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ABSTRACT
In order to perform later studies on the transcriptional regulation of hormone-dependent genes in fish liver, we firstly examined the potential of trout liver nuclear extracts in a cell-free transcription system. As reporter genes, we used DNA sequences without G (G-free cassettes) under the control of three promoters derived from the 5′ flanking sequence of the Xenopus vitellogenin B1 gene; two of them were responsive to the oestrogen receptor (ER) through oestrogen responsive elements (ERE). Maximal transcriptional activity was obtained within a range of 40–130 μg protein per extract depending on the extract preparation. Transcription was maximal in reactions carried out at 25 °C.
Similar transcriptional activities for the three promoters were observed when transcription was performed in extracts from untreated male trout. In contrast, we observed a 4·5- to 6-fold increase in the transcription with ERE-containing promoters in comparison with that with the minimal promoter bearing only a TATA box when extracts from oestradiol-treated male trout were used. This effect was correlated with the increase in the nuclear ER concentration induced by in vivo hormonal treatment. This enhanced transcription was specifically inhibited by the addition of a 25- to 100-fold excess of ERE oligonucleotide competitor.
These data demonstrated, therefore, that transcription was ERE-dependent in this system and suggest strongly that it was mediated by the trout ER. Addition of oestradiol or the anti-oestrogens hydroxytamoxifen or ICI 164384 had no effect on the transcriptional activity of the two ERE-containing promoters, indicating that transcription was hormone-independent in trout liver nuclear extracts.
Servicio de Endocrinología, Hospital Carlos III-C.I.C., Instituto de Salud Carlos III, Sinesio Delgado, 10-12, 28029 Madrid, Spain.
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Servicio de Endocrinología, Hospital Carlos III-C.I.C., Instituto de Salud Carlos III, Sinesio Delgado, 10-12, 28029 Madrid, Spain.
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Servicio de Endocrinología, Hospital Carlos III-C.I.C., Instituto de Salud Carlos III, Sinesio Delgado, 10-12, 28029 Madrid, Spain.
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Servicio de Endocrinología, Hospital Carlos III-C.I.C., Instituto de Salud Carlos III, Sinesio Delgado, 10-12, 28029 Madrid, Spain.
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Servicio de Endocrinología, Hospital Carlos III-C.I.C., Instituto de Salud Carlos III, Sinesio Delgado, 10-12, 28029 Madrid, Spain.
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). Previous studies have provided evidence of an important role for cAMP not only in the regulation of lactotroph functions, such as secretion, synthesis and transcriptional regulation of PRL ( Maurer 1981 , Swennen & Denef 1982 , Liang et al. 1992
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Oestrogens protect against ischaemic heart disease in the post-menopausal female by increasing serum concentrations of apolipoprotein (apo) AI and the abundance of high-density lipoprotein particles. In men and experimental male animals, the administration of oestrogen has variable effects on apo AI expression. As the major mode of oestrogen action on target genes involves regulating promoter activity and hence transcription, oestrogen is expected to alter transcription of the apo AI gene. To test this hypothesis, the effect of 17beta-oestradiol (E(2)), on rat apo AI promoter activity in male hepatoma HuH-7 cells, was tested by co-transfecting a reporter template, pAI.474.CAT containing-474 to-7 of the rat apo AI promoter and an oestrogen receptor (ER) expression vector, pCMV-ER. Transfected cells exposed to E(2) showed a dose-dependent decrease in chloramphenicol acetyltransferase (CAT)-activity, with a maximum 91+/-1.5% reduction at 1 microM E(2). Deletional analysis of the promoter localized the inhibitory effect of ER and E(2) to site B (-170 to-144) with an adjacent 5' contiguous motif, site S (-186 to-171) acting as an amplifier. HuH-7 cell nuclear extracts showed binding activities with both sites S and B, but recombinant human ER did not. Furthermore, nuclear extracts from E(2)-treated HuH-7 cells showed weaker binding activity to site B, but not to site S. In summary, the inhibitory effect of ER and E(2) on rat apo AI gene activity is mediated by a promoter element, site B. This inhibitory effect arises from a mechanism that does not involve direct ER binding to the B-element. The conclusion that E(2) inhibits apo AI transcription was confirmed in vivo. Treatment of male adult Sprague-Dawley rats with up to 200 microg E(2) for 7 days decreased apo AI protein and hepatic mRNA by 72+/-21% and 68+/-1.4% respectively. Results of 'run-on' transcription of the apo AI gene in isolated hepatic nuclei showed a 55% decrease in hormone-treated male rats. These findings suggest that E(2) exerts primarily an inhibitory effect within male hepatic nuclei.
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A contemporary view of hormone action at the transcriptional level requires knowledge of the transcription factors including the hormone receptor that may bind to promoters or enhancers, together with the chromosomal context within which these regulatory proteins function. Nuclear receptors provide the best examples of transcriptional control through the targeted recruitment of large protein complexes that modify chromosomal components and reversibly stabilize or destabilize chromatin. Ligand-dependent recruitment of transcriptional coactivators destabilizes chromatin by mechanisms including histone acetylation and contacts with the basal transcriptional machinery. In contrast, the recruitment of corepressors in the absence of ligand or in the presence of hormone antagonists serves to stabilize chromatin by the targeting of histone deacetylases. Both activation and repression require the action of other chromatin remodeling engines of the switch 2/sucrose non-fermentable 2 (SWI2/SNF2) class. Here we summarize this information and integrate hormone action into a chromatin context.
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of adult tissues ( Daftary & Taylor 2006 ). In general, HOX genes encode transcription factors that bind to promoters of various target genes through their homeodomain controlling their expression. HOX genes are associated in specifying primary
Department of Environmental and Occupational Medicine, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
Environmental and Occupational Health Sciences Institute and
Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington DC 20057, USA
The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA
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Department of Environmental and Occupational Medicine, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
Environmental and Occupational Health Sciences Institute and
Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington DC 20057, USA
The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA
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Department of Environmental and Occupational Medicine, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
Environmental and Occupational Health Sciences Institute and
Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington DC 20057, USA
The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA
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Department of Environmental and Occupational Medicine, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
Environmental and Occupational Health Sciences Institute and
Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington DC 20057, USA
The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA
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Department of Environmental and Occupational Medicine, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
Environmental and Occupational Health Sciences Institute and
Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington DC 20057, USA
The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA
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Department of Environmental and Occupational Medicine, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, New Brunswick, NJ 08903, USA
Environmental and Occupational Health Sciences Institute and
Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington DC 20057, USA
The Cancer Institute of New Jersey, New Brunswick, New Jersey 08903, USA
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receptors (ERαand ERβ), ligand-activated transcription factors present in target tissues (Katzenellenbogen et al. 2000, McKenna & O’Malley 2002 , Thomas et al. 2004 ). In general, estrogenic action involves the binding of the ligand to the ER, which
Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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Laboratory of Cellular Biology of Hypertension and Molecular Medicine, Department of Medicine, Centre Hospitalier de l’Université de Montréal, Montreal, Quebec, Canada
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controls ( Antonini et al. 2004 ). This suggests that abnormalities in transcription factors or co-factors could be responsible for the ectopic GIP-R expression in these patients. The recently cloned rat promoter does not have TATA or CAAT boxes
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This study evaluates the transcriptional and post-transcriptional regulation of prolactin (PRL) by vasoactive intestinal peptide (VIP). Pituitary nuclei from laying (control), incubating (with enhanced VIP secretion), and VIP-immunized laying turkey hens, and from pituitary cells cultured with or without VIP were used in nuclear run-on transcription assays. Cytoplasmic PRL mRNA was analyzed by slot blot hybridization. PRL transcription was greater in hyperprolactinemic incubating birds (PRL/beta-actin=3.33) than in laying birds (PRL/beta-actin=1.83). VIP-immunoneutralized birds had 47% and 51% decreases in PRL transcription and cytoplasmic PRL mRNA, respectively when compared with laying birds. In primary pituitary cell cultures, VIP significantly increased the transcription rate of PRL (3.8-fold) and cytoplasmic PRL mRNA (3.2-fold) compared with that of non-VIP-treated pituitary cells. The stability of pre-existing PRL mRNA was measured by Northern blot analysis after addition of actinomycin D. PRL mRNA half-lives were calculated using a two-component model, with a first-long component of 18.0+/-1.0 h and a second-short component of 3.7+/-0.7 h in non-VIP-treated pituitary cells. Both half-lives were significantly increased (53. 2+/-6.9 and 26.3+/-4.3 h) in VIP-treated cells. The present data show that VIP acts to stimulate PRL expression by up-regulating the transcription rate of PRL and by enhancing PRL mRNA stability.
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The effect of protein kinase C (PKC) delta on the transcriptional activity of the mouse estrogen receptor was investigated. The receptor was expressed transiently in Cos-1 and NIH3T3 cells in the presence of wild-type, dominant negative or constitutively active forms of PKC delta. Transfection experiments demonstrated that PKC delta stimulated both unliganded and liganded estrogen receptor transcriptional activity. This stimulatory effect was not observed using PKC alpha or PKC epsilon. 4-Hydroxytamoxifen and the pure anti-estrogen ICI 164,384 reduced receptor transcriptional activity in the presence of PKC delta. The stimulatory effect of PKC delta on estrogen receptor transcriptional activity was mediated by the N-terminal activation function 1 (AF-1) domain. The reduced stimulatory effect of PKC delta on transcriptional activity of the phosphorylation defective mutant of estrogen receptor suggests that phosphorylation of serine 122 in the AF-1 region may mediate the modulatory effect of PKC delta. Wild-type PKC delta caused a twofold increase in estrogen receptor phosphorylation, while a dominant negative mutant of PKC delta reduced the receptor phosphorylation to five percent of that caused by wild-type PKC delta. Our results suggest that PKC delta participates in the signaling pathways that lead to estrogen receptor phosphorylation and its effect on estrogen receptor transcriptional activation is both cell type and promoter specific.
Department of Reproductive Medicine, Center for Food and Nutritional Genomics Research, Division of Animal Biotechnology, Department of Biological Sciences, Cancer Research Institute and Department of Pathology, Aging Research Center, Department of Internal Medicine, School of Life Sciences and Biotechnology, University of California, San Diego, 9500 Gilman Drives, La Jolla, California 92093, USA
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Department of Reproductive Medicine, Center for Food and Nutritional Genomics Research, Division of Animal Biotechnology, Department of Biological Sciences, Cancer Research Institute and Department of Pathology, Aging Research Center, Department of Internal Medicine, School of Life Sciences and Biotechnology, University of California, San Diego, 9500 Gilman Drives, La Jolla, California 92093, USA
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Department of Reproductive Medicine, Center for Food and Nutritional Genomics Research, Division of Animal Biotechnology, Department of Biological Sciences, Cancer Research Institute and Department of Pathology, Aging Research Center, Department of Internal Medicine, School of Life Sciences and Biotechnology, University of California, San Diego, 9500 Gilman Drives, La Jolla, California 92093, USA
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degradation of unfolded and/or misfolded proteins using three ER-localized transmembrane proteins: inositol-requiring protein-1 (IRE1 (ERN1)), protein kinase RNA (PKR)-like ER kinase (PERK), and activating transcription factor-6 (ATF6) ( Schroder & Kaufman
