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Özden-Yılmaz G, Savas B, Bursalı A, Eray A, Arıbaş A, Senturk S, Karaca E, Karakülah G, Erkek-Ozhan S. Differential Occupancy and Regulatory Interactions of KDM6A in Bladder Cell Lines. Cells 2023; 12:cells12060836. [PMID: 36980177 PMCID: PMC10047809 DOI: 10.3390/cells12060836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 02/16/2023] [Accepted: 03/01/2023] [Indexed: 03/30/2023] Open
Abstract
Epigenetic deregulation is a critical theme which needs further investigation in bladder cancer research. One of the most highly mutated genes in bladder cancer is KDM6A, which functions as an H3K27 demethylase and is one of the MLL3/4 complexes. To decipher the role of KDM6A in normal versus tumor settings, we identified the genomic landscape of KDM6A in normal, immortalized, and cancerous bladder cells. Our results showed differential KDM6A occupancy in the genes involved in cell differentiation, chromatin organization, and Notch signaling depending on the cell type and the mutation status of KDM6A. Transcription factor motif analysis revealed HES1 to be enriched at KDM6A peaks identified in the T24 bladder cancer cell line; moreover, it has a truncating mutation in KDM6A and lacks a demethylase domain. Our co-immunoprecipitation experiments revealed TLE co-repressors and HES1 as potential truncated and wild-type KDM6A interactors. With the aid of structural modeling, we explored how truncated KDM6A could interact with TLE and HES1, as well as RUNX and HHEX transcription factors. These structures provide a solid means of studying the functions of KDM6A independently of its demethylase activity. Collectively, our work provides important contributions to the understanding of KDM6A malfunction in bladder cancer.
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Affiliation(s)
| | - Busra Savas
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
- Izmir International Biomedicine and Genome Institute, Dokuz Eylül University, Inciralti, 35340 Izmir, Turkey
| | - Ahmet Bursalı
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
| | - Aleyna Eray
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
- Izmir International Biomedicine and Genome Institute, Dokuz Eylül University, Inciralti, 35340 Izmir, Turkey
| | - Alirıza Arıbaş
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
| | - Serif Senturk
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
- Izmir International Biomedicine and Genome Institute, Dokuz Eylül University, Inciralti, 35340 Izmir, Turkey
| | - Ezgi Karaca
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
- Izmir International Biomedicine and Genome Institute, Dokuz Eylül University, Inciralti, 35340 Izmir, Turkey
| | - Gökhan Karakülah
- Izmir Biomedicine and Genome Center, Inciralti, 35340 Izmir, Turkey
- Izmir International Biomedicine and Genome Institute, Dokuz Eylül University, Inciralti, 35340 Izmir, Turkey
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Yu G, Chen Y, Hu Y, Zhou Y, Ding X, Zhou X. Roles of transducin-like enhancer of split (TLE) family proteins in tumorigenesis and immune regulation. Front Cell Dev Biol 2022; 10:1010639. [PMID: 36438567 PMCID: PMC9692235 DOI: 10.3389/fcell.2022.1010639] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/31/2022] [Indexed: 08/16/2023] Open
Abstract
Mammalian transducin-like enhancer of split family proteins (TLEs) are homologous to Drosophila Groucho (Gro) and are essential transcriptional repressors. Seven TLE family members, TLE1-7, have been identified to date. These proteins do not bind DNA directly; instead, they bind a set of transcription factors and thereby inhibit target gene expression. Loss of TLEs in mice usually leads to defective early development; however, TLE functions in developmentally mature cells are unclear. Recent studies have revealed that TLEs are dysregulated in certain human cancer types and may function as oncogenes or tumor suppressors in different contexts. TLE levels also affect the efficacy of cancer treatments and the development of drug resistance. In addition, TLEs play critical roles in the development and function of immune cells, including macrophages and lymphocytes. In this review, we provide updates on the expression, function, and mechanism of TLEs; discuss the roles played by TLEs in tumorigenesis and the inflammatory response; and elaborate on several TLE-associated signaling pathways, including the Notch, Wnt, and MAPK pathways. Finally, we discuss potential strategies for targeting TLEs in cancer therapy.
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Affiliation(s)
- Guiping Yu
- Department of Immunology, Nantong University, School of Medicine, Nantong, China
- Department of Cardiothoracic Surgery, The Affiliated Jiangyin Hospital of Nantong University, Jiangyin, China
| | - Yiqi Chen
- Department of Immunology, Nantong University, School of Medicine, Nantong, China
| | - Yuwen Hu
- Department of Immunology, Nantong University, School of Medicine, Nantong, China
| | - Yan Zhou
- Department of Periodontology, The Affiliated Nantong Stomatological Hospital of Nantong University, Nantong, China
| | - Xiaoling Ding
- Department of Gastroenterology, The Affiliated Hospital of Nantong University, Nantong, China
| | - Xiaorong Zhou
- Department of Immunology, Nantong University, School of Medicine, Nantong, China
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3
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Guo Y, Zhu Z, Huang Z, Cui L, Yu W, Hong W, Zhou Z, Du P, Liu CY. CK2-induced cooperation of HHEX with the YAP-TEAD4 complex promotes colorectal tumorigenesis. Nat Commun 2022; 13:4995. [PMID: 36008411 PMCID: PMC9411202 DOI: 10.1038/s41467-022-32674-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/11/2022] [Indexed: 11/23/2022] Open
Abstract
Dysregulation of Hippo pathway leads to hyperactivation of YAP-TEAD transcriptional complex in various cancers, including colorectal cancer (CRC). In this study, we observed that HHEX (Hematopoietically expressed homeobox) may enhance transcription activity of the YAP-TEAD complex. HHEX associates with and stabilizes the YAP-TEAD complex on the regulatory genomic loci to coregulate the expression of a group of YAP/TEAD target genes. Also, HHEX may indirectly regulate these target genes by controlling YAP/TAZ expression. Importantly, HHEX is required for the pro-tumorigenic effects of YAP during CRC progression. In response to serum stimulation, CK2 (Casein Kinase 2) phosphorylates HHEX and enhances its interaction with TEAD4. A CK2 inhibitor CX-4945 diminishes the interaction between HHEX and TEAD4, leading to decreased expression of YAP/TEAD target genes. CX-4945 synergizes the antitumor activity of YAP-TEAD inhibitors verteporfin and Super-TDU. Elevated expression of HHEX is correlated with hyperactivation of YAP/TEAD and associated with poor prognosis of CRC patients. Overall, our study identifies HHEX as a positive modulator of YAP/TEAD to promote colorectal tumorigenesis, providing a new therapeutic strategy for targeting YAP/TEAD in CRC. Hippo signalling is often deregulated in cancers. Here the authors show that CK2 enhances the cooperation of HHEX with YAP-TEAD complex to promote colorectal tumorigenesis.
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Affiliation(s)
- Yuegui Guo
- Department of Colorectal and Anal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.,Shanghai Colorectal Cancer Research Center, Shanghai, 200092, China
| | - Zhehui Zhu
- Department of Colorectal and Anal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.,Shanghai Colorectal Cancer Research Center, Shanghai, 200092, China.,State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China
| | - Zhenyu Huang
- Department of Colorectal and Anal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.,Shanghai Colorectal Cancer Research Center, Shanghai, 200092, China
| | - Long Cui
- Department of Colorectal and Anal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China.,Shanghai Colorectal Cancer Research Center, Shanghai, 200092, China
| | - Wei Yu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China
| | - Wanjin Hong
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), 61, Biopolis Drive, Proteos, Singapore, 138673, Singapore
| | - Zhaocai Zhou
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai, 200438, China.
| | - Peng Du
- Department of Colorectal and Anal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China. .,Shanghai Colorectal Cancer Research Center, Shanghai, 200092, China.
| | - Chen-Ying Liu
- Department of Colorectal and Anal Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, China. .,Shanghai Colorectal Cancer Research Center, Shanghai, 200092, China.
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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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Divvela SSK, Saberi D, Brand-Saberi B. Atoh8 in Development and Disease. BIOLOGY 2022; 11:biology11010136. [PMID: 35053134 PMCID: PMC8773363 DOI: 10.3390/biology11010136] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/10/2022] [Accepted: 01/11/2022] [Indexed: 01/07/2023]
Abstract
Atoh8 belongs to a large superfamily of transcriptional regulators called basic helix-loop-helix (bHLH) proteins. bHLH proteins have been identified in a wide range of organisms from yeast to humans. The members of this special group of transcription factors were found to be involved not only in embryonic development but also in disease initiation and its progression. Given their importance in several fundamental processes, the translation, subcellular location and turnover of bHLH proteins is tightly regulated. Alterations in the expression of bHLH proteins have been associated with multiple diseases also in context with Atoh8 which seems to unfold its functions as both transcriptional activator and repressor. Like many other bHLH transcription factors, so far, Atoh8 has also been observed to be involved in both embryonic development and carcinogenesis where it mainly acts as tumor suppressor. This review summarizes our current understanding of Atoh8 structure, function and regulation and its complex and partially controversial involvement in development and disease.
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Affiliation(s)
| | - Darius Saberi
- Department of Neurology, University Medical Center, 37099 Göttingen, Germany;
| | - Beate Brand-Saberi
- Department of Anatomy and Molecular Embryology, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany;
- Correspondence:
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Laidlaw BJ, Duan L, Xu Y, Vazquez SE, Cyster JG. The transcription factor Hhex cooperates with the corepressor Tle3 to promote memory B cell development. Nat Immunol 2020; 21:1082-1093. [PMID: 32601467 PMCID: PMC7442689 DOI: 10.1038/s41590-020-0713-6] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 05/15/2020] [Indexed: 11/08/2022]
Abstract
Memory B cells (MBCs) are essential for long-lived humoral immunity. However, the transcription factors involved in MBC differentiation are poorly defined. Here, using single-cell RNA sequencing analysis, we identified a population of germinal center (GC) B cells in the process of differentiating into MBCs. Using an inducible CRISPR-Cas9 screening approach, we identified the hematopoietically expressed homeobox protein Hhex as a transcription factor regulating MBC differentiation. The corepressor Tle3 was also identified in the screen and was found to interact with Hhex to promote MBC development. Bcl-6 directly repressed Hhex in GC B cells. Reciprocally, Hhex-deficient MBCs exhibited increased Bcl6 expression and reduced expression of the Bcl-6 target gene Bcl2. Overexpression of Bcl-2 was able to rescue MBC differentiation in Hhex-deficient cells. We also identified Ski as an Hhex-induced transcription factor involved in MBC differentiation. These findings establish an important role for Hhex-Tle3 in regulating the transcriptional circuitry governing MBC differentiation.
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Affiliation(s)
- Brian J Laidlaw
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- Division of Allergy and Immunology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Lihui Duan
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Ying Xu
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Sara E Vazquez
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Jason G Cyster
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA.
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA.
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7
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El Beaino M, Jupiter DC, Assi T, Rassy E, Lazar AJ, Araujo DM, Lin PP. Diagnostic Value of TLE1 in Synovial Sarcoma: A Systematic Review and Meta-Analysis. Sarcoma 2020; 2020:7192347. [PMID: 32322158 PMCID: PMC7166261 DOI: 10.1155/2020/7192347] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 01/06/2020] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Synovial sarcoma can present morphologically in multiple forms, including biphasic and monophasic subtypes. As a result, the histological diagnosis can sometimes be challenging. Transducin-Like Enhancer 1 (TLE1) is a transcriptional corepressor that normally is involved in embryogenesis and hematopoiesis but is also expressed in certain tumors. This systematic review examines the potential role of TLE1 as a diagnostic biomarker for the synovial sarcoma. Materials and Methods. A literature review and meta-analysis were conducted using the electronic databases Pubmed, the Cochrane Library, and Google Scholar. Thirteen studies met our eligibility criteria and were selected for in-depth analysis. RESULTS The mean sensitivity and specificity of TLE1 in detecting synovial sarcoma were 94% (95% CI 91%-97%) and 81% (95% CI 72%-91%), respectively, when all studies were aggregated together. The mean positive predictive value (PPV) of TLE1 was 75% (95% CI 62%-87%), whereas the negative predictive value (NPV) was 96% (95% CI 93%-98%). CONCLUSION TLE1 is a sensitive and specific marker for synovial sarcoma that can aid in its diagnosis. Due to its involvement in several relevant signaling pathways, TLE1 might have direct relevance to the pathophysiology of the disease.
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Affiliation(s)
- Marc El Beaino
- Department of Orthopaedic Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Orthopaedic Surgery and Rehabilitation Medicine, State University of New York, Downstate Medical Center, Brooklyn, NY, USA
| | - Daniel C. Jupiter
- Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, TX, USA
- Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, TX, USA
| | - Tarek Assi
- Department of Cancer Medicine, Gustave Roussy Institute, F-94805 Villejuif, France
| | - Elie Rassy
- Department of Cancer Medicine, Gustave Roussy Institute, F-94805 Villejuif, France
| | - Alexander J. Lazar
- Departments of Pathology & Genomic Medicine, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Dejka M. Araujo
- Department of Sarcoma Medical Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Patrick P. Lin
- Department of Orthopaedic Oncology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
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Pukhalskaya T, Smoller BR. TLE1 expression fails to distinguish between synovial sarcoma, atypical fibroxanthoma, and dermatofibrosarcoma protuberans. J Cutan Pathol 2019; 47:135-138. [PMID: 31614009 DOI: 10.1111/cup.13596] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 10/02/2019] [Accepted: 10/07/2019] [Indexed: 11/29/2022]
Abstract
Transducin-like enhancer of split 1 (TLE1) belongs to the Groucho/TLE/Grg family. It functions as a transcriptional corepressor and is widely used as a biomarker of synovial sarcoma (SS). Within the skin, atypical fibroxanthoma (AFX) and dermatofibrosarcoma protuberans (DFSP) often enter the histopathologic differential diagnosis. TLE1 expression has not been evaluated in these neoplasms. We examined archived tissues sections from the surgical pathology files from 10 adult patients diagnosed with AFX and 10 adult patients diagnosed with DFSP. We found nuclear staining in 10 of 10 AFX and 2 of 10 DFSP. We also noticed three patterns of staining in AFX: predominantly spindle component, predominantly epithelioid component, or mixed pattern of both epithelioid and spindle components. The group with the predominantly spindle pattern expressed the strongest nuclear TLE1 staining. In the DFSP group, one lesion demonstrated staining of epithelioid cells, with strong, diffuse nuclear TLE 1 expression, and the second lesion stained only the spindled cells, with weak nuclear TLE1 marking. In conclusion, TLE1, while a sensitive marker for SS, is not specific. A wide range of cutaneous spindle cell neoplasms also express TLE1. AFX and DFSP should be added to this list. TLE1 might be added to a diagnostic panel in this differential diagnosis.
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Affiliation(s)
- Tatsiana Pukhalskaya
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York
| | - Bruce R Smoller
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York
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Hhex induces promyelocyte self-renewal and cooperates with growth factor independence to cause myeloid leukemia in mice. Blood Adv 2019; 2:347-360. [PMID: 29453249 DOI: 10.1182/bloodadvances.2017013243] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 01/24/2018] [Indexed: 12/16/2022] Open
Abstract
The hematopoietically expressed homeobox (Hhex) transcription factor is overexpressed in human myeloid leukemias. Conditional knockout models of murine acute myeloid leukemia indicate that Hhex maintains leukemia stem cell self-renewal by enabling Polycomb-mediated epigenetic repression of the Cdkn2a tumor suppressor locus, encoding p16Ink4a and p19Arf However, whether Hhex overexpression also affects hematopoietic differentiation is unknown. To study this, we retrovirally overexpressed Hhex in hematopoietic progenitors. This enabled serial replating of myeloid progenitors, leading to the rapid establishment of interleukin-3 (IL-3)-dependent promyelocytic cell lines. Use of a Hhex-ERT2 fusion protein demonstrated that continuous nuclear Hhex is required for transformation, and structure function analysis demonstrated a requirement of the DNA-binding and N-terminal-repressive domains of Hhex for promyelocytic transformation. This included the N-terminal promyelocytic leukemia protein (Pml) interaction domain, although deletion of Pml failed to prevent Hhex-induced promyelocyte transformation, implying other critical partners. Furthermore, deletion of p16Ink4a or p19Arf did not promote promyelocyte transformation, indicating that repression of distinct Hhex target genes is required for this process. Indeed, transcriptome analysis showed that Hhex overexpression resulted in repression of several myeloid developmental genes. To test the potential for Hhex overexpression to contribute to leukemic transformation, Hhex-transformed promyelocyte lines were rendered growth factor-independent using a constitutively active IL-3 receptor common β subunit (βcV449E). The resultant cell lines resulted in a rapid promyelocytic leukemia in vivo. Thus, Hhex overexpression can contribute to myeloid leukemia via multiple mechanisms including differentiation blockade and enabling epigenetic repression of the Cdkn2a locus.
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Proline-Rich Homeodomain protein (PRH/HHEX) is a suppressor of breast tumour growth. Oncogenesis 2017; 6:e346. [PMID: 28604763 PMCID: PMC5519192 DOI: 10.1038/oncsis.2017.42] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 03/23/2017] [Accepted: 04/20/2017] [Indexed: 12/27/2022] Open
Abstract
Breast tumours progress from hyperplasia to ductal carcinoma in situ (DCIS) and invasive breast carcinoma (IBC). PRH/HHEX (proline-rich homeodomain/haematopoietically expressed homeobox) is a transcription factor that displays both tumour suppressor and oncogenic activity in different disease contexts; however, the role of PRH in breast cancer is poorly understood. Here we show that nuclear localization of the PRH protein is decreased in DCIS and IBC compared with normal breast. Our previous work has shown that PRH phosphorylation by protein kinase CK2 prevents PRH from binding to DNA and regulating the transcription of multiple genes encoding growth factors and growth factor receptors. Here we show that transcriptionally inactive phosphorylated PRH is elevated in DCIS and IBC compared with normal breast. To determine the consequences of PRH loss of function in breast cancer cells, we generated inducible PRH depletion in MCF-7 cells. We show that PRH depletion results in increased MCF-7 cell proliferation in part at least due to increased vascular endothelial growth factor signalling. Moreover, we demonstrate that PRH depletion increases the formation of breast cancer cells with cancer stem cell-like properties. Finally, and in keeping with these findings, we show that PRH overexpression inhibits the growth of mammary tumours in mice. Collectively, these data indicate that PRH plays a tumour suppressive role in the breast and they provide an explanation for the finding that low PRH mRNA levels are associated with a poor prognosis in breast cancer.
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Uhrig JF, Huang LJ, Barghahn S, Willmer M, Thurow C, Gatz C. CC-type glutaredoxins recruit the transcriptional co-repressor TOPLESS to TGA-dependent target promoters in Arabidopsis thaliana. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2017; 1860:218-226. [DOI: 10.1016/j.bbagrm.2016.11.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Revised: 10/28/2016] [Accepted: 11/08/2016] [Indexed: 01/13/2023]
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CK2 abrogates the inhibitory effects of PRH/HHEX on prostate cancer cell migration and invasion and acts through PRH to control cell proliferation. Oncogenesis 2017; 6:e293. [PMID: 28134934 PMCID: PMC5294245 DOI: 10.1038/oncsis.2016.82] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 12/16/2015] [Accepted: 01/26/2016] [Indexed: 01/02/2023] Open
Abstract
PRH/HHEX (proline-rich homeodomain protein/haematopoietically expressed homeobox protein) is a transcription factor that controls cell proliferation, cell differentiation and cell migration. Our previous work has shown that in haematopoietic cells, Protein Kinase CK2-dependent phosphorylation of PRH results in the inhibition of PRH DNA-binding activity, increased cleavage of PRH by the proteasome and the misregulation of PRH target genes. Here we show that PRH and hyper-phosphorylated PRH are present in normal prostate epithelial cells, and that hyper-phosphorylated PRH levels are elevated in benign prostatic hyperplasia, prostatic adenocarcinoma, and prostate cancer cell lines. A reduction in PRH protein levels increases the motility of normal prostate epithelial cells and conversely, PRH over-expression inhibits prostate cancer cell migration and blocks the ability of these cells to invade an extracellular matrix. We show that CK2 over-expression blocks the repression of prostate cancer cell migration and invasion by PRH. In addition, we show that PRH knockdown in normal immortalised prostate cells results in an increase in the population of cells capable of colony formation in Matrigel, as well as increased cell invasion and decreased E-cadherin expression. Inhibition of CK2 reduces PRH phosphorylation and reduces prostate cell proliferation but the effects of CK2 inhibition on cell proliferation are abrogated in PRH knockdown cells. These data suggest that the increased phosphorylation of PRH in prostate cancer cells increases both cell proliferation and tumour cell migration/invasion.
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Shields BJ, Jackson JT, Metcalf D, Shi W, Huang Q, Garnham AL, Glaser SP, Beck D, Pimanda JE, Bogue CW, Smyth GK, Alexander WS, McCormack MP. Acute myeloid leukemia requires Hhex to enable PRC2-mediated epigenetic repression of Cdkn2a. Genes Dev 2016; 30:78-91. [PMID: 26728554 PMCID: PMC4701980 DOI: 10.1101/gad.268425.115] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Here, Shields et al. demonstrate that the hematopoietically expressed homeobox gene Hhex is overexpressed in acute myeloid leukemia (AML) and is essential for the initiation and propagation of MLL-ENL-induced AML but dispensable for normal myelopoiesis, indicating a specific requirement for Hhex for leukemic growth. The findings in this study describe for the first time a nonclustered homeobox transcription factor that is essential for AML initiation and maintenance and provide mechanistic insight into these processes. Unlike clustered HOX genes, the role of nonclustered homeobox gene family members in hematopoiesis and leukemogenesis has not been extensively studied. Here we found that the hematopoietically expressed homeobox gene Hhex is overexpressed in acute myeloid leukemia (AML) and is essential for the initiation and propagation of MLL-ENL-induced AML but dispensable for normal myelopoiesis, indicating a specific requirement for Hhex for leukemic growth. Loss of Hhex leads to expression of the Cdkn2a-encoded tumor suppressors p16INK4a and p19ARF, which are required for growth arrest and myeloid differentiation following Hhex deletion. Mechanistically, we show that Hhex binds to the Cdkn2a locus and directly interacts with the Polycomb-repressive complex 2 (PRC2) to enable H3K27me3-mediated epigenetic repression. Thus, Hhex is a potential therapeutic target that is specifically required for AML stem cells to repress tumor suppressor pathways and enable continued self-renewal.
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Affiliation(s)
- Benjamin J Shields
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia
| | - Jacob T Jackson
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Donald Metcalf
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia
| | - Wei Shi
- Bioinformatics Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia; Computing and Information Systems, University of Melbourne, Parkville, Victoria 3050, Australia
| | - Qiutong Huang
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia
| | - Alexandra L Garnham
- Bioinformatics Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3050, Australia
| | - Stefan P Glaser
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia
| | - Dominik Beck
- Lowy Cancer Research Centre and the Prince of Wales Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - John E Pimanda
- Lowy Cancer Research Centre and the Prince of Wales Clinical School, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Clifford W Bogue
- Yale University School of Medicine, New Haven, Connecticut 06510, USA
| | - Gordon K Smyth
- Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia; Mathematics and Statistics, University of Melbourne, Parkville, Victoria 3050, Australia
| | - Warren S Alexander
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia
| | - Matthew P McCormack
- Cancer and Haematology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria 3050, Australia
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14
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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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15
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Agarwal M, Kumar P, Mathew SJ. The Groucho/Transducin-like enhancer of split protein family in animal development. IUBMB Life 2015; 67:472-81. [PMID: 26172616 DOI: 10.1002/iub.1395] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 06/15/2015] [Indexed: 01/30/2023]
Abstract
Corepressors are proteins that cannot bind DNA directly but repress transcription by interacting with partner proteins. The Groucho/Transducin-Like Enhancer of Split (TLE) are a conserved family of corepressor proteins present in animals ranging from invertebrates such as Drosophila to vertebrates such as mice and humans. Groucho/TLE proteins perform important functions throughout the life span of animals, interacting with several pathways and regulating fundamental processes such as metabolism. However, these proteins have especially crucial functions in animal development, where they are required in multiple tissues in a temporally regulated manner. In this review, we summarize the functions of the Groucho/TLE proteins during animal development, emphasizing on specific tissues where they play essential roles.
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Affiliation(s)
- Megha Agarwal
- Regional Centre for Biotechnology, NCR Bio-Science Cluster, Faridabad, Haryana, India
| | - Pankaj Kumar
- Regional Centre for Biotechnology, NCR Bio-Science Cluster, Faridabad, Haryana, India
| | - Sam J Mathew
- Regional Centre for Biotechnology, NCR Bio-Science Cluster, Faridabad, Haryana, India
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16
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Goodings C, Smith E, Mathias E, Elliott N, Cleveland SM, Tripathi RM, Layer JH, Chen X, Guo Y, Shyr Y, Hamid R, Du Y, Davé UP. Hhex is Required at Multiple Stages of Adult Hematopoietic Stem and Progenitor Cell Differentiation. Stem Cells 2015; 33:2628-41. [PMID: 25968920 DOI: 10.1002/stem.2049] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 03/03/2015] [Accepted: 04/22/2015] [Indexed: 01/03/2023]
Abstract
Hhex encodes a homeodomain transcription factor that is widely expressed in hematopoietic stem and progenitor cell populations. Its enforced expression induces T-cell leukemia and we have implicated it as an important oncogene in early T-cell precursor leukemias where it is immediately downstream of an LMO2-associated protein complex. Conventional Hhex knockouts cause embryonic lethality precluding analysis of adult hematopoiesis. Thus, we induced highly efficient conditional knockout (cKO) using vav-Cre transgenic mice. Hhex cKO mice were viable and born at normal litter sizes. At steady state, we observed a defect in B-cell development that we localized to the earliest B-cell precursor, the pro-B-cell stage. Most remarkably, bone marrow transplantation using Hhex cKO donor cells revealed a more profound defect in all hematopoietic lineages. In contrast, sublethal irradiation resulted in normal myeloid cell repopulation of the bone marrow but markedly impaired repopulation of T- and B-cell compartments. We noted that Hhex cKO stem and progenitor cell populations were skewed in their distribution and showed enhanced proliferation compared to WT cells. Our results implicate Hhex in the maintenance of LT-HSCs and in lineage allocation from multipotent progenitors especially in stress hematopoiesis.
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Affiliation(s)
| | | | | | - Natalina Elliott
- MRC Molecular Hematology Unit, University of Oxford, Oxford, United Kingdom
| | | | | | | | - Xi Chen
- Department of Biostatistics, Center for Quantitative Sciences
| | - Yan Guo
- Department of Biostatistics, Center for Quantitative Sciences
| | - Yu Shyr
- Department of Biostatistics, Center for Quantitative Sciences
| | - Rizwan Hamid
- Division of Medical Genetics, Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Yang Du
- Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Utpal P Davé
- Department of Cancer Biology.,Division of Hematology/Oncology.,Tennessee Valley Healthcare System, Nashville VA, Nashville, Tennessee, USA
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17
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Lin G, Doyle LA. An update on the application of newly described immunohistochemical markers in soft tissue pathology. Arch Pathol Lab Med 2015; 139:106-21. [PMID: 25549147 DOI: 10.5858/arpa.2014-0488-ra] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
CONTEXT During the last 5 to 10 years, significant progress has been made in the molecular characterization of soft tissue tumors, predominantly with the identification of recurrent translocations or amplification of certain genes in different tumor types. Alongside this, translational efforts have identified many novel and diagnostically useful immunohistochemical markers for many of these tumor types. OBJECTIVE This article reviews a select group of recently described immunohistochemical markers of particular use in the evaluation of mesenchymal neoplasms; the underlying biology of the protein product, practical utility, and limitations of each marker are discussed in detail. DATA SOURCES Literature review, authors' research data, and personal practice experience serve as sources. CONCLUSIONS There are many diagnostically useful immunohistochemical markers to help confirm the diagnosis of many different soft tissue tumor types, some of which have reduced the need for additional, and more costly, studies, such as fluorescence in situ hybridization. However, no one marker is 100% specific for a given tumor, and knowledge of potential pitfalls and overlap in patterns of staining among other tumor types is crucial to ensure the appropriate application of these markers in clinical practice.
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Affiliation(s)
- George Lin
- From the Department of Laboratory Medicine, Geisinger Medical Center, Danville, Pennsylvania (Dr Lin); and the Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts (Dr Doyle)
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18
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Gro/TLE enables embryonic stem cell differentiation by repressing pluripotent gene expression. Dev Biol 2015; 397:56-66. [DOI: 10.1016/j.ydbio.2014.10.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 09/21/2014] [Accepted: 10/14/2014] [Indexed: 01/03/2023]
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19
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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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20
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Growth-promoting and tumourigenic activity of c-Myc is suppressed by Hhex. Oncogene 2014; 34:3011-22. [PMID: 25220416 DOI: 10.1038/onc.2014.240] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 06/18/2014] [Accepted: 06/30/2014] [Indexed: 12/12/2022]
Abstract
c-Myc transcription factor is a key protein involved in cellular growth, proliferation and metabolism. c-Myc is one of the most frequently activated oncogenes, highlighting the need to identify intracellular molecules that interact directly with c-Myc to suppress its function. Here we show that Hhex is able to interact with the basic region/helix-loop-helix/leucine zipper of c-Myc. Knockdown of Hhex increases proliferation rate in hepatocellular carcinoma cells, whereas Hhex expression cell-autonomously reduces cell proliferation rate in multiple cell lines by increasing G1 phase length through a c-Myc-dependent mechanism. Global transcriptomic analysis shows that Hhex counter-regulates multiple c-Myc targets involved in cell proliferation and metabolism. Concomitantly, Hhex expression leads to reduced cell size, lower levels of cellular RNA, downregulation of metabolism-related genes, decreased sensitivity to methotrexate and severe reduction in the ability to form tumours in nude mouse xenografts, all indicative of decreased c-Myc activity. Our data suggest that Hhex is a novel regulator of c-Myc function that limits c-Myc activity in transformed cells.
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21
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Zhang J, McKenna LB, Bogue CW, Kaestner KH. The diabetes gene Hhex maintains δ-cell differentiation and islet function. Genes Dev 2014; 28:829-34. [PMID: 24736842 PMCID: PMC4003275 DOI: 10.1101/gad.235499.113] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The homeodomain transcription factor HHEX (hematopoietically expressed homeobox) has been linked to type 2 diabetes mellitus in genome-wide association studies. Zhang et al. discover that Hhex is selectively expressed in the somatostatin-secreting δ cell of the adult pancreas. Hhex was required for δ-cell differentiation, and the reduced somatostatin levels in Hhex-deficient islets caused disrupted paracrine inhibition of insulin release from δ cells. This study identifies Hhex as the first transcriptional regulator specifically required for islet δ cells and suggests compromised paracrine control as a contributor to type 2 diabetes. The homeodomain transcription factor HHEX (hematopoietically expressed homeobox) has been repeatedly linked to type 2 diabetes mellitus (T2DM) using genome-wide association studies. We report here that within the adult endocrine pancreas, Hhex is selectively expressed in the somatostatin-secreting δ cell. Using two mouse models with Hhex deficiency in the endocrine pancreas, we show that Hhex is required for δ-cell differentiation. Decreased somatostatin levels in Hhex-deficient islets cause disrupted paracrine inhibition of insulin release from β cells. These findings identify Hhex as the first transcriptional regulator specifically required for islet δ cells and suggest compromised paracrine control as a contributor to T2DM.
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Affiliation(s)
- Jia Zhang
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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22
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HHEX promotes hepatic-lineage specification through the negative regulation of eomesodermin. PLoS One 2014; 9:e90791. [PMID: 24651531 PMCID: PMC3961246 DOI: 10.1371/journal.pone.0090791] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2013] [Accepted: 02/05/2014] [Indexed: 01/21/2023] Open
Abstract
Human embryonic stem cells (hESCs) could provide a major window into human developmental biology, because the differentiation methods from hESCs mimic human embryogenesis. We previously reported that the overexpression of hematopoietically expressed homeobox (HHEX) in the hESC-derived definitive endoderm (DE) cells markedly promotes hepatic specification. However, it remains unclear how HHEX functions in this process. To reveal the molecular mechanisms of hepatic specification by HHEX, we tried to identify the genes directly targeted by HHEX. We found that HHEX knockdown considerably enhanced the expression level of eomesodermin (EOMES). In addition, HHEX bound to the HHEX response element located in the first intron of EOMES. Loss-of-function assays of EOMES showed that the gene expression levels of hepatoblast markers were significantly upregulated, suggesting that EOMES has a negative role in hepatic specification from the DE cells. Furthermore, EOMES exerts its effects downstream of HHEX in hepatic specification from the DE cells. In conclusion, the present results suggest that HHEX promotes hepatic specification by repressing EOMES expression.
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23
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Smith S, Tripathi R, Goodings C, Cleveland S, Mathias E, Hardaway JA, Elliott N, Yi Y, Chen X, Downing J, Mullighan C, Swing DA, Tessarollo L, Li L, Love P, Jenkins NA, Copeland NG, Thompson MA, Du Y, Davé UP. LIM domain only-2 (LMO2) induces T-cell leukemia by two distinct pathways. PLoS One 2014; 9:e85883. [PMID: 24465765 PMCID: PMC3897537 DOI: 10.1371/journal.pone.0085883] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/03/2013] [Indexed: 02/03/2023] Open
Abstract
The LMO2 oncogene is deregulated in the majority of human T-cell leukemia cases and in most gene therapy-induced T-cell leukemias. We made transgenic mice with enforced expression of Lmo2 in T-cells by the CD2 promoter/enhancer. These transgenic mice developed highly penetrant T-ALL by two distinct patterns of gene expression: one in which there was concordant activation of Lyl1, Hhex, and Mycn or alternatively, with Notch1 target gene activation. Most strikingly, this gene expression clustering was conserved in human Early T-cell Precursor ALL (ETP-ALL), where LMO2, HHEX, LYL1, and MYCN were most highly expressed. We discovered that HHEX is a direct transcriptional target of LMO2 consistent with its concordant gene expression. Furthermore, conditional inactivation of Hhex in CD2-Lmo2 transgenic mice markedly attenuated T-ALL development, demonstrating that Hhex is a crucial mediator of Lmo2's oncogenic function. The CD2-Lmo2 transgenic mice offer mechanistic insight into concordant oncogene expression and provide a model for the highly treatment-resistant ETP-ALL subtype.
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Affiliation(s)
- Stephen Smith
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Rati Tripathi
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Charnise Goodings
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Susan Cleveland
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Elizabeth Mathias
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - J. Andrew Hardaway
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Natalina Elliott
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Yajun Yi
- Division of Genetic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Xi Chen
- Department of Biostatistics, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - James Downing
- Department of Pathology, St Jude Children's Research Hospital, Memphis, Tennessee, United States of America
| | - Charles Mullighan
- Department of Pathology, St Jude Children's Research Hospital, Memphis, Tennessee, United States of America
| | - Deborah A. Swing
- Mouse Cancer Genetics Program, National Cancer Institute, Frederick, Maryland, United States of America
| | - Lino Tessarollo
- Mouse Cancer Genetics Program, National Cancer Institute, Frederick, Maryland, United States of America
| | - Liqi Li
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Paul Love
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Nancy A. Jenkins
- The Methodist Hospital Research Institute, Houston, Texas, United States of America
| | - Neal G. Copeland
- The Methodist Hospital Research Institute, Houston, Texas, United States of America
| | - Mary Ann Thompson
- Department of Pathology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Yang Du
- Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Utpal P. Davé
- Division of Hematology/Oncology, Vanderbilt University Medical Center and the Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
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24
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Kershaw RM, Siddiqui YH, Roberts D, Jayaraman PS, Gaston K. PRH/HHex inhibits the migration of breast and prostate epithelial cells through direct transcriptional regulation of Endoglin. Oncogene 2013; 33:5592-600. [PMID: 24240683 DOI: 10.1038/onc.2013.496] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 09/19/2013] [Accepted: 10/11/2013] [Indexed: 12/16/2022]
Abstract
PRH/HHex (proline-rich homeodomain protein) is a transcription factor that controls cell proliferation and cell differentiation in a variety of tissues. Aberrant subcellular localisation of PRH is associated with breast cancer and thyroid cancer. Further, in blast crisis chronic myeloid leukaemia, and a subset of acute myeloid leukaemias, PRH is aberrantly localised and its activity is downregulated. Here we show that PRH is involved in the regulation of cell migration and cancer cell invasion. We show for the first time that PRH is expressed in prostate cells and that a decrease in PRH protein levels increases the migration of normal prostate epithelial cells. We show that a decrease in PRH protein levels also increases the migration of normal breast epithelial cells. Conversely, PRH overexpression inhibits cell migration and cell invasion by PC3 and DU145 prostate cancer cells and MDA-MB-231 breast cancer cells. Previous work has shown that the transforming growth factor-β co-receptor Endoglin inhibits the migration of prostate and breast cancer cells. Here we show that PRH can bind to the Endoglin promoter in immortalised prostate and breast cells. PRH overexpression in these cells results in increased Endoglin protein expression, whereas PRH knockdown results in decreased Endoglin protein expression. Moreover, we demonstrate that Endoglin overexpression abrogates the increased migration shown by PRH knockdown cells. Our data suggest that PRH controls the migration of multiple epithelial cell lineages in part at least through the direct transcriptional regulation of Endoglin. We discuss these results in terms of the functions of PRH in normal cells and the mislocalisation of PRH seen in multiple cancer cell types.
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Affiliation(s)
- R M Kershaw
- Division of Immunity and Infection, School of Medicine, University of Birmingham, Edgbaston, Birmingham, UK
| | - Y H Siddiqui
- School of Biochemistry, University Walk, University of Bristol, Bristol, UK
| | - D Roberts
- Division of Immunity and Infection, School of Medicine, University of Birmingham, Edgbaston, Birmingham, UK
| | - P-S Jayaraman
- Division of Immunity and Infection, School of Medicine, University of Birmingham, Edgbaston, Birmingham, UK
| | - K Gaston
- School of Biochemistry, University Walk, University of Bristol, Bristol, UK
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25
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Xia H, Li M, Chen L, Leng W, Yuan D, Pang X, Chen L, Li R, Tang Q, Bi F. Suppression of RND3 activity by AES downregulation promotes cancer cell proliferation and invasion. Int J Mol Med 2013; 31:1081-6. [PMID: 23546594 DOI: 10.3892/ijmm.2013.1321] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 01/02/2013] [Indexed: 02/05/2023] Open
Abstract
Amino-terminal enhancer of split (AES) is a member of the Groucho/TLE family. Although it has no DNA-binding site, AES can regulate transcriptional activity by interacting with transcriptional factors. Emerging evidence indicates that AES may play an important role in tumor metastasis, but the molecular mechanism is still poorly understood. In this study, we found that knockdown of AES by RNA interference (RNAi) downregulated RND3 expression at the mRNA and protein levels in MDA-MB-231 and HepG2, two cancer cell lines. Furthermore, luciferase assays showed that overexpression of AES significantly enhanced RND3 promoter activity. Moreover, inhibition of AES both in MDA-MB-231 and HepG2 cells by RNAi significantly promoted cell proliferation, cell cycle progression and invasion, consistent with the effects of RNAi-mediated RND3 knockdown in these cells. For the first time, data are presented showing that alteration of the malignant behavior of cancer cells by AES is related to RND3 regulation, and these findings also provide new insights into the mechanism of AES action in regulating tumor malignancy.
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Affiliation(s)
- Hongwei Xia
- Laboratory of Signal Transduction and Molecular Targeted Therapy, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, P.R. China
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26
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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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27
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Noy P, Sawasdichai A, Jayaraman PS, Gaston K. Protein kinase CK2 inactivates PRH/Hhex using multiple mechanisms to de-repress VEGF-signalling genes and promote cell survival. Nucleic Acids Res 2012; 40:9008-20. [PMID: 22844093 PMCID: PMC3467080 DOI: 10.1093/nar/gks687] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Protein kinase CK2 promotes cell survival and the activity of this kinase is elevated in several cancers including chronic myeloid leukaemia. We have shown previously that phosphorylation of the Proline-Rich Homeodomain protein (PRH/Hhex) by CK2 inhibits the DNA-binding activity of this transcription factor. Furthermore, PRH represses the transcription of multiple genes encoding components of the VEGF-signalling pathway and thereby influences cell survival. Here we show that the inhibitory effects of PRH on cell proliferation are abrogated by CK2 and that CK2 inhibits the binding of PRH at the Vegfr-1 promoter. Phosphorylation of PRH by CK2 also decreases the nuclear association of PRH and induces its cleavage by the proteasome. Moreover, cleavage of phosphorylated PRH produces a stable truncated cleavage product which we have termed PRHΔC (HhexΔC). PRHΔC acts as a transdominant negative regulator of full-length PRH by sequestering TLE proteins that function as PRH co-repressors. We show that this novel regulatory mechanism results in the alleviation of PRH-mediated repression of Vegfr-1. We suggest that the re-establishment of PRH function through inhibition of CK2 could be of value in treatment of myeloid leukaemias, as well as other tumour types in which PRH is inactivated by phosphorylation.
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Affiliation(s)
- Peter Noy
- Division of Immunity and Infection, School of Medicine, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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The proline rich homeodomain protein PRH/Hhex forms stable oligomers that are highly resistant to denaturation. PLoS One 2012; 7:e35984. [PMID: 22540015 PMCID: PMC3335068 DOI: 10.1371/journal.pone.0035984] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 03/29/2012] [Indexed: 11/19/2022] Open
Abstract
Background Many transcription factors control gene expression by binding to specific DNA sequences at or near the genes that they regulate. However, some transcription factors play more global roles in the control of gene expression by altering the architecture of sections of chromatin or even the whole genome. The ability to form oligomeric protein assemblies allows many of these proteins to manipulate extensive segments of DNA or chromatin via the formation of structures such as DNA loops or protein-DNA fibres. Principal Findings Here we show that the proline rich homeodomain protein PRH/Hhex forms predominantly octameric and/or hexadecameric species in solution as well as larger assemblies. We show that these assemblies are highly stable resisting denaturation by temperature and chemical denaturants. Conclusion These data indicate that PRH is functionally and structurally related to the Lrp/AsnC family of proteins, a group of proteins that are known to act globally to control gene expression in bacteria and archaea.
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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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Causier B, Ashworth M, Guo W, Davies B. The TOPLESS interactome: a framework for gene repression in Arabidopsis. PLANT PHYSIOLOGY 2012; 158:423-38. [PMID: 22065421 PMCID: PMC3252085 DOI: 10.1104/pp.111.186999] [Citation(s) in RCA: 365] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 11/04/2011] [Indexed: 05/17/2023]
Abstract
Transcription factors activate or repress target gene expression or switch between activation and repression. In animals and yeast, Groucho/Tup1 corepressor proteins are recruited by diverse transcription factors to induce context-specific transcriptional repression. Two groups of Groucho/Tup1-like corepressors have been described in plants. LEUNIG and LEUNIG_HOMOLOG constitute one group and TOPLESS (TPL) and the four TPL-related (TPR) corepressors form the other. To discover the processes in which TPL and the TPR corepressors operate, high-throughput yeast two-hybrid approaches were used to identify interacting proteins. We found that TPL/TPR corepressors predominantly interact directly with specific transcription factors, many of which were previously implicated in transcriptional repression. The interacting transcription factors reveal that the TPL/TPR family has been coopted multiple times to modulate gene expression in diverse processes, including hormone signaling, stress responses, and the control of flowering time, for which we also show biological validation. The interaction data suggest novel mechanisms for the involvement of TPL/TPR corepressors in auxin and jasmonic acid signaling. A number of short repression domain (RD) sequences have previously been identified in Arabidopsis (Arabidopsis thaliana) transcription factors. All known RD sequences were enriched among the TPL/TPR interactors, and novel TPL-RD interactions were identified. We show that the presence of RD sequences is essential for TPL/TPR recruitment. These data provide a framework for TPL/TPR-dependent transcriptional repression. They allow for predictions about new repressive transcription factors, corepressor interactions, and repression mechanisms and identify a wide range of plant processes that utilize TPL/TPR-mediated gene repression.
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Abstract
Drosophila Groucho (Gro) is the founding member of a family of metazoan corepressors. Gro mediates repression through interactions with a myriad of DNA-binding repressor proteins to direct the silencing of genes involved in many developmental processes, including neurogenesis and patterning of the main body axis, as well as receptor tyrosine kinase/Ras/MAPK, Notch, Wingless (Wg)/Wnt, and Decapentaplegic (Dpp) signaling. Gro mediates repression by multiple molecular mechanisms, depending on the regulatory context. Because Gro is a broadly expressed nuclear factor, whereas its repressor partners display restricted temporal and spatial distribution, it was presumed that this corepressor played permissive rather than instructive roles in development. However, a wide range of studies demonstrates that this is not the case. Gro can sense and integrate many cellular inputs to modulate the expression of variety of genes, making it a versatile corepressor with crucial instructive roles in development and signaling.
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Affiliation(s)
- Wiam Turki-Judeh
- Department of Chemistry & Biochemistry and Molecular Biology Institute, University of California, Los Angeles, California, USA
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Abstract
NK-like (NKL) homeobox genes code for transcription factors, which can act as key regulators in fundamental cellular processes. NKL genes have been implicated in divergent types of cancer. In this review, we summarize the involvement of NKL genes in cancer and leukemia in particular. NKL genes can act as tumor-suppressor genes and as oncogenes, depending on tissue type. Aberrant expression of NKL genes is especially common in T-cell acute lymphoblastic leukemia (T-ALL). In T-ALL, 8 NKL genes have been reported to be highly expressed in specific T-ALL subgroups, and in ~30% of cases, high expression is caused by chromosomal rearrangement of 1 of 5 NKL genes. Most of these NKL genes are normally not expressed in T-cell development. We hypothesize that the NKL genes might share a similar downstream effect that promotes leukemogenesis, possibly due to mimicking a NKL gene that has a physiological role in early hematopoietic development, such as HHEX. All eight NKL genes posses a conserved Eh1 repressor motif, which has an important role in regulating downstream targets in hematopoiesis and possibly in leukemogenesis as well. Identification of a potential common leukemogenic NKL downstream pathway will provide a promising subject for future studies.
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Sarma NJ, Yaseen NR. Amino-terminal enhancer of split (AES) interacts with the oncoprotein NUP98-HOXA9 and enhances its transforming ability. J Biol Chem 2011; 286:38989-9001. [PMID: 21937451 DOI: 10.1074/jbc.m111.297952] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
NUP98-HOXA9 is the prototype of NUP98 fusion oncoproteins that cause acute myeloid leukemia. It consists of an N-terminal FG-rich portion of the nucleoporin NUP98 fused to the homeodomain region of the homeobox protein HOXA9, and acts as an aberrant transcription factor. To identify interacting partners of NUP98-HOXA9, we used a cytoplasmic yeast two-hybrid assay to avoid the nonspecific trans-activation that would occur with the traditional yeast two-hybrid assay due to the transactivating properties of NUP98-HOXA9. We identified amino-terminal enhancer of split (AES), a transcriptional regulator of the transducin-like enhancer/Groucho family as a novel interaction partner of NUP98-HOXA9. The interaction was confirmed by in vitro pulldown and co-immunoprecipitation assays and was shown to require the FG repeat region of NUP98-HOXA9. Immunofluorescence analysis showed that AES localizes primarily to the interior of the nucleus. AES also showed a strong interaction with wild-type NUP98. AES augmented the transcriptional activity of NUP98-HOXA9. In the presence of NUP98-HOXA9, AES caused an increase in long-term proliferation of primary human CD34+ cells with a marked increase in the numbers of primitive cells. These effects of AES were not observed in the absence of NUP98-HOXA9. AES knockdown diminished the transcriptional and proliferative effects of NUP98-HOXA9. AES caused a shift away from the erythroid lineage in cells expressing NUP98-HOXA9. These data establish AES as an interacting partner of NUP98-HOXA9 and show that it cooperates with NUP98-HOXA9 in transcriptional regulation and cell transformation.
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Affiliation(s)
- Nayan J Sarma
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Rimsza LM, Unger JM, Tome ME, Leblanc ML. A strategy for full interrogation of prognostic gene expression patterns: exploring the biology of diffuse large B cell lymphoma. PLoS One 2011; 6:e22267. [PMID: 21829609 PMCID: PMC3150354 DOI: 10.1371/journal.pone.0022267] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 06/21/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Gene expression profiling yields quantitative data on gene expression used to create prognostic models that accurately predict patient outcome in diffuse large B cell lymphoma (DLBCL). Often, data are analyzed with genes classified by whether they fall above or below the median expression level. We sought to determine whether examining multiple cut-points might be a more powerful technique to investigate the association of gene expression with outcome. METHODOLOGY/PRINCIPAL FINDINGS We explored gene expression profiling data using variable cut-point analysis for 36 genes with reported prognostic value in DLBCL. We plotted two-group survival logrank test statistics against corresponding cut-points of the gene expression levels and smooth estimates of the hazard ratio of death versus gene expression levels. To facilitate comparisons we also standardized the expression of each of the genes by the fraction of patients that would be identified by any cut-point. A multiple comparison adjusted permutation p-value identified 3 different patterns of significance: 1) genes with significant cut-point points below the median, whose loss is associated with poor outcome (e.g. HLA-DR); 2) genes with significant cut-points above the median, whose over-expression is associated with poor outcome (e.g. CCND2); and 3) genes with significant cut-points on either side of the median, (e.g. extracellular molecules such as FN1). CONCLUSIONS/SIGNIFICANCE Variable cut-point analysis with permutation p-value calculation can be used to identify significant genes that would not otherwise be identified with median cut-points and may suggest biological patterns of gene effects.
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Affiliation(s)
- Lisa M Rimsza
- Department of Pathology, University of Arizona, Tucson, Arizona, United States of America.
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Foo WC, Cruise MW, Wick MR, Hornick JL. Immunohistochemical staining for TLE1 distinguishes synovial sarcoma from histologic mimics. Am J Clin Pathol 2011; 135:839-44. [PMID: 21571956 DOI: 10.1309/ajcp45ssnaopxyxu] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Transducer-like enhancer of split 1 (TLE1) is overexpressed in synovial sarcomas. We investigated TLE1 expression by immunohistochemical analysis in a well-characterized series of synovial sarcomas and other mesenchymal tumors most commonly considered in the differential diagnosis. Whole tissue sections of 212 tumors were evaluated: 73 synovial sarcomas (23 biphasic, 28 monophasic, 22 poorly differentiated), 47 malignant peripheral nerve sheath tumors (MPNSTs), 49 solitary fibrous tumors (SFTs), 20 fibrosarcomatous variants of dermatofibrosarcoma protuberans, and 23 Ewing sarcomas/primitive neuroectodermal tumors (PNETs). All monophasic and poorly differentiated SSs and Ewing sarcoma/PNETs were previously confirmed to harbor t(X;18) and EWSR1 gene rearrangements, respectively. In total, 60 (82%) of 73 synovial sarcomas were positive for TLE1, including 18 biphasic (78%), 22 monophasic (79%), and 20 poorly differentiated (91%) tumors. Of the other tumors, only 7 MPNSTs (15%) and 4 SFTs (8%) were positive for TLE1, most of which showed only weak staining. TLE1 is a sensitive and specific marker for synovial sarcoma and can be helpful to distinguish synovial sarcoma from histologic mimics, particularly if moderate or strong staining is observed. In this study, only a small subset of MPNSTs and SFTs showed limited staining for TLE1.
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Abstract
The human Transducin-like Enhancer of Split (TLE) and mouse homologue, Groucho gene-related protein (GRG), represent a family of conserved non-DNA binding transcriptional modulatory proteins divided into two subgroups based upon size. The long TLE/GRGs consist of four pentadomain proteins that are dedicated co-repressors for multiple transcription factors (TF). The second TLE/GRG subgroup is composed of the Amino-terminal Enhancer of Split (AES) in humans and its mouse homolog GRG5 (AES/GRG5). In contrast to the dedicated co-repressor function of long TLE/GRGs, AES/GRG5 can both positively or negatively modulate various TF as well as non-TF proteins in a long TLE/GRG-dependent or -independent manner. Therefore, AES/GRG5 is a functionally dynamic protein that is not exclusively defined by its role as a long TLE/GRG antagonist. AES/GRG5 may function in various developmental and pathological processes but the functional characteristics of endogenous AES/GRG5 in a physiologically relevant context remains to be determined. Developmental Dynamics 239:2795–2805, 2010. © 2010 Wiley-Liss, Inc.
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Affiliation(s)
- Brandon Beagle
- Department of Anesthesiology, University of Rochester, Rochester, New York 14642, USA
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Chen E, Huang X, Zheng Y, Li YJ, Chesney A, Ben-David Y, Yang E, Hough MR. Phosphorylation of HOX11/TLX1 on Threonine-247 during mitosis modulates expression of cyclin B1. Mol Cancer 2010; 9:246. [PMID: 20846384 PMCID: PMC2949800 DOI: 10.1186/1476-4598-9-246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Accepted: 09/16/2010] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The HOX11/TLX1 (hereafter referred to as HOX11) homeobox gene was originally identified at a t(10;14)(q24;q11) translocation breakpoint, a chromosomal abnormality observed in 5-7% of T cell acute lymphoblastic leukemias (T-ALLs). We previously reported a predisposition to aberrant spindle assembly checkpoint arrest and heightened incidences of chromosome missegregation in HOX11-overexpressing B lymphocytes following exposure to spindle poisons. The purpose of the current study was to evaluate cell cycle specific expression of HOX11. RESULTS Cell cycle specific expression studies revealed a phosphorylated form of HOX11 detectable only in the mitotic fraction of cells after treatment with inhibitors to arrest cells at different stages of the cell cycle. Mutational analyses revealed phosphorylation on threonine-247 (Thr247), a conserved amino acid that defines the HOX11 gene family and is integral for the association with DNA binding elements. The effect of HOX11 phosphorylation on its ability to modulate expression of the downstream target, cyclin B1, was tested. A HOX11 mutant in which Thr247 was substituted with glutamic acid (HOX11 T247E), thereby mimicking a constitutively phosphorylated HOX11 isoform, was unable to bind the cyclin B1 promoter or enhance levels of the cyclin B1 protein. Expression of the wildtype HOX11 was associated with accelerated progression through the G2/M phase of the cell cycle, impaired synchronization in prometaphase and reduced apoptosis whereas expression of the HOX11 T247E mutant restored cell cycle kinetics, the spindle checkpoint and apoptosis. CONCLUSIONS Our results demonstrate that the transcriptional activity of HOX11 is regulated by phosphorylation of Thr247 in a cell cycle-specific manner and that this phosphorylation modulates the expression of the target gene, cyclin B1. Since it is likely that Thr247 phosphorylation regulates DNA binding activity to multiple HOX11 target sequences, it is conceivable that phosphorylation functions to regulate the expression of HOX11 target genes involved in the control of the mitotic spindle checkpoint.
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Affiliation(s)
- Edwin Chen
- Institute of Medical Science, University of Toronto, Toronto, Ontario M5S1A8, Canada
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Uncx regulates proliferation of neural progenitor cells and neuronal survival in the olfactory epithelium. Mol Cell Neurosci 2010; 45:398-407. [PMID: 20692344 DOI: 10.1016/j.mcn.2010.07.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 07/21/2010] [Accepted: 07/27/2010] [Indexed: 12/31/2022] Open
Abstract
Uncx (Phd1, Chx4) is a paired homeobox transcription factor gene. It and its probable functional partners, Tle co-repressors, were expressed by neurally-fated basal progenitor cells and olfactory sensory neurons of the olfactory epithelium. Uncx expression was rare in olfactory epithelia of Ascl1(-/-) mice, but common in Neurog1(-/-) mice. In Uncx(-/-) mice olfactory progenitor cell proliferation, progenitor cell number, olfactory sensory neuron survival, and Umodl1 and Kcnc4 mRNAs were reduced. Evidence of sensory neuron activity and functional connections to the olfactory bulb argue that decreased neuronal survival was not due to loss of trophic support or activity-dependent mechanisms. These data suggest that UNCX acts downstream of neural determination factors to broadly control transcriptional mechanisms used by neural progenitor cells to specify neural phenotypes.
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Soufi A, Sawasdichai A, Shukla A, Noy P, Dafforn T, Smith C, Jayaraman PS, Gaston K. DNA compaction by the higher-order assembly of PRH/Hex homeodomain protein oligomers. Nucleic Acids Res 2010; 38:7513-25. [PMID: 20675722 PMCID: PMC2995075 DOI: 10.1093/nar/gkq659] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein-DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents.
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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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Ferreira ME, Berndt KD, Nilsson J, Wright APH. WD40 domain divergence is important for functional differences between the fission yeast Tup11 and Tup12 co-repressor proteins. PLoS One 2010; 5:e11009. [PMID: 20544037 PMCID: PMC2882346 DOI: 10.1371/journal.pone.0011009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 04/28/2010] [Indexed: 11/19/2022] Open
Abstract
We have previously demonstrated that subsets of Ssn6/Tup target genes have distinct requirements for the Schizosaccharomyces pombe homologs of the Tup1/Groucho/TLE co-repressor proteins, Tup11 and Tup12. The very high level of divergence in the histone interacting repression domains of the two proteins suggested that determinants distinguishing Tup11 and Tup12 might be located in this domain. Here we have combined phylogenetic and structural analysis as well as phenotypic characterization, under stress conditions that specifically require Tup12, to identify and characterize the domains involved in Tup12-specific action. The results indicate that divergence in the repression domain is not generally relevant for Tup12-specific function. Instead, we show that the more highly conserved C-terminal WD40 repeat domain of Tup12 is important for Tup12-specific function. Surface amino acid residues specific for the WD40 repeat domain of Tup12 proteins in different fission yeasts are clustered in blade 3 of the propeller-like structure that is characteristic of WD40 repeat domains. The Tup11 and Tup12 proteins in fission yeasts thus provide an excellent model system for studying the functional divergence of WD40 repeat domains.
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Affiliation(s)
- Monica E. Ferreira
- School of Life Sciences, Södertörn University, Huddinge, Sweden
- Center for Biosciences, Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Kurt D. Berndt
- School of Life Sciences, Södertörn University, Huddinge, Sweden
- Center for Biosciences, Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Johan Nilsson
- School of Life Sciences, Södertörn University, Huddinge, Sweden
| | - Anthony P. H. Wright
- School of Life Sciences, Södertörn University, Huddinge, Sweden
- Department of Laboratory Medicine, Karolinska Institutet, Huddinge, Sweden
- Center for Biosciences, Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
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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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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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Marfil V, Moya M, Pierreux CE, Castell JV, Lemaigre FP, Real FX, Bort R. Interaction between Hhex and SOX13 modulates Wnt/TCF activity. J Biol Chem 2009; 285:5726-37. [PMID: 20028982 DOI: 10.1074/jbc.m109.046649] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fine-tuning of the Wnt/TCF pathway is crucial for multiple embryological processes, including liver development. Here we describe how the interaction between Hhex (hematopoietically expressed homeobox) and SOX13 (SRY-related high mobility group box transcription factor 13), modulates Wnt/TCF pathway activity. Hhex is a homeodomain factor expressed in multiple endoderm-derived tissues, like the liver, where it is essential for proper development. The pleiotropic expression of Hhex during embryonic development and its dual role as a transcriptional repressor and activator suggest the presence of different tissue-specific partners capable of modulating its activity and function. While searching for developmentally regulated Hhex partners, we set up a yeast two-hybrid screening using an E9.5-10.5 mouse embryo library and the N-terminal domain of Hhex as bait. Among the putative protein interactors, we selected SOX13 for further characterization. We found that SOX13 interacts directly with full-length Hhex, and we delineated the interaction domains within the two proteins. SOX13 is known to repress Wnt/TCF signaling by interacting with TCF1. We show that Hhex is able to block the SOX13-dependent repression of Wnt/TCF activity by displacing SOX13 from the SOX13 x TCF1 complex. Moreover, Hhex de-repressed the Wnt/TCF pathway in the ventral foregut endoderm of cultured mouse embryos electroporated with a SOX13-expressing plasmid. We conclude that the interaction between Hhex and SOX13 may contribute to control Wnt/TCF signaling in the early embryo.
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Affiliation(s)
- Vanessa Marfil
- Unitat de Biologia Cellular i Molecular, Institut Municipal d'Investigació Mèdica, Universitat Pompeu Fabra, Barcelona 08003, Spain
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Prospective Evaluation of TLE1 as a Diagnostic Immunohistochemical Marker in Synovial Sarcoma. Am J Surg Pathol 2009; 33:1743-51. [DOI: 10.1097/pas.0b013e3181b7ed36] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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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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Larder R, Mellon PL. Otx2 induction of the gonadotropin-releasing hormone promoter is modulated by direct interactions with Grg co-repressors. J Biol Chem 2009; 284:16966-16978. [PMID: 19401468 PMCID: PMC2719334 DOI: 10.1074/jbc.m109.002485] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Hormonal communication between the hypothalamus, pituitary, and gonads orchestrates the development and regulation of mammalian reproductive function. In mice, gonadotropin-releasing hormone (GnRH) expression is limited to approximately 1000 neurons that originate in the olfactory placode then migrate to specific positions scattered throughout the hypothalamus. Coordination of the hypothalamic-pituitary-gonadal axis is dependent upon correct migration of GnRH neurons into the hypothalamus followed by the appropriate synthesis and pulsatile secretion of GnRH. Defects in any one of these processes can cause infertility. Recently, substantial progress has been made in identifying transcription factors, and their cofactors, that regulate not only adult expression of GnRH, but also the maturation of GnRH neurons. Here, we show that expression of Otx2, a homeodomain protein required for the formation of the forebrain, is dramatically up-regulated during GnRH neuronal maturation and that overexpression of Otx2 increases GnRH promoter activity in GnRH neuronal cell lines. Furthermore, Otx2 transcriptional activity is modulated by Grg4, a member of the Groucho-related-gene (Grg) family. Using mutational analysis, we show that a WRPW peptide motif within the Otx2 protein is required for physical interaction between Otx2 and Grg4. Without this physical interaction, Grg4 cannot repress Otx2-dependent activation of GnRH gene transcription. Taken together, these data show that Otx2 is important for GnRH expression and that direct interaction between Otx2 and Grg co-repressors regulates GnRH gene expression in hypothalamic neurons.
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Affiliation(s)
- Rachel Larder
- From the Department of Reproductive Medicine and Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, California 92093-0674
| | - Pamela L Mellon
- From the Department of Reproductive Medicine and Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, California 92093-0674.
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Sharma M, Brantley JG, Vassmer D, Chaturvedi G, Baas J, Vanden Heuvel GB. The homeodomain protein Cux1 interacts with Grg4 to repress p27 kip1 expression during kidney development. Gene 2009; 439:87-94. [PMID: 19332113 DOI: 10.1016/j.gene.2009.03.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 03/13/2009] [Accepted: 03/14/2009] [Indexed: 01/19/2023]
Abstract
The homeodomain protein Cux1 is highly expressed in the nephrogenic zone of the developing kidney where it functions to regulate cell proliferation. Here we show that Cux1 directly interacts with the co-repressor Grg4 (Groucho 4), a known effector of Notch signaling. Promoter reporter based luciferase assays revealed enhanced repression of p27(kip1) promoter activity by Cux1 in the presence of Grg4. Chromatin immunoprecipitation (ChIP) assays demonstrated the direct interaction of Cux1 with p27(kip1) in newborn kidney tissue in vivo. ChIP assays also identified interactions of Cux1, Grg4, HDAC1, and HDAC3 with p27(kip1) at two separate sites in the p27(kip1) promoter. DNAse1 footprinting experiments revealed that Cux1 binds to the p27(kip1) promoter on the sequence containing two Sp1 sites and a CCAAT box approximately 500 bp from the transcriptional start site, and to an AT rich sequence approximately 1.5 kb from the transcriptional start site. Taken together, these results identify Grg4 as an interacting partner for Cux1 and suggest a mechanism of p27(kip1) repression by Cux1 during kidney development.
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Affiliation(s)
- Madhulika Sharma
- Department of Anatomy, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
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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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Riz I, Lee HJ, Baxter KK, Behnam R, Hawley TS, Hawley RG. Transcriptional activation by TLX1/HOX11 involves Gro/TLE corepressors. Biochem Biophys Res Commun 2009; 380:361-5. [PMID: 19250647 DOI: 10.1016/j.bbrc.2009.01.099] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2008] [Accepted: 01/16/2009] [Indexed: 11/25/2022]
Abstract
The role of Groucho/transducin-like Enhancer of split (Gro/TLE) family members as corepressors of transcription is well documented. TLX1 is a homeodomain transcription factor involved in splenogenesis and neuron formation, and its aberrant expression gives rise to T-cell acute lymphoblastic leukemia. We demonstrate by glutathione-S-transferase pull-down assays, in vivo biotinylation tagging and confocal laser microscopy that TLX1 interacts with TLE1 via an Eh1-like motif. Paradoxically, we found that this motif is essential for optimal transcriptional activation of two TLX1 target genes, Aldh1a1 and Fhl1. Using a well characterized target of the Hairy/Enhancer of split 1 (HES1).TLE1 repressor complex, the ASCL1 gene, we show that TLX1 counteraction of ASCL1 repression by HES1 in SK-N-BE(2) neuroblastoma cells is associated with dismissal of TLE1 from the ASCL1 promoter and requires the Eh1-like motif for maximal effect. Collectively, these results indicate that TLX1-mediated target gene activation can occur in part via derepression strategies involving Gro/TLE corepressors.
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Affiliation(s)
- Irene Riz
- Department of Anatomy and Regenerative Biology, The George Washington University Medical Center, 2300 I Street NW, Washington, DC 20037, USA
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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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