scholarly journals Original article. Transcription factors regulate Forkhead box O1 gene promoter activity in pancreatic β-cells

2011 ◽  
Vol 5 (4) ◽  
pp. 433-439 ◽  
Author(s):  
Ying Luo ◽  
Yan Lin ◽  
Xiao Han
Keyword(s):  
Transcription Factors ◽  
Promoter Activity ◽  
Screening Method ◽  
Gene Promoter ◽  
Luciferase Reporter ◽  
Upstream Region ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Forkhead Box ◽  
Foxo1 Gene

Abstract Background: Transcription factors of the Forkhead box O (Fox O) family have important roles in cellular proliferation, apoptosis, differentiation, and stress resistance. In pancreatic β-cells, FoxO1 protein plays an important role in β-cells development. The molecular mechanism of transcriptional regulation of basal FoxO1 gene expression in pancreatic β-cells is not fully understood. Objectives: Explore the potential transcription factors regulating FoxO1 promoter activity using pancreatic β-cell line (RINm5F cells) Methods: Promoter screening method, luciferase reporter gene analysis, transient expression assay system, and deletion analysis of a -974/-18 bp 5’ upstream region of the mouse FoxO1 gene were used in this study. Results: An inhibition domain (-974/-321) and an activation domain (-321/-18) was identified through deletion analysis of a -974/-18 bp 5’ upstream region of the mouse FoxO1 gene. Using the promoter screening method, several transcription factors were selected. Luciferase reporter studies showed that these factors could regulate FoxO1 promoter activity in RINm5F cells. Among these factors, cAMP response-element binding protein (CREB) could positively regulate FoxO1 promoter activity. Signal transducer and activator of transcription 1 (STAT1) played a negative role on FoxO1 promoter. In addition, ETS oncogene family member Elk-1 did not affect the FoxO1 promoter activity. Conclusion: Two transcription factors (CREB and STAT1) could effectively regulate the mouse FoxO1 gene promoter activity.

scholarly journals Dynamic Regulation of PDX-1 and FoxO1 Expression by FoxA2 in Dexamethasone-Induced Pancreatic β-cells Dysfunction

Endocrinology ◽  
2011 ◽  
Vol 152 (5) ◽  
pp. 1779-1788 ◽  
Author(s):  
Fang Chen ◽  
Yunxia Zhu ◽  
Xinyi Tang ◽  
Yidan Sun ◽  
Weiping Jia ◽  
...  
Keyword(s):  
Protein Expression ◽  
Gene Promoter ◽  
Dependent Manner ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Dynamic Regulation ◽  
Forkhead Box ◽  
Mrna And Protein Expression ◽  
Foxo1 Gene ◽  
First Time

Transcription factors forkhead box (Fox)O1 and pancreatic and duodenal homeobox-1 (PDX-1) are involved in dexamethasone (DEX)-induced dysfunction in pancreatic β-cells. However, the molecular mechanism underlying the regulation of FoxO1 and PDX-1 expression in β-cells treated with DEX is not fully understood. In this study, we found that DEX markedly increased FoxO1 mRNA and protein expression, whereas it decreased PDX-1 mRNA and protein expression in a dose- and time-dependent manner. Further study showed that FoxA2 was involved in regulation of FoxO1 and PDX-1 expression in DEX-induced pancreatic β-cells dysfunction. Interestingly, we demonstrated for the first time that FoxA2 could bind to the FoxO1 gene promoter and positively regulate FoxO1 expression. Moreover, we found that DEX increased the activity of FoxA2 binding to the FoxO1 promoter but decreased the activity of FoxA2 binding to the PDX-1 promoter of RINm5F cells. Knockdown of FoxA2 by RNA interference inhibited FoxO1 expression and restored PDX-1 expression in pancreatic β-cells treated with DEX. However, DEX had no effect on the expression of FoxA2. Together, the results of the present study demonstrated that FoxA2 could dynamically regulate FoxO1 and PDX-1 expression in pancreatic β-cells treated with DEX, which provides new important information on the transcriptional regulation of FoxO1 and PDX-1 in DEX-induced pancreatic β-cells. Inhibition of FoxA2 can effectively protect β-cells against DEX-induced dysfunction.

scholarly journals Endoplasmic reticulum stress induces Wfs1 gene expression in pancreatic β-cells via transcriptional activation

2005 ◽  
Vol 153 (1) ◽  
pp. 167-176 ◽  
Author(s):  
Kohei Ueda ◽  
June Kawano ◽  
Komei Takeda ◽  
Toshiaki Yujiri ◽  
Katsuya Tanabe ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Stress Responses ◽  
Gene Promoter ◽  
Luciferase Reporter ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Min6 Cells ◽  
Insulinoma Cells

Objective: The WFS1 gene encodes an endoplasmic reticulum (ER) membrane-embedded protein. Homozygous WFS1 gene mutations cause Wolfram syndrome, characterized by insulin-deficient diabetes mellitus and optic atropy. Pancreatic β-cells are selectively lost from the patient’s islets. ER localization suggests that WFS1 protein has physiological functions in membrane trafficking, secretion, processing and/or regulation of ER calcium homeostasis. Disturbances or overloading of these functions induces ER stress responses, including apoptosis. We speculated that WFS1 protein might be involved in these ER stress responses. Design and methods: Islet expression of the Wfs1 protein was analyzed immunohistochemically. Induction of Wfs1 upon ER stress was examined by Northern and Western blot analyses using three different models: human skin fibroblasts, mouse pancreatic β-cell-derived MIN6 cells, and Akita mouse-derived Ins2 96Y/Y insulinoma cells. The human WFS1 gene promoter-luciferase reporter analysis was also conducted. Result: Islet β-cells were the major site of Wfs1 expression. This expression was also found in δ-cells, but not in α-cells. WFS1 expression was transcriptionally up-regulated by ER stress-inducing chemical insults. Treatment of fibroblasts and MIN6 cells with thapsigargin or tunicamycin increased WFS1 mRNA. WFS1 protein also increased in response to thapsigargin treatment in these cells. WFS1 gene expression was also increased in Ins2 96Y/Y insulinoma cells. In these cells, ER stress was intrinsically induced by mutant insulin expression. The WFS1 gene promoter-luciferase reporter system revealed that the human WFS1 promoter was activated by chemically induced ER stress in MIN6 cells, and that the promoter was more active in Ins2 96Y/Y cells than Ins2 wild/wild cells. Conclusion: Wfs1 expression, which is localized to β- and δ-cells in pancreatic islets, increases in response to ER stress, suggesting a functional link between Wfs1 and ER stress.

scholarly journals Elevated Glucose Attenuates Human Insulin Gene Promoter Activity in INS-1 Pancreatic β-Cells via Reduced Nuclear Factor Binding to the A5/Core and Z Element

2005 ◽  
Vol 19 (5) ◽  
pp. 1343-1360 ◽  
Author(s):  
Maria F. Pino ◽  
Diana Z. Ye ◽  
Katrina D. Linning ◽  
Christopher D. Green ◽  
Barton Wicksteed ◽  
...  
Keyword(s):  
Human Insulin ◽  
Promoter Activity ◽  
Gene Promoter ◽  
Insulin Gene ◽  
Nuclear Factor ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Factor Binding ◽  
Human Insulin Gene ◽  
Elevated Glucose

Sumoylation of PDX-1 Regulates the Rat Insulin 2 Gene Transcription

2014 ◽  
Vol 556-562 ◽  
pp. 253-256
Author(s):  
Nan Wang ◽  
Ruo Lei Jian ◽  
Feng Po Wang ◽  
Li Bin Mao ◽  
Tong Cun Zhang
Keyword(s):  
Glucose Homeostasis ◽  
Gene Promoter ◽  
Glucose Sensing ◽  
Insulin Gene ◽  
Luciferase Reporter ◽  
Reporter Assay ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Post Translational Modifications ◽  
Promoter Sequences

Insulin is essential for maintaining glucose homeostasis and is synthesized and secreted almost exclusively from pancreatic β-cells in the islets of Langerhans. The analysis of rat insulin2 promoter sequences indicates that it has pancreatic and duodenal homeobox factor-1 (PDX-1) binding site. In mature β-cells, PDX-1 transactivates the insulin and other genes involved in glucose sensing and metabolism. The function of PDX-1 can be regulated by post-translational modifications. Sumoylation plays an important role in regulating numerous physiological and pathological processes through altering the function of its target proteins. In this paper, to understand the function and transcription activities of insulin gene promoter, we constructed rat insulin 2 promoter (RIP II). Then we investigated whether sumoylation of PDX-1 activated this promoter transcription by luciferase reporter assay in HepG-2 cells. Results indicated that sumoylation enhanced PDX-1 activity for the insulin gene promoter transcription.

scholarly journals Upstream region of rat serum albumin gene promoter contributes to promoter activity: presence of functional binding site for hepatocyte nuclear factor-3

1999 ◽  
Vol 338 (2) ◽  
pp. 241-249 ◽  
Author(s):  
Chin-Hui HSIANG ◽  
Norman W. MARTEN ◽  
Daniel S. STRAUS
Keyword(s):  
Serum Albumin ◽  
Hepg2 Cells ◽  
Promoter Activity ◽  
Gene Promoter ◽  
Upstream Region ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Rat Serum ◽  
Albumin Gene ◽  
Rat Serum Albumin

Transcription of the serum albumin gene occurs almost exclusively in the liver and is controlled in part by a strong liver-specific promoter. The upstream region of the serum albumin gene promoter is highly conserved among species and is footprinted in vitro by a number of nuclear proteins. However, the role of the upstream promoter region in regulating transcription and the identity of the transcription factors that bind to this region have not been established. In the present study, deletion analysis of the rat serum albumin promoter in transiently transfected HepG2 cells demonstrated that elimination of the region between -207 and -153 bp caused a two-fold decrease in promoter activity (P< 0.05). Additional analysis of the -207 to -124 bp promoter interval led to the identification of two potential binding sites for hepatocyte nuclear factor-3 (HNF-3) located at -168 to -157 bp (site X) and -145 to -134 bp (site Y). Electrophoretic mobility-shift assays performed with the HNF-3 X and Y sites demonstrated that both sites are capable of binding HNF-3α and HNF-3β. Placement of a single copy of the HNF-3 X site upstream from a minimal promoter increased promoter activity by about four-fold in HepG2 cells, and the reporter construct containing this site could be transactivated if co-transfected with an HNF-3 expression construct. Furthermore, inactivation of the HNF-3 X site by site-directed mutagenesis within the context of the -261 bp albumin promoter construct resulted in a 40% decrease in transcription (P< 0.05). These results indicate that the positive effect of the -207 to -153 bp promoter interval is attributable to the presence of the HNF-3 X site within this interval. Additional results obtained with transfected HepG2 cells suggest that the HNF-3 Y site plays a lesser role in activation of transcription than the X site.

scholarly journals Glucose enhances insulin promoter activity in MIN6 β-cells independently of changes in intracellular Ca2+ concentration and insulin secretion

1999 ◽  
Vol 342 (2) ◽  
pp. 275-280 ◽  
Author(s):  
Helen J. KENNEDY ◽  
Imran RAFIQ ◽  
Aristea E. POULI ◽  
Guy A. RUTTER
Keyword(s):  
Promoter Activity ◽  
Photon Counting ◽  
Firefly Luciferase ◽  
Receptor Activation ◽  
Luciferase Reporter ◽  
Β Cells ◽  
Viral Promoter ◽  
Luciferase Reporter Construct ◽  
Insulin Promoter ◽  
Firefly Luciferase Reporter

Recent studies have suggested that glucose may activate insulin gene transcription through increases in intracellular Ca2+ concentration, possibly acting via the release of stored insulin. We have investigated this question by dynamic photon-counting imaging of insulin- and c-fos-promoter-firefly luciferase reporter construct activity. Normalized to constitutive viral promoter activity, insulin promoter activity in MIN6 β-cells was increased 1.6-fold after incubation at 30 mM compared with 3 mM glucose, but was unaltered at either glucose concentration by the presence of insulin (100 nM) or the Ca2+ channel inhibitor, verapamil (100 μM). Increases in intracellular [Ca2+] achieved by plasma membrane depolarization with KCl failed to enhance either insulin or c-fos promoter activity in MIN6 cells, but increased c-fos promoter activity 5-fold in AtT20 cells. Together, these results demonstrate that glucose can exert a direct effect on insulin promoter activity in islet β-cells, via a signalling pathway which does not require increases in intracellular [Ca2+] nor insulin release and insulin receptor activation.

scholarly journals Foxa3 (HNF-3γ) binds to and activates the rat proglucagon gene promoter but is not essential for proglucagon gene expression

2002 ◽  
Vol 366 (2) ◽  
pp. 633-641 ◽  
Author(s):  
Yuanfang LIU ◽  
Wei SHEN ◽  
Patricia L. BRUBAKER ◽  
Klaus H. KAESTNER ◽  
Daniel J. DRUCKER
Keyword(s):  
Gene Expression ◽  
Cell Lines ◽  
Promoter Activity ◽  
Gene Promoter ◽  
Forkhead Box ◽  
Mild Hypoglycaemia ◽  
Element Binding Protein ◽  
Prolonged Fast

Members of the Forkhead box a (Foxa) transcription factor family are expressed in the liver, pancreatic islets and intestine and both Foxa1 and Foxa2 regulate proglucagon gene transcription. As Foxa proteins exhibit overlapping DNA-binding specificities, we examined the role of Foxa3 [hepatocyte nuclear factor (HNF)-3γ] in control of proglucagon gene expression. Foxa3 was detected by reverse transcriptase PCR in glucagon-producing cell lines and binds to the rat proglucagon gene G2 promoter element in GLUTag enteroendocrine cells. Although Foxa3 increased rat proglucagon promoter activity in BHK fibroblasts, augmentation of Foxa3 expression did not increase proglucagon promoter activity in GLUTag cells. Furthermore, adenoviral Foxa3 expression did not affect endogenous proglucagon gene expression in islet or intestinal endocrine cell lines. Although Foxa3-/- mice exhibit mild hypoglycaemia during a prolonged fast, the levels of proglucagon-derived peptides and proglucagon mRNA transcripts were comparable in tissues from wild-type and Foxa3-/- mice. These findings identify Foxa3 as a member of the proglucagon gene G2 element binding-protein family that, unlike Foxa1, is not essential for control of islet or intestinal proglucagon gene expression in vivo.

A 3-Bp Deletion Between Transcription Factor Binding Motifs In the HBS1L-MYB Intergenic Region on Chromosome 6q23 Is Associated with HbF Expression

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1013-1013
Author(s):  
John J. Farrell ◽  
Richard M. Sherva ◽  
Zhi-yi Chen ◽  
Luo Hong-yuan ◽  
Banjamin F. Chu ◽  
...  
Keyword(s):  
Hong Kong ◽  
Transcription Factors ◽  
Dna Sequences ◽  
Globin Gene ◽  
Gene Promoter ◽  
Proximal Promoter ◽  
Luciferase Reporter ◽  
Deletion Polymorphism ◽  
Functional Motif ◽  
A Genome

Abstract Abstract 1013 More than 3% of Chinese in Hong Kong are heterozygous carriers of β-thalassemia. Homozygotes or compound heterozygotes for β-thalassemia are usually severely ill and require monthly transfusions. Increased production of fetal hemoglobin (HbF) can modulate the disease severity by compensating for the shortfall of HbA caused by the β-thalassemia mutations. HbF level in adults varies and is regulated as a multigenic trait. Three major HbF quantitative trait loci (QTL) have been identified: the C/T SNP also known as the Xmn I site at the Gγ-globin gene promoter, the BCL11A polymorphism on chromosome 2p16, and the HBS1L-MYB intergenic polymorphism (HMIP) on chromosome 6q23. The functional motif for each of these 3 QTLs responsible for their effects upon HbF is not known. We undertook a genome-wide association study (GWAS), using Illumina Human 610-Quad BeadChip array, on 619 Chinese β-thalassemia heterozygotes from Hong Kong. In this population, the variance in HbF due to HMIP is 13.5%, significantly higher than that due to BCL11A polymorphism (6.4%). We used 1,000 Genomes Project data, SNP imputation, comparisons of association results across populations, predicted binding of transcription factors, and phylogenetic conservation to identify the functional variant in HMIP. Based on these lines of evidence, a hitherto unreported association between HbF expression and a 3-bp deletion on chromosome 6q23 was found. In 335 Chinese β-thalassemia heterozygotes, the 3-bp deletion polymorphism is in complete linkage disequilibrium with rs9399137, the SNP found in multiple GWAS to be most significantly associated with HbF (P=1.4E-24 in the Chinese cohort GWAS). Flanking this deletion are conserved binding sites for TAL1/SCL1, E47, GATA, and RUNX1/AML1, which are essential erythropoiesis-related transcription factors. The 3-bp deletion changes the normal DNA binding configuration of these transcription factors and spatial configuration for DNA-protein binding and/or protein-protein interactions. Furthermore, this 3-bp deletion polymorphism resides within a likely erythroid distal regulatory region manifested by DNase I hypersensitivity and GATA-1 binding (Wahlberg et al, Blood 114:1254, 2009). We hypothesized that a 61-bp fragment of DNA that encompasses the site of the 3-bp deletion polymorphism might have enhancer-like activity. When ligated to the Gγ-globin gene 1.4 kb proximal promoter linked to a luciferase reporter gene, the 61-bp fragment of DNA enhances the Gγ-globin gene promoter activity by more than 3-fold after transient transfection into K562 cells. A 58-bp fragment of DNA that includes the 3-bp deletion has 60% more enhancer-like activity than the 61-bp fragment without the deletion. These findings suggest that this 3-bp deletion polymorphism is most likely the functional motif accounting for HMIP modulation of HbF. Further studies are needed to identify target genes for this enhancer-like activity mediated by the DNA sequences encompassing the 3-bp deletion polymorphism in HMIP. These studies also suggest that this experimental approach could be used to identify functional motifs in other genotype-phenotype association studies. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Regulation of basal promoter activity of the human thiamine pyrophosphate transporter SLC44A4 in human intestinal epithelial cells

2015 ◽  
Vol 308 (9) ◽  
pp. C750-C757 ◽  
Author(s):  
Svetlana M. Nabokina ◽  
Mel Brendan Ramos ◽  
Judith E. Valle ◽  
Hamid M. Said
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Epithelial Cells ◽  
Promoter Activity ◽  
Minimal Promoter ◽  
Thiamine Pyrophosphate ◽  
Luciferase Reporter ◽  
Uptake System ◽  
Colonic Epithelial Cells ◽  
Basal Promoter Activity

Microbiota of the large intestine synthesize considerable amount of vitamin B1 in the form of thiamine pyrophosphate (TPP). There is a specific high-affinity regulated carrier-mediated uptake system for TPP in human colonocytes (product of the SLC44A4 gene). The mechanisms of regulation of SLC44A4 gene expression are currently unknown. In this study, we characterized the SLC44A4 minimal promoter region and identified transcription factors important for basal promoter activity in colonic epithelial cells. The 5′-regulatory region of the SLC44A4 gene (1,022 bp) was cloned and showed promoter activity upon transient transfection into human colonic epithelial NCM460 cells. With the use of a series of 5′- and 3′-deletion luciferase reporter constructs, the minimal genomic region that required basal transcription of the SLC44A4 gene expression was mapped between nucleotides −178 and +88 (using the distal transcriptional start site as +1). Mutational analysis performed on putative cis-regulatory elements established the involvement of ETS/ELF3 [E26 transformation-specific sequence (ETS) proteins], cAMP-responsive element (CRE), and SP1/GC-box sequence motifs in basal SLC44A4 promoter activity. By means of EMSA, binding of ELF3 and CRE-binding protein-1 (CREB-1) transcription factors to the SLC44A4 minimal promoter was shown. Contribution of CREB into SLC44A4 promoter activity was confirmed using NCM460 cells overexpressing CREB. We also found high expression of ELF3 and CREB-1 in colonic (NCM460) compared with noncolonic (ARPE19) cells, suggesting their possible contribution to colon-specific pattern of SLC44A4 expression. This study represents the first characterization of the SLC44A4 promoter and reports the importance of both ELF3 and CREB-1 transcription factors in the maintenance of basal promoter activity in colonic epithelial cells.

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