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Jackson JT, Nutt SL, McCormack MP. The Haematopoietically-expressed homeobox transcription factor: roles in development, physiology and disease. Front Immunol 2023; 14:1197490. [PMID: 37398663 PMCID: PMC10313424 DOI: 10.3389/fimmu.2023.1197490] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 06/01/2023] [Indexed: 07/04/2023] Open
Abstract
The Haematopoietically expressed homeobox transcription factor (Hhex) is a transcriptional repressor that is of fundamental importance across species, as evident by its evolutionary conservation spanning fish, amphibians, birds, mice and humans. Indeed, Hhex maintains its vital functions throughout the lifespan of the organism, beginning in the oocyte, through fundamental stages of embryogenesis in the foregut endoderm. The endodermal development driven by Hhex gives rise to endocrine organs such as the pancreas in a process which is likely linked to its role as a risk factor in diabetes and pancreatic disorders. Hhex is also required for the normal development of the bile duct and liver, the latter also importantly being the initial site of haematopoiesis. These haematopoietic origins are governed by Hhex, leading to its crucial later roles in definitive haematopoietic stem cell (HSC) self-renewal, lymphopoiesis and haematological malignancy. Hhex is also necessary for the developing forebrain and thyroid gland, with this reliance on Hhex evident in its role in endocrine disorders later in life including a potential role in Alzheimer's disease. Thus, the roles of Hhex in embryological development throughout evolution appear to be linked to its later roles in a variety of disease processes.
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Affiliation(s)
- Jacob T. Jackson
- Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Stephen L. Nutt
- Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
| | - Matthew P. McCormack
- The Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
- iCamuno Biotherapeutics, Melbourne, VIC, Australia
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2
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Watanabe H, Okada H, Hirose J, Omata Y, Matsumoto T, Matsumoto M, Nakamura M, Saito T, Miyamoto T, Tanaka S. Transcription factor Hhex negatively regulates osteoclast differentiation by controlling cyclin‐dependent kinase inhibitors. JBMR Plus 2022; 6:e10608. [PMID: 35434453 PMCID: PMC9009129 DOI: 10.1002/jbm4.10608] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 01/05/2022] [Accepted: 01/19/2022] [Indexed: 11/11/2022] Open
Abstract
We investigated the role of hematopoietically expressed homeobox protein (Hhex) in osteoclast development. Trimethylation of lysine 27 of histone H3 at the cis‐regulatory element of Hhex was maintained and that of lysine 4 was reduced during receptor activator of nuclear factor κB ligand (RANKL)‐induced osteoclastogenesis, which was associated with a reduction of Hhex expression. Overexpression of Hhex in bone marrow–derived macrophages inhibited, whereas Hhex suppression promoted, RANKL‐induced osteoclastogenesis in vitro. Conditional deletion of Hhex in osteoclast‐lineage cells promoted osteoclastogenesis and reduced cancellous bone volume in mice, confirming the negative regulatory role of Hhex in osteoclast differentiation. Expression of cyclin‐dependent kinase inhibitors such as Cdkn2a and Cdkn1b in osteoclast precursors was negatively regulated by Hhex, and Hhex deletion increased the ratio of cells at the G1 phase of the cell cycle. In conclusion, Hhex is an inhibitor of osteoclast differentiation that is regulated in an epigenetic manner and regulates the cell cycle of osteoclast precursors and the skeletal homeostasis. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
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Affiliation(s)
- Hisato Watanabe
- Department of Orthopaedic Surgery, Faculty of Medicine The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku Tokyo Japan
| | - Hiroyuki Okada
- Center for Disease Biology and Integrative Medicine, Graduate School of Medicine The University of Tokyo Tokyo Japan
| | - Jun Hirose
- Department of Orthopaedic Surgery, Faculty of Medicine The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku Tokyo Japan
| | - Yasunori Omata
- Department of Orthopaedic Surgery, Faculty of Medicine The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku Tokyo Japan
| | - Takumi Matsumoto
- Department of Orthopaedic Surgery, Faculty of Medicine The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku Tokyo Japan
| | - Morio Matsumoto
- Department of Orthopaedic Surgery Keio University School of Medicine Tokyo Japan
| | - Masaya Nakamura
- Department of Orthopaedic Surgery Keio University School of Medicine Tokyo Japan
| | - Taku Saito
- Department of Orthopaedic Surgery, Faculty of Medicine The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku Tokyo Japan
| | - Takeshi Miyamoto
- Department of Orthopedic Surgery Kumamoto University Kumamoto Japan
| | - Sakae Tanaka
- Department of Orthopaedic Surgery, Faculty of Medicine The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku Tokyo Japan
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Nagel S, Pommerenke C, MacLeod RAF, Meyer C, Kaufmann M, Drexler HG. The NKL-code for innate lymphoid cells reveals deregulated expression of NKL homeobox genes HHEX and HLX in anaplastic large cell lymphoma (ALCL). Oncotarget 2020; 11:3208-3226. [PMID: 32922661 PMCID: PMC7456612 DOI: 10.18632/oncotarget.27683] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 07/07/2020] [Indexed: 12/26/2022] Open
Abstract
NKL homeobox genes encode developmental transcription factors and display an NKL-code according to their physiological expression pattern in hematopoiesis. Here, we analyzed public transcriptome data from primary innate lymphoid cells (ILCs) for NKL homeobox gene activities and found that ILC3 expressed exclusively HHEX while in ILC1 and ILC2 these genes were silenced. Deregulation of the NKL-code promotes hematopoietic malignancies, including anaplastic large cell lymphoma (ALCL) which reportedly may derive from ILC3. Accordingly, we analyzed NKL homeobox gene activities in ALCL cell lines and investigated their role in this malignancy. Transcriptome analyses demonstrated low expression levels of HHEX but powerfully activated HLX. Forced expression of HHEX in ALCL cell lines induced genes involved in apoptosis and ILC3 differentiation, indicating tumor suppressor activity. ALCL associated NPM1-ALK and JAK-STAT3-signalling drove enhanced expression of HLX while discounting HHEX. Genomic profiling revealed copy number gains at the loci of HLX and STAT3 in addition to genes encoding both STAT3 regulators (AURKA, BCL3, JAK3, KPNB1, NAMPT, NFAT5, PIM3, ROCK1, SIX1, TPX2, WWOX) and targets (BATF3, IRF4, miR135b, miR21, RORC). Transcriptome data of ALCL cell lines showed absence of STAT3 mutations while MGA was mutated and downregulated, encoding a novel potential STAT3 repressor. Furthermore, enhanced IL17F-signalling activated HLX while TGFbeta-signalling inhibited HHEX expression. Taken together, our data extend the scope of the NKL-code for ILCs and spotlight aberrant expression of NKL homeobox gene HLX in ALCL. HLX represents a direct target of ALCL hallmark factor STAT3 and deregulates cell survival and differentiation in this malignancy.
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Affiliation(s)
- Stefan Nagel
- Department of Human and Animal Cell Lines, Leibniz Institute, DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Claudia Pommerenke
- Department of Human and Animal Cell Lines, Leibniz Institute, DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Roderick A F MacLeod
- Department of Human and Animal Cell Lines, Leibniz Institute, DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Corinna Meyer
- Department of Human and Animal Cell Lines, Leibniz Institute, DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Maren Kaufmann
- Department of Human and Animal Cell Lines, Leibniz Institute, DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Hans G Drexler
- Department of Human and Animal Cell Lines, Leibniz Institute, DSMZ - German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
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Kitchen P, Lee KY, Clark D, Lau N, Lertsuwan J, Sawasdichai A, Satayavivad J, Oltean S, Afford S, Gaston K, Jayaraman PS. A Runaway PRH/HHEX-Notch3-Positive Feedback Loop Drives Cholangiocarcinoma and Determines Response to CDK4/6 Inhibition. Cancer Res 2019; 80:757-770. [PMID: 31843982 DOI: 10.1158/0008-5472.can-19-0942] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 10/16/2019] [Accepted: 12/10/2019] [Indexed: 12/21/2022]
Abstract
Aberrant Notch and Wnt signaling are known drivers of cholangiocarcinoma (CCA), but the underlying factors that initiate and maintain these pathways are not known. Here, we show that the proline-rich homeodomain protein/hematopoietically expressed homeobox (PRH/HHEX) transcription factor forms a positive transcriptional feedback loop with Notch3 that is critical in CCA. PRH/HHEX expression is elevated in CCA, and depletion of PRH reduces CCA tumor growth in a xenograft model. Overexpression of PRH in primary human biliary epithelial cells is sufficient to increase cell proliferation and produce an invasive phenotype. Interrogation of the gene networks regulated by PRH and Notch3 reveals that unlike Notch3, PRH directly activates canonical Wnt signaling. These data indicate that hyperactivation of Notch and Wnt signaling is independent of the underlying mutational landscape and has a common origin in dysregulation of PRH. Moreover, they suggest new therapeutic options based on the dependence of specific Wnt, Notch, and CDK4/6 inhibitors on PRH activity. SIGNIFICANCE: The PRH/HHEX transcription factor is an oncogenic driver in cholangiocarcinoma that confers sensitivity to CDK4/6 inhibitors.
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Affiliation(s)
- Philip Kitchen
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Ka Ying Lee
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Danielle Clark
- Department of Biochemistry, Medical School, University of Bristol, Bristol, United Kingdom
| | - Nikki Lau
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Jomnarong Lertsuwan
- Laboratory of Chemical Carcinogenesis, Chulabhorn Research Institute, Bangkok, Thailand
| | - Anyaporn Sawasdichai
- Laboratory of Chemical Carcinogenesis, Chulabhorn Research Institute, Bangkok, Thailand
| | | | - Sebastian Oltean
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
| | - Simon Afford
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Kevin Gaston
- Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, United Kingdom.
| | - Padma-Sheela Jayaraman
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
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Selection of reliable reference genes for normalization of quantitative RT-PCR from different developmental stages and tissues in amphioxus. Sci Rep 2016; 6:37549. [PMID: 27869224 PMCID: PMC5116582 DOI: 10.1038/srep37549] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 11/01/2016] [Indexed: 12/13/2022] Open
Abstract
Amphioxus is a closest living proxy to the ancestor of cephalochordates with vertebrates, and key animal for novel understanding in the evolutionary origin of vertebrate body plan, genome, tissues and immune system. Reliable analyses using quantitative real-time PCR (qRT-PCR) for answering these scientific questions is heavily dependent on reliable reference genes (RGs). In this study, we evaluated stability of thirteen candidate RGs in qRT-PCR for different developmental stages and tissues of amphioxus by four independent (geNorm, NormFinder, BestKeeper and deltaCt) and one comparative algorithms (RefFinder). The results showed that the top two stable RGs were the following: (1) S20 and 18 S in thirteen developmental stages, (2) EF1A and ACT in seven normal tissues, (3) S20 and L13 in both intestine and hepatic caecum challenged with lipopolysaccharide (LPS), and (4) S20 and EF1A in gill challenged with LPS. The expression profiles of two target genes (EYA and HHEX) in thirteen developmental stages were used to confirm the reliability of chosen RGs. This study identified optimal RGs that can be used to accurately measure gene expression under these conditions, which will benefit evolutionary and functional genomics studies in amphioxus.
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Saulle E, Petronelli A, Pelosi E, Coppotelli E, Pasquini L, Ilari R, Lo-Coco F, Testa U. PML-RAR alpha induces the downmodulation of HHEX: a key event responsible for the induction of an angiogenetic response. J Hematol Oncol 2016; 9:33. [PMID: 27052408 PMCID: PMC4823896 DOI: 10.1186/s13045-016-0262-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 03/30/2016] [Indexed: 12/14/2022] Open
Abstract
Background Recent studies indicate that angiogenesis is important in the pathogenesis of acute myeloid leukemias (AMLs). Among the various AMLs, the bone marrow angiogenetic response is particularly pronounced in acute promyelocytic leukemia (APL). However, the molecular mechanisms responsible for this angiogenetic response are largely unknown. In the present study, we have explored the role of HHEX, a homeodomain transcription factor, as a possible mediator of the pro-angiogenetic response observed in APL. This transcription factor seems to represent an ideal candidate for this biologic function because it is targeted by PML-RARα, is capable of interaction with PML and PML-RARα, and acts as a regulator of the angiogenetic response. Methods We used various cellular systems of APL, including primary APL cells and leukemic cells engineered to express PML-RARα, to explore the role of the PML-RARα fusion protein on HHEX expression. Molecular and biochemical techniques have been used to investigate the mechanisms through which PML-RARα downmodulates HHEX and the functional consequences of this downmodulation at the level of the expression of various angiogenetic genes, cell proliferation and differentiation. Results Our results show that HHEX expression is clearly downmodulated in APL and that this effect is directly mediated by a repressive targeting of the HHEX gene promoter by PML-RARα. Studies carried out in primary APL cells and in a cell line model of APL with inducible PML-RARα expression directly support the view that this fusion protein through HHEX downmodulation stimulates the expression of various genes involved in angiogenesis and inhibits cell differentiation. Conclusions Our data suggest that HHEX downmodulation by PML-RARα is a key event during APL pathogenesis. Electronic supplementary material The online version of this article (doi:10.1186/s13045-016-0262-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ernestina Saulle
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Alessia Petronelli
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Elvira Pelosi
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Elena Coppotelli
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Luca Pasquini
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Ramona Ilari
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy
| | - Francesco Lo-Coco
- Department of Biomedicine and Prevention, University of Rome "Tor Vergata" and Fondazione Santa Lucia, Rome, Italy
| | - Ugo Testa
- Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy.
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Gaston K, Tsitsilianos MA, Wadey K, Jayaraman PS. Misregulation of the proline rich homeodomain (PRH/HHEX) protein in cancer cells and its consequences for tumour growth and invasion. Cell Biosci 2016; 6:12. [PMID: 26877867 PMCID: PMC4752775 DOI: 10.1186/s13578-016-0077-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 02/01/2016] [Indexed: 02/07/2023] Open
Abstract
The proline rich homeodomain protein (PRH), also known as haematopoietically expressed homeobox (HHEX), is an essential transcription factor in embryonic development and in the adult. The PRH protein forms oligomeric complexes that bind to tandemly repeated PRH recognition sequences within or at a distance from PRH-target genes and recruit a variety of PRH-interacting proteins. PRH can also bind to other transcription factors and co-regulate specific target genes either directly through DNA binding, or indirectly through effects on the activity of its partner proteins. In addition, like some other homeodomain proteins, PRH can regulate the translation of specific mRNAs. Altered PRH expression and altered PRH intracellular localisation, are associated with breast cancer, liver cancer and thyroid cancer and some subtypes of leukaemia. This is consistent with the involvement of multiple PRH-interacting proteins, including the oncoprotein c-Myc, translation initiation factor 4E (eIF4E), and the promyelocytic leukaemia protein (PML), in the control of cell proliferation and cell survival. Similarly, multiple PRH target genes, including the genes encoding vascular endothelial growth factor (VEGF), VEGF receptors, Endoglin, and Goosecoid, are known to be important in the control of cell proliferation and cell survival and/or the regulation of cell migration and invasion. In this review, we summarise the evidence that implicates PRH in tumourigenesis and we review the data that suggests PRH levels could be useful in cancer prognosis and in the choice of treatment options.
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Affiliation(s)
- Kevin Gaston
- School of Biochemistry, University Walk, University of Bristol, Bristol, BS8 1TD UK
| | | | - Kerry Wadey
- School of Biochemistry, University Walk, University of Bristol, Bristol, BS8 1TD UK
| | - Padma-Sheela Jayaraman
- Division of Immunity and Infection, School of Medicine, University of Birmingham, Edgbaston, Birmingham, B15 2TT UK
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Abstract
The hematopoietically expressed homeobox gene, Hhex, is a transcription factor that is important for development of definitive hematopoietic stem cells (HSCs) and B cells, and that causes T-cell leukemia when overexpressed. Here, we have used an Hhex inducible knockout mouse model to study the role of Hhex in adult hematopoiesis. We found that loss of Hhex was tolerated in HSCs and myeloid lineages, but resulted in a progressive loss of B lymphocytes in the circulation. This was accompanied by a complete loss of B-cell progenitors in the bone marrow and of transitional B-cell subsets in the spleen. In addition, transplantation and in vitro culture experiments demonstrated an almost complete failure of Hhex-null HSCs to contribute to lymphoid lineages beyond the common lymphoid precursor stage, including T cells, B cells, NK cells, and dendritic cells. Gene expression analysis of Hhex-deleted progenitors demonstrated deregulated expression of a number of cell cycle regulators. Overexpression of one of these, cyclin D1, could rescue the B-cell developmental potential of Hhex-null lymphoid precursors. Thus, Hhex is a key regulator of early lymphoid development, functioning, at least in part, via regulation of the cell cycle.
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Jalili S, Karami L, Schofield J. Study of base pair mutations in proline-rich homeodomain (PRH)-DNA complexes using molecular dynamics. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2013; 42:427-40. [PMID: 23385423 DOI: 10.1007/s00249-013-0892-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/11/2012] [Accepted: 01/21/2013] [Indexed: 11/26/2022]
Abstract
Proline-rich homeodomain (PRH) is a regulatory protein controlling transcription and gene expression processes by binding to the specific sequence of DNA, especially to the sequence 5'-TAATNN-3'. The impact of base pair mutations on the binding between the PRH protein and DNA is investigated using molecular dynamics and free energy simulations to identify DNA sequences that form stable complexes with PRH. Three 20-ns molecular dynamics simulations (PRH-TAATTG, PRH-TAATTA and PRH-TAATGG complexes) in explicit solvent water were performed to investigate three complexes structurally. Structural analysis shows that the native TAATTG sequence forms a complex that is more stable than complexes with base pair mutations. It is also observed that upon mutation, the number and occupancy of the direct and water-mediated hydrogen bonds decrease. Free energy calculations performed with the thermodynamic integration method predict relative binding free energies of 0.64 and 2 kcal/mol for GC to AT and TA to GC mutations, respectively, suggesting that among the three DNA sequences, the PRH-TAATTG complex is more stable than the two mutated complexes. In addition, it is demonstrated that the stability of the PRH-TAATTA complex is greater than that of the PRH-TAATGG complex.
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Affiliation(s)
- Seifollah Jalili
- Department of Chemistry, K. N. Toosi University of Technology, P.O. Box 15875-4416, Tehran, Iran.
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Jalili S, Karami L. Study of intermolecular contacts in the proline-rich homeodomain (PRH)–DNA complex using molecular dynamics simulations. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 41:329-40. [DOI: 10.1007/s00249-012-0790-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 01/03/2012] [Accepted: 01/16/2012] [Indexed: 10/14/2022]
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Abstract
The development and emergence of the hematopoietic stem cell involves a series of tightly regulated molecular events that are not well characterized. The hematopoietically expressed homeobox (Hhex) gene, a member of the homeobox gene family, is an essential regulator of embryogenesis and hematopoietic progenitor development. To investigate the role of Hhex in hematopoiesis we adapted a murine embryonic stem (ES) cell coculture system, in which ES cells can differentiate into CD41(+) and CD45(+) hematopoietic progenitors in vitro. Our results show that in addition to delayed hemangioblast development, Hhex(-/-) ES-derived progeny accumulate as CD41(+) and CD41(+)c-kit(+) cells, or the earliest definitive hematopoietic progenitors. In addition, Hhex(-/-) ES-derived progeny display a significantly reduced ability to develop into mature CD45(+) hematopoietic cells. The observed reduction in hematopoietic maturation was accompanied by reduced proliferation, because Hhex(-/-) CD41(+)CD45(-)c-kit(+) hematopoietic progenitors accumulated in the G(2) phase of the cell cycle. Thus, Hhex is a critical regulator of hematopoietic development and is necessary for the maturation and proliferation of the earliest definitive hematopoietic progenitors.
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12
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PRH/Hhex controls cell survival through coordinate transcriptional regulation of vascular endothelial growth factor signaling. Mol Cell Biol 2010; 30:2120-34. [PMID: 20176809 DOI: 10.1128/mcb.01511-09] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The proline-rich homeodomain protein (PRH) plays multiple roles in the control of gene expression during embryonic development and in the adult. Vascular endothelial growth factor (VEGF) is a mitogen that stimulates cell proliferation and survival via cell surface receptors including VEGFR-1 and VEGFR-2. VEGF signaling is of critical importance in angiogenesis and hematopoiesis and is elevated in many tumors. Here we show that PRH binds directly to the promoter regions of the Vegf, Vegfr-1, and Vegfr-2 genes and that in each case PRH represses transcription. We demonstrate that overexpression or knockdown of PRH directly impinges on the survival of both leukemic and tumor cells and that the modulation of VEGF and VEGF receptor signaling by PRH mediates these effects. Our findings demonstrate that PRH is a key regulator of the VEGF signaling pathway and describe a mechanism whereby PRH plays an important role in tumorigenesis and leukemogenesis.
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Ploski JE, Topisirovic I, Park KW, Borden KLB, Radu A. A mechanism of nucleocytoplasmic trafficking for the homeodomain protein PRH. Mol Cell Biochem 2009; 332:173-81. [PMID: 19588232 DOI: 10.1007/s11010-009-0188-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 06/25/2009] [Indexed: 11/24/2022]
Abstract
Proline-rich homeodomain (PRH)/hematopoietically expressed homeodomain (Hex) is a homeodomain protein that plays an important role in early embryonic patterning and hematopoiesis. PRH can act as either a tumor suppressor or an oncogene and its expression is dysregulated in certain types of lymphoid and myeloid leukemias. Aberrant exclusion of PRH from the nuclei has been associated with thyroid and breast cancers and a subset of myeloid leukemias. Accordingly, nuclear localization of PRH was found to be necessary for the inhibition of eIF4E-dependent transformation. Since PRH's nuclear-cytoplasmic localization has been associated with neoplastic transformation we sought to better understand how PRH is transported to the nuclear compartment. Here, we report an essential element that controls the mechanism of PRH nucleocytoplasmic trafficking, namely that it is imported into the nuclei by Karyopherin/Importin 7. Kap7 was identified as a binding partner for PRH in a GST-pull down from a HeLa cell protein lysate, followed by mass-spectrometry. The Kap7-PRH complex is dissociated in the presence of RanGTP, as expected for a nuclear import complex. Kap7 can bind directly to PRH in a GST-pull down assay with purified proteins, as well as mediates the transport of PRH to the nuclear compartment in a digitonin permeabilized cells assay. Finally, in vivo depletion of Kap7 dramatically reduces accumulation of PRH in the nucleus. Our data open the way for investigations of the mechanism of perturbed PRH localization in tumors and possible therapeutic interventions.
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Soufi A, Noy P, Buckle M, Sawasdichai A, Gaston K, Jayaraman PS. CK2 phosphorylation of the PRH/Hex homeodomain functions as a reversible switch for DNA binding. Nucleic Acids Res 2009; 37:3288-300. [PMID: 19324893 PMCID: PMC2691835 DOI: 10.1093/nar/gkp197] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The proline-rich homeodomain protein (PRH/Hex) regulates transcription by binding to specific DNA sequences and regulates mRNA transport by binding to translation initiation factor eIF4E. Protein kinase CK2 plays multiple roles in the regulation of gene expression and cell proliferation. Here, we show that PRH interacts with the β subunit of CK2 in vitro and in cells and that CK2 phosphorylates PRH. Phosphorylation of PRH by CK2 inhibits the DNA binding activity of this protein and dephosphorylation restores DNA binding indicating that this modification acts as a reversible switch. We show that phosphorylation of the homeodomain is sufficient to block DNA binding and we identify two amino acids within this the domain that are phosphorylated by CK2: S163 and S177. Site-directed mutagenesis demonstrates that mutation of either of these residues to glutamic acid partially mimics phosphorylation but is insufficient to completely block DNA binding whereas an S163E/S177E double mutation severely inhibits DNA binding. Significantly, the S163E and S177E mutations and the S163E/S177E double mutation all inhibit the ability of PRH to regulate transcription in cells. Since these amino acids are conserved between many homeodomain proteins, our results suggest that CK2 may regulate the activity of several homeodomain proteins in this manner.
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Affiliation(s)
- Abdenour Soufi
- Institute for Biomedical Research, Birmingham University Medical School, Edgbaston, Birmingham, B15 2TT, UK
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15
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Abstract
The PRH (proline-rich homeodomain) [also known as Hex (haematopoietically expressed homeobox)] protein is a transcription factor that functions as an important regulator of vertebrate development and many other processes in the adult including haematopoiesis. The Groucho/TLE (transducin-like enhancer) family of co-repressor proteins also regulate development and modulate the activity of many DNA-binding transcription factors during a range of diverse cellular processes including haematopoiesis. We have shown previously that PRH is a repressor of transcription in haematopoietic cells and that an Eh-1 (Engrailed homology) motif present within the N-terminal transcription repression domain of PRH mediates binding to Groucho/TLE proteins and enables co-repression. In the present study we demonstrate that PRH regulates the nuclear retention of TLE proteins during cellular fractionation. We show that transcriptional repression and the nuclear retention of TLE proteins requires PRH to bind to both TLE and DNA. In addition, we characterize a trans-dominant-negative PRH protein that inhibits wild-type PRH activity by sequestering TLE proteins to specific subnuclear domains. These results demonstrate that transcriptional repression by PRH is dependent on TLE availability and suggest that subnuclear localization of TLE plays an important role in transcriptional repression by PRH.
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Williams H, Jayaraman PS, Gaston K. DNA wrapping and distortion by an oligomeric homeodomain protein. J Mol Biol 2008; 383:10-23. [PMID: 18755198 DOI: 10.1016/j.jmb.2008.08.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 07/04/2008] [Accepted: 08/01/2008] [Indexed: 12/29/2022]
Abstract
Many transcription factors alter DNA or chromatin structure. Changes in chromatin structure are often brought about by the recruitment of chromatin-binding proteins, chromatin-modifying proteins, or other transcription co-activator or co-repressor proteins. However, some transcription factors form oligomeric assemblies that may themselves induce changes in DNA conformation and chromatin structure. The proline-rich homeodomain (PRH/Hex) protein is a transcription factor that regulates cell differentiation and cell proliferation, and has multiple roles in embryonic development. Earlier, we showed that PRH can repress transcription by multiple mechanisms, including the recruitment of co-repressor proteins belonging to the TLE family of chromatin-binding proteins. Our in vivo crosslinking studies have shown that PRH forms oligomeric complexes in cells and a variety of biophysical techniques suggest that the protein forms octamers. However, as yet we have little knowledge of the role played by PRH oligomerisation in the regulation of promoter activity or of the architecture of promoters that are regulated directly by PRH in cells. Here, we compare the binding of PRH and the isolated PRH homeodomain to DNA fragments with single and multiple PRH sites, using gel retardation assays and DNase I and chemical footprinting. We show that the PRH oligomer binds to multiple sites within the human Goosecoid promoter with high affinity and that the binding of PRH brings about DNA distortion. We suggest that PRH octamers wrap DNA in order to bring about transcriptional repression.
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Affiliation(s)
- Hannah Williams
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, UK
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17
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Abstract
The PRH (proline-rich homeodomain) [also known as Hex (haematopoietically expressed homeobox)] protein is a critical regulator of vertebrate development. PRH is able to regulate cell proliferation and differentiation and is required for the formation of the vertebrate body axis, the haematopoietic and vascular systems and the formation of many vital organs. PRH is a DNA-binding protein that can repress and activate the transcription of its target genes using multiple mechanisms. In addition, PRH can regulate the nuclear transport of specific mRNAs making PRH a member of a select group of proteins that control gene expression at the transcriptional and translational levels. Recent biophysical analysis of the PRH protein has shown that it forms homo-oligomeric complexes in vivo and in vitro and that the proline-rich region of PRH forms a novel dimerization interface. Here we will review the current literature on PRH and discuss the complex web of interactions centred on this multifunctional protein.
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18
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Soufi A, Smith C, Clarke AR, Gaston K, Jayaraman PS. Oligomerisation of the developmental regulator proline rich homeodomain (PRH/Hex) is mediated by a novel proline-rich dimerisation domain. J Mol Biol 2006; 358:943-62. [PMID: 16540119 DOI: 10.1016/j.jmb.2006.02.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 02/02/2006] [Accepted: 02/02/2006] [Indexed: 11/22/2022]
Abstract
Homeodomain proteins regulate multiple developmental pathways by altering gene expression temporally and in a tissue-specific fashion. The Proline Rich Homeodomain protein (PRH/Hex) is a transcription factor and an essential regulator of embryonic development and haematopoiesis. Recent discoveries have implicated self-association as an important feature of transcription factor function. Here, we show using a variety of techniques including gel-filtration, analytical ultracentrifugation, electron microscopy and in vitro cross-linking, that purified recombinant PRH is oligomeric and we use in vivo cross-linking to confirm that this protein exists as oligomers in cells. This is the first demonstration that a homeodomain protein can oligomerise in vivo. Consistent with these findings we show that a fraction of endogenous and exogenous PRH appears as discrete foci within the nucleus and at the nuclear periphery. The N-terminal domain of PRH is involved in the regulation of cell proliferation and transcriptional repression and can make multiple protein-protein interactions. We show that this region of PRH contains a novel proline-rich dimerisation domain that mediates oligomerisation. We propose a model that explains how PRH forms oligomers and we discuss how these oligomers might control transcription.
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Affiliation(s)
- Abdenour Soufi
- Department of Biochemistry, University of Bristol, University Walk, Bristol BS81TD, UK
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19
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Soufi A, Gaston K, Jayaraman PS. Purification and characterisation of the PRH homeodomain: Removal of the N-terminal domain of PRH increases the PRH homeodomain-DNA interaction. Int J Biol Macromol 2006; 39:45-50. [PMID: 16494938 DOI: 10.1016/j.ijbiomac.2006.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Revised: 01/18/2006] [Accepted: 01/18/2006] [Indexed: 11/27/2022]
Abstract
The Proline-Rich Homeodomain (PRH) protein is a regulator of transcription and translation and plays a key role in the control of cell proliferation and cell differentiation. PRH contains an N-terminal proline-rich domain that can repress transcription when expressed as a fusion protein with an unrelated DNA binding domain, a central homeodomain that binds to specific DNA sequences and an acidic C-terminal domain of no known function. In order to investigate the structure and functions of PRH we have purified the full-length protein and truncated proteins corresponding to different domains of PRH fused to histidine tags. Here we compare the effects of elution conditions and column volume on protein purification and we investigate the DNA binding activity of these proteins. We show that the PRH homeodomain co-purifies with nucleic acids even after nuclease treatment and that a high salt-wash is required to remove bound nucleic acids. In contrast with the full-length PRH protein, the PRH homeodomain binds to DNA with high affinity. We show that a truncated protein comprising the homeodomain and C-terminal domain also binds to DNA with high affinity and we conclude that the N-terminal domain of PRH inhibits the homeodomain-DNA interaction.
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Affiliation(s)
- Abdenour Soufi
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK
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20
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Djavani M, Topisirovic I, Zapata JC, Sadowska M, Yang Y, Rodas J, Lukashevich IS, Bogue CW, Pauza CD, Borden KLB, Salvato MS. The proline-rich homeodomain (PRH/HEX) protein is down-regulated in liver during infection with lymphocytic choriomeningitis virus. J Virol 2005; 79:2461-73. [PMID: 15681447 PMCID: PMC546565 DOI: 10.1128/jvi.79.4.2461-2473.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The proline-rich homeodomain protein, PRH/HEX, participates in the early development of the brain, thyroid, and liver and in the later regenerative processes of damaged liver, vascular endothelial, and hematopoietic cells. A virulent strain of lymphocytic choriomeningitis virus (LCMV-WE) that destroys hematopoietic, vascular, and liver functions also alters the transcription and subcellular localization of PRH. A related virus (LCMV-ARM) that does not cause disease in primates can infect cells without affecting PRH. Biochemical experiments demonstrated the occurrence of binding between the viral RING protein (Z) and PRH, and genetic experiments mapped the PRH-suppressing phenotype to the large (L) segment of the viral genome, which encodes the Z and polymerase genes. The Z protein is clearly involved with PRH, but other viral determinants are needed to relocate PRH and to promote disease. By down-regulating PRH, the arenavirus is able to eliminate the antiproliferative effects of PRH and to promote liver cell division. The interaction of an arenavirus with a homeodomain protein suggests a mechanism for viral teratogenic effects and for the tissue-specific manifestations of arenavirus disease.
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Affiliation(s)
- Mahmoud Djavani
- Institute of Human Virology, University of Maryland Biotechnology Institute, 725 West Lombard St., Baltimore, MD 21201, USA
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21
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Kubo A, Chen V, Kennedy M, Zahradka E, Daley GQ, Keller G. The homeobox gene HEX regulates proliferation and differentiation of hemangioblasts and endothelial cells during ES cell differentiation. Blood 2005; 105:4590-7. [PMID: 15728128 PMCID: PMC1895005 DOI: 10.1182/blood-2004-10-4137] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this report we have investigated the role of the homeobox gene Hex in the development and differentiation of the blast colony-forming cell (BL-CFC), a progenitor with hemangioblast characteristics generated in embryonic stem (ES) cell-derived embryoid bodies (EBs). Molecular analysis showed that Hex is expressed in mesoderm, in populations that contain BL-CFCs, and in blast cell colonies, the progeny of the BL-CFCs. Hex(-/-) EBs displayed a defect in macrophage development but generated higher numbers of BL-CFCs than did wild-type EBs. In addition to differences in these progenitor populations, we also found that endothelial cells from the Hex(-/-) EBs showed enhanced proliferative potential compared with those from wild-type EBs. Forced expression of Hex at the onset of ES cell differentiation resulted in reduced EB cellularity, fetal liver kinase-1 (Flk-1) expression, and BL-CFC development. Taken together, these findings demonstrate that Hex functions at multiple stages of development within the differentiating EBs and uncover a novel role for this transcription factor as a negative regulator of the hemangioblast and the endothelial lineage.
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Affiliation(s)
- Atsushi Kubo
- Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA
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22
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Swingler TE, Bess KL, Yao J, Stifani S, Jayaraman PS. The proline-rich homeodomain protein recruits members of the Groucho/Transducin-like enhancer of split protein family to co-repress transcription in hematopoietic cells. J Biol Chem 2004; 279:34938-47. [PMID: 15187083 DOI: 10.1074/jbc.m404488200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proline-rich homeodomain protein (PRH/Hex) is important in the control of cell proliferation and differentiation and in the regulation of multiple processes in embryonic development. We have shown previously that PRH contains two domains that can independently bring about transcriptional repression. The PRH homeodomain represses transcription by binding to TATA box sequences, whereas the proline-rich N-terminal domain of PRH can repress transcription when attached to a heterologous DNA-binding domain. The Groucho/transducin-like enhancer of split (TLE) family of proteins are transcriptional co-repressors that interact with a number of DNA-bound transcription factors and play multiple roles in development. Here we demonstrate that the proline-rich N-terminal domain of PRH binds to TLE1 in vitro and in yeast two-hybrid assays. We show that PRH and TLE proteins are co-expressed in hematopoietic cells and interact in co-immunoprecipitation assays. We demonstrate that TLE1 increases repression by PRH in transient transfection assays and that titration of endogenous TLE proteins by co-expression of Grg5, a natural trans-dominant negative protein, alleviates transcriptional repression by PRH. Finally, we show that a mutation in the PRH N-terminal domain that blocks the PRH-TLE1 interaction in vitro eliminates co-repression. We discuss these results in terms of the roles of PRH and TLE in cell differentiation and development.
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Affiliation(s)
- Tracey E Swingler
- Department of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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23
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Sato A, Keng VW, Yamamoto T, Kasamatsu S, Ban T, Tanaka H, Satoh SI, Yamada K, Noguchi T. Identification and Characterization of the Hematopoietic Cell-Specific Enhancer-Like Element of the Mouse Hex Gene. J Biochem 2004; 135:259-68. [PMID: 15047729 DOI: 10.1093/jb/mvh031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hex is one of the homeobox genes suggested to be important for hematopoietic cell differentiation. However, its biological function and mechanism of transcriptional regulation in hematopoietic cells remain elusive. We have identified the regulatory region necessary for transcription of the mouse Hex gene in K562 leukemia cells through transient reporter assays involving various deletion mutants. This region, comprising +775 to +1177 in the first intron, had enhancer-like properties and showed high activity in other hematopoietic cell lines such as U937, HEL, and RAW264.7, but little activity in other Hex-expressing cell lines such as MH(1)C(1) and H4IIE hepatoma cells, suggesting that this region functions as a hematopoietic cell-specific enhancer-like element. Binding site mutation of hematopoietic transcription factors, such as GATAs and c-Myb present in the enhancer-like element, significantly decreased the luciferase reporter gene expression in K562 cells. Electrophoretic mobility shift assays showed that GATA-1, GATA-2, or c-Myb actually binds to three of these putative binding sites, and also suggested that several unidentified factors might interact with the enhancer-like element. Overexpression of GATA-1, GATA-2, or c-Myb stimulated the enhancer-like activity via these three binding sites. Thus, we conclude that Hex expression in hematopoietic cells is mainly regulated by GATA-1, GATA-2, and c-Myb via this intronic enhancer-like element.
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Affiliation(s)
- Ayuko Sato
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601
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24
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George A, Morse HC, Justice MJ. The homeobox gene Hex induces T-cell-derived lymphomas when overexpressed in hematopoietic precursor cells. Oncogene 2003; 22:6764-73. [PMID: 14555989 DOI: 10.1038/sj.onc.1206822] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Proviral insertions at the viral insertion site Lvis1 occur frequently in B- and T-cell leukemias and lymphomas in AKXD mice and activate two nearby genes, the divergent homeobox gene Hex and the kinesin-related spindle protein gene Eg5. To determine whether Hex misexpression results in the altered differentiation or neoplastic transformation of hematopoietic lineages, we have transplanted mice with bone marrow cells transduced with retrovirus containing the Hex coding region. High levels of Hex expression in hematopoietic precursor cells inhibit contribution to mature blood cell lineages by these precursors. Hex bone marrow transplant recipient mice also develop hematologic neoplasms that appear to originate in the bone marrow. The tumors have clonal rearrangements of the TCR locus, are Thy1+, and are CD4+CD8+, CD4-CD8-, or mixed, indicating tumor origin from a precursor T-cell population. Tumors in transplant mice contain clonal and transcriptionally active Hex proviral insertions, demonstrating a causal role for Hex misexpression in the onset of these neoplasms. Our results demonstrate that Hex can act as a T lineage oncogene when misexpressed in hematopoietic precursor cells.
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Affiliation(s)
- Alex George
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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25
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Bess KL, Swingler TE, Rivett AJ, Gaston K, Jayaraman PS. The transcriptional repressor protein PRH interacts with the proteasome. Biochem J 2003; 374:667-75. [PMID: 12826010 PMCID: PMC1223646 DOI: 10.1042/bj20030769] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2003] [Accepted: 06/25/2003] [Indexed: 02/07/2023]
Abstract
PRH (proline-rich homeodomain protein)/Hex is important in the control of cell proliferation and differentiation. We have shown previously that PRH contains two domains that can bring about transcriptional repression independently; the PRH homeodomain represses transcription by binding to TATA box sequences, whereas the proline-rich N-terminal domain can repress transcription by interacting with members of the Groucho/TLE (transducin-like enhancer of split) family of co-repressor proteins. The proteasome is a multi-subunit protein complex involved in the processing and degradation of proteins. Some proteasome subunits have been suggested to play a role in the regulation of transcription. In the present study, we show that PRH interacts with the HC8 subunit of the proteasome in the context of both 20 and 26 S proteasomes. Moreover, we show that PRH is associated with the proteasome in haematopoietic cells and that the proline-rich PRH N-terminal domain is responsible for this interaction. Whereas PRH can be cleaved by the proteasome, it does not appear to be degraded rapidly in vitro or in vivo, and the proteolytic activity of the proteasome is not required for transcriptional repression by PRH. However, proteasomal digestion of PRH can liberate truncated PRH proteins that retain the ability to bind to DNA. We discuss these findings in terms of the biological role of PRH in gene regulation and the control of cell proliferation.
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Affiliation(s)
- Kirstin L Bess
- Department of Biochemistry, University of Bristol, University Walk, Bristol BS81TD, UK
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26
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Butcher AJ, Gaston K, Jayaraman PS. Purification of the proline-rich homeodomain protein. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 786:3-6. [PMID: 12650996 DOI: 10.1016/s1570-0232(02)00740-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The proline-rich homeodomain protein (PRH), also known as Hex, is a transcriptional repressor expressed in a variety of cell types. The PRH protein contains a proline-rich N-terminal domain that can repress transcription when attached to a heterologous DNA binding domain, a central homeodomain that mediates sequence-specific DNA binding, and an acidic C-terminal domain of unknown function. Although individual domains of PRH have been expressed in bacterial cells as GST- and histidine-tagged fusion proteins, attempts to express and purify the full-length protein have met with little success. Here we describe the purification of a histidine-tagged full-length PRH fusion protein. The protein described here will allow us to determine the mechanisms whereby PRH represses transcription.
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Affiliation(s)
- Amy J Butcher
- Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol, UK BS8 1TD
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27
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Drabkin HA, Parsy C, Ferguson K, Guilhot F, Lacotte L, Roy L, Zeng C, Baron A, Hunger SP, Varella-Garcia M, Gemmill R, Brizard F, Brizard A, Roche J. Quantitative HOX expression in chromosomally defined subsets of acute myelogenous leukemia. Leukemia 2002; 16:186-95. [PMID: 11840284 DOI: 10.1038/sj.leu.2402354] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2001] [Accepted: 09/25/2001] [Indexed: 02/02/2023]
Abstract
We used a degenerate RT-PCR screen and subsequent real-time quantitative RT-PCR assays to examine the expression of HOX and TALE-family genes in 34 cases of chromosomally defined AML for which outcome data were available. AMLs with favorable cytogenetic features were associated with low overall HOX gene expression whereas poor prognostic cases had high levels. Characteristically, multiple HOXA family members including HOXA3-HOXA10 were jointly overexpressed in conjunction with HOXB3, HOXB6, MEIS1 and PBX3. Higher levels of expression were also observed in the FAB subtype, AML-M1. Spearmann correlation coefficients indicated that the expression levels for many of these genes were highly inter-related. While we did not detect any significant correlations between HOX expression and complete response rates or age in this limited set of patients, there was a significant correlation between event-free survival and HOXA7 with a trend toward significance for HoxA9, HoxA4 and HoxA5. While patients with elevated HOX expression did worse, there were notable exceptions. Thus, although HOX overexpression and clinical resistance to chemotherapy often coincide, they are not inextricably linked. Our results indicate that quantitative HOX analysis has the potential to add new information to the management of patients with AML, especially where characteristic chromosomal alterations are lacking.
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Affiliation(s)
- H A Drabkin
- Division of Medical Oncology, University of Colorado Health Sciences and Cancer Centers, Denver, CO 80262, USA
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28
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Guiral M, Bess K, Goodwin G, Jayaraman PS. PRH represses transcription in hematopoietic cells by at least two independent mechanisms. J Biol Chem 2001; 276:2961-70. [PMID: 11054411 DOI: 10.1074/jbc.m004948200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PRH (proline-rich homeodomain protein) is strongly expressed in the hematopoietic compartment. Here we show that PRH is a repressor of transcription in hematopoietic cells. A fragment of PRH that includes the homeodomain can bind to TATA box sequences in vitro and can also bind to the TATA box-binding protein. PRH represses transcription from TATA box-containing promoters in intact cells but does not repress transcription from a promoter lacking a TATA box. A mutation in the PRH homeodomain that blocks binding to DNA but that has little or no effect on binding to the TATA box-binding protein significantly reduces the ability of the protein to repress transcription and provides the first clear demonstration that a homeodomain can bring about transcriptional repression in vivo by binding to a TATA box. However, we also show that mutation of the PRH homeodomain does not block the ability of PRH to repress transcription when this protein is tethered upstream of the TATA box via a heterologous DNA-binding domain. PRH also contains an N-terminal proline-rich repression domain that is separate from the homeodomain. Deletion mapping suggests that this repression domain contains at least two regions that both independently contribute to transcriptional repression.
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Affiliation(s)
- M Guiral
- Department of Biochemistry, University of Bristol, University Walk, Bristol, United Kingdom
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