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Michele Sawadogo - One of the best experts on this subject based on the ideXlab platform.

  • In Vivo Regulation of Follicle-Stimulating Hormone Receptor by the Transcription Factors Upstream Stimulatory Factor 1 and Upstream Stimulatory Factor 2 Is Cell Specific
    Endocrinology, 2008
    Co-Authors: Brian P Hermann, Kaori I Hornbaker, Daren A Rice, Michele Sawadogo, Leslie L Heckert
    Abstract:

    Pituitary FSH promotes pubertal timing and normal gametogenesis by binding its receptor (FSHR) located on Sertoli and granulosa cells of the testis and ovary, respectively. Studies on Fshr transcription provide substantial evidence that upstream stimulatory factor (USF) 1 and USF2, basic helix-loop-helix leucine zipper proteins, regulate Fshr through an E-box within its promoter. However, despite the strong in vitro support for USF1 and USF2 in Fshr regulation, there is currently no in vivo corroborating evidence. In the present study, chromatin immunoprecipitation demonstrated specific binding of USF1 and USF2 to the Fshr promoter in both Sertoli and granulosa cells, in vivo. Control cells lacking Fshr expression showed no USF-Fshr promoter binding, thus correlating USF-promoter binding to gene activity. Evaluation of Fshr expression in Usf1 and USF2 null mice further explored USF’s role in Fshr transcription. Loss of either gene significantly reduced ovarian Fshr levels, whereas testis levels were unalt...

  • in vivo regulation of fsh receptor fshr by the transcription factors usf1 and USF2 is cell specific short title fshr regulation by usf in vivo
    2008
    Co-Authors: Brian P Hermann, Kaori I Hornbaker, Daren A Rice, Michele Sawadogo, Leslie L Heckert
    Abstract:

    "This is an un-copyedited author manuscript copyrighted by The Endocrine Society. This may not be duplicated or reproduced, other than for personal use or within the rule of “Fair Use of Copyrighted Materials” (section 107, Title 17, U.S. Code) without permission of the copyright owner, The Endocrine Society. From the time of acceptance following peer review, the full text of this manuscript is made freely available by The Endocrine Society at http://www.endojournals.org/. The final copy edited article can be found at http://www.endojournals.org/. The Endocrine Society disclaims any responsibility or liability for errors or omissions in this version of the manuscript or in any version derived from it by the National Institutes of Health or other parties. The citation of this article must include the following information: author(s), article title, journal title, year of publication and DOI.”

  • Decreased tumorigenicity of c-Myc-transformed fibroblasts expressing active USF2.
    Experimental cell research, 2005
    Co-Authors: Chungyoul Choe, Nanyue Chen, Michele Sawadogo
    Abstract:

    USF is a small family of basic helix-loop-helix leucine zipper (bHLH-zip) transcription factors with DNA binding specificities similar to that of the c-Myc oncoprotein. Evidence for a role of USF in growth control includes inhibition of c-Myc-dependent cellular transformation in vitro and loss of USF transcriptional activity in many cancer cell lines. However, a direct effect of USF on the tumorigenicity of an established cell line has never been demonstrated. Here, cell lines derived from rat embryo fibroblasts transformed by c-Ha-Ras and either c-Myc or E1A were used as model system to investigate the tumor suppression ability of USF. Overexpression of USF2 stimulated transcription and inhibited colony formation in c-Myc-transformed, but not E1A-transformed, fibroblasts. Stable clones expressing high USF2 levels were constructed from c-Myc-transformed fibroblasts. In two of these clones, overexpressed USF2 did not activate transcription, and there was no significant change in the transformed phenotype. In contrast, a clone that expressed transcriptionally active USF2 exhibited altered morphology and a strongly decreased ability to proliferate in semisolid medium. The ability of these cells to form tumors in nude mice was also decreased by a factor of more than 30 as compared to the parental cell line or cells overexpressing transcriptionally inactive USF2. Cotransfection assays with USF- or Myc-specific dominant-negative mutants indicated that active USF2 inhibited cellular transformation by preventing transcriptional repression by c-Myc.

  • Molecular characterization and role of bovine upstream stimulatory factor 1 and 2 in the regulation of the prostaglandin G/H synthase-2 promoter in granulosa cells.
    The Journal of biological chemistry, 2003
    Co-Authors: Khampoune Sayasith, Michele Sawadogo, Nadine Bouchard, Jacques G. Lussier, Jean Sirois
    Abstract:

    The transcriptional activation of the prostaglandin G/H synthase-2 (PGHS-2) gene in granulosa cells is required for ovulation. To directly study the ability of upstream stimulatory factor 1 (USF1) and USF2 to trans-activate the bovine PGHS-2 promoter in granulosa cells, USF1 or USF2 expression vectors were cotransfected with the PGHS-2/luciferase (LUC) chimeric construct, -149/-2PGHS-2.LUC. Results revealed that overexpression of USF1 or USF2 caused a marked and significant increase in basal and forskolin-inducible promoter activities (p

  • The IGF2 receptor is a USF2-specific target in nontumorigenic mammary epithelial cells but not in breast cancer cells.
    The Journal of biological chemistry, 2003
    Co-Authors: Marilyn N. Szentirmay, Hui-xin Yang, Snehalata A. Pawar, Charles Vinson, Michele Sawadogo
    Abstract:

    The antiproliferative activities of the USF proteins and the frequent loss of USF function in cancer cells suggest a role for these ubiquitous transcription factors in tumor suppression. However, the cellular targets that mediate the effects of USF on cellular proliferation and transformation remain uncharacterized. IGF2R, with multiple functions in both normal growth and cancer, was investigated here as a possible USF target in both nontumorigenic and tumorigenic breast cell lines. The 5'-flanking sequences of the human IGF2R gene contain multiple, highly conserved E boxes almost identical to the consensus USF DNA-binding sequence. These E boxes were found to be essential for IGF2R promoter activity in the nontumorigenic mammary epithelial cell line MCF-10A. USF1 and USF2 bound the IGF2R promoter in vitro, and both USF1 and USF2, but not c-Myc, were present within the IGF2R promoter-associated chromatin in vivo. Overexpressed USF2, but not USF1, transactivated the IGF2R promoter, and IGF2R mRNA was markedly decreased by expression of a USF-specific dominant negative mutant, identifying IGF2R as a USF2 target. IGF2R promoter-driven expression was USF-independent in both MCF-7 and MDA-MB-231 breast cancer cell lines, suggesting that a defect in USF function may contribute to down-regulation of IGF2R expression in cancer cells.

Sophie Vaulont - One of the best experts on this subject based on the ideXlab platform.

  • Upstream Stimulatory Factors 1 and 2 activate the human hepatic lipase promoter via E-box dependent and independent mechanisms
    Biochimica et biophysica acta, 2009
    Co-Authors: Diederik Van Deursen, Sophie Vaulont, Marije Van Leeuwen, Hans Jansen, Adrie J.m. Verhoeven
    Abstract:

    We studied the transcriptional regulation of the HL gene by USF1 and USF2 in HepG2 cells. The transcriptional activity of the HL(-685/+13) promoter construct was increased up to 25-fold by co-transfection with USF1 and USF2. Silencing of USF1 by RNA interference reduced promoter activity by 30-40%. Chromatin immunoprecipitation assays showed binding of endogenous USF1 and USF2 to the proximal HL promoter region. In gel shift assays, USF1 and USF2 bound to E-boxes at -307/-312 and -510/-516, and to the TATA-Inr region. Although the -514C-->T substitution abolished in vitro USF binding to the -510/-516 E-box, the increase in HL promoter activity by USF1 and USF2 was unaffected. Deletion and mutation analysis of the HL promoter region, and insertion of multiple E-box copies in front of a heterologous promoter, revealed that upregulation by USFs was mainly mediated through the -307/-312 E-box and the TATA-Inr region. We conclude that in HepG2 cells USF1 and USF2 regulate transcriptional activity of the HL gene through their binding to the E-box at -307/-312 and the TATA-Inr region.

  • Targeted disruption of the hepcidin 1 gene results in severe hemochromatosis
    Blood, 2006
    Co-Authors: Jeanne-claire Lesbordes-brion, Axel Kahn, Lydie Viatte, Myriam Bennoun, Dan-qing Lou, Guillemette Ramey, Christophe Houbron, Ghislaine Hamard, Sophie Vaulont
    Abstract:

    We previously reported that mice made deficient for the transcriptional factor USF2 fail to express hepcidin 1 and hepcidin 2 genes as a consequence of targeted disruption of the USF2 gene lying just upstream in the locus. These mice developed an iron overload phenotype with excess iron deposition in parenchymal cells and decreased reticuloendothelial iron. At that time, although the role of USF2 was still confounding, we proposed for the first time the role of hepcidin as a negative regulator of iron absorption and iron release from macrophages. Accordingly, we subsequently demonstrated that hyperexpression of hepcidin 1, but not hepcidin 2, resulted in a profound hyposideremic anemia. To analyze the consequences of hepcidin 1 deletion on iron metabolism without any disturbance due to USF2 deficiency, we disrupted the hepcidin 1 gene by targeting almost all the coding region. Confirming our prior results, Hepc1(-/-) mice developed early and severe multivisceral iron overload, with sparing of the spleen macrophages, and demonstrated increased serum iron and ferritin levels as compared with their controls.

  • Transcriptional Regulation of Adipocyte Hormone-Sensitive Lipase by Glucose
    Diabetes, 2002
    Co-Authors: Fatima Smih, Marta Casado, Sophie Vaulont, Philippe Rouet, Stéphanie Lucas, Aline Mairal, Coralie Sengenès, Max Lafontan, Dominique Langin
    Abstract:

    Hormone-sensitive lipase (HSL) catalyzes the rate-limiting step in the mobilization of fatty acids from adipose tissue, thus determining the supply of energy substrates in the body. HSL mRNA was positively regulated by glucose in human adipocytes. Pools of stably transfected 3T3-F442A adipocytes were generated with human adipocyte HSL promoter fragments from -2,400/+38 to -31/+38 bp linked to the luciferase gene. A glucose-responsive region was mapped within the proximal promoter (-137 bp). Electromobility shift assays showed that upstream stimulatory factor (USF)-1 and USF2 and Sp1 and Sp3 bound to a consensus E-box and two GC-boxes in the -137-bp region. Cotransfection of the -137/+38 construct with USF1 and USF2 expression vectors produced enhanced luciferase activity. Moreover, HSL mRNA levels were decreased in USF1- and USF2-deficient mice. Site-directed mutagenesis of the HSL promoter showed that the GC-boxes, although contributing to basal promoter activity, were dispensable for glucose responsiveness. Mutation of the E-box led to decreased promoter activity and suppression of the glucose response. Analogs and metabolites were used to determine the signal metabolite of the glucose response. The signal is generated downstream of glucose-6-phosphate in the glycolytic pathway before the triose phosphate step.

  • Lack of hepcidin gene expression and severe tissue iron overload in upstream stimulatory factor 2 (USF2) knockout mice.
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: Gaël Nicolas, Axel Kahn, Myriam Bennoun, Isabelle Devaux, Carole Beaumont, Bernard Grandchamp, Sophie Vaulont
    Abstract:

    We previously reported the disruption of the murine gene encoding the transcription factor USF2 and its consequences on glucose-dependent gene regulation in the liver. We report here a peculiar phenotype of USF2(-/-) mice that progressively develop multivisceral iron overload; plasma iron overcomes transferrin binding capacity, and nontransferrin-bound iron accumulates in various tissues including pancreas and heart. In contrast, the splenic iron content is strikingly lower in knockout animals than in controls. To identify genes that may account for the abnormalities of iron homeostasis in USF2(-/-) mice, we used suppressive subtractive hybridization between livers from USF2(-/-) and wild-type mice. We isolated a cDNA encoding a peptide, hepcidin (also referred to as LEAP-1, for liver-expressed antimicrobial peptide), that was very recently purified from human blood ultrafiltrate and from urine as a disulfide-bonded peptide exhibiting antimicrobial activity. Accumulation of iron in the liver has been recently reported to up-regulate hepcidin expression, whereas our data clearly show that a complete defect in hepcidin expression is responsible for progressive tissue iron overload. The striking similarity of the alterations in iron metabolism between HFE knockout mice, a murine model of hereditary hemochromatosis, and the USF2(-/-) hepcidin-deficient mice suggests that hepcidin may function in the same regulatory pathway as HFE. We propose that hepcidin acts as a signaling molecule that is required in conjunction with HFE to regulate both intestinal iron absorption and iron storage in macrophages.

  • essential role in vivo of upstream stimulatory factors for a normal dietary response of the fatty acid synthase gene in the liver
    Journal of Biological Chemistry, 1999
    Co-Authors: Marta Casado, Virginie S Vallet, Axel Kahn, Sophie Vaulont
    Abstract:

    Abstract In the liver, transcription of several genes encoding lipogenic and glycolytic enzymes, in particular the gene for fatty acid synthase (FAS), is known to be stimulated by dietary carbohydrates. The molecular dissection of the FAS promoter pointed out the critical role of an E box motif, located at position −65 with respect to the start site of transcription, in mediating the glucose- and insulin-dependent regulation of the gene. Upstream stimulatory factors (USF1 and USF2) and sterol response element binding protein 1 (SREBP1) were shown to be able to interact in vitro with this E box. However, to date, the relative contributions of USFs and SREBP1 ex vivo remain controversial. To gain insight into the specific roles of these factorsin vivo, we have analyzed the glucose responsiveness of hepatic FAS gene expression in USF1 and USF2 knock-out mice. In both types of mouse lines, defective in either USF1 or USF2, induction of the FAS gene by refeeding a carbohydrate-rich diet was severely delayed, whereas expression of SREBP1 was almost normal and insulin response unchanged. Therefore, USF transactivators, and especially USF1/USF2 heterodimers, seem to be essential to sustain the dietary induction of the FAS gene in the liver.

Shuxia Wang - One of the best experts on this subject based on the ideXlab platform.

  • Role of upstream stimulatory factor 2 in diabetic nephropathy
    Frontiers in Biology, 2015
    Co-Authors: Shuxia Wang
    Abstract:

    Diabetic nephropathy (DN) is the most common cause of end-stage renal disease (ESRD). About 20%–30% of people with type 1 and type 2 diabetes develop DN. DN is characterized by both glomerulosclerosis with thickening of the glomerular basement membrane and mesangial matrix expansion, and tubulointerstitial fibrosis. Hyperglycemia and the activation of the intra-renal renin-angiotensin system (RAS) in diabetes have been suggested to play a critical role in the pathogenesis of DN. However, the mechanisms are not well known. Studies from our laboratory demonstrated that the transcription factor—upstream stimulatory factor 2 (USF2) is an important regulator of DN. Moreover, the renin gene is a downstream target of USF2. Importantly, USF2 transgenic (Tg) mice demonstrate a specific increase in renal renin expression and angiotensin II (AngII) levels in kidney and exhibit increased urinary albumin excretion and extracellular matrix deposition in glomeruli, supporting a role for USF2 in the development of diabetic nephropathy. In this review, we summarize our findings of the mechanisms by which diabetes regulates USF2 in kidney cells and its role in regulation of renal renin-angiotensin system and the development of diabetic nephropathy.

  • High Glucose Upregulates Upstream Stimulatory Factor 2 in Human Renal Proximal Tubular Cells through Angiotensin II-Dependent Activation of CREB
    Nephron. Experimental nephrology, 2010
    Co-Authors: Nishant P. Visavadiya, Shuxia Wang
    Abstract:

    We have previously demonstrated that a transcription factor, upstream stimulatory factor 2 (USF2), regulates glucose-induced thrombospondin 1 expression and transforming growth factor-β activity in mesangial cells, and plays an important role in diabetic glomerulopathy. In this study, we determined whether USF2 expression in renal proximal tubular cells is regulated by glucose and contributes to diabetic tubulointerstitial fibrosis. Human renal proximal tubular cells (HK-2 cells) were treated with normal- or high-glucose medium for 24 h. After treatment, real-time PCR or immunoblotting was used to determine the expression of USF2 and other components of the renin-angiotensin system in HK-2 cells. High glucose upregulated USF2 expression and increased extracellular matrix accumulation in HK-2 cells; both were inhibited by siRNA-mediated USF2 knockdown. In addition, high glucose stimulated angiotensinogen and renin expression, increased renin activity, and resulted in increased angiotensin II formation. Treatment of HK-2 cells with an angiotensin II receptor 1 (AT1) blocker--losartan--prevented high-glucose-induced USF2 expression and high-glucose-enhanced phosphorylation of CREB (cAMP response element-binding protein). Our data established that high glucose stimulated USF2 expression in HK-2 cells, at least in part, through angiotensin II-AT1-dependent activation of CREB, which can contribute to diabetic tubulointerstitial fibrosis. Copyright © 2010 S. Karger AG, Basel.

  • Glycated albumin upregulates upstream stimulatory factor 2 gene transcription in mesangial cells
    American journal of physiology. Renal physiology, 2010
    Co-Authors: Shuxia Wang
    Abstract:

    Diabetic nephropathy (DN) is the most common cause of end-stage renal failure. We previously demonstrated that a transcription factor called upstream stimulatory factor 2 (USF2) was upregulated in the kidneys from diabetic animals in vivo as well as in mesangial cells (MCs) exposed to high-glucose media in vitro. USF2 mediates glucose-induced thrombospondin 1 expression and transforming growth factor-beta activity in MCs and plays a role in DN. Glycated proteins have been shown to accumulate in the kidneys of diabetic patients and contribute to DN. However, whether glycated proteins regulate USF2 expression in MCs and play a role in DN is unknown. In the present studies, we determined the effect of glycated albumin on UFS2 gene expression in primary rat MCs. We found that glycated albumin upregulated USF2 expression (mRNA and protein) in a dose- and time-dependent manner. We also demonstrated that glycated albumin stimulated USF2 gene expression at the transcriptional level. By using the luciferase-promoter deletion assay, site-directed mutagenesis, and transactivation assay, we identified a glycated albumin-responsive region in the USF2 gene promoter (-837 to -430, relative to the transcription start site) and demonstrated that glycated albumin-induced USF2 expression was mediated through NF-kappaB-dependent transactivation of the USF2 promoter. Furthermore, glycated albumin increased nuclear NF-kappaB subunit-p65 protein levels. siRNA-mediated p65 knockdown prevented glycated albumin-induced USF2 gene expression (promoter activity, mRNA, and protein levels). Taken together, these data suggest that glycated albumin upregulated USF2 gene transcription in MCs through NF-kappaB-dependent transactivation of the USF2 promoter.

  • High glucose levels upregulate upstream stimulatory factor 2 gene transcription in mesangial cells
    Journal of cellular biochemistry, 2008
    Co-Authors: Lihua Shi, Shu Liu, Dejan Nikolic, Shuxia Wang
    Abstract:

    Previously, we demonstrated that upstream stimulatory factor 2 (USF2) mediates high glucose-induced thrombospondin1 (TSP1) gene expression and TGF-beta activity in glomerular mesangial cells and plays a role in diabetic renal complications. In the present studies, we further determined the molecular mechanisms by which high glucose levels regulate USF2 gene expression. In primary rat mesangial cells, we found that glucose treatment time and dose-dependently up-regulated USF2 expression (mRNA and protein). By using cycloheximide to block the de novo protein synthesis, similar rate of USF2 degradation was found under either normal glucose or high glucose conditions. USF2 mRNA stability was not altered by high glucose treatment. Furthermore, high glucose treatment stimulated USF2 gene promoter activity. By using the luciferase-promoter deletion assay, site-directed mutagenesis, and transactivation assay, we identified a glucose-responsive element in the USF2 gene promoter (-1,740 to -1,620, relative to the transcription start site) and demonstrated that glucose-induced USF2 expression is mediated through a cAMP-response element-binding protein (CREB)-dependent transactivation of the USF2 promoter. Furthermore, siRNA-mediated CREB knock down abolished glucose-induced USF2 expression. Taken together, these data indicate that high glucose levels up-regulate USF2 gene transcription in mesangial cells through CREB-dependent transactivation of the USF2 promoter.

  • Overexpression of upstream stimulatory factor 2 accelerates diabetic kidney injury
    American journal of physiology. Renal physiology, 2007
    Co-Authors: Shu Liu, Lihua Shi, Shuxia Wang
    Abstract:

    Diabetic nephropathy is the most common cause of end-stage renal failure in the United States. Hyperglycemia is an important factor in the pathogenesis of diabetic nephropathy. Hyperglycemia upregulates the expression of transforming growth factor-beta (TGF-beta), which stimulates extracellular matrix deposition in the kidney, contributing to the development of diabetic nephropathy. Our previous studies demonstrated that the transcription factor, upstream stimulatory factor 2 (USF2), was upregulated by high glucose, which bound to an 18-bp sequence in the thrombospondin 1 (TSP1) gene promoter and regulated high glucose-induced TSP1 expression and TGF-beta activity in mesangial cells, suggesting that USF2 might play a role in the development of diabetic nephropathy. In the present studies, we examined the effect of overexpression of USF2 on the development of diabetic nephropathy. Type 1 diabetes was induced in USF2 transgenic mice [USF2 (Tg)] and their wild-type littermates (WT) by injection of streptozotocin. Four groups of mice were studied: control WT, control USF2 (Tg), diabetic WT, and diabetic USF2 (Tg). Mice were killed after 15 wk of diabetes onset. At the end of studies, control USF2 (Tg) mice ( approximately 6 mo old) exhibited increased urinary albumin excretion. These mice also exhibited glomerular hypertrophy, accompanied by increased TSP1, active TGF-beta, fibronectin accumulation in the glomeruli compared with control WT littermates. Type 1 diabetes onset further augmented the urinary albumin excretion and glomerular hypertrophy in the USF2 (Tg) mice. These findings suggest that overexpression of USF2 accelerates the development of diabetic nephropathy.

Elzora M. Jordan - One of the best experts on this subject based on the ideXlab platform.

  • Upstream stimulatory factor 2 stimulates transcription through an initiator element in the mouse cytochrome c oxidase subunit Vb promoter.
    Biochimica et biophysica acta, 2000
    Co-Authors: Gail A. M. Breen, Elzora M. Jordan
    Abstract:

    Upstream stimulatory factor (USF) is a basic helix-loop-helix-leucine zipper transcription factor that plays an important role in transcriptional activation and cell proliferation. In this article, we demonstrate that the mouse cytochrome c oxidase subunit Vb gene (Cox5b) can be transactivated by ectopic expression of USF2 through an initiator (Inr) element in the core promoter. Importantly, using a dominant-negative mutant of USF2, we demonstrate the role of endogenous USF2 proteins in the transcriptional activation of the Cox5b Inr. Domains of USF2 encoded by exon 4, exon 5 and the USF-specific region are important for maximum activation of the Cox5b Inr. Using the adenovirus E1A oncoprotein, we show that p300/CBP acts as a coactivator in the USF2-dependent activation of the Cox5b Inr. We also demonstrate that although expression of multifunctional regulatory factor, Yin Yang 1 (YY1), can stimulate transcription of the Cox5b Inr to a modest extent, expression of YY1 together with USF2 greatly reduces the level of activation of the Cox5b Inr. Furthermore, we show that the transcription factor, Sp1, represses both the YY1- and the USF2-dependent activation of the Cox5b Inr, indicating competition among Sp1, YY1, and USF2.

  • Transcriptional activation of the F1F0 ATP synthase α-subunit initiator element by USF2 is mediated by p300
    Biochimica et Biophysica Acta, 1999
    Co-Authors: Gail A. M. Breen, Elzora M. Jordan
    Abstract:

    Abstract We have been studying the transcriptional regulation of the mammalian F 1 F 0 ATP synthase α-subunit gene ( ATPA ), a TATA-less initiator-containing gene. We have previously determined that the transcription factor, upstream stimulatory factor 2 (USF2), can activate the ATPA gene through an initiator element in the core promoter. Here, we demonstrate that the coactivator p300 interacts functionally with USF2 proteins to potentiate the activation of the ATPA initiator element by USF2. The physiological relevance of this interaction was shown in vivo by expression of the adenovirus E1A oncoprotein. Wild-type E1A, but not E1A mutants that lacked p300-binding sites, inhibited the USF2-dependent transactivation of the ATPA initiator element. Furthermore, overexpression of p300 could reverse the inhibitory effect of E1A. Collectively, our results indicate that the USF2-dependent transcriptional activation of the ATPA initiator element is mediated by p300.

  • Upstream stimulatory factor 2 activates the mammalian F1F0 ATP synthase alpha-subunit gene through an initiator element.
    Gene expression, 1998
    Co-Authors: Gail A. M. Breen, Elzora M. Jordan
    Abstract:

    The F1F0 ATP synthase is the central enzyme complex of the mitochondrial oxidative phosphorylation system synthesizing ATP from ADP and Pi. Our laboratory has been studying the transcriptional regulation of the nuclear gene that encodes the alpha-subunit of the mammalian mitochondrial ATP synthase complex (ATPA). We have previously identified an initiator element in the core promoter that plays an important role in expression of this gene. In this article, we demonstrate that ectopic expression of the transcription factor, upstream stimulatory factor 2 (USF2), transactivates the ATPA gene through this initiator element. Importantly, cotransfection of a dominant-negative USF2 mutant significantly reduces both the basal activity and the level of activation of the ATPA initiator by coexpressed USF2 demonstrating the role of endogenous USF2 proteins in this activation. We also identify several nucleotides in the ATPA initiator element that are important for both basal activity and USF2-dependent transactivation. We have also previously determined that the binding of the multifunctional regulatory protein, YY1, to this initiator element can positively regulate the ATPA gene. Here, we show that expression of YY1 together with USF2 results in a decreased level of activation of the ATPA initiator relative to expression of USF2 alone, suggesting competition between these two regulatory proteins.

  • Regulation of the Nuclear Gene That Encodes the α-Subunit of the Mitochondrial F0F1-ATP Synthase Complex ACTIVATION BY UPSTREAM STIMULATORY FACTOR 2
    The Journal of biological chemistry, 1997
    Co-Authors: Gail A. M. Breen, Elzora M. Jordan
    Abstract:

    Abstract We have previously identified several positivecis-acting regulatory regions in the promoters of the bovine and human nuclear-encoded mitochondrial F0F1-ATP synthase α-subunit genes (ATPA). One of these cis-acting regions contains the sequence 5′-CACGTG-3′ (an E-box), to which a number of transcription factors containing a basic helix-loop-helix motif can bind. This E-box element is required for maximum activity of theATPA promoter in HeLa cells. The present study identifies the human transcription factor, upstream stimulatory factor 2 (USF2), as a nuclear factor that binds to the ATPA E-box and demonstrates that USF2 plays a critical role in the activation of theATPA gene in vivo. Evidence includes the following. Antiserum directed against USF2 recognized factors present in HeLa nuclear extracts that interact with the ATPApromoter in mobility shift assays. Wild-type USF2 proteins synthesized from expression vectors trans-activated theATPA promoter through the E-box, whereas truncated USF2 proteins devoid of the amino-terminal activation domains did not. Importantly, expression of a dominant-negative mutant of USF2 lacking the basic DNA binding domain but able to dimerize with endogenous USF proteins significantly reduced the level of activation of theATPA promoter caused by ectopically coexpressed USF2, demonstrating the importance of endogenous USF2 in activation of theATPA gene.

Elitsa Y. Dimova - One of the best experts on this subject based on the ideXlab platform.

  • Loss of USF2 promotes proliferation, migration and mitophagy in a redox-dependent manner
    Redox biology, 2020
    Co-Authors: Tabughang Franklin Chi, Thomas Kietzmann, Fawzi Khoder-agha, Daniela Mennerich, Sakari Kellokumpu, Iikka Miinalainen, Elitsa Y. Dimova
    Abstract:

    Abstract The upstream stimulatory factor 2 (USF2) is a transcription factor implicated in several cellular processes and among them, tumor development seems to stand out. However, the data with respect to the role of USF2 in tumor development are conflicting suggesting that it acts either as tumor promoter or suppressor. Here we show that absence of USF2 promotes proliferation and migration. Thereby, we reveal a previously unknown function of USF2 in mitochondrial homeostasis. Mechanistically, we demonstrate that deficiency of USF2 promotes survival by inducing mitophagy in a ROS-sensitive manner by activating both ERK1/2 and AKT. Altogether, this study supports USF2′s function as tumor suppressor and highlights its novel role for mitochondrial function and energy homeostasis thereby linking USF2 to conditions such as insulin resistance, type-2 diabetes mellitus, and the metabolic syndrome.

  • Cyclin-Dependent Kinase 5 (CDK5)-Mediated Phosphorylation of Upstream Stimulatory Factor 2 (USF2) Contributes to Carcinogenesis.
    Cancers, 2019
    Co-Authors: Tina Horbach, Claudia Götz, Thomas Kietzmann, Elitsa Y. Dimova
    Abstract:

    The transcription factor USF2 is supposed to have an important role in tumor development. However, the regulatory mechanisms contributing to the function of USF2 are largely unknown. Cyclin-dependent kinase 5 (CDK5) seems to be of importance since high levels of CDK5 were found in different cancers associated with high USF2 expression. Here, we identified USF2 as a phosphorylation target of CDK5. USF2 is phosphorylated by CDK5 at two serine residues, serine 155 and serine 222. Further, phosphorylation of USF2 at these residues was shown to stabilize the protein and to regulate cellular growth and migration. Altogether, these results delineate the importance of the CDK5-USF2 interplay in cancer cells.

  • The nuclear fraction of protein kinase CK2 binds to the upstream stimulatory factors (USFs) in the absence of DNA.
    Cellular signalling, 2015
    Co-Authors: Sarah Spohrer, Elitsa Y. Dimova, Thomas Kietzmann, Mathias Montenarh, Claudia Götz
    Abstract:

    The functions of the upstream stimulatory factors USF1 and USF2 are, like those of other transcription factors, regulated by reversible phosphorylation. Besides many other kinases also protein kinase CK2 phosphorylates USF1 but not USF2. In a yeast-two-hybrid screen, however, the non-catalytic CK2β subunit of CK2 was identified as a binding partner of USF2. This surprising observation prompted us to investigate the CK2/USF interaction in more detail in the present study. By using immunofluorescence analyses as well as co-immunoprecipitations we found that USF1 and USF2 bound to CK2α and CK2β exclusively in the nucleus, though CK2β and to a minor amount CK2α were also present in the cytoplasm. Furthermore, we found that unlike other substrates the phosphorylation of USF1 required the presence of the regulatory CK2β subunit; the catalytic α-subunit of CK2 alone was not able to phosphorylate USF1. Thus, the correct phosphorylation of USF1 is only guaranteed and strictly controlled in particular by nuclear CK2β. Although the data indicated that a nuclear subfraction of CK2 subunits associated with USF proteins, DNA pull down experiments revealed that the CK2 subunits did not co-localize with DNA bound USF proteins indicating that the USF/CK2 interaction has a pre- or post DNA binding function.

  • GSK3β-Dependent Phosphorylation Alters DNA Binding, Transactivity and Half-Life of the Transcription Factor USF2
    PloS one, 2014
    Co-Authors: Tina Horbach, Claudia Götz, Elitsa Y. Dimova, Tabughang Franklin Chi, Satyan Sharma, André H. Juffer, Thomas Kietzmann
    Abstract:

    The upstream stimulatory factor 2 (USF2) is a regulator of important cellular processes and is supposed to have also a role during tumor development. However, the knowledge about the mechanisms that control the function of USF2 is limited. The data of the current study show that USF2 function is regulated by phosphorylation and identified GSK3β as an USF2-phosphorylating kinase. The phosphorylation sites within USF2 could be mapped to serine 155 and threonine 230. In silico analyses of the 3-dimensional structure revealed that phosphorylation of USF2 by GSK3β converts it to a more open conformation which may influence transactivity, DNA binding and target gene expression. Indeed, experiments with GSK-3β-deficient cells revealed that USF2 transactivity, DNA binding and target gene expression were reduced upon lack of GSK3β. Further, experiments with USF2 variants mimicking GSK3β phosphorylated USF2 in GSK3β-deficient cells showed that phosphorylation of USF2 by GSK3β did not affect cell proliferation but increased cell migration. Together, this study reports a new mechanism by which USF2 may contribute to cancerogenesis.

  • The upstream stimulatory factor USF1 is regulated by protein kinase CK2 phosphorylation
    Cellular signalling, 2014
    Co-Authors: Sarah Lupp, Tina Horbach, Claudia Götz, Thomas Kietzmann, Elitsa Y. Dimova, Sunia Khadouma, Anna-maria Bohrer, Mathias Montenarh
    Abstract:

    The upstream stimulatory factors 1 (USF1) and 2 (USF2) are transcription factors which bind to E-box motifs of various promoters regulating a variety of different cellular processes. Only little is known about the regulation of USFs. Here, we identified protein kinase CK2 as an enzyme that phosphorylates USF1 but not USF2. Using deletion mutants and point mutants we were able to identify threonine 100 as the major phosphorylation site for CK2. It is well known that USF1 and USF2 form hetero-dimers. Binding studies revealed that the inhibition of CK2 kinase activity by a specific inhibitor enhanced binding of USF1 to USF2. Furthermore, transactivation studies showed that the inhibition of CK2 phosphorylation of USF1 stimulated transcription from the glucokinase promoter as well as the fatty acid synthetase promoter but not from the heme oxygenase-1 promoter. Thus, we have shown for the first time that CK2 phosphorylation of USF1 modulates two functionally important properties of USF1, namely hetero-dimerization and transactivation.

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