共查询到20条相似文献,搜索用时 0 毫秒
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Effect of the CCAAT/enhancer binding protein on expression of the gene for chicken malic enzyme 总被引:1,自引:0,他引:1
The gene for malic enzyme is expressed at a high level in chick embryo-hepatocytes (CEH) treated with triiodothyronine (T3) and at a low level in the absence of T3. In chick-embryo fibroblasts (CEF), expression of the malic enzyme gene is low and not regulated by T3. Specific nuclear proteins from both CEH and CEF bound to a consensus CCAAT/enhancer binding protein (C/EBP) site at -335 to -327 bp of the malic enzyme gene. The level of binding was much higher in extracts from CEH than in extracts of CEF, and the complexes formed had different mobilities. C/EBPalpha was present in the complex that bound to the C/EBP site in nuclear extracts from CEH but not in those from CEF. The C/EBP element was necessary and sufficient to bestow full T3 responsiveness to 5800 bp of 5'-flanking DNA of the malic enzyme gene in CEH. C/EBPalpha was not detectable in wild-type CEF, and deletion of the C/EBP binding site had no effect on expression of transgenes containing 5800 bp of 5'-flanking DNA of the malic enzyme gene. In CEF, overexpression of C/EBPalpha stimulated promoter activity of constructs that contained the C/EBP site linked to the malic enzyme promoter or a heterologous reporter. The results suggest that C/EBPalpha or a closely related isoform is involved in the tissue-specific expression of the malic enzyme gene. 相似文献
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Mouthiers A Baillet A Deloménie C Porquet D Mejdoubi-Charef N 《Molecular endocrinology (Baltimore, Md.)》2005,19(5):1135-1146
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Attard FA Wang L Potter JJ Rennie-Tankersley L Mezey E 《Archives of biochemistry and biophysics》2000,378(1):57-64
Acetaldehyde was previously shown to activate the alpha1(I) and alpha2(I) collagen promoters and to increase collagen production in activated stellate cells. Also, CCAAT/enhancer binding protein beta (C/EBPbeta) binds and activates the mouse alpha1(I) collagen promoter. This study investigates the role of C/EBPbeta in mediating the activation of the alpha1(I) collagen promoter by acetaldehyde. Nuclear extracts isolated from cultured activated rat hepatic stellate cells formed four protein-DNA complexes on electrophoretic mobility shift assay with an oligonucleotide including the C/EBP binding site between -365 and -335 in the alpha1(I) collagen promoter. The four complexes were identified to represent C/EBPbeta binding to the oligonucleotide by supershift with C/EBPbeta antibody. The principal C/EBP isoform found in the nuclear extracts from stellate cells was C/EBPbeta, with very low amounts of C/EBPalpha detected. Acetaldehyde (200 microM) increased C/EBPbeta protein in stellate nuclear extracts, increased its binding to the promoter, and activated the alpha1(I) collagen promoter in transfected stellate cells. Mutation of the C/EBPbeta binding site markedly decreased nuclear protein binding. A transfected promoter, mutated at the C/EBP binding site, had decreased basal activity, was not activated by acetaldehyde, and was not activated when cotransfected with a C/EBPbeta expression vector. This study shows that C/EBPbeta is the predominant C/EBP isoform found in activated stellate cells and that increased C/EBPbeta protein and C/EBPbeta binding to a proximal C/EBP binding site in the promoter mediates the activating effect of acetaldehyde. 相似文献
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Interaction between CCAAT/enhancer binding protein and cyclic AMP response element binding protein 1 regulates human immunodeficiency virus type 1 transcription in cells of the monocyte/macrophage lineage 下载免费PDF全文
Ross HL Nonnemacher MR Hogan TH Quiterio SJ Henderson A McAllister JJ Krebs FC Wigdahl B 《Journal of virology》2001,75(4):1842-1856
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The CCAAT/enhancer binding protein beta (C/EBPbeta) was previously shown to bind to the alpha(1)(I) collagen promoter at -365 to -335 (site 1) and to activate it. Acetaldehyde also activates the promoter, and this effect is mediated by an increase in stellate-cell C/EBPbeta protein and C/EBPbeta binding. The present study identified two additional distal sites (sites 2 and 3) of binding of C/EBPbeta, in the nuclear extracts of stellate cells, at -399 to -370 and -623 to -592 in the alpha(1)(I) collagen promoter. The C/EBPbeta protein activates the promoter at all three sites. Acetaldehyde increases C/EBPbeta binding to all three sites. Activation by acetaldehyde is abrogated in the transfected promoter mutated at either site 1 or site 3 but is not affected by mutation at site 2. Binding of the 20-kDa C/EBPbeta isoform (p20C/EBPbeta), which is eliminated by mutation at the distal site 3 of C/EBP binding, is necessary for the activation by acetaldehyde of the alpha(1)(I) collagen promoter. 相似文献
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The yolk protein 1 gene (yp1) of Drosophila melanogaster is expressed only in the ovarian follicle cells and the fat bodies of adult females. We have previously shown that a different cis-acting DNA region is required for each of these tissue specificities. In this paper we use germ line transformation to localize and characterized one of these tissue-specific regulatory regions. We demonstrate that a 125 bp segment of DNA located 196 bp upstream of the yp1 cap site is sufficient to determine the sex-, stage-, and fat body-specific expression of the yp1 gene. We also find that this region can confer yp1-specific expression on a heterologous Drosophila promoter. This specificity is retained when the region is in different orientations and at different distances from the heterologous promoter. Thus a small regulatory region acts in vivo as a positive enhancer to determine the fat body expression pattern of yp1. 相似文献
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