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Razy-Krajka F, Gravez B, Kaplan N, Racioppi C, Wang W, Christiaen L. An FGF-driven feed-forward circuit patterns the cardiopharyngeal mesoderm in space and time. eLife 2018; 7:e29656. [PMID: 29431097 PMCID: PMC5809146 DOI: 10.7554/elife.29656] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 01/26/2018] [Indexed: 12/16/2022] Open
Abstract
In embryos, multipotent progenitors divide to produce distinct progeny and express their full potential. In vertebrates, multipotent cardiopharyngeal progenitors produce second-heart-field-derived cardiomyocytes, and branchiomeric skeletal head muscles. However, the mechanisms underlying these early fate choices remain largely elusive. The tunicate Ciona emerged as an attractive model to study early cardiopharyngeal development at high resolution: through two asymmetric and oriented divisions, defined cardiopharyngeal progenitors produce distinct first and second heart precursors, and pharyngeal muscle (aka atrial siphon muscle, ASM) precursors. Here, we demonstrate that differential FGF-MAPK signaling distinguishes between heart and ASM precursors. We characterize a feed-forward circuit that promotes the successive activations of essential ASM determinants, Hand-related, Tbx1/10 and Ebf. Finally, we show that coupling FGF-MAPK restriction and cardiopharyngeal network deployment with cell divisions defines the timing of gene expression and permits the emergence of diverse cell types from multipotent progenitors.
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Affiliation(s)
- Florian Razy-Krajka
- Center for Developmental Genetics, Department of BiologyCollege of Arts and Science, New York UniversityNew YorkUnited States
| | - Basile Gravez
- Center for Developmental Genetics, Department of BiologyCollege of Arts and Science, New York UniversityNew YorkUnited States
| | - Nicole Kaplan
- Center for Developmental Genetics, Department of BiologyCollege of Arts and Science, New York UniversityNew YorkUnited States
| | - Claudia Racioppi
- Center for Developmental Genetics, Department of BiologyCollege of Arts and Science, New York UniversityNew YorkUnited States
| | - Wei Wang
- Center for Developmental Genetics, Department of BiologyCollege of Arts and Science, New York UniversityNew YorkUnited States
| | - Lionel Christiaen
- Center for Developmental Genetics, Department of BiologyCollege of Arts and Science, New York UniversityNew YorkUnited States
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2
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Chambers M, Turki-Judeh W, Kim MW, Chen K, Gallaher SD, Courey AJ. Mechanisms of Groucho-mediated repression revealed by genome-wide analysis of Groucho binding and activity. BMC Genomics 2017; 18:215. [PMID: 28245789 PMCID: PMC5331681 DOI: 10.1186/s12864-017-3589-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Accepted: 02/13/2017] [Indexed: 12/24/2022] Open
Abstract
Background The transcriptional corepressor Groucho (Gro) is required for the function of many developmentally regulated DNA binding repressors, thus helping to define the gene expression profile of each cell during development. The ability of Gro to repress transcription at a distance together with its ability to oligomerize and bind to histones has led to the suggestion that Gro may spread along chromatin. However, much is unknown about the mechanism of Gro-mediated repression and about the dynamics of Gro targeting. Results Our chromatin immunoprecipitation sequencing analysis of temporally staged Drosophila embryos shows that Gro binds in a highly dynamic manner primarily to clusters of discrete (<1 kb) segments. Consistent with the idea that Gro may facilitate communication between silencers and promoters, Gro binding is enriched at both cis-regulatory modules, as well as within the promotors of potential target genes. While this Gro-recruitment is required for repression, our data show that it is not sufficient for repression. Integration of Gro binding data with transcriptomic analysis suggests that, contrary to what has been observed for another Gro family member, Drosophila Gro is probably a dedicated repressor. This analysis also allows us to define a set of high confidence Gro repression targets. Using publically available data regarding the physical and genetic interactions between these targets, we are able to place them in the regulatory network controlling development. Through analysis of chromatin associated pre-mRNA levels at these targets, we find that genes regulated by Gro in the embryo are enriched for characteristics of promoter proximal paused RNA polymerase II. Conclusions Our findings are inconsistent with a one-dimensional spreading model for long-range repression and suggest that Gro-mediated repression must be regulated at a post-recruitment step. They also show that Gro is likely a dedicated repressor that sits at a prominent highly interconnected regulatory hub in the developmental network. Furthermore, our findings suggest a role for RNA polymerase II pausing in Gro-mediated repression. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3589-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Michael Chambers
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
| | - Wiam Turki-Judeh
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA.,Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Min Woo Kim
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
| | - Kenny Chen
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
| | - Sean D Gallaher
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA.,Department of Energy, Institute of Genomics and Proteomics, University of California, Los Angeles, CA, 90095, USA
| | - Albert J Courey
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA. .,Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA.
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3
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Bai G, Ren K, Dubner R. Epigenetic regulation of persistent pain. Transl Res 2015; 165:177-99. [PMID: 24948399 PMCID: PMC4247805 DOI: 10.1016/j.trsl.2014.05.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/19/2014] [Accepted: 05/20/2014] [Indexed: 02/09/2023]
Abstract
Persistent or chronic pain is tightly associated with various environmental changes and linked to abnormal gene expression within cells processing nociceptive signaling. Epigenetic regulation governs gene expression in response to environmental cues. Recent animal model and clinical studies indicate that epigenetic regulation plays an important role in the development or maintenance of persistent pain and possibly the transition of acute pain to chronic pain, thus shedding light in a direction for development of new therapeutics for persistent pain.
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Affiliation(s)
- Guang Bai
- Program in Neuroscience, Department of Neural and Pain Sciences, University of Maryland Dental School, University of Maryland, Baltimore, MD.
| | - Ke Ren
- Program in Neuroscience, Department of Neural and Pain Sciences, University of Maryland Dental School, University of Maryland, Baltimore, MD
| | - Ronald Dubner
- Program in Neuroscience, Department of Neural and Pain Sciences, University of Maryland Dental School, University of Maryland, Baltimore, MD
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4
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Genome-wide screens for in vivo Tinman binding sites identify cardiac enhancers with diverse functional architectures. PLoS Genet 2013; 9:e1003195. [PMID: 23326246 PMCID: PMC3542182 DOI: 10.1371/journal.pgen.1003195] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2012] [Accepted: 11/08/2012] [Indexed: 12/20/2022] Open
Abstract
The NK homeodomain factor Tinman is a crucial regulator of early mesoderm patterning and, together with the GATA factor Pannier and the Dorsocross T-box factors, serves as one of the key cardiogenic factors during specification and differentiation of heart cells. Although the basic framework of regulatory interactions driving heart development has been worked out, only about a dozen genes involved in heart development have been designated as direct Tinman target genes to date, and detailed information about the functional architectures of their cardiac enhancers is lacking. We have used immunoprecipitation of chromatin (ChIP) from embryos at two different stages of early cardiogenesis to obtain a global overview of the sequences bound by Tinman in vivo and their linked genes. Our data from the analysis of ∼50 sequences with high Tinman occupancy show that the majority of such sequences act as enhancers in various mesodermal tissues in which Tinman is active. All of the dorsal mesodermal and cardiac enhancers, but not some of the others, require tinman function. The cardiac enhancers feature diverse arrangements of binding motifs for Tinman, Pannier, and Dorsocross. By employing these cardiac and non-cardiac enhancers in machine learning approaches, we identify a novel motif, termed CEE, as a classifier for cardiac enhancers. In vivo assays for the requirement of the binding motifs of Tinman, Pannier, and Dorsocross, as well as the CEE motifs in a set of cardiac enhancers, show that the Tinman sites are essential in all but one of the tested enhancers; although on occasion they can be functionally redundant with Dorsocross sites. The enhancers differ widely with respect to their requirement for Pannier, Dorsocross, and CEE sites, which we ascribe to their different position in the regulatory circuitry, their distinct temporal and spatial activities during cardiogenesis, and functional redundancies among different factor binding sites. The Drosophila homeodomain protein Tinman was the first transcription factor found to control the development and differentiation of the heart in any species. In spite of that, our knowledge of the number, identities, and mode of regulation of the downstream target genes of Tinman that are necessary to exert its cardiogenic functions is still very incomplete. To address these issues, we have performed a genome-wide analysis of DNA regions associated with Tinman-binding in embryos and the genes linked to them. The combined data from our in-depth in vivo assays of sequence elements with high Tinman occupancy allow the following general conclusions: (1) The majority of such sequences are active as regulatory elements (called enhancers) in mesodermal tissues that include Tinman-expressing cells. (2) The enhancers active in the heart progenitor cells and the heart generally are dependent on tinman gene activity, whereas those active in non-cardiac mesoderm are often bound neutrally by Tinman. (3) Tinman binding motifs in most cases are essential for cardiac enhancer activity, but in some cases they can be functionally-redundant with those of other cardiogenic factors. (4) Tinman-occupied cardiac enhancers are enriched for a newly discovered binding motif for an unknown factor that is functional in vivo.
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5
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Cande JD, Chopra VS, Levine M. Evolving enhancer-promoter interactions within the tinman complex of the flour beetle, Tribolium castaneum. Development 2009; 136:3153-60. [PMID: 19700619 DOI: 10.1242/dev.038034] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Modifications of cis-regulatory DNAs, particularly enhancers, underlie changes in gene expression during animal evolution. Here, we present evidence for a distinct mechanism of regulatory evolution, whereby a novel pattern of gene expression arises from altered gene targeting of a conserved enhancer. The tinman gene complex (Tin-C) controls the patterning of dorsal mesodermal tissues, including the dorsal vessel or heart in Drosophila. Despite broad conservation of Tin-C gene expression patterns in the flour beetle (Tribolium castaneum), the honeybee (Apis mellifera) and the fruit fly (Drosophila melanogaster), the expression of a key pericardial determinant, ladybird, is absent from the dorsal mesoderm of Tribolium embryos. Evidence is presented that this loss in expression is replaced by expression of C15, the neighboring gene in the complex. This switch in expression from ladybird to C15 appears to arise from an inversion within the tinman complex, which redirects a conserved ladybird 3' enhancer to regulate C15. In Drosophila, this enhancer fails to activate C15 expression owing to the activity of an insulator at the intervening ladybird early promoter. By contrast, a chromosomal inversion allows the cardiac enhancer to bypass the ladybird insulator in Tribolium. Given the high frequency of genome rearrangements in insects, it is possible that such enhancer switching might be widely used in the diversification of the arthropods.
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Affiliation(s)
- Jessica Doran Cande
- Department of Molecular and Cell Biology, Division of Genetics, Genomics and Development, Center for Integrative Genomics, University of California at Berkeley, Berkeley, CA 94720, USA
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6
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Ahn JW, Lee YA, Ahn JH, Choi CY. Covalent conjugation of Groucho with SUMO-1 modulates its corepressor activity. Biochem Biophys Res Commun 2009; 379:160-5. [DOI: 10.1016/j.bbrc.2008.12.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 12/09/2008] [Indexed: 10/21/2022]
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7
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Choi DW, Seo YM, Kim EA, Sung KS, Ahn JW, Park SJ, Lee SR, Choi CY. Ubiquitination and degradation of homeodomain-interacting protein kinase 2 by WD40 repeat/SOCS box protein WSB-1. J Biol Chem 2007; 283:4682-9. [PMID: 18093972 DOI: 10.1074/jbc.m708873200] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Homeodomain-interacting protein kinase 2 (HIPK2) is a member of the nuclear protein kinase family, which induces both p53- and CtBP-mediated apoptosis. Levels of HIPK2 were increased by UV irradiation and cisplatin treatment, thereby implying the degradation of HIPK2 in cells under normal conditions. Here, we indicate that HIPK2 is ubiquitinated and degraded by the WD40-repeat/SOCS box protein WSB-1, a process that is blocked under DNA damage conditions. Yeast two-hybrid screening was conducted to identify the proteins that interact with HIPK2. WSB-1, an E3 ubiquitin ligase, was characterized as an HIPK2-interacting protein. The coexpression of WSB-1 resulted in the degradation of HIPK2 via its C-terminal region. Domain analysis of WSB-1 showed that WD40-repeats and the SOCS box were required for its interaction with and degradation of HIPK2, respectively. In support of the degradation of HIPK2 by WSB-1, HIPK2 was polyubiquitinated by WSB-1 in vitro and in vivo. The knockdown of endogenous WSB-1 with the expression of short hairpin RNA against WSB-1 increases the stability of endogenous HIPK2 and resulted in the accumulation of HIPK2. The ubiquitination and degradation of HIPK2 by WSB-1 was inhibited completely via the administration of DNA damage reagents, including Adriamycin and cisplatin. These findings effectively illustrate the regulatory mechanisms by which HIPK2 is maintained at a low level, by WSB-1 in cells under normal conditions, and stabilized by genotoxic stresses.
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Affiliation(s)
- Dong Wook Choi
- Department of Biological Science, Sungkyunkwan University, 300 Chunchundong, Suwon 440-746, Republic of Korea
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8
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Nagel S, Meyer C, Quentmeier H, Kaufmann M, Drexler HG, MacLeod RAF. MEF2C is activated by multiple mechanisms in a subset of T-acute lymphoblastic leukemia cell lines. Leukemia 2007; 22:600-7. [PMID: 18079734 DOI: 10.1038/sj.leu.2405067] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In T-cell acute lymphoblastic leukemia (T-ALL) the cardiac homeobox gene NKX2-5 (at 5q35) is variously deregulated by regulatory elements coordinating with BCL11B (at 14q32.2), or the T-cell receptor gene TRD (at 14q11.2), respectively. NKX2-5 is normally expressed in developing spleen and heart, regulating fundamental processes, including differentiation and survival. In this study we investigated whether NKX2-5 expression in T-ALL cell lines reactivates these embryonal pathways contributing to leukemogenesis. Among 18 known targets analyzed, we identified three genes regulated by NKX2-5 in T-ALL cells, including myocyte enhancer factor 2C (MEF2C). Knockdown and overexpression assays confirmed MEF2C activation by NKX2-5 at both the RNA and protein levels. Direct interactions between NKX2-5 and GATA3 as indicated by co-immunoprecipitation data may contribute to MEF2C regulation. In T-ALL cell lines LOUCY and RPMI-8402 MEF2C expression was correlated with a 5q14 deletion, encompassing noncoding proximal gene regions. Fusion constructs with green fluorescent protein permitted subcellular detection of MEF2C protein in nuclear speckles interpretable as repression complexes. MEF2C consistently inhibits expression of NR4A1/NUR77, which regulates apoptosis via BCL2 transformation. Taken together, our data identify distinct mechanisms underlying ectopic MEF2C expression in T-ALL, either as a downstream target of NKX2-5, or via chromosomal aberrations deleting proximal gene regions.
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Affiliation(s)
- S Nagel
- Human and Animal Cell Cultures, DSMZ, Braunschweig, Germany.
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9
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Rice KL, Kees UR, Greene WK. Transcriptional regulation of FHL1 by TLX1/HOX11 is dosage, cell-type and promoter context-dependent. Biochem Biophys Res Commun 2007; 367:707-13. [PMID: 18073142 DOI: 10.1016/j.bbrc.2007.12.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 12/02/2007] [Indexed: 10/25/2022]
Abstract
TLX1/HOX11 encodes an NK-like homeodomain transcription factor that is both normally required for embryonic development and aberrantly expressed in T-cell acute lymphoblastic leukemia. Previous studies have shown that TLX1 can regulate target genes including ALDH1A1 and FHL1. However, whereas ALDH1A1 is consistently regulated by TLX1, endogenous FHL1 is only induced in a proportion of fibroblast or T-cell clones stably expressing TLX1. Here, we provide an explanation for these findings by demonstrating that the induction of FHL1, but not ALDH1A1, requires a high level of TLX1 expression in NIH 3T3 cells. In luciferase reporter assays, TLX1-mediated repression rather than activation of the FHL1 gene promoter and the magnitude of this effect was strongly influenced by the cellular background. Together, these results characterize TLX1 as a dual function regulator whose activity in respect to FHL1 is critically dependent upon its cellular concentration, as well as cell type and promoter context.
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Affiliation(s)
- Kim L Rice
- School of Veterinary and Biomedical Sciences, Division of Health Sciences, Murdoch University, Perth, WA 6150, Australia
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10
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Li T, Li YM, Jia ZQ, Chen P, Ma KT, Zhou CY. Carboxyl Terminus of NKX2.5 Impairs its Interaction with p300. J Mol Biol 2007; 370:976-92. [PMID: 17544441 DOI: 10.1016/j.jmb.2007.05.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 04/18/2007] [Accepted: 05/14/2007] [Indexed: 11/20/2022]
Abstract
The transcription factor Nkx2.5 plays critical roles in controlling cardiac-specific gene expression. Previous reports demonstrated that Nkx2.5 is only a modest transactivator due to the auto-inhibitory effect of its C-terminal domain. Deletion of the C-terminal domain, mimicking conformational change, evokes vigorous transactivation activity. Here, we show that a C-terminal defective mutant of Nkx2.5 improves the occupation of p300 at the ANF promoter compared with full-length Nkx2.5, leading to hyperacetylation of histone H4. We reveal that p300 is a cofactor of Nkx2.5, markedly potentiating Nkx2.5-dependent transactivation, whereas E1A antigen impairs Nkx2.5 activity. Furthermore, p300 can acetylate Nkx2.5 and display an acetyltransferase-independent mechanism to coactivate Nkx2.5. Physical interaction between the N-terminal activation domain of Nkx2.5 and the C/H3 domain of p300 are identified by GST pull-down assay. Point mutants of the N-terminal modify the transcriptional activity of Nkx2.5 and interaction with p300. Deletion of the C-terminal domain greatly facilitates p300 binding and improves the susceptibility of Nkx2.5 to histone deacetylase inhibitor. These results establish that p300 acts as an Nkx2.5 cofactor and facilitates increased Nkx2.5 activity by relieving the conformational impediment of its inhibitory C-terminal domain.
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Affiliation(s)
- Tao Li
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100083, China
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11
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Ryan KM, Hendren JD, Helander LA, Cripps RM. The NK homeodomain transcription factor Tinman is a direct activator of seven-up in the Drosophila dorsal vessel. Dev Biol 2007; 302:694-702. [PMID: 17098220 DOI: 10.1016/j.ydbio.2006.10.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 09/20/2006] [Accepted: 10/14/2006] [Indexed: 11/16/2022]
Abstract
A complex regulatory cascade is required for normal cardiac development, and many aspects of this network are conserved from Drosophila to mammals. In Drosophila, the seven-up (svp) gene, an ortholog of the vertebrate chick ovalbumin upstream promoter transcription factors (COUP-TFI and II), is initially activated in the cardiac mesoderm and is subsequently restricted to cells forming the cardiac inflow tracts. Here, we investigate svp regulation in the developing cardiac tube. Using bioinformatics, we identify a 1007-bp enhancer of svp which recapitulates its entire expression in the embryonic heart and other mesodermal derivatives, and we show that this enhancer is initially activated by the NK homeodomain factor Tinman (Tin) via two conserved Tin binding sites. Mutation of the Tin binding sites significantly reduces enhancer activity both during normal development and in response to ectopic Tin. This is the first identification of an enhancer for the complex svp gene, demonstrating the effectiveness of bioinformatics tools in assisting in unraveling transcriptional regulatory networks. Our studies define a critical component of the svp regulatory cascade and place gene regulatory events in direct apposition to the formation of critical cardiac structures.
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Affiliation(s)
- Kathryn M Ryan
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
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12
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Choi Y, Rajkovic A. Characterization of NOBOX DNA Binding Specificity and Its Regulation of Gdf9 and Pou5f1 Promoters. J Biol Chem 2006; 281:35747-56. [PMID: 16997917 DOI: 10.1074/jbc.m604008200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nobox (newborn ovary homeobox gene) deficiency disrupts early folliculogenesis and the expression of oocyte-specific genes in mice. Here, we identified several cis-acting sites, TAATTG, TAGTTG, and TAATTA as NOBOX DNA binding elements (NBEs) using a library of randomly generated oligonucleotides by cyclic amplification of sequence target assay and mutation analyses. We show that NOBOX preferentially binds to the NOBOX binding elements with high affinity. In addition, we found that promoter regions of mouse Pou5f1 and Gdf9 contain one (-426) and three NOBOX binding elements (-786, -967, and -1259), respectively. NOBOX binds to these putative NOBOX binding elements with high affinity and augmented transcriptional activity of luciferase reporter driven by mouse Pou5f1 and Gdf9 promoters containing the NOBOX binding elements. In chromatin immunoprecipitation assays, DNA sequences from Pou5f1 and Gdf9 promoters co-precipitated with anti-NOBOX antibody. These results suggest that NOBOX directly regulates the transcription of Pou5f1 and Gdf9 in oocytes during early folliculogenesis.
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Affiliation(s)
- Youngsok Choi
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas 77030, USA
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13
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Zaffran S, Reim I, Qian L, Lo PC, Bodmer R, Frasch M. Cardioblast-intrinsic Tinman activity controls proper diversification and differentiation of myocardial cells in Drosophila. Development 2006; 133:4073-83. [PMID: 16987868 DOI: 10.1242/dev.02586] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The NK homeobox gene tinman (tin) is required for the specification of the cardiac, visceral muscle and somatic muscle progenitors in the early dorsal mesoderm of Drosophila. Like its vertebrate counterpart Nkx2.5, the expression of tin is maintained in cardiac cells during cardiac maturation and differentiation; however, owing to the complete lack of a dorsal vessel in tin mutant embryos, the function of tin in these cells has not been defined. Here we show that myocardial cells and dorsal vessels can form even though they lack Tin, and that viable adults can develop, as long as Tin is provided in the embryonic precardiac mesoderm. However, embryos in which tin expression is specifically missing from cardial cells show severe disruptions in the normal diversification of the myocardial cells, and adults exhibit severe defects in cardiac remodeling and function. Our study reveals that the normal expression and activity of Tin in four of the six bilateral cardioblasts within each hemisegment of the heart allows these cells to adopt a cell fate as ;working' myocardium, as opposed to a fate as inflow tract (ostial) cells. This function of tin involves the repression of Dorsocross (Doc) T-box genes and, hence, the restriction of Doc to the Tin-negative cells that will form ostia. We conclude that tin has a crucial role within myocardial cells that is required for the proper diversification, differentiation, and post-embryonic maturation of cardiomyocytes, and we present a pathway involving regulatory interactions among seven-up, midline, tinman and Dorsocross that establishes these developmental events upon myocardial cell specification.
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Affiliation(s)
- Stéphane Zaffran
- Brookdale Department of Molecular, Cell and Developmental Biology, Box 1020, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
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14
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Clark IBN, Boyd J, Hamilton G, Finnegan DJ, Jarman AP. D-six4 plays a key role in patterning cell identities deriving from the Drosophila mesoderm. Dev Biol 2006; 294:220-31. [PMID: 16595131 DOI: 10.1016/j.ydbio.2006.02.044] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 02/24/2006] [Accepted: 02/27/2006] [Indexed: 11/21/2022]
Abstract
Patterning of the Drosophila embryonic mesoderm requires the regulation of cell type-specific factors in response to dorsoventral and anteroposterior axis information. For the dorsoventral axis, the homeodomain gene, tinman, is a key patterning mediator for dorsal mesodermal fates like the heart. However, equivalent mediators for more ventral fates are unknown. We show that D-six4, which encodes a Six family transcription factor, is required for the appropriate development of most cell types deriving from the non-dorsal mesoderm - the fat body, somatic cells of the gonad, and a specific subset of somatic muscles. Misexpression analysis suggests that D-Six4 and its likely cofactor, Eyes absent, are sufficient to impose these fates on other mesodermal cells. At stage 10, the mesodermal expression patterns of D-six4 and tin are complementary, being restricted to the dorsal and non-dorsal regions respectively. Our data suggest that D-six4 is a key mesodermal patterning mediator at this stage that regulates a variety of cell-type-specific factors and hence plays an equivalent role to tin. At stage 9, however, D-six4 and tin are both expressed pan-mesodermally. At this stage, tin function is required for full D-six4 expression. This may explain the known requirement for tin in some non-dorsal cell types.
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Affiliation(s)
- Ivan B N Clark
- Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh EH8 9XD, UK
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15
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Simmons S, Horowitz J. Nkx3.1 binds and negatively regulates the transcriptional activity of Sp-family members in prostate-derived cells. Biochem J 2006; 393:397-409. [PMID: 16201967 PMCID: PMC1383699 DOI: 10.1042/bj20051030] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Nkx3.1 is a homeodomain-containing transcription factor that is expressed early in the development of the prostate gland and is believed to play an important role in the differentiation of prostatic epithelia. Loss of Nkx3.1 protein expression is often an early event in prostate tumorigenesis, and the abundance of Nkx3.1-negative epithelial cells increases with disease progression. In a number of systems, homeodomain proteins collaborate with zinc-finger-containing transcription factors to bind and regulate target genes. In the present paper, we report that Nkx3.1 collaborates with Sp-family members in the regulation of PSA (prostate-specific antigen) in prostate-derived cells. Nkx3.1 forms protein complexes with Sp proteins that are dependent on their respective DNA-binding domains and an N-terminal segment of Nkx3.1, and Nkx3.1 negatively regulates Sp-mediated transcription via Trichostatin A-sensitive and -insensitive mechanisms. A distal 1000 bp portion of the PSA promoter is required for transrepression by Nkx3.1, although Nkx3.1 DNA-binding activity is itself not required. We conclude that Nkx3.1 negatively regulates Sp-mediated transcription via the tethering of histone deacetylases and/or by inhibiting the association of Sp proteins with co-activators.
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Affiliation(s)
- Steven O. Simmons
- Graduate Program in Toxicology and Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, U.S.A
| | - Jonathan M. Horowitz
- Graduate Program in Toxicology and Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough Street, Raleigh, NC 27606, U.S.A
- To whom correspondence should be addressed (email )
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16
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Elliott DA, Solloway MJ, Wise N, Biben C, Costa MW, Furtado MB, Lange M, Dunwoodie S, Harvey RP. A tyrosine-rich domain within homeodomain transcription factor Nkx2-5 is an essential element in the early cardiac transcriptional regulatory machinery. Development 2006; 133:1311-22. [PMID: 16510504 DOI: 10.1242/dev.02305] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Homeodomain factor Nkx2-5 is a central component of the transcription factor network that guides cardiac development; in humans, mutations in NKX2.5 lead to congenital heart disease (CHD). We have genetically defined a novel conserved tyrosine-rich domain (YRD) within Nkx2-5 that has co-evolved with its homeodomain. Mutation of the YRD did not affect DNA binding and only slightly diminished transcriptional activity of Nkx2-5 in a context-specific manner in vitro. However, the YRD was absolutely essential for the function of Nkx2-5 in cardiogenesis during ES cell differentiation and in the developing embryo. Furthermore, heterozygous mutation of all nine tyrosines to alanine created an allele with a strong dominant-negative-like activity in vivo: ES cell<-->embryo chimaeras bearing the heterozygous mutation died before term with cardiac malformations similar to the more severe anomalies seen in NKX2.5 mutant families. These studies suggest a functional interdependence between the NK2 class homeodomain and YRD in cardiac development and evolution, and establish a new model for analysis of Nkx2-5 function in CHD.
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MESH Headings
- Amino Acid Sequence
- Animals
- Animals, Newborn
- Blotting, Western
- Cell Line
- Cells, Cultured
- Cephalopoda
- Conserved Sequence
- Electrophoretic Mobility Shift Assay
- Embryo, Mammalian
- Embryo, Nonmammalian
- Gene Expression Regulation, Developmental
- Gene Targeting
- Genes, Reporter
- Glutathione Transferase/metabolism
- Green Fluorescent Proteins/metabolism
- Heterozygote
- Homeobox Protein Nkx-2.5
- Homeodomain Proteins/chemistry
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- In Situ Hybridization
- Luciferases/metabolism
- Mice
- Molecular Sequence Data
- Mutation
- Myocardium/cytology
- Myocardium/metabolism
- Myocardium/pathology
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/metabolism
- Phylogeny
- Protein Structure, Tertiary
- Recombinant Fusion Proteins/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Transcription Factors/chemistry
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription, Genetic
- Transcriptional Activation
- Tyrosine/chemistry
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Affiliation(s)
- David A Elliott
- Victor Chang Cardiac Research Institute, Darlinghurst, Sydney 2010, Australia
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17
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Kim EA, Noh YT, Ryu MJ, Kim HT, Lee SE, Kim CH, Lee C, Kim YH, Choi CY. Phosphorylation and Transactivation of Pax6 by Homeodomain-interacting Protein Kinase 2. J Biol Chem 2006; 281:7489-97. [PMID: 16407227 DOI: 10.1074/jbc.m507227200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pax6 is a transcriptional activator that contains two DNA binding domains and a potent transcription activation domain in the C terminus, which regulates organogenesis of the eye, nose, pancreas, and central nervous system. Homeodomain-interacting protein kinase 2 (HIPK2) interacts with transcription factors, including homeoproteins, and regulates activities of transcription factors. Here we show that HIPK2 phosphorylates the activation domain of Pax6, which augments Pax6 transactivation by enhancing its interaction with p300. Mass spectrometric analysis identified three Pax6 phosphorylation sites as threonines 281, 304, and 373. The substitutions of these threonines with alanines decreased Pax6 transactivation, whereas substitutions to glutamic acids increased transactivation in mimicry of phosphorylation. Furthermore, the knock-down of either endogenous or exogenous HIPK2 expression with HIPK2 shRNA markedly inhibited Pax6 phosphorylation and its transactivating function on proglucagon promoter in cultured cells. These results strongly indicate that HIPK2 is an upstream protein kinase for Pax6 and suggest that it modulates Pax6-mediated transcriptional regulation.
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Affiliation(s)
- Eun A Kim
- Department of Biological Science, Sungkyunkwan University, 300 Chunchundong, Jangangu, Suwon 440-746, South Korea
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18
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Goldstein RE, Cook O, Dinur T, Pisanté A, Karandikar UC, Bidwai A, Paroush Z. An eh1-like motif in odd-skipped mediates recruitment of Groucho and repression in vivo. Mol Cell Biol 2006; 25:10711-20. [PMID: 16314497 PMCID: PMC1316973 DOI: 10.1128/mcb.25.24.10711-10720.2005] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Drosophila Groucho, like its vertebrate Transducin-like Enhancer-of-split homologues, is a corepressor that silences gene expression in numerous developmental settings. Groucho itself does not bind DNA but is recruited to target promoters by associating with a large number of DNA-binding negative transcriptional regulators. These repressors tether Groucho via short conserved polypeptide sequences, of which two have been defined. First, WRPW and related tetrapeptide motifs have been well characterized in several repressors. Second, a motif termed Engrailed homology 1 (eh1) has been found predominantly in homeodomain-containing transcription factors. Here we describe a yeast two-hybrid screen that uncovered physical interactions between Groucho and transcription factors, containing eh1 motifs, with different types of DNA-binding domains. We show that one of these, the zinc finger protein Odd-skipped, requires its eh1-like sequence for repressing specific target genes in segmentation. Comparison between diverse eh1 motifs reveals a bias for the phosphoacceptor amino acids serine and threonine at a fixed position, and a mutational analysis of Odd-skipped indicates that these residues are critical for efficient interactions with Groucho and for repression in vivo. Our data suggest that phosphorylation of these phosphomeric residues, if it occurs, will down-regulate Groucho binding and therefore repression, providing a mechanism for posttranslational control of Groucho-mediated repression.
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Affiliation(s)
- Robert E Goldstein
- Department of Biochemistry, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
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19
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Zaffran S, Frasch M. The homeodomain of Tinman mediates homo- and heterodimerization of NK proteins. Biochem Biophys Res Commun 2005; 334:361-9. [PMID: 16004970 DOI: 10.1016/j.bbrc.2005.06.090] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Accepted: 06/17/2005] [Indexed: 11/18/2022]
Abstract
Cardiac development requires the action of transcription factors, which control the specification and differentiation of cardiac cell types. One of these factors, encoded by the homeobox gene tinman (tin), is essential for the specification of all cardiac cells in Drosophila. An increasing number of examples show that protein-protein interactions can be important for determining the specific transcriptional activities of homeodomain proteins, in addition to their binding to specific DNA target sites. Here, we show that Tin and Bagpipe (Bap), another homeodomain protein, form homo- and heterodimeric complexes. We demonstrate that homo- and heterodimerization of Tin is mediated through its homeodomain and that the region required for this interaction corresponds to the first two helices that are also necessary for DNA binding. We further show that, in the yeast system, the homeodomain can function as a transcriptional repressor domain. These findings suggest that protein-protein interactions of Tin play a role in its transcriptional and developmental functions.
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Affiliation(s)
- Stéphane Zaffran
- Brookdale Department of Molecular, Cell and Developmental Biology, Box 1020, Mount Sinai School of Medicine, New York, NY 10029, USA.
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20
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Kumar R, Gururaj AE, Vadlamudi RK, Rayala SK. The clinical relevance of steroid hormone receptor corepressors. Clin Cancer Res 2005; 11:2822-31. [PMID: 15837729 DOI: 10.1158/1078-0432.ccr-04-1276] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Steroid hormone receptors are ligand-dependent transcription factors that control a variety of essential physiologic and developmental processes in humans. The functional activity of a steroid receptor is regulated not only by hormones but also by an array of regulatory proteins such as coactivators, corepressors, and chromatin modifiers. Contrary to an earlier notion that corepressors and coactivators exist in separate complexes, these molecules, which have apparently opposite functions, are increasingly being found in the same complex, which allows for efficient transcriptional control mechanisms. These control mechanisms are in turn regulated by an array of post-translational modifications under the influence of upstream and local signaling networks. Because the outcome of steroidal hormone receptor transcriptional complexes is measured in terms of the expression of target genes, any dysregulation of coregulator complexes perturbs normal homeostasis and could contribute to the development and maintenance of malignant phenotypes. Increasing evidence implicating steroid hormone receptors and their coregulators in various pathophysiologic conditions has elicited interest in their structure and biology. Further advances in this field of study should open up a unique window for novel targeted therapies for diseases such as cancer. Here we briefly review the clinical relevance of corepressors, with a particular focus on their role in the development of cancerous phenotypes.
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Affiliation(s)
- Rakesh Kumar
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
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21
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Rave-Harel N, Miller NLG, Givens ML, Mellon PL. The Groucho-related gene family regulates the gonadotropin-releasing hormone gene through interaction with the homeodomain proteins MSX1 and OCT1. J Biol Chem 2005; 280:30975-83. [PMID: 16002402 PMCID: PMC2773698 DOI: 10.1074/jbc.m502315200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) is exclusively expressed in a unique population of hypothalamic neurons that controls reproductive function. GnRH gene expression is highly dynamic. Its transcriptional activity is regulated in a complex spatiotemporal manner during embryonic development and postnatal life. Although a variety of transcription factors have been identified as regulators of GnRH transcription, most are promiscuous in their DNA-binding requirements, and none are solely expressed in GnRH neurons. Their specific activity is probably determined by interactions with distinct cofactors. Here we find that the Groucho-related gene (GRG) family of co-repressors is expressed in a model cell line for the GnRH neuron and co-expresses with GnRH during prenatal development. GRG proteins associate in vivo with the GnRH promoter. Furthermore, GRG proteins interact with two regulators of GnRH transcription, the homeodomain proteins MSX1 and OCT1. Co-transfection experiments indicate that GRG proteins regulate GnRH promoter activity. The long GRG forms enhance MSX1 repression and counteract OCT1 activation of the GnRH gene. In contrast, the short form, GRG5, has a dominant-negative effect on MSX1-dependent repression. Taken together, these data suggest that the dynamic switch between activation and repression of GnRH transcription is mediated by recruitment of the GRG co-regulators.
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Affiliation(s)
- Naama Rave-Harel
- Department of Reproductive Medicine, University of California, San Diego, La Jolla, California, 92093-0674
| | - Nichol L. G. Miller
- Department of Reproductive Medicine, University of California, San Diego, La Jolla, California, 92093-0674
| | - Marjory L. Givens
- Department of Reproductive Medicine, University of California, San Diego, La Jolla, California, 92093-0674
| | - Pamela L. Mellon
- Department of Reproductive Medicine, University of California, San Diego, La Jolla, California, 92093-0674
- Department of Neurosciences, University of California, San Diego, La Jolla, California, 92093-0674
- To whom correspondence should be addressed: Dept. of Reproductive Medicine, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0674. Tel.: 858-534-1312; Fax: 858-534-1438;
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22
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Choi CY, Kim YH, Kim YO, Park SJ, Kim EA, Riemenschneider W, Gajewski K, Schulz RA, Kim Y. Phosphorylation by the DHIPK2 protein kinase modulates the corepressor activity of Groucho. J Biol Chem 2005; 280:21427-36. [PMID: 15802274 DOI: 10.1074/jbc.m500496200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Groucho function is essential for Drosophila development, acting as a corepressor for specific transcription factors that are downstream targets of various signaling pathways. Here we provide evidence that Groucho is phosphorylated by the DHIPK2 protein kinase. Phosphorylation modulates Groucho corepressor activity by attenuating its protein-protein interaction with a DNA-bound transcription factor. During eye development, DHIPK2 modifies Groucho activity, and eye phenotypes generated by overexpression of Groucho differ depending on its phosphorylation state. Moreover, analysis of nuclear extracts fractionated by column chromatography further shows that phospho-Groucho associates poorly with the corepressor complex, whereas the unphosphorylated form binds tightly. We propose that Groucho phosphorylation by DHIPK2 and its subsequent dissociation from the corepressor complex play a key role in relieving the transcriptional repression of target genes regulated by Groucho, thereby controlling cell fate determination during development.
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Affiliation(s)
- Cheol Yong Choi
- Laboratory Research program, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA.
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23
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Tsuji S, Hashimoto C. Choice of either beta-catenin or Groucho/TLE as a co-factor for Xtcf-3 determines dorsal-ventral cell fate of diencephalon during Xenopus development. Dev Genes Evol 2005; 215:275-84. [PMID: 15747128 DOI: 10.1007/s00427-005-0474-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Accepted: 01/23/2005] [Indexed: 11/29/2022]
Abstract
Co-repressor Groucho/Transducin-Like Enhancer of split (TLE) interacts with transcription factors that are expressed in the central nervous system (CNS), and regulates transcriptional activities. In this study, we examined the contribution of Groucho/TLE to CNS development in Xenopus. The functional inhibition of Groucho/TLE using the WRPW motif as a competitor resulted in the conversion of the ventral cell into the dorsal fate in the prospective diencephalon. We also found that the neural plate was expanded laterally without inhibiting neural crest development. In tailbud, the disturbance of trigeminal ganglion development was observed. These observations allow us to conclude that Groucho/TLE plays important roles in the induction and patterning of distinct CNS territories. We found that Xtcf-3 is involved in some of the patterning in these territories. We generated the variant of Xtcf-3, Xtcf-3BDN-, which is suspected to interfere with the interaction between endogenous Groucho/TLE and Xtcf-3. The transcriptional activation of the Xtcf-3-target genes in response to endogenous Wnt/beta-catenin signaling by the overexpression of Xtcf-3BDN- led to a reduction of the ventral diencephalon. This result indicates that transcriptional repression by the Groucho/TLE-Xtcf-3 complex is important for ventral diencephalon patterning. This idea is supported by the finding that the overexpression of the dominant-negative form of Xtcf-3 or axil causes the expansion of the ventral diencephalon. Based on these data, we propose that the localized activation of Wnt/beta-catenin signaling, which converts Tcf from a repressor to an activator, is required for the establishment of dorsal-ventral patterning in the prospective diencephalon.
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Affiliation(s)
- Saori Tsuji
- Department of Biology, Graduate School of Science, Osaka University, Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
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24
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Dorval KM, Bobechko BP, Ahmad KF, Bremner R. Transcriptional activity of the paired-like homeodomain proteins CHX10 and VSX1. J Biol Chem 2005; 280:10100-8. [PMID: 15647262 DOI: 10.1074/jbc.m412676200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
CHX10 and VSX1 are homeodomain (HD) proteins essential for normal retinal development. CHX10 is required first for retinal progenitor cell proliferation and later for bipolar cell differentiation, whereas VSX1 is important in the terminal differentiation of a subset of bipolar cells. Elucidating the transcriptional activity of CHX10 and VSX1 is required to understand how these factors control retinal development. We show that CHX10 and Vsx1 can function as transcriptional repressors. When tethered to a promoter by a heterologous LexA DNA-binding domain or its HD, CHX10 repressed multiple classes of activators in different immortalized cell lines. CHX10 blocked TATA-containing and TATA-less promoters, repressed at a distance, and inhibited a complex enhancer positioned upstream or downstream of the reporter gene, whereas retinoblastoma protein (RB) inhibited the downstream enhancer only. Interestingly, CHX10 mildly potentiated a subset of activators in chick neuronal cultures. Thus, CHX10 is both a versatile repressor and a context-specific weak activator. The CHX10 HD and CVC domains were sufficient for DNA binding and repression. VSX1 contains closely related homeo and CVC domains and, like CHX10, also repressed transcription. A VSX1 HD mutation, R166W, that impairs DNA binding and causes keratoconus in humans, hindered repressor function. Therefore, CHX10 and VSX1 may control retinal bipolar cell specification or differentiation by repressing genes required for the development of other cell types.
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Affiliation(s)
- Kimberley M Dorval
- Toronto Western Research Institute, University Health Network Program, University of Toronto, Toronto, Ontario M5T 2S8, Canada
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25
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Kasamatsu S, Sato A, Yamamoto T, Keng VW, Yoshida H, Yamazaki Y, Shimoda M, Miyazaki JI, Noguchi T. Identification of the transactivating region of the homeodomain protein, hex. J Biochem 2004; 135:217-23. [PMID: 15047723 DOI: 10.1093/jb/mvh025] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The homeodomain-containing protein Hex acts as an activator as well as a repressor of transcription in animals. While its repression domain has been mapped to the amino-terminal region, the activation domain has never been identified. Here, we show that the homeodomain and the acidic carboxyl-terminal region are necessary for full activation of the sodium-dependent bile acid cotransporter gene promoter in a cell type-independent manner, suggesting that the carboxyl-terminal region comprising residues 197 to 271 functions as the activation domain. In addition, we observed that a Hex mutant without this activation domain acts as a dominant-negative mutant as to the transactivating function of Hex.
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Affiliation(s)
- Shinya Kasamatsu
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya 464-8601
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26
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Stepchenko A, Nirenberg M. Mapping activation and repression domains of the vnd/NK-2 homeodomain protein. Proc Natl Acad Sci U S A 2004; 101:13180-5. [PMID: 15340160 PMCID: PMC516545 DOI: 10.1073/pnas.0404775101] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A transient transfection assay using Drosophila S2 tissue culture cells and WT and mutant Drosophila vnd/NK-2 homeobox cDNAs was used to localize repression and activation domains of vnd/NK-2 homeodomain protein. A repression domain was identified near the N terminus of vnd/NK-2 homeodomain protein (amino acid residues 154-193), which contains many hydrophobic amino acid residues. The major determinants of the repression domain were shown to be amino acid residues F155, W158, I161, L162, L163, and W166. Truncated protein consisting of the N-terminal repression domain and the DNA-binding homeodomain repressed transcription as efficiently as WT vnd/NK-2 protein. An activation domain was identified between the tinman domain and the homeodomain (amino acid residues 277-543), which consists of a glutamine-rich subdomain and two acidic subdomains. No effect was detected of the tinman domain or the NK-2-specific domain on either activation or repression of a beta-galactosidase reporter gene.
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Affiliation(s)
- Alexander Stepchenko
- Laboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Building10, Room 7N-315, Bethesda, MD 20892-1654, USA
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27
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Kim DW, Kempf H, Chen RE, Lassar AB. Characterization of Nkx3.2 DNA binding specificity and its requirement for somitic chondrogenesis. J Biol Chem 2003; 278:27532-9. [PMID: 12746429 DOI: 10.1074/jbc.m301461200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously shown that Nkx3.2, a member of the NK class of homeoproteins, functions as a transcriptional repressor to promote somitic chondrogenesis. However, it has not been addressed whether Nkx3.2 can bind to DNA in a sequence-specific manner and whether DNA binding by Nkx3.2 is required for its biological activity. In this work, we employed a DNA binding site selection assay, which identified TAAGTG as a high affinity Nkx3.2 binding sequence. Sequence-specific binding of Nkx3.2 to the TAAGTG motif in vitro was confirmed by electrophoretic mobility shift assays, and mutagenesis of this sequence revealed that HRAGTG (where H represents A, C, or T, and R represents A or G) comprises the consensus DNA binding site for Nkx3.2. Consistent with these findings, the expression of a reporter gene containing reiterated Nkx3.2 binding sites was repressed in vivo by Nkx3.2 co-expression. In addition, we have generated a DNA nonbinding point mutant of Nkx3.2 (Nkx3.2-N200Q), which contains an asparagine to glutamine missense mutation in the homeodomain. Interestingly, despite being defective in DNA binding, Nkx3.2-N200Q still retains its intrinsic transcriptional repressor function. Finally, we demonstrate that unlike wild-type Nkx3.2, Nkx3.2-N200Q is unable to activate the chondrocyte differentiation program in somitic mesoderm, indicating that DNA binding by Nkx3.2 is critical for this factor to induce somitic chondrogenesis.
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Affiliation(s)
- Dae-Won Kim
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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28
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Ganga M, Espinoza HM, Cox CJ, Morton L, Hjalt TA, Lee Y, Amendt BA. PITX2 isoform-specific regulation of atrial natriuretic factor expression: synergism and repression with Nkx2.5. J Biol Chem 2003; 278:22437-45. [PMID: 12692125 DOI: 10.1074/jbc.m210163200] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PITX2 and Nkx2.5 are two of the earliest known transcriptional markers of vertebrate heart development. Pitx2-/- mice present with severe cardiac malformations and embryonic lethality, demonstrating a role for PITX2 in heart development. However, little is known about the downstream targets of PITX2 in cardiogenesis. We report here that the atrial natriuretic factor (ANF) promoter is a target of PITX2. PITX2A, PITX2B, and PITX2C isoforms differentially activate the ANF promoter. However, only PITX2C can synergistically activate the ANF promoter in the presence of Nkx2.5. We further demonstrate that the procollagen lysyl hydroxylase (PLOD1) promoter is regulated by Nkx2.5. Mechanistically, PITX2C and Nkx2.5 synergistically regulate ANF and PLOD1 expression through binding to their respective DNA elements. Surprisingly, PITX2A activation of the ANF and PLOD1 promoters is repressed by co-transfection of Nkx2.5 in the C3H10T1/2 embryonic fibroblast cell line. Pitx2a and Pitx2c are endogenously expressed in C3H10T1/2 cells, and these cells express factors that differentially regulate PITX2 isoform activities. We provide a new mechanism for the regulation of heart development by PITX2 isoforms through the regulation of ANF and PLOD1 gene expression and Nkx2.5 transcriptional activity.
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Affiliation(s)
- Mrudula Ganga
- Department of Biological Science, The University of Tulsa, Tulsa, Oklahoma 74104-3189, USA
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29
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Nuthall HN, Joachim K, Palaparti A, Stifani S. A role for cell cycle-regulated phosphorylation in Groucho-mediated transcriptional repression. J Biol Chem 2002; 277:51049-57. [PMID: 12397081 DOI: 10.1074/jbc.m111660200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcriptional corepressors of the Groucho/transducin-like Enhancer of split (Gro/TLE) family are involved in a variety of cell differentiation mechanisms in both invertebrates and vertebrates. They become recruited to specific promoter regions by forming complexes with a number of different DNA-binding proteins thereby contributing to the regulation of multiple genes. To understand how the functions of Gro/TLE proteins are regulated, it was asked whether their ability to mediate transcriptional repression might be controlled by cell cycle-dependent phosphorylation events. It is shown here that activation of p34(cdc2) kinase (cdc2) with okadaic acid is correlated with hyperphosphorylation of Gro/TLEs. Moreover, pharmacological inhibition of cdc2 activity results in Gro/TLE dephosphorylation. In agreement with these findings, a purified cdc2-cyclin B complex can directly phosphorylate Gro/TLEs in vitro. Two separate Gro/TLE domains, the CcN and SP regions, contain sequences that are phosphorylated by cdc2. Deletion of these sequences is correlated with loss of Gro/TLE phosphorylation by cdc2 in vitro and okadaic acid-induced Gro/TLE hyperphosphorylation in vivo. In addition, Gro/TLEs are phosphorylated during the G(2)/M phase of the cell cycle, and this is correlated with a decreased nuclear interaction. Finally, the transcription repression ability of Gro/TLEs is enhanced by pharmacological inhibition of cdc2. Taken together, these results demonstrate that Gro/TLE proteins are phosphorylated as a function of the cell cycle and implicate phosphorylation events occurring during mitosis in the negative regulation of Gro/TLE activity.
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Affiliation(s)
- Hugh N Nuthall
- Center for Neuronal Survival, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada
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30
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Nikaido T, Iseki K, Mori T, Takaki H, Yokoya S, Hagino S, Takeda J, Zhang Y, Takeuchi M, Kikuchi SI, Wanaka A. Expression of OASIS, a CREB/ATF family transcription factor, in CNS lesion and its transcriptional activity. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2002; 108:129-38. [PMID: 12480185 DOI: 10.1016/s0169-328x(02)00521-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We reported the expression patterns of a novel member of the CREB/ATF family, OASIS, in central nervous system (CNS) lesions and its transcriptional activity. OASIS gene expression was upregulated in the stab-injured spinal cord. Double labeling experiments revealed that the distribution of OASIS mRNA-positive cells overlapped with a population of GFAP-immunoreactive cells. This finding suggested that OASIS might regulate expression of important downstream molecules in certain subset of the reactive astrocytes (e.g. inhibitory substances in injured brain). In gel shift assays, OASIS was able to specifically bind to CRE as CREB family members were. We then examined transcriptional activity of full-length OASIS with GAL4-UAS-luciferase reporter assay in COS7 cells. OASIS protein activated transcription, but did not inhibit basal transcription driven by AdML promoter. To determine critical portion(s) of the OASIS protein in transcriptional activation, we examined the activity of various deletion constructs of OASIS gene. The assay revealed that a strong transcriptional activation domain lay in the N-terminal region where acidic amino acids clustered and a possible repression domain, which had not been reported for other CREB/ATF family members, lay in the more C-terminal region. We therefore proposed that OASIS protein positively regulated gene transcription in a subset of reactive astrocytes, and thereby influenced the reaction of injured CNS tissues.
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Affiliation(s)
- Takuya Nikaido
- Department of Cell Science, Institute of Biomedical Sciences, Fukushima Medical University School of Medicine, Japan
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31
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Li X, Kimbrel EA, Kenan DJ, McDonnell DP. Direct interactions between corepressors and coactivators permit the integration of nuclear receptor-mediated repression and activation. Mol Endocrinol 2002; 16:1482-91. [PMID: 12089344 DOI: 10.1210/mend.16.7.0860] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The unliganded thyroid hormone receptor beta (TRbeta) represses the basal transcriptional activity of target genes, in part through interactions with the nuclear receptor corepressor (N-CoR). In this study we have identified a rather unexpected interaction between N-CoR and the nuclear receptor coactivator ACTR. We have demonstrated in vitro and in intact cells that N-CoR directly associates with ACTR and that the interaction surfaces on N-CoR and ACTR are distinct from those required for TR binding. The significance of this finding was demonstrated by showing that N-CoR facilitates an interaction between unliganded-TRbeta and ACTR. One possible consequence of the formation of the trimeric complex of N-CoR/ACTR/unliganded-TR is that N-CoR may raise the local concentration of ACTR at target gene promoters. In support of this hypothesis it was demonstrated that the presence of N-CoR can enhance TRbeta-mediated transcriptional activation. It is proposed, therefore, that TRbeta- mediated activation and repression are integrally linked in a manner that is not predicted by the current models of nuclear receptor action.
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Affiliation(s)
- Xiaolin Li
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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32
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Zhu CC, Dyer MA, Uchikawa M, Kondoh H, Lagutin OV, Oliver G. Six3-mediated auto repression and eye development requires its interaction with members of the Groucho-related family of co-repressors. Development 2002; 129:2835-49. [PMID: 12050133 DOI: 10.1242/dev.129.12.2835] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent findings suggest that Six3, a member of the evolutionarily conserved So/Six homeodomain family, plays an important role in vertebrate visual system development. However, little is known about the molecular mechanisms by which this function is accomplished. Although several members of the So/Six gene family interact with members of the eyes absent (Eya) gene family and function as transcriptional activators, Six3 does not interact with any known member of the Eya family. Here, we report that Grg4 and Grg5, mouse counterparts of the Drosophila transcriptional co-repressor Groucho, interact with mouse Six3 and its closely related member Six6, which may also be involved in vertebrate eye development. The specificity of the interaction was validated by co-immunoprecipitation of Six3 and Grg4 complexes from cell lines. We also show that the interaction between Six3 and Grg5 requires the Q domain of Grg5 and a conserved phenylalanine residue present in an eh1-like motif located in the Six domain of Six3. The pattern of Grg5 expression in the mouse ventral forebrain and developing optic vesicles overlapped that previously reported for Six3 and Six6. Using PCR, we identified a specific DNA motif that is bound by Six3 and we demonstrated that Six3 acts as a potent transcriptional repressor upon its interaction with Groucho-related members. We also demonstrated that this interaction is required for Six3 auto repression. The biological significance of this interaction in the retina and lens was assessed by overexpression experiments using either wild type full-length Six3 cDNA or a mutated form of this gene in which the interaction with Groucho proteins was disrupted. Overexpression of wild type Six3 by in vivo retroviral infection of newborn rat retinae led to an altered photoreceptor phenotype, while the in ovo electroporation of chicken embryos resulted in failure of lens placode invagination and production of delta-crystallin-negative cells within the placode. These specific alterations were not seen when the mutated form of Six3 cDNA was used in similar experimental approaches, indicating that Six3 interaction with Groucho proteins plays an essential role in vertebrate eye development.
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Affiliation(s)
- Changqi C Zhu
- Department of Genetics, St. Jude Children's Research Hospital, 332 North Lauderdale, Memphis, TN 38105-2794, USA
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33
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Li X, McDonnell DP. The transcription factor B-Myb is maintained in an inhibited state in target cells through its interaction with the nuclear corepressors N-CoR and SMRT. Mol Cell Biol 2002; 22:3663-73. [PMID: 11997503 PMCID: PMC133817 DOI: 10.1128/mcb.22.11.3663-3673.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The B-Myb transcription factor has been implicated in coordinating the expression of genes involved in cell cycle regulation. Although it is expressed in a ubiquitous manner, its transcriptional activity is repressed until the G(1)-S phase of the cell cycle by an unknown mechanism. In this study we used biochemical and cell-based assays to demonstrate that the nuclear receptor corepressors N-CoR and SMRT interact with B-Myb. The significance of these B-Myb-corepressor interactions was confirmed by the finding that B-Myb mutants, which were unable to bind N-CoR, exhibited constitutive transcriptional activity. It has been shown previously that phosphorylation of B-Myb by cdk2/cyclin A enhances its transcriptional activity. We have now determined that phosphorylation by cdk2/cyclin A blocks the interaction between B-Myb and N-CoR and that mutation of the corepressor binding site within B-Myb bypasses the requirement for this phosphorylation event. Cumulatively, these findings suggest that the nuclear corepressors N-CoR and SMRT serve a previously unappreciated role as regulators of B-Myb transcriptional activity.
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Affiliation(s)
- Xiaolin Li
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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34
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Cripps RM, Olson EN. Control of cardiac development by an evolutionarily conserved transcriptional network. Dev Biol 2002; 246:14-28. [PMID: 12027431 DOI: 10.1006/dbio.2002.0666] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Formation of the heart is dependent on an intricate cascade of developmental decisions. Analysis of the molecules and mechanisms involved in the specification of cardiac cell fates, differentiation and diversification of cardiac muscle cells, and morphogenesis and patterning of different cardiac cell types has revealed an evolutionarily conserved network of signaling pathways and transcription factors that underlies these processes. The regulatory network that controls the formation of the primitive heart in fruit flies has been elaborated upon to form the complex multichambered heart of mammals. We compare and contrast the mechanisms involved in heart formation in fruit flies and mammals in the context of a network of transcriptional interactions and point to unresolved questions for the future.
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Affiliation(s)
- Richard M Cripps
- Department of Biology, University of New Mexico, Albuquerque 87131-1091, USA.
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35
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Abstract
Transcription factors can regulate the expression of other genes in a tissue-specific and quantitative manner and are thus major regulators of embryonic developmental processes. Several transcription factors that regulate cardiac genes specifically have been described, and the recent discovery that dominant inherited transcription factor mutations cause congenital heart defects in humans has brought direct medical relevance to the study of cardiac transcription factors in heart development. Although this field of study is extensive, several major gaps in our knowledge of the transcriptional control of heart development still exist. This review will concentrate on recent developments in the field of cardiac transcription factors and their roles in heart formation.
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Affiliation(s)
- Benoit G Bruneau
- Division of Cardiovascular Research and Programme in Developmental Biology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8.
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36
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Henningfeld KA, Friedle H, Rastegar S, Knöchel W. Autoregulation of Xvent-2B; direct interaction and functional cooperation of Xvent-2 and Smad1. J Biol Chem 2002; 277:2097-103. [PMID: 11704665 DOI: 10.1074/jbc.m108524200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Members of the Xvent-2 homeodomain transcription factor family are immediate response genes of BMP-4 signaling. The bone morphogenetic protein response element (BRE) of Xvent-2B was previously identified and characterized with respect to Smad1 and Smad4 binding sites. In this study, we further report on the transcriptional regulation of Xvent-2B. We provide evidence that Xvent-2B (Xvent-2) maintains its own expression through autoregulation. This activity was demonstrated for the endogenous gene by reverse transcriptase-PCR analysis and was found to be insensitive to cycloheximide. Localized by DNase I footprinting were several Xvent-2 binding sites within the proximal upstream region including the BRE. In the early Xenopus embryo, the BRE was shown to be sufficient to drive expression of a green fluorescent protein reporter in a similar pattern compared with the endogenous gene. Furthermore, Xvent-2B was able to activate the BRE in luciferase reporter assays, and in co-injection experiments Xvent-2B and Smad1 were found to synergistically activate the BRE. Moreover, glutathione S-transferase pull-down experiments demonstrated that Xvent-2B directly and specifically interacts with Smad1. This association was mediated by the MH1 domain of Smad1 and required the C-terminal domain of Xvent-2. The failure of an Xvent-2 mutant lacking the C terminus to stimulate the BRE underlines the significance of the C-terminal domain in the described autoregulatory loop.
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Affiliation(s)
- Kristine A Henningfeld
- Abteilung Biochemie, Universität Ulm, Albert-Einstein Allee 11, 89081 Ulm, Germany and the Abteilung Entwicklungsbiochemie, Universität Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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37
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Lee SK, Pfaff SL. Transcriptional networks regulating neuronal identity in the developing spinal cord. Nat Neurosci 2001; 4 Suppl:1183-91. [PMID: 11687828 DOI: 10.1038/nn750] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The spinal cord is composed of anatomically distinct classes of neurons that perform sensory and motor functions. Because of its relative simplicity, the spinal cord has served as an important system for defining molecular mechanisms that contribute to the assembly of circuits in the central nervous system. At early embryonic stages, the neural tube contains multipotential cells whose identity becomes specified by cell-to-cell signaling. This review will focus on the progress made in understanding the transcriptional networks that become activated by these cell-cell interactions, with particular emphasis on the neurons that contribute to locomotor control. Remarkably, many of the transcription factors implicated in neuronal specification in the spinal cord are found to inhibit transcription, which has led to a 'derepression' model for cell fate specification in the developing spinal cord.
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Affiliation(s)
- S K Lee
- Gene Expression Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd., La Jolla, California 92037, USA
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38
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Gajewski K, Zhang Q, Choi CY, Fossett N, Dang A, Kim YH, Kim Y, Schulz RA. Pannier is a transcriptional target and partner of Tinman during Drosophila cardiogenesis. Dev Biol 2001; 233:425-36. [PMID: 11336505 DOI: 10.1006/dbio.2001.0220] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During Drosophila embryogenesis, the homeobox gene tinman is expressed in the dorsal mesoderm where it functions in the specification of precursor cells of the heart, visceral, and dorsal body wall muscles. The GATA factor gene pannier is similarly expressed in the dorsal-most part of the mesoderm where it is required for the formation of the cardial cell lineage. Despite these overlapping expression and functional properties, potential genetic and molecular interactions between the two genes remain largely unexplored. Here, we show that pannier is a direct transcriptional target of Tinman in the heart-forming region. The resulting coexpression of the two factors allows them to function combinatorially in the regulation of cardiac gene expression, and a physical interaction of the proteins has been demonstrated in cultured cells. We also define functional domains of Tinman and Pannier that are required for their synergistic activation of the D-mef2 differentiation gene in vivo. Together, these results provide important insights into the genetic mechanisms controlling heart formation in the Drosophila model system.
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Affiliation(s)
- K Gajewski
- Department of Biochemistry and Molecular Biology, Graduate Program in Genes & Development, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA
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39
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Affiliation(s)
- M Mannervik
- Department of Molecular and Cellular Biology, Division of Genetics, 401 Barker Hall, University of California, Berkeley, CA 94720, USA
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40
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Brantjes H, Roose J, van De Wetering M, Clevers H. All Tcf HMG box transcription factors interact with Groucho-related co-repressors. Nucleic Acids Res 2001; 29:1410-9. [PMID: 11266540 PMCID: PMC31284 DOI: 10.1093/nar/29.7.1410] [Citation(s) in RCA: 282] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Tcf/Lef family transcription factors are the downstream effectors of the Wingless/Wnt signal transduction pathway. Upon Wingless/Wnt signalling, beta-catenin translocates to the nucleus, interacts with Tcf (1-3) and thus activates transcription of target genes (4,5). Tcf factors also interact with members of the Groucho (Grg/TLE) family of transcriptional co-repressors (6). We have now tested all known mammalian Groucho family members for their ability to interact specifically with individual Tcf/Lef family members. Transcriptional activation by any Tcf could be repressed by Grg-1, Grg-2/TLE-2, Grg-3 and Grg-4 in a reporter assay. Specific interactions between Tcf and Grg proteins may be achieved in vivo by tissue- or cell type-limited expression. To address this, we determined the expression of all Tcf and Grg/TLE family members in a panel of cell lines. Within any cell line, several Tcfs and TLEs are co-expressed. Thus, redundancy in Tcf/Grg interactions appears to be the rule. The 'long' Groucho family members containing five domains are repressors of Tcf-mediated transactivation, whereas Grg-5, which only contains the first two domains, acts as a de-repressor. As previously shown for Drosophila Groucho, we show that long Grg proteins interact with histone deacetylase-1. Although Grg-5 contains the GP homology domain that mediates HDAC binding in long Grg proteins, Grg-5 fails to bind this co-repressor, explaining how it can de-repress transcription.
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Affiliation(s)
- H Brantjes
- Department of Immunology, University Medical Center Utrecht, PO Box 85500, 3508 GA, Utrecht, The Netherlands
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41
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Muhr J, Andersson E, Persson M, Jessell TM, Ericson J. Groucho-mediated transcriptional repression establishes progenitor cell pattern and neuronal fate in the ventral neural tube. Cell 2001; 104:861-73. [PMID: 11290324 DOI: 10.1016/s0092-8674(01)00283-5] [Citation(s) in RCA: 304] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The pattern of neuronal specification in the ventral neural tube is controlled by homeodomain transcription factors expressed by neural progenitor cells, but no general logic has emerged to explain how these proteins determine neuronal fate. We show that most of these homeodomain proteins possess a conserved eh1 motif that mediates the recruitment of Gro/TLE corepressors. The eh1 motif underlies the function of these proteins as repressors during neural patterning in vivo. Inhibition of Gro/TLE-mediated repression in vivo results in a deregulation of cell pattern in the neural tube. These results imply that the pattern of neurogenesis in the neural tube is achieved through the spatially controlled repression of transcriptional repressors-a derepression strategy of neuronal fate specification.
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Affiliation(s)
- J Muhr
- Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, S-171 77 Stockholm, Sweden
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42
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Sparrow DB, Cai C, Kotecha S, Latinkic B, Cooper B, Towers N, Evans SM, Mohun TJ. Regulation of the tinman homologues in Xenopus embryos. Dev Biol 2000; 227:65-79. [PMID: 11076677 DOI: 10.1006/dbio.2000.9891] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vertebrate homologues of the Drosophila tinman transcription factor have been implicated in the processes of specification and differentiation of cardiac mesoderm. In Xenopus three members of this family have been isolated to date. Here we show that the XNkx2-3, Xnkx2-5, and XNkx2-10 genes are expressed in increasingly distinctive patterns in endodermal and mesodermal germ layers through early development, suggesting that their protein products (either individually or in different combinations) perform distinct functions. Using amphibian transgenesis, we find that the expression pattern of one of these genes, XNkx2-5, can be reproduced using transgenes containing only 4.3 kb of promoter sequence. Sequence analysis reveals remarkable conservation between the distalmost 300 bp of the Xenopus promoter and a portion of the AR2 element upstream of the mouse and human Nkx2-5 genes. Interestingly, only the 3' half of this evolutionarily conserved sequence element is required for correct transgene expression in frog embryos. Mutation of conserved GATA sites or a motif resembling the dpp-response element in the Drosophila tinman tinD enhancer dramatically reduces the levels of transgene expression. Finally we show that, despite its activity in Xenopus embryos, in transgenic mice the Xenopus Nkx2-5 promoter is able to drive reporter gene expression only in a limited subset of cells expressing the endogenous gene. This intriguing result suggests that despite evolutionary conservation of some cis-regulatory sequences, the regulatory controls on Nkx2-5 expression have diverged between mammals and amphibians.
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Affiliation(s)
- D B Sparrow
- Division of Developmental Biology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, United Kingdom
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43
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Abstract
In the last 5 years, many co-repressors have been identified in eukaryotes that function in a wide range of species, from yeast to Drosophila and humans. Co-repressors are coregulators that are recruited by DNA-bound transcriptional silencers and play essential roles in many pathways including differentiation, proliferation, programmed cell death, and cell cycle. Accordingly, it has been shown that aberrant interactions of co-repressors with transcriptional silencers provide the molecular basis of a variety of human diseases. Co-repressors mediate transcriptional silencing by mechanisms that include direct inhibition of the basal transcription machinery and recruitment of chromatin-modifying enzymes. Chromatin modification includes histone deacetylation, which is thought to lead to a compact chromatin structure to which the accessibility of transcriptional activators is impaired. In a general mechanistic view, the overall picture suggests that transcriptional silencers and co-repressors act in analogy to transcriptional activators and coactivators, but with the opposite effect leading to gene silencing. We provide a comprehensive overview of the currently known higher eukaryotic co-repressors, their mechanism of action, and their involvement in biological and pathophysiological pathways. We also show the different pathways that lead to the regulation of co-repressor-silencer complex formation.
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Affiliation(s)
- L J Burke
- Genetic Institute, Justus Liebig University, Heinrich Buff Ring 58-62, D-35392 Giessen, Germany
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44
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Denson LA, Karpen SJ, Bogue CW, Jacobs HC. Divergent homeobox gene hex regulates promoter of the Na(+)-dependent bile acid cotransporter. Am J Physiol Gastrointest Liver Physiol 2000; 279:G347-55. [PMID: 10915644 DOI: 10.1152/ajpgi.2000.279.2.g347] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The divergent homeobox gene Hex is expressed in both developing and mature liver. A putative Hex binding site was identified in the promoter region of the liver-specific Na(+)-bile acid cotransporter gene (ntcp), and we hypothesized that Hex regulates the ntcp promoter through this site. Successive 5'-deletions of the ntcp promoter in a luciferase reporter construct transfected into Hep G2 cells confirmed a Hex response element (HRE) within the ntcp promoter (nt -733/-714). Moreover, p-CMHex transactivated a heterologous promoter construct containing HRE multimers (p4xHRELUC), whereas a 5-bp mutation of the core HRE eliminated transactivation. A dominant negative form of Hex (p-Hex-DN) suppressed basal luciferase activity of p-4xHRELUC and inhibited activation of this construct by p-CMHex. Interestingly, p-CMHex transactivated the HRE in Hep G2 cells but not in fibroblast-derived COS cells, suggesting the possibility that Hex protein requires an additional liver cell-specific factor(s) for full activity. Electrophoretic mobility shift assays confirmed that liver and Hep G2 cells contain a specific nuclear protein that binds the native HRE. We have demonstrated that the liver-specific ntcp gene promoter is the first known target of Hex and is a useful tool for evaluating function of the Hex protein.
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Affiliation(s)
- L A Denson
- Department of Pediatrics, Yale University, New Haven, CT 06520-8064, USA
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45
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Lannoy VJ, Rodolosse A, Pierreux CE, Rousseau GG, Lemaigre FP. Transcriptional stimulation by hepatocyte nuclear factor-6. Target-specific recruitment of either CREB-binding protein (CBP) or p300/CBP-associated factor (p/CAF). J Biol Chem 2000; 275:22098-103. [PMID: 10811635 DOI: 10.1074/jbc.m000855200] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription factors of the ONECUT class, whose prototype is HNF-6, contain a single cut domain and a divergent homeodomain characterized by a phenylalanine at position 48 and a methionine at position 50. The cut domain is required for DNA binding. The homeodomain is required either for DNA binding or for transcriptional stimulation, depending on the target gene. Transcriptional stimulation by the homeodomain involves the F48M50 dyad. We investigate here how HNF-6 stimulates transcription. We identify transcriptionally active domains of HNF-6 that are conserved among members of the ONECUT class and show that the cut domain of HNF-6 participates to DNA binding and, via a LXXLL motif, to transcriptional stimulation. We also demonstrate that, on a target gene to which HNF-6 binds without requirement for the homeodomain, transcriptional stimulation involves an interaction of HNF-6 with the coactivator CREB-binding protein (CBP). This interaction depends both on the LXXLL motif of the cut domain and on the F48M50 dyad of the homeodomain. On a target gene for which the homeodomain is required for DNA binding, but not for transcriptional stimulation, HNF-6 interacts with the coactivator p300/CBP-associated factor but not with CBP. These data show that a transcription factor can act via different, sequence-specific, mechanisms that combine distinct modes of DNA binding with the use of different coactivators.
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Affiliation(s)
- V J Lannoy
- Hormone and Metabolic Research Unit, Université catholique de Louvain and Christian de Duve Institute of Cellular Pathology (ICP), Avenue Hippocrate 75, B-1200 Brussels, Belgium
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46
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Fossett N, Zhang Q, Gajewski K, Choi CY, Kim Y, Schulz RA. The multitype zinc-finger protein U-shaped functions in heart cell specification in the Drosophila embryo. Proc Natl Acad Sci U S A 2000; 97:7348-53. [PMID: 10861002 PMCID: PMC16548 DOI: 10.1073/pnas.97.13.7348] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multitype zinc-finger proteins of the Friend of GATA/U-shaped (Ush) class function as transcriptional regulators of gene expression through their modulation of GATA factor activity. To better understand intrinsic properties of these proteins, we investigated the expression and function of the ush gene during Drosophila embryogenesis. ush is dynamically expressed in the embryo, including several cell types present within the mesoderm. The gene is active in the cardiogenic mesoderm, and a loss of function results in an overproduction of both cardial and pericardial cells, indicating a requirement for the gene in the formation of these distinct cardiac cell types. Conversely, ectopic expression of ush results in a decrease in the number of cardioblasts in the heart and the inhibition of a cardial cell enhancer normally regulated by the synergistic activity of the Pannier and Tinman cardiogenic factors. These findings suggest that, similar to its known function in thoracic bristle patterning, Ush functions in the control of heart cell specification through its modulation of Pannier transcriptional activity. ush is also required for mesodermal cell migration early in embryogenesis, where it shows a genetic interaction with the Heartless fibroblast growth factor receptor gene. Taken together, these results demonstrate a critical role for the Ush transcriptional regulator in several diverse processes of mesoderm differentiation and heart formation.
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Affiliation(s)
- N Fossett
- Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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47
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Rastegar M, Rousseau GG, Lemaigre FP. CCAAT/enhancer-binding protein-alpha is a component of the growth hormone-regulated network of liver transcription factors. Endocrinology 2000; 141:1686-92. [PMID: 10803577 DOI: 10.1210/endo.141.5.7478] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
GH regulates gene expression by modulating the concentration or activity of transcription factors. To identify transcription factors that mediate the effects of GH in liver we analyzed the promoter of the gene coding for hepatocyte nuclear factor-6 (HNF-6), whose expression in liver is stimulated by GH. In protein-DNA interaction studies and in transfection experiments, we found that the liver-enriched transcription factor CCAAT/enhancer-binding protein-alpha (C/EBPalpha) binds to the hnf6 gene and inhibits its expression. This inhibitory effect involved an N-terminal subdomain of C/EBPalpha and two sites in the hnf6 gene promoter. Using liver nuclear extracts from GH-treated hypophysectomized rats, we found that GH induces a rapid, transient decrease in the amount of C/EBPalpha protein. This GH-induced change is concomitant with the transient stimulatory effect of GH on the hnf6 gene. Stimulation of the hnf6 gene by GH therefore involves lifting of the repression exerted by C/EBPalpha in addition to the known GH-induced stimulatory effects of STAT5 (signal transducer and activator of transcription-5) and HNF-4 on that gene. Our data provide further evidence that GH controls a network of liver transcription factors and show that C/EBPalpha participates in this process.
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Affiliation(s)
- M Rastegar
- Hormone and Metabolic Research Unit, Université Catholique de Louvain, Belgium
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Missero C, Pirro MT, Di Lauro R. Multiple ras downstream pathways mediate functional repression of the homeobox gene product TTF-1. Mol Cell Biol 2000; 20:2783-93. [PMID: 10733581 PMCID: PMC85494 DOI: 10.1128/mcb.20.8.2783-2793.2000] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of oncogenic Ras in thyroid cells results in loss of expression of several thyroid-specific genes and inactivation of TTF-1, a homeodomain-containing transcription factor required for normal development of the thyroid gland. In an effort to understand how signal transduction pathways downstream of Ras may be involved in suppression of the differentiated phenotype, we have tested mutants of the Ras effector region for their ability to affect TTF-1 transcriptional activity in a transient-transfection assay. We find that V12S35 Ras, a mutant known to interact specifically with Raf but not with RalGDS or phosphatidylinositol 3-kinase (PI3 kinase) inhibits TTF-1 activity. Expression of an activated form of Raf (Raf-BXB) also inhibits TTF-1 function to a similar extent, while the MEK inhibitors U0126 and PD98059 partially relieve Ras-mediated inactivation of TTF-1, suggesting that the extracellular signal-regulated kinase (ERK) pathway is involved in this process. Indeed, ERK directly phosphorylates TTF-1 at three serine residues, and concomitant mutation of these serines to alanines completely abolishes ERK-mediated phosphorylation both in vitro and in vivo. Since activation of the Raf/MEK/ERK pathway accounts for only part of the activity elicited by oncogenic Ras on TTF-1, other downstream pathways are likely to be involved in this process. We find that activation of PI3 kinase, Rho, Rac, and RalGDS has no effect on TTF-1 transcriptional activity. However, a poorly characterized Ras mutant, V12N38 Ras, can partially repress TTF-1 transcriptional activity through an ERK-independent pathway. Importantly, concomitant expression of constitutive activated Raf and V12N38 Ras results in almost complete loss of TTF-1 activity. Our data indicate that the Raf/MEK/ERK cascade may act in concert with an as-yet-uncharacterized signaling pathway activated by V12N38 Ras to repress TTF-1 function and ultimately to inhibit thyroid cell differentiation.
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Affiliation(s)
- C Missero
- Stazione Zoologica "A. Dohrn" Villa Comunale, 80121 Naples, Italy
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