1
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Xu Z, Feng Y, Yan Y, Jin H, Chen Y, Han Y, Huang S, Feng F, Fu H, Yin Y, Huang Y, Wang H, Cheng W. HHEX suppresses advanced thyroid cancer by interacting with TLE3. Mol Cell Endocrinol 2023; 574:111988. [PMID: 37302518 DOI: 10.1016/j.mce.2023.111988] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 06/08/2023] [Accepted: 06/09/2023] [Indexed: 06/13/2023]
Abstract
Haematopoietically Expressed Homeobox (HHEX) gene is highly expressed in the thyroid gland and plays critical roles in the development and differentiation of the thyroid gland. While it has been indicated to be downregulated in thyroid cancer, its function and the underlying mechanism remain unclear. Herein, we observed low expression and aberrant cytoplasmic localization of HHEX in thyroid cancer cell lines. Knockdown of HHEX significantly enhanced cell proliferation, migration and invasion, while overexpression of HHEX showed the opposite effects in vitro and in vivo. These data provide evidence that HHEX is a tumor suppressor in thyroid cancer. Additionally, our results showed that HHEX overexpression upregulated the expression of sodium iodine symporter (NIS) mRNA and also enhanced NIS promoter activity, suggesting a favorable effect of HHEX in promoting thyroid cancer differentiation. Mechanistically, HHEX exerted a regulatory effect on the expression of transducin-like enhancer of split 3 (TLE3) protein, which inhibited the Wnt/β-catenin signaling pathway. Nuclear localized HHEX bound to and upregulated TLE3 expression by preventing TLE3 protein from being distributed to the cytoplasm and being ubiquitinated. In conclusion, our study suggested that restoring HHEX expression has the potential to be a new strategy in the treatment of advanced thyroid cancer.
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Affiliation(s)
- Zhongyun Xu
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Yiyuan Feng
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Yeqing Yan
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Hongfu Jin
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Yuanyuan Chen
- Institute for Developmental and Regenerative Cardiovascular Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Yali Han
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China; Shanghai Center of Thyroid Diseases, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China
| | - Shuo Huang
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Fang Feng
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Hongliang Fu
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Yafu Yin
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China
| | - Yueye Huang
- Department of Endocrinology and Metabolism, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China; Shanghai Center of Thyroid Diseases, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, PR China.
| | - Hui Wang
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China.
| | - Weiwei Cheng
- Department of Nuclear Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China; Institute for Developmental and Regenerative Cardiovascular Medicine, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, 200092, PR China.
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2
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Jackson JT, Nutt SL, McCormack MP. The Haematopoietically-expressed homeobox transcription factor: roles in development, physiology and disease. Front Immunol 2023; 14:1197490. [PMID: 37398663 PMCID: PMC10313424 DOI: 10.3389/fimmu.2023.1197490] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 06/01/2023] [Indexed: 07/04/2023] Open
Abstract
The Haematopoietically expressed homeobox transcription factor (Hhex) is a transcriptional repressor that is of fundamental importance across species, as evident by its evolutionary conservation spanning fish, amphibians, birds, mice and humans. Indeed, Hhex maintains its vital functions throughout the lifespan of the organism, beginning in the oocyte, through fundamental stages of embryogenesis in the foregut endoderm. The endodermal development driven by Hhex gives rise to endocrine organs such as the pancreas in a process which is likely linked to its role as a risk factor in diabetes and pancreatic disorders. Hhex is also required for the normal development of the bile duct and liver, the latter also importantly being the initial site of haematopoiesis. These haematopoietic origins are governed by Hhex, leading to its crucial later roles in definitive haematopoietic stem cell (HSC) self-renewal, lymphopoiesis and haematological malignancy. Hhex is also necessary for the developing forebrain and thyroid gland, with this reliance on Hhex evident in its role in endocrine disorders later in life including a potential role in Alzheimer's disease. Thus, the roles of Hhex in embryological development throughout evolution appear to be linked to its later roles in a variety of disease processes.
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Affiliation(s)
- Jacob T. Jackson
- Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
| | - Stephen L. Nutt
- Immunology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
- Department of Medical Biology, University of Melbourne, Parkville, VIC, Australia
| | - Matthew P. McCormack
- The Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, Australia
- iCamuno Biotherapeutics, Melbourne, VIC, Australia
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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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4
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The transcription factor Hhex regulates inflammation-related genes in microglia. J Pharmacol Sci 2022; 149:166-171. [DOI: 10.1016/j.jphs.2022.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 04/05/2022] [Accepted: 04/18/2022] [Indexed: 11/18/2022] Open
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5
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Kitchen P, Lee KY, Clark D, Lau N, Lertsuwan J, Sawasdichai A, Satayavivad J, Oltean S, Afford S, Gaston K, Jayaraman PS. A Runaway PRH/HHEX-Notch3-Positive Feedback Loop Drives Cholangiocarcinoma and Determines Response to CDK4/6 Inhibition. Cancer Res 2019; 80:757-770. [PMID: 31843982 DOI: 10.1158/0008-5472.can-19-0942] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 10/16/2019] [Accepted: 12/10/2019] [Indexed: 12/21/2022]
Abstract
Aberrant Notch and Wnt signaling are known drivers of cholangiocarcinoma (CCA), but the underlying factors that initiate and maintain these pathways are not known. Here, we show that the proline-rich homeodomain protein/hematopoietically expressed homeobox (PRH/HHEX) transcription factor forms a positive transcriptional feedback loop with Notch3 that is critical in CCA. PRH/HHEX expression is elevated in CCA, and depletion of PRH reduces CCA tumor growth in a xenograft model. Overexpression of PRH in primary human biliary epithelial cells is sufficient to increase cell proliferation and produce an invasive phenotype. Interrogation of the gene networks regulated by PRH and Notch3 reveals that unlike Notch3, PRH directly activates canonical Wnt signaling. These data indicate that hyperactivation of Notch and Wnt signaling is independent of the underlying mutational landscape and has a common origin in dysregulation of PRH. Moreover, they suggest new therapeutic options based on the dependence of specific Wnt, Notch, and CDK4/6 inhibitors on PRH activity. SIGNIFICANCE: The PRH/HHEX transcription factor is an oncogenic driver in cholangiocarcinoma that confers sensitivity to CDK4/6 inhibitors.
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Affiliation(s)
- Philip Kitchen
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Ka Ying Lee
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Danielle Clark
- Department of Biochemistry, Medical School, University of Bristol, Bristol, United Kingdom
| | - Nikki Lau
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Jomnarong Lertsuwan
- Laboratory of Chemical Carcinogenesis, Chulabhorn Research Institute, Bangkok, Thailand
| | - Anyaporn Sawasdichai
- Laboratory of Chemical Carcinogenesis, Chulabhorn Research Institute, Bangkok, Thailand
| | | | - Sebastian Oltean
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, United Kingdom
| | - Simon Afford
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Kevin Gaston
- Division of Cancer and Stem Cells, School of Medicine, University of Nottingham, Nottingham, United Kingdom.
| | - Padma-Sheela Jayaraman
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
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6
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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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7
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Li Y, Wang W, Wang F, Wu Q, Li W, Zhong X, Tian K, Zeng T, Gao L, Liu Y, Li S, Jiang X, Du G, Zhou Y. Paired related homeobox 1 transactivates dopamine D2 receptor to maintain propagation and tumorigenicity of glioma-initiating cells. J Mol Cell Biol 2018; 9:302-314. [PMID: 28486630 DOI: 10.1093/jmcb/mjx017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 05/05/2017] [Indexed: 12/22/2022] Open
Abstract
Glioblastoma multiforme (GBM) is a highly invasive brain tumor with limited therapeutic means and poor prognosis. Recent studies indicate that glioma-initiating cells/glioma stem cells (GICs/GSCs) may be responsible for tumor initiation, infiltration, and recurrence. GICs could aberrantly employ molecular machinery balancing self-renewal and differentiation of embryonic neural precursors. Here, we find that paired related homeobox 1 (PRRX1), a homeodomain transcription factor that was previously reported to control skeletal development, is expressed in cortical neural progenitors and is required for their self-renewal and proper differentiation. Further, PRRX1 is overrepresented in glioma samples and labels GICs. Glioma cells and GICs depleted with PRRX1 could not propagate in vitro or form tumors in the xenograft mouse model. The GIC self-renewal function regulated by PRRX1 is mediated by dopamine D2 receptor (DRD2). PRRX1 directly binds to the DRD2 promoter and transactivates its expression in GICs. Blockage of the DRD2 signaling hampers GIC self-renewal, whereas its overexpression restores the propagating and tumorigenic potential of PRRX1-depleted GICs. Finally, PRRX1 potentiates GICs via DRD2-mediated extracellular signal-related kinase (ERK) and AKT activation. Thus, our study suggests that therapeutic targeting the PRRX1-DRD2-ERK/AKT axis in GICs is a promising strategy for treating GBMs.
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Affiliation(s)
- Yamu Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Wen Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Fangyu Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Qiushuang Wu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Wei Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Xiaoling Zhong
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Kuan Tian
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
| | - Tao Zeng
- Department of Neurosurgery, The Tenth Affiliated Hospital, Tongji University, Shanghai 200072, China.,Department of Neurosurgery, Fujian Medical University Union Hospital, Fuzhou 350001, China
| | - Liang Gao
- Department of Neurosurgery, The Tenth Affiliated Hospital, Tongji University, Shanghai 200072, China
| | - Ying Liu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China.,Medical Research Institute, Wuhan University, Wuhan 430072, China
| | - Shu Li
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China.,Medical Research Institute, Wuhan University, Wuhan 430072, China
| | - Xiaobing Jiang
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
| | - Guangwei Du
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, TX 77225, USA
| | - Yan Zhou
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences at Wuhan University, Wuhan 430072, China
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8
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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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9
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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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10
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Noy PJ, Swain RK, Khan K, Lodhia P, Bicknell R. Sprouting angiogenesis is regulated by shedding of the C-type lectin family 14, member A (CLEC14A) ectodomain, catalyzed by rhomboid-like 2 protein (RHBDL2). FASEB J 2016; 30:2311-23. [PMID: 26939791 DOI: 10.1096/fj.201500122r] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 02/18/2016] [Indexed: 11/11/2022]
Abstract
C-type lectin family 14, member A (CLEC14A), is a single-pass transmembrane glycoprotein that is overexpressed in tumor endothelial cells, and it promotes sprouting angiogenesis and modulates endothelial function via interactions with extracellular matrix proteins. Here, we show that CLEC14A is cleaved by rhomboid-like protein 2 (RHBDL2), one of 3 catalytic mammalian rhomboid-like (RHBDL) proteases, but that it is not cleaved by RHBDL1 or -3. Site-directed mutagenesis identified the precise site at which RHBDL2 cleaves CLEC14A, and targeted, small interfering RNAs that knockdown endogenous CLEC14A and RHBDL2 in human endothelial cells validated the specificity of CLEC14A shedding by RHBDL2. Loss of endogenous cleaved CLEC14A increased endothelial migration 2-fold, whereas that addition of recombinant cleaved CLEC14A inhibited the sprouting of human and murine endothelial cells 3-fold in several in vitro models. We assessed the in vivo role of cleaved CLEC14A in angiogenesis by using the rodent subcutaneous sponge implant model, and we found that CLEC14A protein inhibited vascular density by >50%. Finally, we show that cleaved CLEC14A binds to sprouting endothelial tip cells. Our data show that the ectodomain of CLEC14A regulates sprouting angiogenesis and suggests a role for RHBDL2 in endothelial function.-Noy, P. J., Swain, R. K., Khan, K., Lodhia, P., Bicknell, R. Sprouting angiogenesis is regulated by shedding of the C-type lectin family 14, member A (CLEC14A) ectodomain, catalyzed by rhomboid-like 2 protein (RHBDL2).
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Affiliation(s)
- Peter J Noy
- Angiogenesis Laboratory, Institutes for Cardiovascular Sciences and Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Rajeeb K Swain
- Angiogenesis Laboratory, Institutes for Cardiovascular Sciences and Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Kabir Khan
- Angiogenesis Laboratory, Institutes for Cardiovascular Sciences and Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Puja Lodhia
- Angiogenesis Laboratory, Institutes for Cardiovascular Sciences and Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Roy Bicknell
- Angiogenesis Laboratory, Institutes for Cardiovascular Sciences and Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
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11
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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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12
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Blocking CLEC14A-MMRN2 binding inhibits sprouting angiogenesis and tumour growth. Oncogene 2015; 34:5821-31. [PMID: 25745997 PMCID: PMC4724939 DOI: 10.1038/onc.2015.34] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 11/03/2014] [Accepted: 12/12/2014] [Indexed: 12/16/2022]
Abstract
We previously identified CLEC14A as a tumour endothelial marker. Here we show CLEC14A is a regulator of sprouting angiogenesis in vitro and in vivo. Using a HUVEC spheroid sprouting assay we found CLEC14A to be a regulator of sprout initiation. Analysis of endothelial sprouting in aortic ring and in vivo subcutaneous sponge assays from clec14a+/+ and clec14a−/− mice revealed defects in sprouting angiogenesis in CLEC14A deficient animals. Tumour growth was retarded and vascularity reduced in clec14a−/− mice. Pulldown and co-immunoprecipitation experiments confirmed MMRN2 binds to the extracellular region of CLEC14A. The CLEC14A-MMRN2 interaction was interrogated using mouse monoclonal antibodies. Monoclonal antibodies were screened for their ability to block this interaction. Clone C4 but not C2 blocked CLEC14A-MMRN2 binding. C4 antibody perturbed tube formation and endothelial sprouting in vitro and in vivo, with a similar phenotype to loss of CLEC14A. Significantly, tumour growth was impaired in C4 treated animals and vascular density was also reduced in the C4 treated group. We conclude that CLEC14A-MMRN2 binding has a role in inducing sprouting angiogenesis during tumour growth, that has the potential to be manipulated in future anti-angiogenic therapy design.
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13
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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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14
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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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15
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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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16
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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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17
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Nimmo ER, Stevens C, Phillips AM, Smith A, Drummond HE, Noble CL, Quail M, Davies G, Aldhous MC, Wilson DC, Satsangi J. TLE1 modifies the effects of NOD2 in the pathogenesis of Crohn's disease. Gastroenterology 2011; 141:972-981.e1-2. [PMID: 21699783 DOI: 10.1053/j.gastro.2011.05.043] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 05/16/2011] [Accepted: 05/20/2011] [Indexed: 12/17/2022]
Abstract
BACKGROUND & AIMS The mechanisms by which specific mutations in NOD2/CARD15 increase the risk for Crohn's disease (CD) are unclear. We identified proteins that interact with NOD2 and investigated them by expression, genetic, and functional analyses. METHODS By using a yeast 2-hybrid screen of an intestinal epithelial library, we identified proteins that interact with NOD2 and confirmed the interactions in mammalian cells using co-immunoprecipitation. We used microarray analysis to analyze gene expression patterns in 302 intestinal biopsy samples (129 from patients with ulcerative colitis [UC], 106 with CD, and 67 controls). Eighty single-nucleotide polymorphisms within the genes that encoded 6 interacting proteins were genotyped in a discovery cohort (869 cases of inflammatory bowel disease [IBD], 885 controls) and a replication cohort (504 patients with IBD, 713 controls). We investigated interaction between transducin-like enhancer of split 1 (TLE1) and NOD2 in HEK293 cells. RESULTS We identified 6 NOD2-interacting proteins (TLE1, UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 2 [GALNT2], HIV-1 Tat interactive protein [HTATIP], Vimentin, fission 1 (mitochondrial outer membrane) homolog [FIS1], and protein phosphatase 2, regulatory subunit B', epsilon isoform [PPP2R5E]). Of these, expression of GALNT2 (CD, P = .004) and vimentin (CD, P = .006; UC, P = .0025) was altered in patients with IBD compared with controls. Single-nucleotide polymorphisms within TLE1 were associated with susceptibility to CD, specifically with ileal disease (rs6559629, P = 3.1 × 10⁻⁵; odds ratio, 1.45). The TLE1 risk allele is required for susceptibility to CD in carriers of NOD2 mutations. In cells, TLE1 and NOD2 co-localized around the nuclear membrane and TLE1 inhibited activation of nuclear factor-κB by NOD2. CONCLUSIONS Epistatic and biological interactions between TLE1 and NOD2 are involved in IBD pathogenesis. NOD2 might be involved in a series of pathways such as epigenetic regulation of expression (via TLE1 and HTATIP), biosynthesis of mucin (via GALNT2), apoptosis (via PPP2R5E and FIS1), and integrity of the intracellular cytoskeleton (vimentin).
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Affiliation(s)
- Elaine R Nimmo
- Gastrointestinal Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh, UK.
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18
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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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19
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Locker J. Transcriptional Control of Hepatocyte Differentiation. MOLECULAR PATHOLOGY LIBRARY 2011. [DOI: 10.1007/978-1-4419-7107-4_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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20
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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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21
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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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22
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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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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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