scholarly journals MON-711 Induction of Apolipoprotein A1 Gene Expression by the Rare Sugar Allulose

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Shrina Parekh
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Promoter Activity ◽  
Gene Promoter ◽  
Apolipoprotein A1 ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Rare Sugar ◽  
Transcription Factor Sp1 ◽  
I Gene

Abstract Apolipoprotein A-I (apo A-I) is the primary protein component of high-density lipoprotein (HDL) and has many well documented properties which promote cardiovascular health. However, clinical trials designed to increase HDL levels by preventing its catabolism have failed in their primary endpoints in decreasing the risk of cardiovascular disease. Alternative strategies to increase de-novo apo A-I production may be more attractive. We recently demonstrated that the rare sugar allulose decreases oxidative stress and endoplasmic reticulum stress in both endothelial cells and hepatocytes. During these studies we demonstrated that allulose also induces apo A-I secretion by HepG2 cells. Apo A-I, albumin, and SP1 levels were measured by Western blot. Apo A-I and glyceraldehyde-3-phosphate (GAPDH) mRNA levels were measured by quantitative real-time polymerase chain reaction. The effect of allulose on apo A-I promoter activity was measured using transient transfection assays with several plasmids containing various segments and mutations in the apo A-I gene promoter. Apo A-I protein and mRNA levels in cells treated with allulose increased more than two-fold in a dose-dependent manner. These changes were due to the ability of allulose to induce apo A-I gene promoter activity. Using a series of deletion constructs, an allulose-response element was identified in the apo A-I gene promoter which was previously shown to confer induction of apo A-I gene expression by insulin and epidermal growth factor (EGF), the insulin response core element (IRCE). Mutation of the IRCE decreased the ability of allulose and insulin to induce apo A-I promoter activity. Allulose treatment also increased expression of the transcription factor SP1, which had been shown previously be essential for the effects of insulin and EGF on apo A-I promoter activity. In conclusion, allulose increased apo A-I gene expression in HepG2 hepatocytes. This effect was mediated by the IRCE in the apo A-I gene promoter and the transcription factor SP1. The rare sugar allulose may have novel anti-atherogenic properties, in part, by increasing HDL levels.

Mechanisms of mammalian zinc-regulated gene expression

2008 ◽  
Vol 36 (6) ◽  
pp. 1262-1266 ◽  
Author(s):  
Kelly A. Jackson ◽  
Ruth A. Valentine ◽  
Lisa J. Coneyworth ◽  
John C. Mathers ◽  
Dianne Ford
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Transcriptional Repression ◽  
Mammalian Cells ◽  
Gene Promoter ◽  
Mrna Levels ◽  
Promoter Regions ◽  
Mrna Stabilization ◽  
Transcriptional Regulatory ◽  
Regulated Gene Expression

Mechanisms through which gene expression is regulated by zinc are central to cellular zinc homoeostasis. In this context, evidence for the involvement of zinc dyshomoeostasis in the aetiology of diseases, including Type 2 diabetes, Alzheimer's disease and cancer, highlights the importance of zinc-regulated gene expression. Mechanisms elucidated in bacteria and yeast provide examples of different possible modes of zinc-sensitive gene regulation, involving the zinc-regulated binding of transcriptional activators and repressors to gene promoter regions. A mammalian transcriptional regulatory mechanism that mediates zinc-induced transcriptional up-regulation, involving the transcription factor MTF1 (metal-response element-binding transcription factor 1), has been studied extensively. Gene responses in the opposite direction (reduced mRNA levels in response to increased zinc availability) have been observed in mammalian cells, but a specific transcriptional regulatory process responsible for such a response has yet to be identified. Examples of single zinc-sensitive transcription factors regulating gene expression in opposite directions are emerging. Although zinc-induced transcriptional repression by MTF1 is a possible explanation in some specific instances, such a mechanism cannot account for repression by zinc of all mammalian genes that show this mode of regulation, indicating the existence of as yet uncharacterized mechanisms of zinc-regulated transcription in mammalian cells. In addition, recent findings reveal a role for effects of zinc on mRNA stability in the regulation of specific zinc transporters. Our studies on the regulation of the human gene SLC30A5 (solute carrier 30A5), which codes for the zinc transporter ZnT5, have revealed that this gene provides a model system by which to study both zinc-induced transcriptional down-regulation and zinc-regulated mRNA stabilization.

scholarly journals Effects of ketoacidosis on rat apolipoprotein A1 gene expression: a link with acidosis but not with ketones

2000 ◽  
Vol 25 (1) ◽  
pp. 129-139 ◽  
Author(s):  
MJ Haas ◽  
K Pun ◽  
D Reinacher ◽  
NC Wong ◽  
AD Mooradian
Keyword(s):  
Gene Expression ◽  
Promoter Activity ◽  
Simian Virus ◽  
Diabetic Rats ◽  
Apolipoprotein A1 ◽  
Mrna Levels ◽  
Hep G2 ◽  
Apoa1 Gene ◽  
Wide Range

To determine if ketoacidosis contributes to reduced apolipoprotein A1 (apoA1) expression in insulin-deficient diabetic rats, we examined the regulation of apoA1 gene expression in response to changes in ambient pH or ketone body concentrations. Hepatic apoAI mRNA levels were reduced 42% in diabetic rats relative to nondiabetic controls (means+/-s.d.; 321.8+/-43.7 vs 438.7+/-58.8 arbitrary units; P<0.03). Neither endogenous apoA1 mRNA nor transcriptional activity of the rat apoA1 gene promoter (from -474 to -7) were altered by sodium butyrate or isobutyramide (0.3 mM to 10 mM) in Hep G2 or Caco-2 cells. Rat hepatic and intestinal apoA1 mRNA levels, and plasma apoA1 concentration, were not altered 24 h after isobutyramide administration (500 mg/kg by gavage). When the effect of altering ambient pH within a wide range commonly encountered in vivo was studied, acidosis (pH 6.7), relative to alkalosis (pH 7.9), decreased apoAI mRNA levels relative to glyceraldehyde-3-phosphate dehydrogenase mRNA by 47% in Hep G2 cells (P<0.025) and by 24% in Caco-2 cells (P<0.017). Acidosis did not alter cytomegalo virus (CMV)-beta-galactosidase activity, or the activity of the simian virus (SV40) early-region promoter, in either cell line transfected with the respective constructs. The lowering of ambient pH was associated with a graded reduction in apoAI promoter activity. At pH 6.7, apoAI promoter activity was reduced by 75% compared with promoter activity at pH 7.9. These observations indicate that acidosis, but not ketosis, contributes to the reduction in apoA1 expression during diabetic ketoacidosis by down-regulating apoAI promoter activity.

scholarly journals Nuclear receptors RXRα:RARα are repressors for human MRP3 expression

2007 ◽  
Vol 292 (5) ◽  
pp. G1221-G1227 ◽  
Author(s):  
Wensheng Chen ◽  
Shi-Ying Cai ◽  
Shuhua Xu ◽  
Lee A. Denson ◽  
Carol J. Soroka ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Promoter Activity ◽  
Regulatory Elements ◽  
Luciferase Reporter ◽  
Dependent Manner ◽  
Site Mutation ◽  
Transcription Factor Sp1 ◽  
Gc Box ◽  
Rna Knockdown ◽  
Interfering Rna

Multidrug resistance-associated protein MRP3/Mrp3 (ABCC3) is upregulated in cholestasis, an adaptive response that may protect the liver from accumulation of toxic compounds, such as bile salts and bilirubin conjugates. However, the mechanism of this upregulation is poorly understood. We and others have previously reported that fetoprotein transcription factor/liver receptor homolog-1 is an activator of MRP3/Mrp3 expression. In searching for additional regulatory elements in the human MRP3 promoter, we have now identified nuclear receptor retinoic X receptor-α:retinoic acid receptor-α (RXRα:RARα) as a repressor of MRP3 activation by transcription factor Sp1. A luciferase reporter assay demonstrated that cotransfection of transcription factor Sp1 stimulates the MRP3 promoter activity and that additions of RXRα:RARα abrogated this activation in a dose-dependent manner. Site mutations and gel shift assays have identified a Sp1 binding GC box motif at −113 to −108 nts upstream from the MRP3 translation start site, where RXRα:RARα specifically reduced Sp1 binding to this site. Mutation of the GC box also reduced MRP3 promoter activity. The functional role of RXRα:RARα as a repressor of MRP3 expression was further confirmed by RARα small-interfering RNA knockdown in HepG2 cells, which upregulated endogenous MRP3 expression. In summary, our results indicate that activator Sp1 and repressor RXRα:RARα act in concert to regulate MRP3 expression. Since RXRα:RARα expression is diminished by cholestatic liver injury, loss of RXRα:RARα may lead to upregulation of MRP3/Mrp3 expression in these disorders.

scholarly journals GATA augments GNRH-mediated increases in Adcyap1 gene expression in pituitary gonadotrope cells

2013 ◽  
Vol 51 (3) ◽  
pp. 313-324 ◽  
Author(s):  
Robin L Thomas ◽  
Natalie M Crawford ◽  
Constance M Grafer ◽  
Weiming Zheng ◽  
Lisa M Halvorson
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Promoter Activity ◽  
Gene Promoter ◽  
Proximal Promoter ◽  
Mrna Levels ◽  
Paracrine Factor ◽  
Mobility Shift ◽  
Subunit Expression ◽  
Mobility Shift Assay

Pituitary adenylate cyclase-activating polypeptide 1 (PACAP or ADCYAP1) regulates gonadotropin biosynthesis and secretion, both alone and in conjunction with GNRH. Initially identified as a hypothalamic-releasing factor, ADCYAP1 subsequently has been identified in pituitary gonadotropes, suggesting it may act as an autocrine–paracrine factor in this tissue. GNRH has been shown to increase pituitaryAdcyap1gene expression through the interaction of CREB and jun/fos with CRE/AP1cis-elements in the proximal promoter. In these studies, we were interested in identifying additional transcription factors and cognatecis-elements which regulateAdcyap1gene promoter activity and chose to focus on the GATA family of transcription factors known to be critical for both pituitary cell differentiation and gonadotropin subunit expression. By transient transfection and electrophoretic mobility shift assay analysis, we demonstrate that GATA2 and GATA4 stimulateAdcyap1promoter activity via a GATAcis-element located at position −191 in the ratAdcyap1gene promoter. Furthermore, we show that addition of GATA2 or GATA4 significantly augments GNRH-mediated stimulation ofAdcyap1gene promoter activity in the gonadotrope LβT2 cell line. Conversely, blunting GATA expression with specific siRNA inhibits the ability of GNRH to stimulate ADCYAP1 mRNA levels in these cells. These data demonstrate a complex interaction between GNRH and GATA on ADCYAP1 expression, providing important new insights into the regulation of gonadotrope function.

scholarly journals Involvement of the ubiquitous Oct-1 transcription factor in hormonal induction of β-casein gene expression

2006 ◽  
Vol 401 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Bing Dong ◽  
Feng-Qi Zhao
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Binding Site ◽  
Promoter Activity ◽  
Regulatory Region ◽  
Binding Motif ◽  
Dependent Manner ◽  
Casein Gene ◽  
Hormonal Induction ◽  
Lactogenic Hormones

Transcription of the milk protein β-casein gene is induced by the lactogenic hormones Prl (prolactin) and glucocorticoids. Multiple transcription factors involved in this induction have been identified, including the STAT5 (signal transducer and activator of transcription 5) and the GR (glucocorticoid receptor). Our previous studies have identified a binding site for the ubiquitous Oct-1 (octamer-binding transcription factor 1) protein in the lactogenic hormonal regulatory region of the mouse β-casein promoter. In the present study, we report that Oct-1 is indeed expressed and binds to the β-casein promoter in mammary epithelial cells. Oct-1 activates hormonally induced β-casein promoter activity in a dose-dependent manner. Hormonal induction of promoter activity was decreased not only by mutating the Oct-1-binding site from ATTAGCAT to GCTAGCAT, which abolishes Oct-1 binding (50% decrease, P<0.01), but also by changing the site to the consensus Oct-1-binding motif ATTTGCAT (40% decrease, P<0.01). Reversing the Oct-1-binding site reduced hormonal induction by 70% (P<0.01), showing that orientation of Oct-1 binding is also critical in hormonal action. In transient transfection experiments, Oct-1 collaboratively transactivated the β-casein gene promoter with STAT5 and/or GR in the presence of Prl receptor in cells treated with the lactogenic hormones. The C-terminus of Oct-1 was not essential to its function. The results of the present study provide biochemical evidence that the ubiquitous Oct-1 transcription factor may be involved in hormonally regulated, tissue-specific β-casein gene expression.

scholarly journals Liver X Receptor-α Gene Expression Is Positively Regulated by Thyroid Hormone

Endocrinology ◽  
2007 ◽  
Vol 148 (10) ◽  
pp. 4667-4675 ◽  
Author(s):  
Koshi Hashimoto ◽  
Shunichi Matsumoto ◽  
Masanobu Yamada ◽  
Teturou Satoh ◽  
Masatomo Mori
Keyword(s):  
Gene Expression ◽  
Thyroid Hormone ◽  
Mrna Expression ◽  
Cross Talk ◽  
Promoter Activity ◽  
Gene Promoter ◽  
Retinoid X Receptor ◽  
Transcriptional Level ◽  
Mrna Levels ◽  
Transcription Analysis

The nuclear oxysterol receptors, liver X receptors (LXRs), and thyroid hormone receptors (TRs) cross talk mutually in many aspects of transcription, sharing the same DNA binding site (direct repeat-4) with identical geometry and polarity. In the current study, we demonstrated that thyroid hormone (T3) up-regulated mouse LXR-α, but not LXR-β, mRNA expression in the liver and that cholesterol administration did not affect the LXR-α mRNA levels. Recently, several groups have reported that human LXR-α autoregulates its own gene promoter through binding to the LXR response element. Therefore, we examined whether TRs regulate the mouse LXR-α gene promoter activity. Luciferase assays showed that TR-β1 positively regulated the mouse LXR-α gene transcription. Analysis of serial deletion mutants of the promoter demonstrated that the positive regulation by TR-β1 was not observed in the −1240/+30-bp construct. EMSA(s) demonstrated that TR-β1 or retinoid X receptor-α did not bind to the region from −1300 to −1240 bp (site A), whereas chromatin-immunoprecipitation assays revealed that TR-β1 and retinoid X receptor-α were recruited to the site A, indicating the presence of intermediating protein between the nuclear receptors and DNA site. We also showed that human LXR-α gene expression and promoter activities were up-regulated by thyroid hormone. These data suggest that LXR-α mRNA expression is positively regulated by TR-β1 and thyroid hormone at the transcriptional level in mammals. This novel insight that thyroid hormone regulates LXR-α mRNA levels and promoter activity should shed light on a cross talk between LXR-α and TR-β1 as a new therapeutic target against dyslipidemia and atherosclerosis.

scholarly journals The Zinc Finger Transcription Factor Gli2 Mediates Bone Morphogenetic Protein 2 Expression in Osteoblasts in Response to Hedgehog Signaling

2006 ◽  
Vol 26 (16) ◽  
pp. 6197-6208 ◽  
Author(s):  
Ming Zhao ◽  
Mei Qiao ◽  
Stephen E. Harris ◽  
Di Chen ◽  
Babatunde O. Oyajobi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Bone Morphogenetic Protein ◽  
Hedgehog Signaling ◽  
Osteoblast Differentiation ◽  
Promoter Activity ◽  
Bone Morphogenetic Protein 2 ◽  
Dependent Manner ◽  
Genetic Ablation ◽  
Morphogenetic Protein

ABSTRACTBone morphogenetic protein 2 (BMP-2) plays a critical role in osteoblast function. InDrosophila, Cubitus interruptus (Ci), which mediates hedgehog signaling, regulates gene expression ofdpp, the ortholog of mammalian BMP-2. Null mutation of the transcription factor Gli2, a mammalian homolog of Ci, results in severe skeletal abnormalities in mice. We hypothesize that Gli2 regulates BMP-2 gene transcription and thus osteoblast differentiation. In the present study, we show that overexpression of Gli2 enhances BMP-2 promoter activity and mRNA expression in osteoblast precursor cells. In contrast, knocking down Gli2 expression by Gli2 small interfering RNA or genetic ablation of the Gli2 gene results in significant inhibition of BMP-2 gene expression in osteoblasts. Promoter analyses, including chromatin immunoprecipitation and electrophoretic mobility shift assays, provided direct evidence that Gli2 physically interacts with the BMP-2 promoter. Functional studies showed that Gli2 is required for osteoblast maturation in a BMP-2-dependent manner. Finally, Sonic hedgehog (Shh) stimulates BMP-2 promoter activity and osteoblast differentiation, and the effects of Shh are mediated by Gli2. Taken together, these results indicate that Gli2 mediates hedgehog signaling in osteoblasts and is a powerful activator of BMP-2 gene expression, which is required in turn for normal osteoblast differentiation.

Ceramide decreases surfactant protein B gene expression via downregulation of TTF-1 DNA binding activity

2006 ◽  
Vol 290 (2) ◽  
pp. L351-L358 ◽  
Author(s):  
Loretta Sparkman ◽  
Hemakumar Chandru ◽  
Vijayakumar Boggaram
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Dna Binding ◽  
Promoter Activity ◽  
Surfactant Protein ◽  
Binding Activity ◽  
Mrna Levels ◽  
Dna Binding Activity ◽  
Surfactant Protein B ◽  
Tnf Α

Ceramide, a sphingolipid, is an important signaling molecule in the inflammatory response. Mediators of acute lung injury such as TNF-α, platelet-activating factor, and Fas/Apo ligand stimulate sphingomyelin hydrolysis to increase intracellular ceramide levels. Surfactant protein B (SP-B), a hydrophobic protein of pulmonary surfactant, is essential for surfactant function and lung stability. In this study we investigated the effects of ceramide on SP-B gene expression in H441 lung epithelial cells. Ceramide decreased SP-B mRNA levels in control and dexamethasone-treated cells after 24-h incubation and inhibition of SP-B mRNA was associated with inhibition of immunoreactive SP-B. In transient transfections assays, ceramide inhibited SP-B promoter activity, indicating that the inhibitory effects are exerted at the transcriptional level. Deletion mapping experiments showed that the ceramide-responsive region is located within the −233/−80-bp region of human SP-B promoter. Electrophoretic mobility shift and reporter assays showed that ceramide reduced the DNA binding activity and transactivation capability of thyroid transcription factor 1 (TTF-1/Nkx2.1), a key factor for SP-B promoter activity. Collectively these data showed that ceramide inhibits SP-B gene expression by reducing the DNA biding activity of TTF-1/Nkx2.1 transcription factor. Protein kinase C inhibitor bisindolylmaleimide and the protein tyrosine kinase inhibitor genistein partially reversed ceramide inhibition, indicating that protein kinases play important roles in the ceramide inhibition of SP-B gene expression. Chemical inhibitors of de novo ceramide synthesis and sphingomyelin hydrolysis had no effect on TNF-α inhibition of SP-B promoter activity and mRNA levels, suggesting that ceramide does not play a role in the inhibition.

5-Aminolaevulinate synthase gene promoter contains two cAMP-response element (CRE)-like sites that confer positive and negative responsiveness to CRE-binding protein (CREB)

2001 ◽  
Vol 353 (2) ◽  
pp. 307-316 ◽  
Author(s):  
Luciana E. GIONO ◽  
Cecilia L. VARONE ◽  
Eduardo T. CÁNEPA
Keyword(s):  
Gene Expression ◽  
Promoter Activity ◽  
Molecular Mechanisms ◽  
Binding Protein ◽  
Phosphorylation Site ◽  
Gene Promoter ◽  
Site Directed Mutagenesis ◽  
Dependent Manner ◽  
Mobility Shift ◽  
Putative Transcription Factor

The first and rate-controlling step of the haem biosynthetic pathway in mammals and fungi is catalysed by the mitochondrial-matrix enzyme 5-aminolaevulinate synthase (ALAS). The purpose of this work was to explore the molecular mechanisms involved in the cAMP regulation of rat housekeeping ALAS gene expression. Thus we have examined the ALAS promoter for putative transcription-factor-binding sites that may regulate transcription in a cAMP-dependent protein kinase (PKA)-induced context. Applying both transient transfection assays with a chloramphenicol acetyltransferase reporter gene driven by progressive ALAS promoter deletions in HepG2, and electrophoresis mobility-shift assays we have identified two putative cAMP-response elements (CREs) at positions -38 and -142. Functional analysis showed that both CRE-like sites were necessary for complete PKA induction, but only one for basal expression. Co-transfection with a CRE-binding protein (CREB) expression vector increased PKA-mediated induction of ALAS promoter transcriptional activity. However, in the absence of co-transfected PKA, CREB worked as a specific repressor for ALAS promoter activity. A CREB mutant deficient in a PKA phosphorylation site was unable to induce expression of the ALAS gene but could inhibit non-stimulated promoter activity. Furthermore, a DNA-binding mutant of CREB did not interfere with ALAS promoter basal activity. Site-directed-mutagenesis studies showed that only the nearest element to the transcription start site was able to inhibit the activity of the promoter. Therefore, we conclude that CREB, through its binding to CRE-like sites, mediates the effect of cAMP on ALAS gene expression. Moreover, we propose that CREB could also act as a repressor of ALAS transcription, but is able to reverse its role after PKA activation. Dephosphorylated CREB would interfere in a spatial-disposition-dependent manner with the transcriptional machinery driving inhibition of gene expression.

scholarly journals Promoters adopt distinct dynamic manifestations depending on transcription factor context

2019 ◽  
Author(s):  
Anders S. Hansen ◽  
Christoph Zechner
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Promoter Activity ◽  
Gene Activation ◽  
Gene Promoter ◽  
Specific Gene ◽  
Gene Promoters ◽  
Genetic Circuits ◽  
External Signals ◽  
Activation Delay

Cells respond to external signals and stresses by activating transcription factors (TF), which induce gene expression changes. Previous work suggests that signal-specific gene expression changes are partly achieved because different gene promoters exhibit varying induction dynamics in response to the same TF input signal. Here, using high-throughput quantitative single-cell measurements and a novel statistical method, we systematically analyzed transcription in individual cells to a large number of dynamic TF inputs. In particular, we quantified the scaling behavior among different transcriptional features extracted from the measured trajectories such as the gene activation delay or duration of promoter activity. Surprisingly, we found that even the same gene promoter can exhibit qualitatively distinct induction and scaling behaviors when exposed to different dynamic TF contexts. That is, promoters can adopt context-dependent “manifestations”. Our analysis suggests that the full complexity of signal processing by genetic circuits may be significantly underestimated when studied in specific contexts only.

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