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Gerganova V, Maurer S, Stoliar L, Japaridze A, Dietler G, Nasser W, Kutateladze T, Travers A, Muskhelishvili G. Upstream binding of idling RNA polymerase modulates transcription initiation from a nearby promoter. J Biol Chem 2015; 290:8095-109. [PMID: 25648898 DOI: 10.1074/jbc.m114.628131] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bacterial gene regulatory regions often demonstrate distinctly organized arrays of RNA polymerase binding sites of ill-defined function. Previously we observed a module of closely spaced polymerase binding sites upstream of the canonical promoter of the Escherichia coli fis operon. FIS is an abundant nucleoid-associated protein involved in adjusting the chromosomal DNA topology to changing cellular physiology. Here we show that simultaneous binding of the polymerase at the canonical fis promoter and an upstream transcriptionally inactive site stabilizes a RNAP oligomeric complex in vitro. We further show that modulation of the upstream binding of RNA polymerase affects the fis promoter activity both in vivo and in vitro. The effect of the upstream RNA polymerase binding on the fis promoter activity depends on the spatial arrangement of polymerase binding sites and DNA supercoiling. Our data suggest that a specific DNA geometry of the nucleoprotein complex stabilized on concomitant binding of RNA polymerase molecules at the fis promoter and the upstream region acts as a topological device regulating the fis transcription. We propose that transcriptionally inactive RNA polymerase molecules can act as accessory factors regulating the transcription initiation from a nearby promoter.
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Affiliation(s)
- Veneta Gerganova
- From the School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
| | - Sebastian Maurer
- From the School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
| | - Liubov Stoliar
- From the School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
| | - Aleksandre Japaridze
- the Laboratory of the Physics of Living Matter, EPFL, CH-1015 Lausanne, Switzerland
| | - Giovanni Dietler
- the Laboratory of the Physics of Living Matter, EPFL, CH-1015 Lausanne, Switzerland
| | - William Nasser
- the UMR5240 CNRS/INSA/UCB, Université de Lyon, F-69003, INSA-Lyon, Villeurbanne, F-69621, France
| | - Tamara Kutateladze
- the Ivane Beritashvili Centre of Experimental Biomedicine, Gotua str.14, Tbilisi, Georgia, and
| | - Andrew Travers
- the MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 QH, United Kingdom
| | - Georgi Muskhelishvili
- From the School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany,
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Weatherspoon-Griffin N, Yang D, Kong W, Hua Z, Shi Y. The CpxR/CpxA two-component regulatory system up-regulates the multidrug resistance cascade to facilitate Escherichia coli resistance to a model antimicrobial peptide. J Biol Chem 2014; 289:32571-82. [PMID: 25294881 DOI: 10.1074/jbc.m114.565762] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A genome-wide susceptibility assay was used to identify specific CpxR-dependent genes that facilitate Escherichia coli resistance to a model cationic antimicrobial peptide, protamine. A total of 115 strains from the Keio Collection, each of which contained a deletion at a demonstrated or predicted CpxR/CpxA-dependent locus, were tested for protamine susceptibility. One strain that exhibited high susceptibility carried a deletion of tolC, a gene that encodes the outer membrane component of multiple tripartite multidrug transporters. Concomitantly, two of these efflux systems, AcrAB/TolC and EmrAB/TolC, play major roles in protamine resistance. Activation of the CpxR/CpxA system stimulates mar transcription, suggesting a new regulatory circuit that enhances the multidrug resistance cascade. Tripartite multidrug efflux systems contribute to bacterial resistance to protamine differently from the Tat system. DNase I footprinting analysis demonstrated that the CpxR protein binds to a sequence located in the -35 and -10 regions of mar promoter. This sequence resembles the consensus CpxR binding site, however, on the opposite strand. aroK, a CpxR-dependent gene that encodes a shikimate kinase in the tryptophan biosynthesis pathway, was also found to facilitate protamine resistance. Specific aromatic metabolites from this pathway, such as indole, can stimulate expression of well studied CpxR-dependent genes degP and cpxP, which are not components of the tripartite multidrug transporters. Thus, we propose a novel mechanism for E. coli to modulate resistance to protamine and likely other cationic antimicrobial peptides in which the CpxR/CpxA system up-regulates mar transcription in response to specific aromatic metabolites, subsequently stimulating the multidrug resistance cascade.
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Affiliation(s)
| | - Dezhi Yang
- the College of Life Sciences, Inner Mongolia University, Hohhot, Inner Mongolia 010021, China, and From The School of Life Sciences, The Center for Infectious Diseases and Vaccinology at the Biodesign Institute, Arizona State University, Tempe, Arizona, 85287-4501
| | - Wei Kong
- The Center for Infectious Diseases and Vaccinology at the Biodesign Institute, Arizona State University, Tempe, Arizona, 85287-4501
| | - Zichun Hua
- The State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Yixin Shi
- From The School of Life Sciences, The Center for Infectious Diseases and Vaccinology at the Biodesign Institute, Arizona State University, Tempe, Arizona, 85287-4501,
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Wang H, Gutierrez-Uzquiza A, Garg R, Barrio-Real L, Abera MB, Lopez-Haber C, Rosemblit C, Lu H, Abba M, Kazanietz MG. Transcriptional regulation of oncogenic protein kinase Cϵ (PKCϵ) by STAT1 and Sp1 proteins. J Biol Chem 2014; 289:19823-38. [PMID: 24825907 DOI: 10.1074/jbc.m114.548446] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Overexpression of PKCϵ, a kinase associated with tumor aggressiveness and widely implicated in malignant transformation and metastasis, is a hallmark of multiple cancers, including mammary, prostate, and lung cancer. To characterize the mechanisms that control PKCϵ expression and its up-regulation in cancer, we cloned an ∼ 1.6-kb promoter segment of the human PKCϵ gene (PRKCE) that displays elevated transcriptional activity in cancer cells. A comprehensive deletional analysis established two regions rich in Sp1 and STAT1 sites located between -777 and -105 bp (region A) and -921 and -796 bp (region B), respectively, as responsible for the high transcriptional activity observed in cancer cells. A more detailed mutagenesis analysis followed by EMSA and ChIP identified Sp1 sites in positions -668/-659 and -269/-247 as well as STAT1 sites in positions -880/-869 and -793/-782 as the elements responsible for elevated promoter activity in breast cancer cells relative to normal mammary epithelial cells. RNAi silencing of Sp1 and STAT1 in breast cancer cells reduced PKCϵ mRNA and protein expression, as well as PRKCE promoter activity. Moreover, a strong correlation was found between PKCϵ and phospho-Ser-727 (active) STAT1 levels in breast cancer cells. Our results may have significant implications for the development of approaches to target PKCϵ and its effectors in cancer therapeutics.
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Affiliation(s)
- HongBin Wang
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Alvaro Gutierrez-Uzquiza
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Rachana Garg
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Laura Barrio-Real
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Mahlet B Abera
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Cynthia Lopez-Haber
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Cinthia Rosemblit
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Huaisheng Lu
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
| | - Martin Abba
- the Centro de Investigaciones Inmunológicas Básicas y Aplicadas, Universidad Nacional de La Plata, CP1900 La Plata, Argentina
| | - Marcelo G Kazanietz
- From the Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 and
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Chutake YK, Costello WN, Lam C, Bidichandani SI. Altered nucleosome positioning at the transcription start site and deficient transcriptional initiation in Friedreich ataxia. J Biol Chem 2014; 289:15194-202. [PMID: 24737321 PMCID: PMC4140879 DOI: 10.1074/jbc.m114.566414] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 04/14/2014] [Indexed: 11/06/2022] Open
Abstract
Most individuals with Friedreich ataxia (FRDA) are homozygous for an expanded GAA triplet repeat (GAA-TR) mutation in intron 1 of the FXN gene, which results in deficiency of FXN transcript. Consistent with the expanded GAA-TR sequence as a cause of variegated gene silencing, evidence for heterochromatin has been detected in intron 1 in the immediate vicinity of the expanded GAA-TR mutation in FRDA. Transcriptional deficiency in FRDA is thought to result from deficient elongation through the expanded GAA-TR sequence because of repeat-proximal heterochromatin and abnormal DNA structures adopted by the expanded repeat. There is also evidence for deficient transcriptional initiation in FRDA, but its relationship to the expanded GAA-TR mutation remains unclear. We show that repressive chromatin extends from the expanded GAA-TR in intron 1 to the upstream regions of the FXN gene, involving the FXN transcriptional start site. Using a chromatin accessibility assay and a high-resolution nucleosome occupancy assay, we found that the major FXN transcriptional start site, which is normally in a nucleosome-depleted region, is rendered inaccessible by altered nucleosome positioning in FRDA. Consistent with the altered epigenetic landscape the FXN gene promoter, a typical CpG island promoter, was found to be in a transcriptionally non-permissive state in FRDA. Both metabolic labeling of nascent transcripts and an unbiased whole transcriptome analysis revealed a severe deficiency of transcriptional initiation in FRDA. Deficient transcriptional initiation, and not elongation, is the major cause of FXN transcriptional deficiency in FRDA, and it is related to the spread of repressive chromatin from the expanded GAA-TR mutation.
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Affiliation(s)
| | | | | | - Sanjay I Bidichandani
- From the Departments of Pediatrics and Biochemistry & Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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Abstract
The tumor invasive phenotype driven by seprase expression/activity has been widely examined in an array of malignant tumor cell types; however, very little is known about the transcriptional regulation of this critical protease. Seprase (also named fibroblast activation protein-α, antiplasmin-cleaving enzyme, and dipeptidyl prolyl peptidase 5) is expressed at high levels by stromal fibroblast, endothelial, and tumor cells in a variety of invasive tumors but is undetectable in the majority of normal adult tissues. To examine the transcriptional regulation of the gene, we cloned the human seprase promoter and demonstrated that endogenous seprase expression and exogenous seprase promoter activity are high in invasive melanoma cells but not in non-invasive melanoma cells/primary melanocytes. In addition, we identified a crucial TGF-β-responsive cis-regulatory element in the proximal seprase promoter region that enabled robust transcriptional activation of the gene. Treatment of metastatic but not normal/non-invasive cells with TGF-β1 caused a rapid and profound up-regulation of endogenous seprase mRNA, which coincided with an abolishment of the negative regulator c-Ski, and an increase in binding of Smad3/4 to the seprase promoter in vivo. Blocking TGF-β signaling in invasive melanoma cells through overexpression of c-Ski, chemically using SB-431542, or with a neutralizing antibody against TGF-β significantly reduced seprase mRNA levels. Strikingly, RNAi of seprase in invasive cells greatly diminished their invasive potential in vitro as did blocking TGF-β signaling using SB-431542. Altogether, we found that seprase is transcriptionally up-regulated in invasive melanoma cells via the canonical TGF-β signaling pathway, supporting the roles of both TGF-β and seprase in tumor invasion and metastasis.
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Affiliation(s)
- Shaun Tulley
- From the Metastasis Research Laboratory, Division of Gynecologic Oncology, Stony Brook Medicine, Stony Brook, New York 11794
| | - Wen-Tien Chen
- From the Metastasis Research Laboratory, Division of Gynecologic Oncology, Stony Brook Medicine, Stony Brook, New York 11794
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Liu C, Chen X, Yang L, Kisseleva T, Brenner DA, Seki E. Transcriptional repression of the transforming growth factor β (TGF-β) Pseudoreceptor BMP and activin membrane-bound inhibitor (BAMBI) by Nuclear Factor κB (NF-κB) p50 enhances TGF-β signaling in hepatic stellate cells. J Biol Chem 2014; 289:7082-7091. [PMID: 24448807 DOI: 10.1074/jbc.m113.543769] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
TLR4 signaling induces down-regulation of the bone morphogenic protein (BMP) and activin membrane-bound inhibitor (BAMBI), which enhances TGF-β signaling during hepatic stellate cell (HSC) activation. We investigated the mechanism by which TLR4 signaling down-regulates BAMBI expression in HSCs and found that TLR4- and TNF-α-mediated BAMBI down-regulation is dependent on regulation of BAMBI promoter activity through the interaction with NF-κBp50 and HDAC1 in HSCs. Bambi was predominantly expressed in HSCs, at high levels in quiescent HSCs but at low levels in in vivo-activated and LPS-stimulated HSCs. In human HSCs, BAMBI expression was down-regulated in response to LPS and TNF-α. A BAMBI reporter assay demonstrated that the regulatory element to repress BAMBI transcription is located between 3384 and 1560 bp upstream from the transcription start site. LPS stimulation down-regulated BAMBI expression in cells with NF-κBp65 knockdown. However, it failed to down-regulate BAMBI in cells with inactivation of NF-κB or NF-κBp50 silencing, indicating that NF-κBp50 is a factor for BAMBI down-regulation. ChIP analysis revealed that LPS and TNF-α induced binding of the NF-κBp50/p50 homodimer to the BAMBI promoter region. We also found that HDAC1 is bound to this region as part of the NF-κBp50-HDAC1 complex, repressing transcriptional activity of the BAMBI promoter. Finally, we confirmed that LPS does not repress BAMBI reporter activity using a BAMBI reporter construct with a mutation at 3166 bp upstream of the coding region. In summary, our study demonstrates that LPS- and TNF-α-induced NF-κBp50-HDAC1 interaction represses BAMBI transcriptional activity, which contributes to TLR4-mediated enhancement of TGF-β signaling in HSCs during liver fibrosis.
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Affiliation(s)
- Cheng Liu
- Division of Gastroenterology, Department of Medicine, University of California San Diego, School of Medicine, La Jolla, California 92093; Scientific Research Center, Shanghai 201508, China; Department of Traditional Chinese Medicine, Shanghai Public Clinical Health Center, Shanghai 201508, China
| | - Xiaorong Chen
- Department of Traditional Chinese Medicine, Shanghai Public Clinical Health Center, Shanghai 201508, China
| | - Ling Yang
- Division of Gastroenterology, Department of Medicine, University of California San Diego, School of Medicine, La Jolla, California 92093
| | - Tatiana Kisseleva
- Division of Gastroenterology, Department of Medicine, University of California San Diego, School of Medicine, La Jolla, California 92093
| | - David A Brenner
- Division of Gastroenterology, Department of Medicine, University of California San Diego, School of Medicine, La Jolla, California 92093
| | - Ekihiro Seki
- Division of Gastroenterology, Department of Medicine, University of California San Diego, School of Medicine, La Jolla, California 92093.
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Jiang WR, Cady G, Hossain MM, Huang QQ, Wang X, Jin JP. Mechanoregulation of h2-calponin gene expression and the role of Notch signaling. J Biol Chem 2014; 289:1617-28. [PMID: 24285540 PMCID: PMC3894341 DOI: 10.1074/jbc.m113.498147] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 11/25/2013] [Indexed: 01/10/2023] Open
Abstract
The essential role of mechanical signals in regulating the function of living cells is universally observed. However, how mechanical signals are transduced in cells to regulate gene expression is largely unknown. We previously demonstrated that the gene encoding h2-calponin (Cnn2) is sensitively regulated by mechanical tension. In the present study, mouse genomic DNA containing the Cnn2 promoter was cloned, and a nested set of 5' truncations was studied. Transcriptional activity of the Cnn2 promoter-reporter constructs was examined in transfected NIH/3T3, HEK293, and C2C12 cells for their responses to the stiffness of culture substrate. The results showed significant transcriptional activities of the -1.00- and -1.24-kb promoter constructs, whereas the -0.61-kb construct was inactive. The -1.38-, -1.57-, and -2.12-kb constructs showed higher transcriptional activity, whereas only the -1.57- and -2.12-kb constructs exhibited repression of expression when the host cells were cultured on low stiffness substrate. Internal deletion of the segment between -1.57 and -1.38 kb in the -2.12-kb promoter construct abolished the low substrate stiffness-induced repression. Site-specific deletion or mutation of an HES-1 transcription factor binding site in this region also abolished this repression effect. The level of HES-1 increased in cells cultured under a low tension condition, corresponding to the down-regulation of h2-calponin. h2-Calponin gene expression is further affected by the treatment of cells with Notch inhibitor and activator, suggesting an upstream signaling mechanism.
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Affiliation(s)
- Wen-rui Jiang
- From the Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Geoffrey Cady
- From the Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - M. Moazzem Hossain
- From the Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Qi-Quan Huang
- From the Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Xin Wang
- From the Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - J.-P. Jin
- From the Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201
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Rather MI, Swamy S, Gopinath KS, Kumar A. Transcriptional repression of tumor suppressor CDC73, encoding an RNA polymerase II interactor, by Wilms tumor 1 protein (WT1) promotes cell proliferation: implication for cancer therapeutics. J Biol Chem 2013; 289:968-76. [PMID: 24257751 DOI: 10.1074/jbc.m113.483255] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Wilms tumor 1 gene (WT1) can either repress or induce the expression of genes. Inconsistent with its tumor suppressor role, elevated WT1 levels have been observed in leukemia and solid tumors. WT1 has also been suggested to act as an oncogene by inducing the expression of MYC and BCL-2. However, these are only the correlational studies, and no functional study has been performed to date. Consistent with its tumor suppressor role, CDC73 binds to RNA polymerase II as part of a PAF1 transcriptional regulatory complex and causes transcriptional repression of oncogenes MYC and CCND1. It also represses β-catenin-mediated transcription. Based on the reduced level of CDC73 in oral squamous cell carcinoma (OSCC) samples in the absence of loss-of-heterozygosity, promoter methylation, and mutations, we speculated that an inhibitory transcription factor is regulating its expression. The bioinformatics analysis predicted WT1 as an inhibitory transcription factor to regulate the CDC73 level. Our results showed that overexpression of WT1 decreased CDC73 levels and promoted proliferation of OSCC cells. ChIP and EMSA results demonstrated binding of WT1 to the CDC73 promoter. The 5-azacytidine treatment of OSCC cells led to an up-regulation of WT1 with a concomitant down-regulation of CDC73, further suggesting regulation of CDC73 by WT1. Exogenous CDC73 attenuated the protumorigenic activity of WT1 by apoptosis induction. An inverse correlation between expression levels of CDC73 and WT1 was observed in OSCC samples. These observations indicated that WT1 functions as an oncogene by repressing the expression of CDC73 in OSCC. We suggest that targeting WT1 could be a therapeutic strategy for cancer, including OSCC.
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Affiliation(s)
- Mohammad Iqbal Rather
- From the Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore 560012, India and
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Takayama H, Misu H, Iwama H, Chikamoto K, Saito Y, Murao K, Teraguchi A, Lan F, Kikuchi A, Saito R, Tajima N, Shirasaki T, Matsugo S, Miyamoto KI, Kaneko S, Takamura T. Metformin suppresses expression of the selenoprotein P gene via an AMP-activated kinase (AMPK)/FoxO3a pathway in H4IIEC3 hepatocytes. J Biol Chem 2013; 289:335-45. [PMID: 24257750 DOI: 10.1074/jbc.m113.479386] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Selenoprotein P (SeP; encoded by SEPP1 in humans) is a liver-derived secretory protein that induces insulin resistance in type 2 diabetes. Suppression of SeP might provide a novel therapeutic approach to treating type 2 diabetes, but few drugs that inhibit SEPP1 expression in hepatocytes have been identified to date. The present findings demonstrate that metformin suppresses SEPP1 expression by activating AMP-activated kinase (AMPK) and subsequently inactivating FoxO3a in H4IIEC3 hepatocytes. Treatment with metformin reduced SEPP1 promoter activity in a concentration- and time-dependent manner; this effect was cancelled by co-administration of an AMPK inhibitor. Metformin also suppressed Sepp1 gene expression in the liver of mice. Computational analysis of transcription factor binding sites conserved among the species resulted in identification of the FoxO-binding site in the metformin-response element of the SEPP1 promoter. A luciferase reporter assay showed that metformin suppresses Forkhead-response element activity, and a ChIP assay revealed that metformin decreases binding of FoxO3a, a direct target of AMPK, to the SEPP1 promoter. Transfection with siRNAs for Foxo3a, but not for Foxo1, cancelled metformin-induced luciferase activity suppression of the metformin-response element of the SEPP1 promoter. The overexpression of FoxO3a stimulated SEPP1 promoter activity and rescued the suppressive effect of metformin. Metformin did not affect FoxO3a expression, but it increased its phosphorylation and decreased its nuclear localization. These data provide a novel mechanism of action for metformin involving improvement of systemic insulin sensitivity through the regulation of SeP production and suggest an additional approach to the development of anti-diabetic drugs.
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Affiliation(s)
- Hiroaki Takayama
- From the Department of Disease Control and Homeostasis, Kanazawa University Graduate School of Medical Sciences, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8641, Japan
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Abstract
The human B cell-specific protein, CD79b (also known as Igβ and B29) constitutes an essential signal transduction component of the B cell receptor. Although its function is central to the triggering of B cell terminal differentiation in response to antigen stimulation, the transcriptional determinants that control CD79b gene expression remain poorly defined. In the present study, we explored these determinants using a series of hCD79b transgenic mouse models. Remarkably, we observed that the previously described hCD79b promoter along with its associated enhancer elements and first exon could be deleted without appreciable loss of hCD79b transcriptional activity or tissue specificity. In this deletion setting, a secondary promoter located within exon 2 maintained full levels and specificity of hCD79b transcription. Of note, this secondary promoter was also active, albeit at lower levels, in the wild-type hCD79b locus. The activity of the secondary promoter was dependent on the action(s) of a conserved sequence element mapping to a chromatin DNase I hypersensitive site located within intron 1. mRNA generated from this secondary promoter is predicted to encode an Igβ protein lacking a signal sequence and thus unable to serve normal B cell receptor function. Although the physiologic role of the hCD79b secondary promoter and its encoded protein remain unclear, the current data suggest that it has the capacity to play a role in normal as well as pathologic states in B cell proliferation and function.
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Affiliation(s)
- Eung Jae Yoo
- Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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Kasaai B, Gaumond MH, Moffatt P. Regulation of the bone-restricted IFITM-like (Bril) gene transcription by Sp and Gli family members and CpG methylation. J Biol Chem 2013; 288:13278-94. [PMID: 23530031 DOI: 10.1074/jbc.m113.457010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND BRIL is a bone-specific membrane protein that is involved in osteogenesis imperfecta type V. RESULTS Bril transcription is activated by Sp1, Sp3, OSX, and GLI2 and by CpG demethylation. CONCLUSION Regulation of Bril involves trans-acting factors integrating at conserved promoter elements and epigenetic modifications. SIGNIFICANCE Identification of the mechanisms governing Bril transcription is important to understand its role in skeletal biology. Bril encodes a small membrane protein present in osteoblasts. In humans, a single recurrent mutation in the 5'-UTR of BRIL causes osteogenesis imperfecta type V. The exact function of BRIL and the mechanism by which it contributes to disease are still unknown. The goal of the current study was to characterize the mechanisms governing Bril transcription in humans, rats, and mice. In the three species, as detected by luciferase reporter assays in UMR106 cells, we found that most of the base-line regulatory activity was localized within ∼250 bp upstream of the coding ATG. Co-transfection experiments indicated that Sp1 and Sp3 were potent inducers of the promoter activity, through the binding of several GC-rich boxes. Osterix was a weak activator but acted cooperatively with Sp1 and GLI2 to synergistically induce the BRIL promoter. GLI2, a mediator of hedgehog signaling pathway, was also a potent activator of BRIL through a single GLI binding site. Correspondingly, agonists of the hedgehog pathway (purmorphamine and Indian hedgehog) in MC3T3 osteoblasts led to increased BRIL levels. The BRIL promoter activity was also found to be negatively modulated through two different mechanisms. First, the ZFP354C zinc finger protein repressed basal and Sp1-induced activity. Second, CpG methylation of the promoter region correlated with an inactive state and prevented Sp1 activation. The data provide the very first analyses of the cis- and trans-acting factors regulating Bril transcription. They revealed key roles for the Sp members and GLI2 that possibly cooperate to activate Bril when the promoter becomes demethylated.
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Affiliation(s)
- Bahar Kasaai
- Shriners Hospital for Children, Montreal, Quebec H3G 1A6, Canada
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