hypothesis, we have discovered DEAF-1 binding sites in other Deformed response elements.

Amino Acid Sequence↗
PubMed1989

Three amino acids of the oestrogen receptor are essential to its ability to distinguish an oestrogen from a glucocorticoid-responsive element.

Steroid hormone receptors activate specific gene transcription by binding as hormone-receptor complexes to DNA enhancer elements termed hormone responsive elements. A highly conserved 66-amino-acid region of the oestrogen and glucocorticoid receptors which corresponds to part of the receptor DNA-binding domain (region C) determines the specificity of target gene recognition. This region contains two subregions (CI and CII), encoded in two separate exons, that are analogous to the 'zinc fingers' of the transcription factor TFIIIA. The N-terminal CI finger determines the recognition specificity of the hormone responsive element. A chimaeric oestrogen receptor, in which the CI finger is replaced with the corresponding glucocorticoid receptor CI finger region, activates transcription from a reporter gene containing a glucocorticoid-responsive element, but not from a reporter gene containing an oestrogen-responsive element. We report here that three amino acids located at the C-terminal side of the oestrogen receptor CI finger play a key part in this specificity.

Amino Acid Sequence↗
PubMed1993

Both the basal and inducible transcription of the tyrosine hydroxylase gene are dependent upon a cAMP response element.

The cAMP response element (CRE) mediates cAMP responsiveness in many eukaryotic genes (Roesler, W. J., Vandenbark, G. R., and Hansen, R. W. (1988) J. Biol. Chem. 263, 9063-9066). The tyrosine hydroxylase gene (TH) contains a single copy of a consensus CRE at -45 to -38 base pair (bp) upstream of the transcription initiation site. Deletional and mutational analyses of the upstream 2400-base pair region of the rat TH gene using transient transfection assay demonstrated that the CRE was essential for both cAMP-mediated induction and basal transcription of the TH gene. Another domain between -365 and -151 bp, containing the AP1 site, contributed to transcription to a smaller degree. Thus, the CRE appears to play an important dual role as a basal promoter element and an inducible enhancer for TH transcription. Interactions between the DNA binding factors in nuclear extract and CRE-containing oligonucleotides were investigated by gel retardation and competition assays. Oligonucleotides corresponding to the CRE regions of the TH or somatostatin gene gave rise to a pair of distinct protein-DNA complexes with identical mobilities in the gel retardation assay, suggesting that similar nuclear factor(s) might bind to the CREs of the TH and somatostatin genes. This study emphasizes a fundamental role of the CRE in transcriptional activation of the TH gene in catecholaminergic cells.

Animals↗
PubMed2002

Ultraviolet B (UVB) induction of the c-fos promoter is mediated by phospho-cAMP response element binding protein (CREB) binding to CRE and c-fos activator protein 1 site (FAP1) cis elements.

The ultraviolet B (UVB) portion (280-320 nm) of the ultraviolet spectrum has been shown to contribute to the development of non-melanoma skin cancer in humans. Research in the human keratinocyte cell line, HaCaT, revealed that UVB irradiation caused the upregulation of the transcription factor activator protein-1 (AP-1). The AP-1 complex formed in UVB-irradiated HaCaT cells is specifically composed of c-fos and Jun D. c-Fos expression was induced in a manner that correlated with the UVB-induced activation of AP-1. To investigate how c-fos expression is regulated by UVB irradiation, the role of each of four cis elements within the c-fos promoter was evaluated. Clustered point mutations at the sis inducible element (SIE), serum response element (SRE), c-fos AP-1 site (FAP1), or cyclic AMP response elements (CRE) significantly inhibited UVB induction of the c-fos promoter. This indicated that all four cis elements are required for maximum promoter activity. The CRE and FAP1 elements were the two most active cis elements that mediate the UVB transactivation of c-fos. Homodimers of phosphorylated cAMP response element binding protein (CREB) were induced by UVB irradiation to bind to each of these elements. Therefore, CREB may function as an important regulatory protein in the UVB-induced expression of c-fos.

Binding Sites↗
PubMed2003

Differential modulation of androgen receptor action by deoxyribonucleic acid response elements.

In addition to the steroid response elements (SREs), which are recognized by several steroid receptors, a second class of DNA elements exhibiting selectivity for the androgen receptor (AR) and named androgen response elements (AREs) has been identified. Here we provide evidence for the differential role of these element classes in modulating AR function. AR complexes attached to response elements representative of each class were purified. Limited protease digests of ARE- or SRE-bound AR complexes led to the generation of different patterns, in line with differential accessibilities. In transactivation assays, mutations in the AR dimerization interface of the DNA-binding domain had various effects, depending on the response elements tested. The R598D mutant displayed much enhanced activity on SREs, whereas far less effect was seen on the selective AREs. The A596T mutant had reduced activity on AREs but not on SREs. Ectopic expression of the coactivators transcriptional intermediary factor 2 (TIF2) and ARA55 stimulated AR activity to different extents, depending on the response element. When using cysteine-rich secretory protein 1 (CRISP-1) SRE as reference, the most significant difference was observed with Pem ARE-2. A differential response of each element class was furthermore observed in the presence of two enzymes involved in the sumoylation pathway. Ubiquitin-conjugating enzyme 9 (Ubc9) overexpression enhanced AR action conveyed by SREs, whereas little effect was seen on Pem ARE-1 and repression on Pem ARE-2. Protein inhibitor of activated STAT (PIAS)xalpha overexpression had little influence on SRE-mediated AR activity but was repressive when using AREs. Altogether, these results demonstrate that DNA response elements play an important modulatory role in transmitting AR action and may be determinative for specificity of gene expression in cell or tissue types.

Animals↗
PubMed1990

A cis-acting element located between the cAMP response elements and CCAAT box augments cell-specific expression of the glycoprotein hormone alpha subunit gene.

Several cis-acting elements interact through their cognate trans-acting factors to confer placenta-specific expression to the alpha subunit gene of glycoprotein hormones. These elements include two tandemly arranged cAMP response elements (CREs, located between base pairs (bp) -146 and -111 relative to the transcription start site), an upstream regulatory element (URE, located between -180 and -150), and a CCAAT box (located between bp -100 and -80). Here, we identify a new regulatory region, junctional regulatory element (JRE), with critical nucleotides located between the CREs and CCAAT box (bp -120 to -100). Although the binding site of the JRE abuts the 3' CRE, methylation interference assays indicate that no overlap occurs between the contact points of the proteins that bind to the JRE and CRE. This new regulatory element is highly conserved across species and contains a palindromic binding site for a 50-kDa nuclear factor(s) which is distinct from the factors that bind the URE, CRE, and CCAAT box of the alpha subunit gene. Finally, gene transfer studies suggest that, although JRE binding activity is found in several cell types, this element acts relatively cell-specifically. We conclude that this element and its cognate trans-acting factor act in conjunction with the complexes formed over the URE, CREs, and CCAAT box to enhance the placenta-specific activity of the alpha subunit promoter.

Base Sequence↗
PubMedDate not supplied

Induction of xenobiotic enzymes by the MAP kinase pathway and the antioxidant or electrophile response element (ARE/EpRE).

Cellular responses to xenobiotic-induced stress can signal proliferation, differentiation, homeostasis, apoptosis, or necrosis. To better understand the underlying molecular mechanisms after exposure to xenobiotics or drugs, we studied the signal transduction pathways, the mitogen-activated protein kinase (MAPK), and the basic leucine zipper transcription factor Nrf2, activated by different agents in the induction of Phase II drug metabolizing enzymes (DMEs). The MAPKs, characterized as proline-directed serine/threonine kinases, are essential components of signaling pathways that convert various extracellular signals into intracellular responses through serial phosphorylation cascades. Once activated, MAPKs can phosphorylate many transcription factors, such as c-Jun, ATF-2, and ultimately lead to changes in gene expression. Two classes of Phase II gene inducers, which are also cancer chemopreventive agents, were studied: (1) the phenolic antioxidants, namely butylated hydroxyanisole (BHA) and its active de-methylated metabolite t-butylhydroquinone (tBHQ), and phenolic flavonoids such as green tea polyphenols (GTP) and (-)-epigallocatechin-3-gallate (EGCG); and (2) the naturally occurring isothiocyanates, namely phenethyl isothiocyanate (PEITC), and sulforaphane. BHA and tBHQ are both well-known phenolic antioxidants used as food preservatives, and strongly activate c-Jun N-terminal kinase 1 (JNK1), extracellular signal-regulated protein kinase 2 (ERK2), or p38, in a time- and dose-dependent fashion. Free radical scavengers N-acetyl-L-cysteine (NAC), or glutathione (GSH), inhibited ERK2 activation and, to a much lesser extent, JNK1 activation by BHA/tBHQ, implicating the role of oxidative stress. Under conditions where MAPKs were activated, BHA or GTP also activated ARE/EpRE (antioxidant/electrophile response element), with the induction of Phase II genes such as NQO. Transfection studies with various cDNAs encoding wild-type or dominant-negative mutants of MAPKs and/or transcription factor Nrf2, substantially modulated ARE-mediated luciferase reporter activity in the presence or absence of phenolic compounds. Other phytochemicals including PEITC, and sulforaphane, also differentially regulated the activities of MAPKs, Nrf2, and ARE-mediated luciferase reporter gene activity and Phase II enzyme induction. A model is proposed where these xenobiotics (BHA, tBHQ, GTP, EGCG, PEITC, sulforaphane) activate the MAPK pathway via an electrophilic-mediated stress response, leading to the transcription activation of Nrf2/Maf heterodimers on ARE/EpRE enhancers, with the subsequent induction of cellular defense/detoxifying genes including Phase II DMEs, which may protect the cells against toxic environmental insults and thereby enhance cell survival. The studies of these signaling pathways may yield insights into the fate of cells upon exposure to xenobiotics.

Animals↗
PubMed1991

Identification of a multiprotein complex interacting with the c-fos serum response element.

The serum response element (SRE) is essential for serum and growth factor stimulation of the c-fos gene. We have examined the nuclear proteins, obtained from tissues with elevated expression of the c-fos gene (proliferating rat liver and hepatocarcinoma), that bind to the SRE sequence. A synthetic oligonucleotide containing the SRE sequence from the mouse c-fos gene promoter (-299 to -322) was radioactively labeled, used as a probe for the mobility shift assay and Southwestern (DNA-protein) blotting, and also used for sequence-specific affinity chromatography. We have identified a group of nuclear proteins of molecular sizes 36, 45, 62, 67, 72, and 112 kDa capable of interacting with the SRE sequence. The 36-, 67-, and 112-kDa proteins have DNA-binding properties, but the presence of the others in the SRE-protein complex could be the result of protein-protein interaction. All of these protein factors were present in nuclei obtained from intact and proliferating rat liver as well as from 5123tc Morris hepatoma. The DNA-binding activity (on Southwestern blots) of the 67- and 112-kDa proteins was not affected by alkaline phosphatase treatment, but the ability of the dephosphorylated nuclear proteins to form the complex with the SRE sequence under gel shift assay conditions was severely impaired. The same alkaline phosphatase treatment completely abolished the DNA-binding properties of the c-fos cyclic AMP-responsive element-specific proteins. Therefore, transcriptional activation of the c-fos gene at the SRE must require the presence of a multiprotein complex the formation of which is governed by phosphorylation. The binding of the 67- and 62-kDa proteins to the c-fos SRE has been previously reported; however, the 36-. 45-, 72-, and 112-kDa proteins are novel factors involved in the multifaceted regulation of c-fos gene expression in vivo.

Animals↗
PubMed2003

Nrf2, not the estrogen receptor, mediates catechol estrogen-induced activation of the antioxidant responsive element.

The antioxidant responsive element (ARE) plays an important role in the gene expression of phase II detoxification enzymes, such as NAD(P)H:quinone oxidoreductase 1 (NQO1), and NF-E2-related factor2 (Nrf2) is the transcription factor for the ARE-driven genes. Interestingly, estrogen receptor (ER) was reported to increase NQO1 gene expression through the ARE. In this study, we investigated the role of ER and Nrf2 in ARE activation using IMR-32 cells and mouse primary astrocytes. Among tested estrogen-related compounds, only catechol estrogens (i.e. 4-hydroxyestradiol) activated the ARE. Since 4-hydroxyestradiol-induced ARE activation was not inhibited by either 17beta-estradiol or tamoxifen, and overexpression of ER-alpha decreased 4-hydroxyestradiol-induced ARE activation, ARE activation by catechol estrogen was independent of ER. Nrf2, however, was very important in the 4-hydroxyestradiol-induced ARE activation. 4-Hydroxyestradiol did not activate the ARE in Nrf2 knockout (-/-) primary astrocytes, but did activate the ARE when Nrf2 was transfected into Nrf2-/- astrocytes. In addition, dominant negative Nrf2 completely blocked 4-hydroxyestradiol-induced ARE activation in Nrf2+/+ astrocytes, and only 4-hydroxyestradiol induced Nrf2 nuclear translocation in IMR-32 cells. A selective phosphatidylinositol 3-kinase (PI3-kinase) inhibitor (LY294002) blocked 4-hydroxyestradiol-induced Nrf2 nuclear translocation and NQO1 activity induction in IMR-32 cells. Taken together, these observations suggest that 4-hydroxyestradiol activates the ARE by a PI3-kinase-Nrf2 dependent mechanism, not involving ER.

Animals↗
PubMed1999

Vitamin D receptor interactions with the rat parathyroid hormone gene: synergistic effects between two negative vitamin D response elements.

Vitamin D response elements (VDREs) that are required for negative regulation of rat parathyroid hormone (rPTH) gene expression have been characterized. Gel mobility shift assays using DNA restriction enzyme fragments and recombinant proteins for vitamin D and retinoic acid X receptors (VDR/RXR) revealed a sequence between -793 and -779 that bound a VDR/RXR heterodimer with high affinity (VDRE1). Furthermore, a lower affinity site (VDRE2) was detected that acted in combination with VDRE1 to bind a second VDR/RXR complex. As determined by ethylation interference analysis, the nucleotide sequence of VDRE1 consisted of GGTTCA GTG AGGTAC, which is remarkably similar to the sequence of the negative VDRE found in the chicken PTH (cPTH) gene. Using the same technique, VDRE2 was identified between positions -760 and -746 and contained the sequence AGGCTA GCC AGTTCA. Functional analysis was determined by transfection studies with plasmid constructs that expressed the gene for chloramphenicol acetyl transferase (CAT). The ability of the VDREs to regulate gene expression was tested in their native context with the rPTH promoter as well as when positioned immediately upstream from the cPTH promoter. With either plasmid construct, exposure to 10(-8)M 1,25(OH)2D3 resulted in a 60-70% decrease in CAT gene expression when both VDRE1 and VDRE2 were present. Examination of the individual VDREs showed that inhibition by 10(-8) M 1,25(OH)2D3 was only 35-40% when just VDRE1 was present. By itself, VDRE2 was even less effective, as significant inhibition of CAT activity (20%) was observed only in the presence of higher concentrations of 1, 25(OH)2D3 (10(-7)M) or when a plasmid vector that overexpressed the VDR protein was cotransfected. In conclusion, the rPTH gene contains two negative VDREs that act in concert to bind two RXR/VDR heterodimer complexes and that both VDREs are required for maximal inhibition by 1,25(OH)2D3.

Animals↗
PubMed1993

Identification of the IL-6-responsive element in an acute-phase-responsive human pancreatic secretory trypsin inhibitor-encoding gene.

Pancreatic secretory trypsin inhibitor (PSTI) has been suggested to be an acute-phase reactant in humans and to be induced by inflammatory cytokines such as the interleukins IL-1 and IL-6. We report that PSTI is synthesized in hepatoma cells and that the gene expression is augmented by IL-6. The start points (tsp) for basal and augmented transcription are exactly the same as the tsp in normal pancreas. Analysis of the PSTI gene revealed that a 40-bp DNA fragment located between kb -3.84 and -3.80 carries the element responsible for both transcriptional activity and IL-6-induced gene expression. This 40-bp fragment contains TTGNNGNAATG, the consensus sequence for the NF-IL6-binding site, which is also known as the IL-6-responsive element that is conserved among various acute-phase genes. The basal activity was augmented by another sequence that lies between kb -4.0 and -3.9.

Acute-Phase Proteins↗
PubMed1994

The insulin and cAMP response elements of the prolactin gene are overlapping sequences.

Prolactin gene expression is affected by numerous signals, but many of the promoter elements required for these responses have not been clearly identified. This report identifies sequences within the prolactin gene promoter that are required for the responses to cAMP and insulin. The cAMP response element, -101 to -92 shares a 6 of 8 base pair homology with previously identified cAMP response elements. Mutation of this element also results in a > 100-fold decrease in basal prolactin gene expression. This is characteristic of cAMP response elements, but the importance of this element to basal prolactin gene transcription was previously unrecognized. The insulin response element, -97 to -67, is not homologous to previously reported insulin response elements and mediates the 10-fold increases in prolactin gene expression due to insulin observed in GH cells. These elements also function to mediate insulin and cAMP responses from the heterologous delta MTV-CAT reporter plasmid. Together, insulin and cAMP increase prolactin gene expression additively. The clustering of these elements may provide clues to the independent and possible coordinate regulation by these effectors.

Animals↗
PubMedDate not supplied

Upregulation of the tracheobronchial mucin gene involves cyclic AMP response elements.

The cAMP response element (CRE)-binding transcription factor CREB can mediate induction of gene transcription in response to cAMP. Since the tracheobronchial mucin gene (TBM) 5'-flanking region contains CREs (located between residues -289 and -376) with an octamer-like motif (TGACGTCC), the cAMP responsiveness of the TBM CREs was investigated in human tracheal epithelial cells HBE1. These cells were isolated from non-cystic fibrosis subjects and immortalized with HPV18 genes E6 and E7 (ref. 1). HBE1 cells express a homolog of canine TBM (as demonstrated by TBM expression at the transcription and translation level). Electrophoretic mobility shift assay (EMSA) indicated that CREs provide a binding site for nuclear proteins. Transient transfection analysis [using the chloramphenicol acetyl transferase (CAT) reporter gene] and nuclear run on analysis indicated cAMP induced transcription of the TBM gene. The transcriptional activity of the HBE1 transfected cells containing CRE was selectively modulated by extracellular 8Br-cAMP in a dose-dependent manner; a 6-fold increase in activity was detected when cells were incubated for 12 hr in the presence of 2 microM vs 1 nM 8BrcAMP. Since mucin gene is over-expressed in diseases such as cystic fibrosis (CF) and asthma, the information presented here will help us understand the mechanisms involved in transcriptional regulation of mucin gene expression in disease states.

Animals↗