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He Y, Deng H, Hu Q, Zhu Z, Liu L, Zheng S, Song Q, Feng Q. Identification of the binding domains and key amino acids for the interaction of the transcription factors BmPOUM2 and BmAbd-A in Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2017; 81:41-50. [PMID: 27986639 DOI: 10.1016/j.ibmb.2016.12.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 12/10/2016] [Accepted: 12/12/2016] [Indexed: 06/06/2023]
Abstract
The transcription factor BmPOUM2 interacted with another transcription factor BmAbd-A to regulate the expression of the wing cuticle protein gene BmWCP4 in Bombyx mori. In this study, the binding domains and amino acids for the interaction between BmPOUM2 and BmAbd-A were reported. Two isoforms of BmPOUM2 were identified. The short isoform (BmPOUM2-S) lacks a 114-amino acid sequence containing a POU-homeodomain and a nuclear localization signal peptide (NLS), as compared to the full-length isoform (BmPOUM2). Both BmPOUM2 and BmPOUM2-S proteins bound to the BmAbd-A through the POU-specific domain. When the six amino acids (Lys166, Gly173, Gln176, Ser192, Glu200 and Asn208) that are highly conserved in POU family genes were mutated, BmPOUM2 did not bind to BmAbd-A. BmAbd-A interacted with BmPOUM2 by the homeobox domain or the LCR2 (low complexity region) domain. When seven amino acids (Phe156/248, His158/250, Ala175/263, Cys180/265, Glu190/268, Trp196/274 and Val214/289) that are shared in the homeobox and LCR2 domains were mutated, BmAbd-A did not bind to BmPOUM2. Overexpression of either BmPOUM2 or BmAbd-A or both increased the activity of BmWCP4 promoter in CHO cells. ChIP assay and EMSA showed that BmAbd-A protein bound to the Hox cis-regulatory element in the BmWCP4 promoter, while the BmPOUM2 bound to the nearby POU CRE. A model for the interaction and action of BmPOUM2 and BmAbd-A in regulation of the BmWCP4 expression is proposed.
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Affiliation(s)
- Yong He
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Huimin Deng
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
| | - Qihao Hu
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Zidan Zhu
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Lin Liu
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Sichun Zheng
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China
| | - Qisheng Song
- Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA
| | - Qili Feng
- Guangzhou Key Laboratory of Insect Development Regulation and Application Research, School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
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Meng M, Cheng DJ, Peng J, Qian WL, Li JR, Dai DD, Zhang TL, Xia QY. The homeodomain transcription factors antennapedia and POU-M2 regulate the transcription of the steroidogenic enzyme gene Phantom in the silkworm. J Biol Chem 2015; 290:24438-52. [PMID: 26253172 DOI: 10.1074/jbc.m115.651810] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Indexed: 12/22/2022] Open
Abstract
The steroid hormone ecdysone, which controls insect molting and metamorphosis, is synthesized in the prothoracic gland (PG), and several steroidogenic enzymes that are expressed specifically in the PG are involved in ecdysteroidogenesis. In this study, we identified new regulators that are involved in the transcriptional control of the silkworm steroidogenic enzyme genes. In silico analysis predicted several potential cis-regulatory elements (CREs) for the homeodomain transcription factors Antennapedia (Antp) and POU-M2 in the proximal promoters of steroidogenic enzyme genes. Antp and POU-M2 are expressed dynamically in the PG during larval development, and their overexpression in silkworm embryo-derived (BmE) cells induced the expression of steroidogenic enzyme genes. Importantly, luciferase reporter analyses, electrophoretic mobility shift assays, and chromatin immunoprecipitation assays revealed that Antp and POU-M2 promote the transcription of the silkworm steroidogenic enzyme gene Phantom (Phm) by binding directly to specific motifs within overlapping CREs in the Phm promoter. Mutations of these CREs in the Phm promoter suppressed the transcriptional activities of both Antp and POU-M2 in BmE cells and decreased the activities of mutated Phm promoters in the silkworm PG. In addition, pulldown and co-immunoprecipitation assays demonstrated that Antp can interact with POU-M2. Moreover, RNA interference-mediated down-regulation of either Antp or POU-M2 during silkworm wandering not only decreased the ecdysone titer but also led to the failure of metamorphosis. In summary, our results suggest that Antp and POU-M2 coordinate the transcription of the silkworm Phm gene directly, indicating new roles for homeodomain proteins in regulating insect ecdysteroidogenesis.
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Affiliation(s)
- Meng Meng
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Dao-Jun Cheng
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Jian Peng
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Wen-Liang Qian
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Jia-Rui Li
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Dan-Dan Dai
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Tian-Lei Zhang
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
| | - Qing-You Xia
- From the State Key Laboratory of Silkworm Genome Biology and the Key Sericultural Laboratory of the Ministry of Agriculture, College of Biotechnology, Southwest University, Chongqing 400715, China
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Gong SY, Huang GQ, Sun X, Qin LX, Li Y, Zhou L, Li XB. Cotton KNL1, encoding a class II KNOX transcription factor, is involved in regulation of fibre development. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:4133-47. [PMID: 24831118 PMCID: PMC4112624 DOI: 10.1093/jxb/eru182] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In this study, the GhKNL1 (KNOTTED1-LIKE) gene, encoding a classical class II KNOX protein was identified in cotton (Gossypium hirsutum). GhKNL1 was preferentially expressed in developing fibres at the stage of secondary cell wall (SCW) biosynthesis. GhKNL1 was localized in the cell nucleus, and could interact with GhOFP4, as well as AtOFP1, AtOFP4, and AtMYB75. However, GhKNL1 lacked transcriptional activation activity. Dominant repression of GhKNL1 affected fibre development of cotton. The expression levels of genes related to fibre elongation and SCW biosynthesis were altered in transgenic fibres of cotton. As a result, transgenic cotton plants produced aberrant, shrunken, and collapsed fibre cells. Length and cell-wall thickness of fibres of transgenic cotton plants were significantly reduced compared with the wild type. Furthermore, overexpression and dominant repression of GhKNL1 in Arabidopsis resulted in a reduction in interfascicular fibre cell-wall thickening of basal stems of transgenic plants. Complementation revealed that GhKNL1 rescued the defective phenotype of Arabidopsis knat7 mutant in some extent. These data suggest that GhKNL1, as a transcription factor, participates in regulating fibre development of cotton.
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Affiliation(s)
- Si-Ying Gong
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Geng-Qing Huang
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Xiang Sun
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Li-Xia Qin
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Yang Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Li Zhou
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Xue-Bao Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
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Impact of CUX2 on the female mouse liver transcriptome: activation of female-biased genes and repression of male-biased genes. Mol Cell Biol 2012; 32:4611-27. [PMID: 22966202 DOI: 10.1128/mcb.00886-12] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The growth hormone-regulated transcription factors STAT5 and BCL6 coordinately regulate sex differences in mouse liver, primarily through effects in male liver, where male-biased genes are upregulated and many female-biased genes are actively repressed. Here we investigated whether CUX2, a highly female-specific liver transcription factor, contributes to an analogous regulatory network in female liver. Adenoviral overexpression of CUX2 in male liver induced 36% of female-biased genes and repressed 35% of male-biased genes. In female liver, CUX2 small interfering RNA (siRNA) preferentially induced genes repressed by adenovirus expressing CUX2 (adeno-CUX2) in male liver, and it preferentially repressed genes induced by adeno-CUX2 in male liver. CUX2 binding in female liver chromatin was enriched at sites of male-biased DNase hypersensitivity and at genomic regions showing male-enriched STAT5 binding. CUX2 binding was also enriched near genes repressed by adeno-CUX2 in male liver or induced by CUX2 siRNA in female liver but not at genes induced by adeno-CUX2, indicating that CUX2 binding is preferentially associated with gene repression. Nevertheless, direct CUX2 binding was seen at several highly female-specific genes that were positively regulated by CUX2, including A1bg, Cyp2b9, Cyp3a44, Tox, and Trim24. CUX2 expression and chromatin binding were high in immature male liver, where repression of adult male-biased genes and expression of adult female-biased genes are common, suggesting that the downregulation of CUX2 in male liver at puberty contributes to the developmental changes establishing adult patterns of sex-specific gene expression.
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Gottwald S, Bauer P, Komatsuda T, Lundqvist U, Stein N. TILLING in the two-rowed barley cultivar 'Barke' reveals preferred sites of functional diversity in the gene HvHox1. BMC Res Notes 2009; 2:258. [PMID: 20017921 PMCID: PMC2803498 DOI: 10.1186/1756-0500-2-258] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 12/17/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The economic importance of cereals such as barley, and the demand for improved yield and quality require a better understanding of the genetic components that modulate biologically and commercially relevant traits. While Arabidopsis thaliana is the premiere model plant system, the spectrum of its traits cannot address all of the fundamental questions of crop plant development. Unlike Arabidopsis, barley is both a crop and a model system for scientific research, and it is increasingly being used for genetic and molecular investigations into the conserved biological processes of cereals. A common challenge in genetic studies in plants with large genomes arises from the very time-consuming work of associating mutant phenotypes with gene sequence information, especially if insertion mutagenesis is not routine, as in barley. Reverse genetics based on chemical mutagenesis represents the best solution to this obstacle. FINDINGS In barley, we generated a new TILLING (Targeting Local Lesions IN Genomes) resource comprising 10,279 M(2 )mutants in the two-rowed malting cultivar 'Barke,' which has been used in the generation of other genomic resources in barley (~150,000 ESTs, DH mapping population). The value of this new resource was tested using selected candidate genes. An average frequency of approximately one mutation per 0.5 Mb was determined by screening ten fragments of six different genes. The ethyl methanesulphonate (EMS)mutagenesis efficiency was studied by recording and relating the mutagenesis-dependent effects found in the three mutant generations (M(1)-M(3)). A detailed analysis was performed for the homeodomain-leucine-zipper (HD-ZIP) gene HvHox1. Thirty-one mutations were identified by screening a 1,270-bp fragment in 7,348 M(2 )lines. Three of the newly identified mutants exhibited either a six-rowed or an intermedium-spike phenotype, and one mutant displayed a significantly altered spikelet morphology compared to that of the 'Barke' wild type. Our results indicate a bias in the frequency of independent functional mutations at specific base pair (bp) positions within the gene HvHox1. CONCLUSIONS A new TILLING population was developed as a resource for high-throughput gene discovery in an alternative barley germplasm. Pilot screening demonstrated a similar or even slightly higher mutation frequency when compared to previously published barley TILLING populations that should allow for the identification of diverse allelic variation. Partial phenotypic evaluation of the M(2 )and M(3 )generations has revealed the presence of a wide spectrum of morphological diversity that highlights the great potential of this resource for use in forward genetic screens. Altogether, our study shows the efficiency of screening and the applicability of the new TILLING population for genetic studies in the barley crop model system.
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Affiliation(s)
- Sven Gottwald
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstr. 3, D-06466 Gatersleben, Germany
| | - Petra Bauer
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstr. 3, D-06466 Gatersleben, Germany
- Saarland University, Dept. Of Biosciences-Botany, Campus A2.4, D-66123 Saarbrücken, Germany
| | - Takao Komatsuda
- National Institute of Agrobiological Sciences (NIAS), Plant Genome Research Unit, Kannondai 1-2-1, Tsukuba, Ibaraki 305 8602, Japan
| | - Udda Lundqvist
- Nordic Genetic Resource Centre, P.O. Box 41, SE-230 53 Alnarp, Sweden
| | - Nils Stein
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstr. 3, D-06466 Gatersleben, Germany
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Schild-Poulter C, Pope L, Giffin W, Kochan JC, Ngsee JK, Traykova-Andonova M, Haché RJ. The binding of Ku antigen to homeodomain proteins promotes their phosphorylation by DNA-dependent protein kinase. J Biol Chem 2001; 276:16848-56. [PMID: 11279128 DOI: 10.1074/jbc.m100768200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Ku antigen (70- and 80-kDa subunits) is a regulatory subunit of DNA-dependent protein kinase (DNA-PK) that promotes the recruitment of the catalytic subunit of DNA-PK (DNA-PKcs) to DNA ends and to specific DNA sequences from which the kinase is activated. Ku and DNA-PKcs plays essential roles in double-stranded DNA break repair and V(D)J recombination and have been implicated in the regulation of specific gene transcription. In a yeast two-hybrid screen of a Jurkat T cell cDNA library, we have identified a specific interaction between the 70-kDa subunit of Ku heterodimer and the homeodomain of HOXC4, a homeodomain protein expressed in the hematopoietic system. Unexpectedly, a similar interaction with Ku was observed for several additional homeodomain proteins including octamer transcription factors 1 and 2 and Dlx2, suggesting that specific binding to Ku may be a property shared by many homeodomain proteins. Ku-homeodomain binding was mediated through the extreme C terminus of Ku70 and was abrogated by amino acid substitutions at Lys595/Lys596. Ku binding allowed the recruitment of the homeodomain to DNA ends and dramatically enhanced the phosphorylation of homeodomain-containing proteins by DNA-PK. These results suggest that Ku functions as a substrate docking protein for signaling by DNA-PK to homeodomain proteins from DNA ends.
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Affiliation(s)
- C Schild-Poulter
- Department of Medicine, The Loeb Health Research Institute at the Ottawa Hospital, University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada
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Kirschmann DA, Seftor EA, Nieva DR, Mariano EA, Hendrix MJ. Differentially expressed genes associated with the metastatic phenotype in breast cancer. Breast Cancer Res Treat 1999; 55:127-36. [PMID: 10481940 DOI: 10.1023/a:1006188129423] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have previously shown that human breast carcinoma cells demonstrating an interconverted phenotype, where keratin (epithelial marker) and vimentin (mesenchymal marker) intermediate filaments are both expressed, have an increased ability to invade a basement membrane matrix in vitro. This increase in invasive potential has been demonstrated in MDA-MB-231 cells, which constitutively express keratins and vimentin, and in MCF-7 cells transfected with the mouse vimentin gene (MoVi). However, vimentin expression alone is not sufficient to confer the complete metastatic phenotype in MoVi cells, as determined by orthotopic administration. Thus, in the present study, differential display analysis was utilized to identify genes that are associated with the invasive and/or metastatic phenotype of several human breast cancer cell lines. Forty-four of 84 PCR fragments were differentially expressed as assessed by Northern hybridization analysis of RNA isolated from MCF-7, MoVi, and MB-231 cell lines. Polyadenylated RNA from a panel of poorly invasive, invasive/non-metastatic, and invasive/metastatic breast carcinoma cell lines was used to differentiate between cell-specific gene expression and genes associated with the invasive and/or metastatic phenotype(s). We observed that lysyl oxidase and a zinc finger transcription factor were expressed only in the invasive and/or metastatic cell lines; whereas, a thiol-specific antioxidant and a heterochromatin protein were down-regulated in these cells. In contrast, tissue factor was expressed only in breast carcinoma cell lines having the highest invasive potential. These results suggest that specific genes involved in breast cancer invasion and metastasis can be separated by differential display methodology to elucidate the molecular basis of tumor cell progression.
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Affiliation(s)
- D A Kirschmann
- Department of Anatomy and Cell Biology, Iowa Cancer Center, College of Medicine, The University of Iowa, Iowa City 52242-1109, USA
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Sepulveda JL, Belaguli N, Nigam V, Chen CY, Nemer M, Schwartz RJ. GATA-4 and Nkx-2.5 coactivate Nkx-2 DNA binding targets: role for regulating early cardiac gene expression. Mol Cell Biol 1998; 18:3405-15. [PMID: 9584181 PMCID: PMC108922 DOI: 10.1128/mcb.18.6.3405] [Citation(s) in RCA: 254] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/1997] [Accepted: 03/18/1998] [Indexed: 02/07/2023] Open
Abstract
The cardiogenic homeodomain factor Nkx-2.5 and serum response factor (SRF) provide strong transcriptional coactivation of the cardiac alpha-actin (alphaCA) promoter in fibroblasts (C. Y. Chen and R. J. Schwartz, Mol. Cell. Biol. 16:6372-6384, 1996). We demonstrate here that Nkx-2.5 also cooperates with GATA-4, a dual C-4 zinc finger transcription factor expressed in early cardiac progenitor cells, to activate the alphaCA promoter and a minimal promoter, containing only multimerized Nkx-2.5 DNA binding sites (NKEs), in heterologous CV-1 fibroblasts. Transcriptional activity requires the N-terminal activation domain of Nkx-2.5 and Nkx-2.5 binding activity through its homeodomain but does not require GATA-4's activation domain. The minimal interactive regions were mapped to the homeodomain of Nkx-2.5 and the second zinc finger of GATA-4. Removal of Nkx-2.5's C-terminal inhibitory domain stimulated robust transcriptional activity, comparable to the effects of GATA-4 on wild-type Nkx-2.5, which in part facilitated Nkx-2.5 DNA binding activity. We postulate the following simple model: GATA-4 induces a conformational change in Nkx-2.5 that displaces the C-terminal inhibitory domain, thus eliciting transcriptional activation of promoters containing Nkx-2.5 DNA binding targets. Therefore, alphaCa promoter activity appears to be regulated through the combinatorial interactions of at least three cardiac tissue-enriched transcription factors, Nkx-2.5, GATA-4, and SRF.
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Affiliation(s)
- J L Sepulveda
- Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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Friedle H, Rastegar S, Paul H, Kaufmann E, Knöchel W. Xvent-1 mediates BMP-4-induced suppression of the dorsal-lip-specific early response gene XFD-1' in Xenopus embryos. EMBO J 1998; 17:2298-307. [PMID: 9545242 PMCID: PMC1170573 DOI: 10.1093/emboj/17.8.2298] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Ectopic expression of the ventralizing morphogen BMP-4 (bone morphogenetic protein-4) in the dorsal lip (Spemann organizer) of Xenopus embryos blocks transcription of dorsal-lip-specific early response genes. We investigated the molecular mechanism underlying the BMP-4-induced inhibition of the fork head gene XFD-1'. The promoter of this gene contains a BMP-triggered inhibitory element (BIE) which prevents activation of this gene at the ventral/vegetal side of the embryo in vivo. In the present study, we show that BMP-4-induced inhibition is not direct but indirect, and is mediated by Xvent homeobox proteins. Micro-injections of Xvent-1 RNA and XFD-1' promoter deletion mutants demonstrate that Xvent-1 mimics the effect of BMP-4 signalling not only by suppression of the XFD-1' gene, but also by utilizing the BIE. Suppression could be reverted using a dominant-negative Xvent-1 mutant. The repressor domain was localized to the N-terminal region of the protein. Gel-shift and footprint analyses prove that Xvent-1 binds to the BIE. Moreover, PCR-based target-site selection for the Xvent-1 homeodomain confirms distinct motifs within the BIE as preferential binding sites. Thus, biological and molecular data suggest that Xvent-1 acts as direct repressor for XFD-1' transcription and mediates BMP-4-induced inhibition.
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Affiliation(s)
- H Friedle
- Abteilung Biochemie, Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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Abstract
The human transcription factor, UEF3, is important in regulating the activity of the urokinase plasminogen activator (uPA) gene enhancer. The UEF3 DNA target site is a regulatory element in the promoters of several growth factor and protease genes. We reported previously that purified UEF3 is a complex of several subunits. In this paper we report the cloning of the cDNA of one of the subunits which encodes for a novel human homeodomain protein, which we have termed Prep1. The Prep1 homeodomain belongs to the TALE class of homeodomains, is most closely related to those of the TGIF and Meis1 proteins, and like these, recognizes a TGACAG motif. We further identify the other UEF3 subunit as a member of the Pbx protein family. Unlike other proteins known to interact with Pbx, Prep1 forms a stable complex with Pbx independent of DNA binding. Heterodimerization of Prep1 and Pbx results in a strong DNA binding affinity towards the TGACAG target site of the uPA promoter. Overall, these data indicate that Prep1 is a stable intracellular partner of Pbx in vivo.
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Affiliation(s)
- J Berthelsen
- Dipartimento di Genetica e Biologia dei Microrganismi dell'Università, DIBIT, H.S. Raffaele, via Olgettina 58, 20132, Milan, Italy
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Abstract
The structure of a complex containing the homeodomain repressor protein MATalpha2 and the MADS-box transcription factor MCM1 bound to DNA has been determined by X-ray crystallography at 2.25 A resolution. It reveals the protein-protein interactions responsible for cooperative binding of MATalpha2 and MCM1 to DNA. The otherwise flexible amino-terminal extension of the MATalpha2 homeodomain forms a beta-hairpin that grips the MCM1 surface through parallel beta-strand hydrogen bonds and close-packed, predominantly hydrophobic, side chains. DNA bending induced by MCM1 brings the two proteins closer together, facilitating their interaction. An unusual feature of the complex is that an eight-amino-acid sequence adopts an alpha-helical conformation in one of two copies of the MATalpha2 monomer and a beta-strand conformation in the other. This 'chameleon' sequence of MATalpha2 may be important for recognizing natural operator sites.
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Affiliation(s)
- S Tan
- ETH-Zurich, Institut für Molekularbiologie und Biophysik, Switzerland
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