Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.14.14.3 (luciferase)
 38,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatostatin receptor subtype 5 (sst5) has been linked to inhibition of PRL and insulin secretion. We characterized the genomic structure of the human sst5. The transcription start site was located 94 nucleotides upstream of the initiator ATG codon. Sequence analysis of 5'-inverse PCR products revealed the presence of a 6.1-kb intron in the 5'-untranslated region. RT-PCR analysis indicated tissue-specific activation of the newly identified upstream promoter in pituitary, but not in small intestine, lung, or placenta. A -1741 promoter directed significant levels of luciferase expression in GH(4) rat pituitary cells, Skut-1B endometrium cells, and JEG3 chorion carcinoma cells, which was absent in COS-7 monkey kidney cells. A minimal -101 promoter was sufficient to allow tissue-specific expression. Its activity in COS-7 cells was not enhanced by cotransfection of the pituitary-specific transcription factor Pit-1. Analysis of deletion constructs revealed a GC-rich region immediately upstream of the transcription start site, which is necessary for promoter activity. Somatostatin led to a significant inhibition, and forskolin and thyroid hormone to a significant stimulation of pituitary-specific promoter activity. Further mapping suggested a cAMP-responsive element located between -101 and the transcription start site, and thyroid hormone-responsive elements between -1741 and -1269 and between -317 and -101. These studies identified an upstream promoter of the sst5 gene with tissue-specific activity.
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PMID:Identification of an upstream pituitary-active promoter of human somatostatin receptor subtype 5. 1207 95

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related chemicals causes a variety of tissue- and species-specific biological and toxicological effects, most of which are mediated by the aryl hydrocarbon receptor (AhR). The AhR complex is a ligand-dependent transcription factor that binds to its specific DNA recognition site as a dimer with the AhR nuclear translocator (ARNT) and activates gene transcription. Here, we have examined the ability of a nuclear corepressor, the silencing mediator of retinoic acid and thyroid hormone receptors (SMRT), to interact with and modulate AhR-dependent gene expression. Using glutathione S-transferase (GST) "pull-down" binding assays, we have mapped a major interaction between these factors to the silencing domain of SMRT and the PAS B ligand binding domain of AhR, and this interaction is unaffected by the addition of an AhR ligand. Association of SMRT with the AhR:ARNT:DNA complex was not detected by GST pull-down or gel retardation assays. Transient cotransfections of mammalian cells (Hepa1c1c7, MCF-7, and BG-1) with SMRT and a TCDD-inducible luciferase reporter containing the dioxin-responsive domain from the mouse CYP1A1 regulatory region revealed that SMRT does not repress, but enhances, AhR signaling. However, when a reporter containing a human CYP1A1 upstream region was cotransfected with SMRT into human MCF-7 cells, AhR-driven reporter activity was decreased by half, suggesting that SMRT acts on the human CYP1A1 promoter via a factor other than the AhR in MCF-7 cells. Furthermore, the interaction between SMRT and the AhR may have implications in pathways other than the AhR signaling pathway.
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PMID:The silencing mediator of retinoic acid and thyroid hormone receptors can interact with the aryl hydrocarbon (Ah) receptor but fails to repress Ah receptor-dependent gene expression. 1213 68

Xenopus laevis is an excellent model for thyroid hormone (T3)-regulated gene expression. T3 initiates two drastically different pathways during metamorphosis: death of larval tissues and growth of adult tissues. The role that each T3 receptor (TR) isotype, alpha and beta, plays in metamorphosis is uncertain. The X.laevis tetraploid genome limits experiments to overexpression, misexpression and dominant negative studies. Ribozymes offer an alternative by suppressing gene activity through specific mRNA reduction. It has been suggested that ribozymes will not work in X.laevis because of the organism's intracellular environment and body temperature. In this study, we show that hammerhead ribozymes are active in vitro against transcribed TRbeta message and in vivo against a TRbeta-luciferase fusion protein. We next show that TRbeta-targeted ribozymes can inhibit T3-induced transcription of a reporter gene in cultured X.laevis cells, using T3 response elements from two T3-responsive transcription factor genes. One has early expression kinetics in response to T3 and is proposed to be TRalpha regulated whereas the other has intermediate induction kinetics and thus may be partially TRbeta regulated. Therefore, ribozymes are a potentially valuable tool for overcoming the limitations in this system for examining gene function in X.laevis.
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PMID:Ribozyme suppression of endogenous thyroid hormone receptor activity in Xenopus laevis cells. 1214 Mar 35

Neuropeptides act within the pituitary as autocrine or paracrine factors, modulating the synthesis and release of primary pituitary hormones, and possibly regulating cell proliferation and/or plasticity. Manipulation of the endocrine status of rats produces dramatic long-term changes in the pituitary expression of several peptides, including the neuropeptides galanin and vasoactive intestinal peptide (VIP). Whether or not these changes are caused indirectly by hypothalamic factors, or by hormone actions directly in the pituitary, has been only partially addressed. To determine if estrogen or thyroid hormone can act directly within the pituitary to regulate VIP and galanin gene expression, cultured female rat pituitary cells were treated with 10 nM 1,17 beta-estradiol (E2) or triiodothyronine (T(3)). E2 treatment for three days resulted in an approximate 5-fold and 7-fold increase in VIP and galanin mRNA, respectively. In contrast, T(3) treatment reduced the mRNA levels of these neuropeptides to approximately 40% and 30% of control values. A time course study indicated that the actions of estrogen on VIP and galanin mRNA, and of thyroid hormone on VIP mRNA were readily apparent after 24h. The rat pituitary tumor cell line RC-4B/C was found to express easily detectable levels of galanin but not VIP mRNA. Galanin gene expression in these cells was moderately increased by E2 and decreased by T(3). Transfection of a series of luciferase plasmids containing 5 kb to 131 bp of the bovine galanin promoter fused to luciferase revealed cell-type specific enhancer sequences located between -452 and -131 bp of the galanin gene transcription start site. However, transfected plasmids were minimally responsive to E2 and T(3) treatment. Overall the results suggest that E2 and T(3) exert significant local actions in the pituitary on VIP and galanin gene expression. The bovine galanin gene fragment used in these studies contains a potential pituitary cell-type specific enhancer, but appears to lack strong E2-and T(3)-responsive sequences.
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PMID:Local action of estrogen and thyroid hormone on vasoactive intestinal peptide (VIP) and galanin gene expression in the rat anterior pituitary. 1214 14

Carnitine palmitoyltransferase-I (CPT-I) catalyzes the rate-controlling step of fatty acid oxidation. CPT-I converts long-chain fatty acyl-CoAs to acylcarnitines for translocation across the mitochondrial membrane. The mRNA levels and enzyme activity of the liver isoform, CPT-Ialpha, are greatly increased in the liver of hyperthyroid animals. Thyroid hormone (T3) stimulates CPT-Ialpha transcription far more robustly in the liver than in non-hepatic tissues. We have shown that the thyroid hormone receptor (TR) binds to a thyroid hormone response element (TRE) located in the CPT-Ialpha promoter. In addition, elements in the first intron participate in the T3 induction of CPT-Ialpha gene expression, but the CPT-Ialpha intron alone cannot confer a T3 response. We found that deletion of sequences in the first intron between +653 and +744 decreased the T3 induction of CPT-Ialpha. Upstream stimulatory factor (USF) and CCAAT enhancer binding proteins (C/EBPs) bind to elements within this region, and these factors are required for the T3 response. The binding of TR and C/EBP to the CPT-Ialpha gene in vivo was shown by the chromatin immunoprecipitation assay. We determined that TR can physically interact with USF-1, USF-2, and C/EBPalpha. Transgenic mice were created that carry CPT-Ialpha-luciferase transgenes with or without the first intron of the CPT-Ialpha gene. In these mouse lines, the first intron is required for T3 induction as well as high levels of hepatic expression. Our data indicate that the T3 stimulates CPT-Ialpha gene expression in the liver through a T3 response unit consisting of the TRE in the promoter and additional factors, C/EBP and USF, bound in the first intron.
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PMID:A thyroid hormone response unit formed between the promoter and first intron of the carnitine palmitoyltransferase-Ialpha gene mediates the liver-specific induction by thyroid hormone. 1249 35

Real-time imaging of the GH gene promoter linked to luciferase in living pituitary cells has revealed surprising heterogeneity and variety of dynamic patterns of gene expression. Cells treated with either forskolin or thyroid hormone generated a consistent and characteristic temporal response from cell populations, but detailed analysis of individual cells revealed different patterns. Approximately 25-26% of cells displayed no response, 25-33% of cells exhibited a sustained progressive rise in luciferase activity, and 41-50% showed a transient phasic, or oscillatory response, after given stimuli. In cells treated consecutively with the two stimuli, the population response to the second stimulus was augmented. Single-cell analysis revealed that this was partly due to an increased number of cells responding, but also that the prevalence of response patterns changed: cells that responded to an initial stimulus were more likely to respond subsequently in a progressive sustained manner. In conclusion, these studies have indicated that GH promoter activity in individual living pituitary cells is unstable and possibly stochastic, with dynamic variations from hour to hour. The prevalence of different temporal patterns of response to hormonal stimulation among a population of cells is altered by the endocrine history of those cells.
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PMID:Dynamic patterns of growth hormone gene transcription in individual living pituitary cells. 1255 47

We have previously demonstrated that liposomes generated from poly(cationic lipid) (PCL) and cholesterol (Chol) have low cytotoxicity, are serum resistant, and display a transfection efficiency in vitro similar to commercially available cationic liposomes. Our in vivo experiments demonstrated that PCL-Chol liposomes bound much less avidly to serum proteins than did liposomes composed of 1,2-bis(dioleoyloxy)-3-(trimethylamonio)propane (DOTAP)-Chol or DOTAP-L-alpha dioleoyl phosphatidylethanolamine (DOPE). Injection of the lipoplexes (PCL-Chol+DNA) through the portal vein after partial hepatectomy (PH) led to much higher reporter gene expression (luciferase) in the liver than did naked DNA injection. Marked green fluorescent protein expression was visualized in almost all hepatocytes in the liver of mice receiving lipoplex injection, even in the absence of PH. Subcutaneous injection of thyroid hormone triiodothyromine (T(3)) significantly promoted hepatocyte regeneration and markedly enhanced PCL-Chol-mediated gene transfer in mouse liver when the lipoplex was administrated through either portal or tail vein. With T(3) pretreatment, PCL-Chol exerted a better gene transfer efficacy in mouse liver than DOTAP-Chol or DOTAP-DOPE. Two injections of lipoplexes through an indwelling catheter in the portal vein extended the transgene expression at a high level when T(3) injection was repeated. In conclusion, our findings demonstrate that the polymerized cationic liposomes are very stable in the blood and are effective agents for in vivo gene delivery, and that thyroid hormone administration offers a non-invasive approach to enhance liposome-mediated liver gene delivery.
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PMID:Poly(cationic lipid)-mediated in vivo gene delivery to mouse liver. 1257 47

Thyroid hormones are important for mammary gland growth and development. The iodothyronine deiodinases play a key role in thyroid hormone metabolism. We have showed that type II 5'-deiodinase (5'D2) activity and mRNA are present in the mouse mammary gland and that their levels are reduced in the lactating gland. To investigate the regulatory mechanism of mouse 5'D2 gene (mdio2) expression in mammary epithelium, we employed the HC11 cell line, which is derived from mouse mammary epithelial cells and retains the ability to express differentiated function. HC11 cells were treated with combinations of insulin, glucocorticoid (GC, dexamethasone), prolactin, and epidermal growth factor (EGF), and 5'D2 activity and the D2-to-GAPDH mRNA ratio were measured by (125)I(-) release from (125)I-labeled thyroxine and semiquantitative RT-PCR, respectively. EGF increased both 5'D2 activity and mRNA levels about twofold. GC reduced both 5'D2 activity and mRNA in a dose-dependent manner, and their levels were decreased to approximately one-tenth and one-fifth, respectively, of control levels. These data demonstrated that mdio2 expression in HC11 cells is upregulated by EGF mainly at the pretranslational level and downregulated by GC at both pre- and posttranslational levels. Furthermore, we showed that GC reduced the promoter activity of the 627- bp 5'-upstream region of the mdio2/luciferase chimeric reporter gene, suggesting that GC exerts its effect, at least in part, at the transcriptional level.
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PMID:Regulation of type II deiodinase expression by EGF and glucocorticoid in HC11 mouse mammary epithelium. 1258 14

Estrogens and thyroid hormones play a significant role in regulating functions and development of the testis. The synthesis of estrogens from androgens is catalyzed by the enzyme complex termed aromatase, which in the testis displays an age-related cellular compartmentalization, primarily in Sertoli cells in immature animals, whereas in adults it is expressed in Leydig and germ cells. T3 induces a precocious terminal differentiation of prepubertal Sertoli cells together with a dramatic decrease of their aromatase activity. In the present work, we have examined the mechanism by which T3 exerts this inhibitory action on aromatase expression. As an experimental model, we used the mouse Sertoli cell line TM4, which conserves a large spectrum of functional features present in immature Sertoli cells. For instance, after revealing the presence of aromatase by immunocytochemistry and measuring its enzymatic activity, we confirmed in this cell line the functional events previously characterized in primary cultures of immature rat Sertoli cells: 1) a strong stimulation of aromatase activity by dibutyryl-cAMP [(Bu)2cAMP] (simulating FSH action); and 2) the inhibition of aromatase activity by incubation with T3 under basal condition and after (Bu)2cAMP stimulation. After identifying promoter II as the regulatory region located immediately upstream of the transcriptional initiation site in the TM4 cell line by rapid amplification of cDNA ends analysis, we conducted experiments to examine the molecular mechanism by which thyroid hormones modulate aromatase gene expression in this cell line. TM4 cells were transfected with plasmids containing different segments of the rat promoter II sequence ligated to a luciferase reporter gene. Analysis of the activities of these promoter fusions demonstrated that T3 inhibits basal and (Bu)2cAMP-stimulated activity of the aromatase promoter. This effect was not revealed in T3-treated cells transfected with construct in which the steroidogenic factor-1 (SF-1) response element was mutated. These results indicate that the inhibitory effect of T3 requires the integrity of the SF-1 response element and are further supported in the EMSA. The EMSA experiments demonstrated that thyroid hormone/thyroid receptor alpha1 complex (TH/TRalpha1) is able to compete with SF-1 in binding to oligonucleotides containing an SF-1 motif, an element essential for the activity of the PII aromatase promoter. The findings suggest that the binding of the thyroid hormone/thyroid receptor alpha1 complex to the SF-1 motif is the molecular mechanism by which T3 exerts an inhibitory effect on aromatase gene expression in the TM4 cell line.
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PMID:Triiodothyronine decreases the activity of the proximal promoter (PII) of the aromatase gene in the mouse Sertoli cell line, TM4. 1258 41

Thyroid hormone has a broad effect on cardiovascular system. 3,3',5-triiodo-l-thyronine (T3), a biologically active form of thyroid hormone, increases cardiac contractility. T3 causes arterial relaxation and reduction of systemic vascular resistance, resulting in an increase in cardiac output. However, the molecular mechanisms of vascular relaxation by T3 are incompletely characterized. We studied the effect of T3 on the angiotensin (Ang) II type 1 receptor (AT1R) expression in vascular smooth muscle cells. T3 dose-dependently decreased expression levels of AT1R mRNA, with a peak at 6 hours of stimulation. Binding assay using [125I]Sar1-Ile8-Ang II revealed that AT1R number was decreased by stimulation with T3 without changing the affinity to Ang II. T3 reduced calcium response of vascular smooth muscle cells to Ang II by 26%. AT1R promoter activity measured by luciferase assay was reduced by 50% after 9 hours of T3 administration. mRNA stability was also decreased by T3. Real-time quantitative reverse transcription-polymerase chain reaction and Western blot analysis revealed that AT1R mRNA and protein were downregulated in the aorta of T3-treated rats. These results suggest that T3 downregulates AT1R expression both at transcriptional and posttranscriptional levels, and attenuates biological function of Ang II. Our results suggest that downregulation of AT1R gene expression may play an important role for T3-induced vascular relaxation.
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PMID:Downregulation of vascular angiotensin II type 1 receptor by thyroid hormone. 1262 65


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