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At least 703 records · Page 39Linked to original sources
PubMed1995

Regulation of H1(0) gene expression by nuclear receptors through an unusual response element: implications for regulation of cell proliferation.

Cloning and sequence analysis of the 5'-flanking region of the human H1(0) histone gene, a differentiation-specific member of the H1 family, has revealed several potential regulatory elements. In this study, we have characterized the interactions of nuclear receptors with an unusual response element consisting of two half-sites arranged as a direct repeat with an 8-bp spacer (DR-8). Thyroid hormone receptors (TR) bind this DR-8 as homodimers and heterodimers with RXR. Retinoic acid receptors (RARs) also bind as heterodimers with RXR to the DR-8, and this binding is enhanced in the presence of retinoic acid (RA) and/or 9-cis RA. Reporter constructs containing the DR-8 allowed a several-fold induction by T3 in the presence of TRs. RAR alpha and RAR beta allowed RA-dependent transcriptional activation whereas RAR gamma mostly increased basal activity. 9-cis RA inhibited the T3 response, indicating a hormonal cross-talk among the subfamily of nuclear receptors. Two orphan receptors, COUP-TF and v-erbA, also bind the DR-8 sequence in the human H1(0) promoter. COUP-TF, which usually represses RAREs, enhances transcriptional activation through the DR-8 whereas v-erbA completely represses TR-RXR induction of the H1(0) gene. Thus, a number of signaling pathways that play important roles during development and differentiation are able to influence the transcription rate of this special H1 subtype directly through a DR-8 response element in its promoter. Because H1(0) expression levels inversely correlate with cell proliferation, our data suggest that several nuclear receptors and the v-erbA oncogene can influence cell proliferation via the regulation of H1(0) expression.

Base Sequence↗
PubMed2000

Leptin and TGF-beta synergistically regulate VIP cytokine response element transcription.

Leptin was originally described as an adipocyte-derived cytokine that signals to the hypothalamus to regulate food intake and energy expenditure. Leptin signals through the Ob receptor, which is closely related to the gp130 cytokine receptor. Here we show that leptin can induce expression of the neuropeptide gene vasoactive intestinal peptide (VIP) through the VIP cytokine response element, the same element that mediates the response to the gp130 cytokines. Leptin acts synergistically with TGF-beta to activate transcription through this element. Transcriptional responses to leptin are increased when transmitted through ObR mutated at Tyr986, the SHP-2 docking domain, yet this mutation does not alter the synergy between TGF-beta and leptin. These data emphasize the functional similarity between leptin and the gp130 cytokines.

Animals↗
PubMed2002

Corepressor SMRT functions as a coactivator for thyroid hormone receptor T3Ralpha from a negative hormone response element.

Nuclear receptors are ligand-modulated transcription factors that transduce the presence of lipophilic ligands into changes in gene expression. Nuclear receptor activity is regulated by ligand-induced interactions with coactivator or corepressor molecules. From a positive hormone response element (pHRE) and in the absence of hormone, corepressors SMRT and N-CoR are bound to some nuclear receptors such as the thyroid hormone (T3Rs) and retinoic acid receptors and mediate inhibition of basal levels of transcription. Ligand binding results in dissociation of corepressors and association of coactivators, resulting in the reversal of inhibition and a net activation of transcription. However, the role of cofactors on the activity of nuclear receptors from negative HREs (nHREs) is poorly understood. Here we show that corepressor SMRT can act as a potent coactivator for T3Ralpha from a nHRE; N-CoR has a similar but significantly attenuated activity. Mutagenesis of residues in the hinge region of T3Ralpha that block binding of SMRT and N-CoR inhibits ligand-independent transcriptional activation by T3Ralpha from a nHRE. These mutations also abrogate SMRT-mediated increase in transcriptional activity by T3Ralpha at a nHRE without significantly affecting ligand-dependent activation at a pHRE. Partial protease digestion coupled to the mobility shift assay indicate differences in the conformation of T3Ralpha-SMRT complexes bound to a pHRE versus a nHRE. These results suggest that allosteric changes resulting from binding of T3Ralpha to different response elements, i.e. pHREs versus nHREs, dictate whether a cofactor will function as a coactivator or a corepressor. This, in turn, greatly expands the repertoire of mechanisms used in modulating transcription without the need for expression of new regulatory molecules.

Allosteric Site↗
PubMed2002

The effects of estrogen-responsive element- and ligand-induced structural changes on the recruitment of cofactors and transcriptional responses by ER alpha and ER beta.

Estrogen signaling is mediated by ER alpha and -beta. ERs are converted from an inactive form to a transcriptionally active state through conformational changes induced by ligand and estrogen-responsive element (ERE) sequences. We show here that ER alpha and ER beta bind to an ERE independently from ER ligands. We found that although the binding affinity of ER beta for an ERE is 2-fold lower than that of ER alpha, both ERs use the same nucleotides for DNA contacts. We show that both EREs and ligands are independent modulators of ER conformation. Specifically, the ERE primarily determines the receptor-DNA affinity, whereas the structure of the ER ligand dictates the affinity of ER for particular cofactors. We found that the ligand-dependent cofactor transcriptional intermediary factor-2, through a distinct surface, also interacts with ER alpha preferentially and independently of ligand. The extent of interaction, however, is dependent upon the ER-ERE affinity. In transfected cells, ER alpha is more transcriptionally active than ER beta. The ERE sequence, however, determines the potency of gene induction when either ER subtype binds to an agonist. Antagonists prevent ERs from inducing transcription independently from ERE sequences. Thus, ERE- and ligand-induced structural changes are independent determinants for the recruitment of cofactors and transcriptional responses. The ability of ER alpha to differentially recruit a cofactor could contribute to ER subtype-specific gene responses.

Animals↗
PubMed1992

Characterization of a non-tissue-specific, 3',5'-cyclic adenosine monophosphate-responsive element in the proximal region of the rat prolactin gene.

The nature of a DNA element located in the -100 to -85 region of the rat PRL gene has been characterized. Previous studies demonstrated that this region may contribute to basal and hormonally regulated expression of the PRL gene. As this region contains a sequence with similarity to a consensus cAMP-responsive element (CRE), a possible role for the cAMP response element binding protein (CREB) has been explored. A point mutation which made the PRL CRE-like sequence less like a consensus CRE had little effect on basal or cAMP-stimulated expression of a PRL-luciferase reporter gene. DNase footprint studies demonstrated that the proximal region of the PRL gene does not contain a high affinity CREB binding site. Mobility shift experiments demonstrated that the major GH3 nuclear protein which interacts with the -100 to -85 region of the PRL gene in vitro is not CREB. Transfection of a dominant inhibitor of CREB action had little or no effect on expression of an indicator gene containing the PRL proximal region. Thus, the PRL proximal region does not contain a high affinity CREB binding site, and it is unlikely that CREB plays a major role in expression of the PRL gene. The functional capabilities of the -100 to -85 region of the PRL gene were then tested in a transfection assay. Synthetic multimers of this region were found to be sufficient to permit a transcriptional response to cAMP or TRH in GH3 cells and cAMP in Rat-1 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Inhibition of gene expression by steroid hormone receptors via a negative glucocorticoid response element: evidence for the involvement of DNA-binding and agonistic effects of the antiglucocorticoid/antiprogestin RU486.

We have used a negative glucocorticoid response element (nGRE) from the bovine prolactin promoter linked to the gene for chloramphenicol acetyltransferase (PRL3CAT) to study the inhibition of gene expression by steroid hormone receptors. This nGRE increased basal expression from a heterologous promoter in COS-7 cells. In the presence of cotransfected glucocorticoid (GR), androgen, or progesterone receptor (PR) expression vectors and their cognate ligands, the expression of PRL3CAT could be repressed, indicating that these steroid receptor subfamily members could function through the same negative response element. No repression was observed with the estrogen receptor, showing that the repressive effect was specific for members of the GR-subfamily. Mutation of three amino acids within the GR-DNA binding domain that determine the specificity of GR-GRE interaction abolished the ability of the GR to inhibit the expression of PRL3CAT, demonstrating the requirement for DNA binding of the GR in the mechanism of repression. The antiglucocorticoid/antiprogestin RU486 when bound to PR or GR also repressed the expression of the PRL3CAT, but higher concentrations of RU486 were required to obtain an effect with the GR when compared to the PR. RU486 was unable to antagonize the effect of progestins on PRL3CAT and only partially antagonized the glucocorticoid repression. Thus, regarding the repression of PRL3CAT, RU486 acted as an agonist when bound to the PR and as a partial agonist when bound to the GR.

Amino Acid Sequence↗
PubMed2003

Prostaglandin E2 stimulates bone sialoprotein (BSP) expression through cAMP and fibroblast growth factor 2 response elements in the proximal promoter of the rat BSP gene.

Bone sialoprotein (BSP), an early marker of osteoblast differentiation, has been implicated in the nucleation of hydroxyapatite during de novo bone formation. Prostaglandin E2 (PGE2) has anabolic effects on proliferation and differentiation of osteoblasts via diverse signal transduction systems. Because PGE2 increases the proportion of functional osteoblasts in fetal rat calvarial cell cultures, we investigated the regulation of BSP, as an osteoblastic marker, by PGE2. Treatment of rat osteosarcoma UMR 106 cells with 3 microm, 300 nm, and 30 nm PGE2 increased the steady state levels of BSP mRNA about 2.7-, 2.5-, and 2.4-fold after 12 h. From transient transfection assays, the constructs including the promoter sequence of nucleotides (nt) -116 to +60 (pLUC3) were found to enhance transcriptional activity 3.8- and 2.2-fold treated with 3 microm and 30 nm PGE2 for 12 h. 2-bp mutations were made in an inverted CCAAT box (between nt -50 and -46), a cAMP response element (CRE; between nt -75 and -68), a fibroblast growth factor 2 response element (FRE; nt -92 to -85), and a pituitary-specific transcription factor-1 motif (between nt -111 and -105) within pLUC3 and pLUC7 constructs. Transcriptional stimulation by PGE2 was almost completed abrogated in constructs that included 2-bp mutations in either the CRE and FRE. In gel shift analyses an increased binding of nuclear extract components to double-stranded oligonucleotide probes containing CRE and FRE was observed following treatment with PGE2. These studies show that PGE2 induces BSP transcription in UMR 106 cells through juxtaposed CRE and FRE elements in the proximal promoter of the BSP gene.

Animals↗
PubMed2001

A novel yeast system for in vivo selection of recognition sequences: defining an optimal c-Myb-responsive element.

Yeast (Saccharomyces cerevisiae) has proved to be a highly valuable tool in a range of screening methods. We present in this work the design and use of a novel yeast effector-reporter system for selection of sequences recognised by DNA-binding proteins in vivo. A dual HIS3-lacZ reporter under the control of a single randomised response element facilitates both positive growth selection of binding sequences and subsequent quantification of the strength of the selected sequence. A galactose-inducible effector allows discrimination between reporter activation caused by the protein under study and activation due to endogenous factors. The system mimics the physiological gene dosage relationship between transcription factor and target genes in vivo by using a low copy effector plasmid and a high copy reporter plasmid, favouring sequence selectivity. The utility of the novel yeast screening system was demonstrated by using it to refine the definition of an optimal recognition element for the c-Myb transcription factor (MRE). We present screening data supporting an extended MRE consensus closely mimicking known strong response elements and where a sequence of 11 nt influences activity. Novel features include a more strict sequence requirement in the second half-site of the MRE where a T-rich sequence is preferred in vivo.

Binding Sites↗
PubMed1991

Estrogen receptor alters the topology of plasmid DNA containing estrogen responsive elements.

We have recently used DNA containing estrogen responsive element (ERE) sequences for affinity purification to prepare calf uterine estrogen receptor (ER) at near homogeneity. The capacity of this purified ER to alter DNA topology upon binding was examined. Although the ER is not a topoisomerase, the presence of ER changes the distribution of topoisomers generated by incubation of plasmid DNA with excess wheat germ topoisomerase I. This effect is larger in plasmids containing a consensus ERE sequence. Two dimensional gel electrophoretic analysis suggested that interaction of ER and ERE causes negative supercoiling in regions of the plasmid accessible to topoisomerase I, resulting from overwinding of DNA contacting the ER. The extent of topological alteration was dependent on ER concentration. We suggest that the observed conformational changes in the DNA could have a role in regulation of transcription.

Animals↗
PubMed1986

A complete library of point substitution mutations in the glucocorticoid response element of mouse mammary tumor virus.

The glucocorticoid response element (GRE) of mouse mammary tumor virus (MMTV) was chemically synthesized as two complementary DNA strands bearing cohesive termini. During automated synthesis, random mutations were introduced into the DNA by "doping" each of the four nucleoside phosphoramidites (A, G, C, and T) with a low level of the other three. These preparations were annealed and cloned into an M13 phage vector to produce a library of GRE mutants. Mutations within the synthesized region were identified by sequencing phage isolates at random. All of the chemically distinct classes of transition and transversion mutations have been observed. Statistical considerations indicate that the library contains all of the possible 90 point substitution mutations within a 30-nucleotide mutagenic target. So far 88 of these substitutions have been isolated, 74 as single mutants. At least two of the three possible single mutants at each of the 30 positions have been identified.

Base Sequence↗
PubMed1995

Succinate dehydrogenase b mRNA of Drosophila melanogaster has a functional iron-responsive element in its 5'-untranslated region.

Iron-responsive elements (IREs) are cis-acting mRNA stem-loop structures that specifically bind cytoplasmic iron regulatory proteins (IRPs). IRP-IRE interactions mediate the coordinate post-transcriptional regulation of key proteins in iron metabolism, such as ferritin, transferrin receptor, and erythroid 5-aminolevulinic acid synthase. Depending on whether the IRE is located in the 5'- or 3'-untranslated region (UTR), binding of IRP will inhibit mRNA translation or degradation, respectively. Here we describe a new IRE in the 5'-UTR of succinate dehydrogenase subunit b (SDHb) mRNA of Drosophila melanogaster. The SDHb IRE binds in vitro to vertebrate and insect IRPs with a high affinity equal to that of human ferritin H chain IRE. Under conditions of iron deprivation, SDHb mRNA of Drosophila SL-2 cells shifts to a non-polysome-bound pool. Moreover, translation of a human growth hormone mRNA with the SDHb IRE in its 5'-UTR is iron-dependent in stably transfected L cells. We conclude that the SDHb IRE mediates translational inhibition both in insect and vertebrate cells. This constitutes the first identification of a functional IRE in insects. Furthermore, Drosophila SDHb represents the second example, after porcine mitochondrial aconitase, of an enzyme of the citric acid cycle whose mRNA possesses all necessary features for translational regulation by cellular iron levels.

Animals↗
PubMedDate not supplied

cDNA cloning of a mouse factor that activates transcription from a metal response element of the mouse metallothionein-I gene in yeast.

A cDNA that encodes a mouse factor that activates expression from a metal response element of the mouse metallothionein-I gene has been isolated by complementation cloning in yeast cells. The cDNA encodes a peptide with a maximum length of 99 amino acids that includes a single zinc finger sequence. In yeast cells, the cloned factor induces transcription from the metal response element in a sequence-specific but metal-independent fashion. The cDNA hybridizes to a 550-base mRNA that is constitutively expressed in mouse tissue culture cells. The ability of the mouse factor to activate transcription in yeast cells is dependent upon the carbon source.

Amino Acid Sequence↗
PubMed1990

Interaction of cytokine- and glucocorticoid-response elements of acute-phase plasma protein genes. Importance of glucocorticoid receptor level and cell type for regulation of the elements from rat alpha 1-acid glycoprotein and beta-fibrinogen genes.

Dexamethasone increased the transscriptional activity of several acute-phase plasma protein genes in cytokine-treated HepG2 cells, suggesting the presence of functional glucocorticoid receptors (GR). The level of GR was, however, insufficient for stimulation of transiently transfected gene constructs containing glucocorticoid-response elements (GRE). By complementation of HepG2 cells with a GR expression vector, a cell system was generated that allowed analysis of the interaction between GRE and cytokine-response elements of the rat alpha 1-acid glycoprotein gene and identification of the principal regulatory elements of the rat beta-fibrinogen gene. Although the expression of plasmid-derived GR mRNA was reduced by dexamethasone treatment, the concentration of GR was sufficient for full, short-term stimulation of GRE-containing vectors. By comparing the pattern of regulation of the cloned GRES in HepG2 and mouse L-cells, an equivalent, cell-type independent dexamethasone response was monitored for the alpha 1-acid glycoprotein element but a response limited to HepG2 cells was found for the beta-fibrinogen element. The data indicate that, although substantial differences exist in the organization and composition of the regulatory elements of the two genes, the overall function is, nevertheless, remarkably similar.

Acute-Phase Proteins↗
PubMed2004

Novel role for a sterol response element binding protein in directing spermatogenic cell-specific gene expression.

Sperm are highly specialized cells, and their formation requires the synthesis of a large number of unique mRNAs. However, little is known about the transcriptional mechanisms that direct male germ cell differentiation. Sterol response element binding protein 2gc (SREBP2gc) is a spermatogenic cell-enriched isoform of the ubiquitous transcription factor SREBP2, which in somatic cells is required for homeostatic regulation of cholesterol. SREBP2gc is selectively enriched in spermatocytes and spermatids, and, due to its novel structure, its synthesis is not subject to cholesterol feedback control. This suggested that SREBP2gc has unique cell- and stage-specific functions during spermatogenesis. Here, we demonstrate that this factor activates the promoter for the spermatogenesis-related gene proacrosin in a cell-specific manner. Multiple SREBP2gc response elements were identified within the 5'-flanking and proximal promoter regions of the proacrosin promoter. Mutating these elements greatly diminished in vivo expression of this promoter in spermatogenic cells of transgenic mice. These studies define a totally new function for an SREBP as a transactivator of male germ cell-specific gene expression. We propose that SREBP2gc is part of a cadre of spermatogenic cell-enriched isoforms of ubiquitously expressed transcriptional coregulators that were specifically adapted in concert to direct differentiation of the male germ cell lineage.

3T3-L1 Cells↗
PubMed1999

Neuroendocrine cell type-specific and inducible expression of the secretogranin II gene: crucial role of cyclic adenosine monophosphate and serum response elements.

Secretogranin II, an acidic protein in the chromogranin/secretogranin family, is widely distributed in neuroendocrine secretory granules. What factors govern such widespread, yet selective, expression? The 5' deletions localized neuroendocrine cell type-specific expression to the proximal mouse secretogranin II promoter: such expression was abolished after deletion past the cAMP response element (CRE; [-67 bp]TGACGTCA[-60 bp]), and transfer of the CRE to a neutral promoter conferred 3.4- to 5.3-fold neuroendocrine selectivity. Thus, the CRE is, at least partly, sufficient to confer tissue-specific expression. Substantial (48-59%) loss of cell type-specific expression also occurred upon deletion past the serum response element (SRE; [-302 bp]GATGTCC[-296 bp]), and transfer of the SRE to a neutral promoter also conferred neuroendocrine selectivity. Expression of both the endogenous gene and the transfected secretogranin II promoter was up-regulated after secretagogues, and the degree of trans-activation of the transfected promoter (2.2- to 5.4-fold) paralleled activation of the endogenous gene (1.8- to 3.2-fold). The 5' promoter deletions revealed complete loss of secretagogue responses after deletion past the CRE. Transfer of the CRE to a neutral promoter conferred secretagogue responses (by 2.2- to 18.6-fold). Substantial (59-74%) falls in secretagogue responses also occurred after deletion past the promoter's SRE. Transfer of the SRE to a neutral promoter conferred secretagogue responses (by 2.7- to 8.3-fold). We conclude that the CRE is a crucial determinant of cell type-specific constitutive and secretagogue-inducible expression of the secretogranin II gene and that the SRE also plays a substantial role in both processes.

Animals↗
PubMed2002

pH dependent conformational changes within the iron responsive element.

The expression of several mRNAs related to iron importation, storage and utilization within mammalian cells are regulated through interactions of iron regulatory proteins with an iron responsive element, an RNA hairpin with a bulged C. A dimethylsulfate modification interference assay was used to demonstrate that the iron responsive element undergoes significant pH dependent conformational changes. Specifically, it was demonstrated that the phylogenetically conserved A within the hairpin loop and an intra-loop C-G base pair are highly sensitive to changes in pH. The conserved C of the bulged loop does not significantly affect the pH dependent conformational changes of the hairpin loop. These studies have structural implications for an RNA-protein interaction that is critical to mammalian iron regulation.

Animals↗
PubMed2004

Tyrosine hydroxylase transcription depends primarily on cAMP response element activity, regardless of the type of inducing stimulus.

In neurons and neuroendocrine cells, tyrosine hydroxylase (TH) gene expression is induced by stimuli that elevate cAMP, by depolarization, and by hypoxia. Using these stimuli, we examined TH promoter mutants, cAMP response element binding protein (CREB) phosphorylation site mutants, and transcriptional interference with dominant negative transcription factors to assess the relative contributions of CREB/AP-1 family members to the regulation of basal and inducible TH transcription in PC12 cells. We found that basal transcription depends on transcription factor activity at the partial dyad (-17 bp), CRE (-45 bp), and AP1 (-205 bp) elements. Induced transcription is regulated primarily by activity at the CRE, with only small contributions from the AP1 or hypoxia response element 1 (HRE1; -225 bp) elements, regardless of inducing stimulus. CREB, ATF-1, and CREMtau all mediate CRE-dependent transcription, with CREB and CREMtau being more effective than ATF-1. Phosphorylation of CREB on Ser133, but not on Ser142 or Ser143, is required for induced transcription, regardless of inducing stimulus.

Animals↗
PubMed2004

An intact DNA-binding domain is not required for peroxisome proliferator-activated receptor gamma (PPARgamma) binding and activation on some PPAR response elements.

Peroxisome proliferator-activated receptor gamma (PPARgamma) interacts with retinoid X receptor (RXR) on PPAR response elements (PPREs) to regulate transcription of PPAR-responsive genes. To investigate the binding of PPARgamma and RXR to PPREs, three mutations were constructed in the DNA-binding domains of PPARgamma; two of the mutants maintained the structure of zinc finger I (PPARgamma-GS and PPARgamma-AA), and a third mutation disrupted the protein structure of zinc finger I (PPARgamma-CS). Results indicated that the mutations of PPARgamma that maintained intact zinc fingers were capable of binding to a variety of PPREs in the presence of RXR and could activate transcription on several PPREs. In parallel, a mutation was created in the DNA-binding domain of RXRalpha that maintained the structure of the zinc fingers (RXR-GS) but did not bind DNA and was transcriptionally inactive. Examination of the 3' half-site of several PPREs revealed that variations from the consensus sequence reduced or abolished transcriptional activity, but conversion to consensus improved transcriptional activity with PPARgamma-GS and PPARgamma-AA. Examination of the 5' half-site indicated that the upstream three nucleotides were more important for transcriptional activity than the downstream three nucleotides. Our data demonstrated that stringent binding of RXR to the 3' half-site of a PPRE is more influential on the binding of the PPARgamma/RXR heterodimer than the ability of PPARgamma to bind DNA. Thus, unlike RXR, PPARgamma exhibits promiscuity in binding on a PPRE, suggesting that the definition of a PPRE for PPARgamma may need to be expanded.

Acyl-CoA Oxidase↗