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Yao H, Zhang M, Wang D. The next decade of SET: from an oncoprotein to beyond. J Mol Cell Biol 2024; 16:mjad082. [PMID: 38157418 PMCID: PMC11267991 DOI: 10.1093/jmcb/mjad082] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 11/22/2023] [Accepted: 12/24/2023] [Indexed: 01/03/2024] Open
Abstract
This year marks the fourth decade of research into the protein SET, which was discovered in 1992. SET was initially identified as an oncoprotein but later shown to be a multifaceted protein involved in regulating numerous biological processes under both physiological and pathophysiological conditions. SET dysfunction is closely associated with diseases, such as cancer and Alzheimer's disease. With the increasing understanding of how SET works and how it is regulated in cells, targeting aberrant SET has emerged as a potential strategy for disease intervention. In this review, we present a comprehensive overview of the advancements in SET studies, encompassing its biological functions, regulatory networks, clinical implications, and pharmacological inhibitors. Furthermore, we provide insights into the future prospects of SET research, with a particular emphasis on its promising potential in the realm of immune modulation.
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Affiliation(s)
- Han Yao
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China
| | - Meng Zhang
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China
| | - Donglai Wang
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100005, China
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Chen J, Jiao Z, Liu Y, Zhang M, Wang D. USP7 interacts with and destabilizes oncoprotein SET. Biochem Biophys Res Commun 2024; 709:149818. [PMID: 38555840 DOI: 10.1016/j.bbrc.2024.149818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 03/21/2024] [Indexed: 04/02/2024]
Abstract
Oncoprotein SE translocation (SET) is frequently overexpressed in different types of tumors and correlated with poor prognosis of cancer patients. Targeting SET has been considered a promising strategy for cancer intervention. However, the mechanisms by which SET is regulated under cellular conditions are largely unknown. Here, by performing a tandem affinity purification-mass spectrometry (TAP-MS), we identify that the ubiquitin-specific protease 7 (USP7) forms a stable protein complex with SET in cancer cells. Further analyses reveal that the acidic domain of SET directly binds USP7 while both catalytic domain and ubiquitin-like (UBL) domains of USP7 are required for SET binding. Knockdown of USP7 has no effect on the mRNA level of SET. However, we surprisingly find that USP7 depletion leads to a dramatic elevation of SET protein levels, suggesting that USP7 plays a key role in destabilizing oncoprotein SET, possibly through an indirect mechanism. To our knowledge, our data report the first deubiquitinase (DUB) that physically associates with oncoprotein SET and imply an unexpected regulatory effect of USP7 on SET stability.
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Affiliation(s)
- Jianyuan Chen
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100005, China
| | - Zishan Jiao
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100005, China
| | - Yajing Liu
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100005, China
| | - Meng Zhang
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100005, China
| | - Donglai Wang
- State Key Laboratory of Common Mechanism Research for Major Diseases & Department of Medical Genetics, Institute of Basic Medical Sciences & School of Basic Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100005, China.
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Xu H, Wu D, Xiao M, Lei Y, Lei Y, Yu X, Shi S. PP2A complex disruptor SET prompts widespread hypertranscription of growth-essential genes in the pancreatic cancer cells. SCIENCE ADVANCES 2024; 10:eadk6633. [PMID: 38277454 PMCID: PMC10816699 DOI: 10.1126/sciadv.adk6633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 12/26/2023] [Indexed: 01/28/2024]
Abstract
Hyperactivation of the oncogenic transcription reflects the epigenetic plasticity of the cancer cells. Su(var)3-9, enhancer of zeste, Trithorax (SET) was described as a nuclear factor that stimulated transcription from the chromatin template. However, the mechanisms of SET-dependent transcription are unknown. Here, we found that overexpression of SET and CDK9 induced very similar transcriptome signatures in multiple cancer cell lines. SET localized in the transcription start site (TSS)-proximal regions and supported the RNA transcription. SET specifically bound the PP2A-C subunit and induced PP2A-A subunit repulsion from the C subunit, which indicated the role of SET as a PP2A-A/C complex disruptor in the TSS-proximal regions. Through blocking PP2A activity, SET assisted CDK9 to maintain Pol II CTD phosphorylation and activated mRNA transcription. Our findings position SET as a key factor that modulates chromatin PP2A activity, promoting the oncogenic transcription in the pancreatic cancer.
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Affiliation(s)
- He Xu
- Department of Pancreatic Surgery, Fudan University Shanghai Cancer Center, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Pancreatic Cancer Institute, Shanghai 200032, China
- Pancreatic Cancer Institute, Fudan University, Shanghai 200032, China
| | - Di Wu
- Department of Pancreatic Surgery, Fudan University Shanghai Cancer Center, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Pancreatic Cancer Institute, Shanghai 200032, China
- Pancreatic Cancer Institute, Fudan University, Shanghai 200032, China
| | - Mingming Xiao
- Department of Pancreatic Surgery, Fudan University Shanghai Cancer Center, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Pancreatic Cancer Institute, Shanghai 200032, China
- Pancreatic Cancer Institute, Fudan University, Shanghai 200032, China
| | - Yubin Lei
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, Zhejiang Province 310024, China
| | - Yalan Lei
- Department of Pancreatic Surgery, Fudan University Shanghai Cancer Center, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Pancreatic Cancer Institute, Shanghai 200032, China
- Pancreatic Cancer Institute, Fudan University, Shanghai 200032, China
| | - Xianjun Yu
- Department of Pancreatic Surgery, Fudan University Shanghai Cancer Center, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Pancreatic Cancer Institute, Shanghai 200032, China
- Pancreatic Cancer Institute, Fudan University, Shanghai 200032, China
| | - Si Shi
- Department of Pancreatic Surgery, Fudan University Shanghai Cancer Center, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Pancreatic Cancer Institute, Shanghai 200032, China
- Pancreatic Cancer Institute, Fudan University, Shanghai 200032, China
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Xing D, Wells JM. Putting a Novel Emphysema Treatment on the SMAP. Am J Respir Cell Mol Biol 2023; 69:491-492. [PMID: 37552790 PMCID: PMC10633842 DOI: 10.1165/rcmb.2023-0263ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 08/08/2023] [Indexed: 08/10/2023] Open
Affiliation(s)
- Dongqi Xing
- Division of Pulmonary, Allergy, and Critical Care Medicine
- Lung Health Center
- Cardiopulmonary Research Program University of Alabama at Birmingham Birmingham, Alabama
| | - J Michael Wells
- Division of Pulmonary, Allergy, and Critical Care Medicine
- Lung Health Center
- Cardiopulmonary Research Program University of Alabama at Birmingham Birmingham, Alabama
- Department of Veterans Affairs Birmingham VA Healthcare System Birmingham, Alabama
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The repression of oncoprotein SET by the tumor suppressor p53 reveals a p53-SET-PP2A feedback loop for cancer therapy. SCIENCE CHINA. LIFE SCIENCES 2023; 66:81-93. [PMID: 35881220 DOI: 10.1007/s11427-021-2123-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 04/30/2022] [Indexed: 02/04/2023]
Abstract
The oncoprotein SET is frequently overexpressed in many types of tumors and contributes to malignant initiation and progression through multiple mechanisms, including the hijacking of the tumor suppressors p53 and PP2A. Targeting aberrant SET represents a promising strategy for cancer intervention. However, the mechanism by which endogenous SET is regulated in cancer cells remains largely unknown. Here, we identified the tumor suppressor p53 as a key regulator that transcriptionally repressed the expression of SET in both normal and cancer cells. In addition, p53 stimulated PP2A phosphatase activity via p53-mediated transcriptional repression of SET, whereby SET-mediated inhibition of PP2A was alleviated. Moreover, targeting the interaction between SET and PP2A catalytic subunit (PP2Ac) with FTY720 enhanced stress-induced p53 activation via PP2A-mediated dephosphorylation of p53 on threonine 55 (Thr55). Therefore, our findings uncovered a previously unknown p53-SET-PP2A regulatory feedback loop. To functionally potentiate this feedback loop, we designed a combined therapeutic strategy by simultaneously administrating a p53 activator and SET antagonist in cancer cells and observed a dramatic synergistic effect on tumor suppression. Our study reveals mechanistic insight into the regulation of the oncoprotein SET and raises a potential strategy for cancer therapy by stimulating the p53-SET-PP2A feedback loop.
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Di Mambro A, Esposito M. Thirty years of SET/TAF1β/I2PP2A: from the identification of the biological functions to its implications in cancer and Alzheimer's disease. Biosci Rep 2022; 42:BSR20221280. [PMID: 36345878 PMCID: PMC9679398 DOI: 10.1042/bsr20221280] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 10/17/2022] [Accepted: 11/07/2022] [Indexed: 10/29/2023] Open
Abstract
The gene encoding for the protein SE translocation (SET) was identified for the first time 30 years ago as part of a chromosomal translocation in a patient affected by leukemia. Since then, accumulating evidence have linked overexpression of SET, aberrant SET splicing, and cellular localization to cancer progression and development of neurodegenerative tauopathies such as Alzheimer's disease. Molecular biology tools, such as targeted genetic deletion, and pharmacological approaches based on SET antagonist peptides, have contributed to unveil the molecular functions of SET and its implications in human pathogenesis. In this review, we provide an overview of the functions of SET as inhibitor of histone and non-histone protein acetylation and as a potent endogenous inhibitor of serine-threonine phosphatase PP2A. We discuss the role of SET in multiple cellular processes, including chromatin remodelling and gene transcription, DNA repair, oxidative stress, cell cycle, apoptosis cell migration and differentiation. We review the molecular mechanisms linking SET dysregulation to tumorigenesis and discuss how SET commits neurons to progressive cell death in Alzheimer's disease, highlighting the rationale of exploiting SET as a therapeutic target for cancer and neurodegenerative tauopathies.
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Affiliation(s)
- Antonella Di Mambro
- The Centre for Integrated Research in Life and Health Sciences, School of Health and Life Science, University of Roehampton, London, U.K
| | - Maria Teresa Esposito
- The Centre for Integrated Research in Life and Health Sciences, School of Health and Life Science, University of Roehampton, London, U.K
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Han D, Wang L, Long L, Su P, Luo D, Zhang H, Li Z, Chen B, Zhao W, Zhang N, Wang X, Liang Y, Li Y, Hu G, Yang Q. The E3 Ligase TRIM4 Facilitates SET Ubiquitin-Mediated Degradation to Enhance ER-α Action in Breast Cancer. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2201701. [PMID: 35843886 PMCID: PMC9443474 DOI: 10.1002/advs.202201701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 06/10/2022] [Indexed: 06/15/2023]
Abstract
Estrogen receptor alpha (ER-α) action is critical for hormone-dependent breast cancer, and ER-α dysregulation can lead to the emergence of resistance to endocrine therapy. Here, it is found that TRIM4 is downregulated in tamoxifen (TAM)-resistant breast cancer cells, while the loss of TRIM4 is associated with an unfavorable prognosis. In vitro and in vivo experiments confirm that TRIM4 increased ER-α expression and the sensitivity of breast cancer cells to TAM. Mechanistically, TRIM4 is found to target SET, and TRIM4-SET interactions are mediated by the RING and B-box domains of TRIM4 and the carboxyl terminus of SET. Moreover, it is determined that TRIM4 catalyzed the K48-linked polyubiquitination of SET (K150 and K172), promoting its proteasomal degradation and disassociation from p53 and PP2A. Once released, p53 and PP2A are able to further promote ESR1 gene transcription and enhance mRNA stability. Moreover, univariate and multivariate Cox proportional hazards regression analyses confirm that TRIM4 expression is an independent predictor of overall survival and recurrence-free survival outcomes in patients with ER-α positive breast cancer. Taken together, the data highlights a previously undiscovered mechanism and suggest that TRIM4 is a valuable biomarker that can be analyzed to predict response to endocrine therapy in breast cancer patients.
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Affiliation(s)
- Dianwen Han
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Lijuan Wang
- Pathology Tissue BankQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Li Long
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
- Mianyang Central HospitalSchool of MedicineUniversity of Electronic Science and Technology of ChinaMianyangSichuan621000China
| | - Peng Su
- Department of PathologyQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Dan Luo
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Hanwen Zhang
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Zheng Li
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Bing Chen
- Pathology Tissue BankQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Wenjing Zhao
- Pathology Tissue BankQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Ning Zhang
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Xiaolong Wang
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Yiran Liang
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Yaming Li
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
| | - Guohong Hu
- The Key Laboratory of Stem Cell BiologyInstitute of Health SciencesShanghai Institutes for Biological SciencesChinese Academy of Sciences & Shanghai Jiao Tong University School of MedicineUniversity of Chinese Academy of SciencesShanghai200233China
| | - Qifeng Yang
- Department of Breast Surgery, General SurgeryQilu Hospital of Shandong UniversityJinanShandong250012China
- Pathology Tissue BankQilu Hospital of Shandong UniversityJinanShandong250012China
- Research Institute of Breast CancerShandong UniversityJinanShandong250012China
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Casado-Combreras MÁ, Rivero-Rodríguez F, Elena-Real CA, Molodenskiy D, Díaz-Quintana A, Martinho M, Gerbaud G, González-Arzola K, Velázquez-Campoy A, Svergun D, Belle V, De la Rosa MA, Díaz-Moreno I. PP2A is activated by cytochrome c upon formation of a diffuse encounter complex with SET/TAF-Iβ. Comput Struct Biotechnol J 2022; 20:3695-3707. [PMID: 35891793 PMCID: PMC9293736 DOI: 10.1016/j.csbj.2022.07.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 07/04/2022] [Accepted: 07/04/2022] [Indexed: 11/25/2022] Open
Abstract
Intrinsic protein flexibility is of overwhelming relevance for intermolecular recognition and adaptability of highly dynamic ensemble of complexes, and the phenomenon is essential for the understanding of numerous biological processes. These conformational ensembles-encounter complexes-lack a unique organization, which prevents the determination of well-defined high resolution structures. This is the case for complexes involving the oncoprotein SET/template-activating factor-Iβ (SET/TAF-Iβ), a histone chaperone whose functions and interactions are significantly affected by its intrinsic structural plasticity. Besides its role in chromatin remodeling, SET/TAF-Iβ is an inhibitor of protein phosphatase 2A (PP2A), which is a key phosphatase counteracting transcription and signaling events controlling the activity of DNA damage response (DDR) mediators. During DDR, SET/TAF-Iβ is sequestered by cytochrome c (Cc) upon migration of the hemeprotein from mitochondria to the cell nucleus. Here, we report that the nuclear SET/TAF-Iβ:Cc polyconformational ensemble is able to activate PP2A. In particular, the N-end folded, globular region of SET/TAF-Iβ (a.k.a. SET/TAF-Iβ ΔC)-which exhibits an unexpected, intrinsically highly dynamic behavior-is sufficient to be recognized by Cc in a diffuse encounter manner. Cc-mediated blocking of PP2A inhibition is deciphered using an integrated structural and computational approach, combining small-angle X-ray scattering, electron paramagnetic resonance, nuclear magnetic resonance, calorimetry and molecular dynamics simulations.
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Key Words
- ANP32B, Acidic leucine-rich nuclear phosphoprotein family member B
- BTFA, 3-bromo-1,1,1-trifluoroacetone
- CD, Circular dichroism
- CDK9, Cyclin-dependent kinase 9
- CW, Continuous wave
- Cc, Cytochrome c
- Cytochrome c
- DDR, DNA damage response
- DEER, Double electron–electron resonance
- DLS, Dynamic light scattering
- DMEM, Dulbecco’s modified Eagle’s medium
- DNA, Deoxyribonucleic acid
- DTT, Dithiotreitol
- Dmax, Maximum dimension
- EDTA, Ethylenediamine tetraacetic acid
- EGTA, Ethyleneglycol tetraacetic acid
- EPR, Electron paramagnetic resonance
- Encounter complex
- FBS, Fetal bovine serum
- GUI, Graphical user interface
- HEK, Human embryonic kidney cells
- HRP, Horseradish peroxidase
- I2PP2A, Inhibitor 2 of the protein phosphatase 2A
- I3PP2A, Inhibitor 3 of the protein phosphatase 2A
- INTAC, Integrator-PP2A complex
- IPTG, Isopropyl-β-D-1-thiogalactopyranoside
- ITC, Isothermal titration calorimetry
- Ip/Id, Intensity ratio of NMR resonances between paramagnetic and diamagnetic samples
- LB, Luria-Bertani
- MD, Molecular dynamics
- MTS, (1-acetoxy-2,2,5,5-tetramethyl-δ-3-pyrroline-3-methyl) methanethiosulfonate
- MTSL, (1-oxyl-2,2,5,5-tetramethyl- δ −3-pyrroline-3-methyl) methanethiosulfonate
- MW, Molecular weight
- Molecular dynamics
- NAP1, Nucleosome assembly protein 1
- NAPL, Nucleosome assembly protein L
- NMA, Normal mode analysis
- NMR, Nuclear magnetic resonance
- NPT, Constant number, pressure and temperature
- NVT, Constant number, volume and temperature
- Nuclear magnetic resonance
- OD600, Optical density measured at 600 nm
- OPC, Optimal 3-charge, 4-point rigid water model
- PCR, Polymerase chain reaction
- PME, Particle mesh Ewald
- PMSF, Phenylmethylsulfonyl fluoride
- PP2A, Protein phosphatase 2A
- PRE, Paramagnetic relaxation enhancement
- PVDF, Polyvinylidene fluoride
- Protein phosphatase 2A
- RNA, Ribonucleic acid
- RNApol II, RNA polymerase II
- Rg, Radius of gyration
- SAXS, Small-angle X-ray scattering
- SC, Sample changer
- SDS-PAGE, Sodium dodecylsulfate-polyacrylamide gel electrophoresis
- SDSL, Site-directed spin labeling
- SEC, Size-exclusion chromatography
- SET/TAF-Iβ
- SET/TAF-Iβ ΔC, SET/template-activating factor-Iβ construct lacking its C-terminal domain
- SET/TAF-Iβ, SET/template-activating factor-Iβ
- SPRi, Surface plasmon resonance imaging
- TAF-Iα, Template-activating factor-Iα
- TPBS, Tween 20-phosphate buffered saline
- VPS75, Vacuolar protein sorting-associated protein 75
- WT, Wild type
- XRD, X-ray diffraction
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Affiliation(s)
- Miguel Á. Casado-Combreras
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
| | - Francisco Rivero-Rodríguez
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
| | - Carlos A. Elena-Real
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
- Centre de Biologie Structurale (CBS), INSERM, Centre National de la Recherche Scientifique (CNRS) and Université de Montpellier. 29 rue de Navacelles, 34090 Montpellier, France
| | - Dmitry Molodenskiy
- European Molecular Biology Laboratory, Hamburg Outstation, c/o Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - Antonio Díaz-Quintana
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
| | - Marlène Martinho
- Aix Marseille Univ. Centre National de la Recherche Scientifique (CNRS), BIP UMR7281, Bioénergétique et Ingénierie des protéines, 13402 Marseille, France
| | - Guillaume Gerbaud
- Aix Marseille Univ. Centre National de la Recherche Scientifique (CNRS), BIP UMR7281, Bioénergétique et Ingénierie des protéines, 13402 Marseille, France
| | - Katiuska González-Arzola
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
| | - Adrián Velázquez-Campoy
- Institute of Biocomputation and Physic of Complex Systems (BIFI), Joint Unit GBsC-CSIC-BIFI, Universidad de Zaragoza. C. de Mariano Esquillor Gómez, Edificio I+D, 50018 Zaragoza, Spain
- Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, C. Pedro Cerbuna, 12, 50009 Zaragoza, Spain
- Instituto de Investigación Sanitaria de Aragón (IIS Aragon), Zaragoza, Spain
- Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas (CIBERehd), C. de Melchor Fernández Almagro, 3, 28029 Madrid, Spain
| | - Dmitri Svergun
- European Molecular Biology Laboratory, Hamburg Outstation, c/o Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - Valérie Belle
- Aix Marseille Univ. Centre National de la Recherche Scientifique (CNRS), BIP UMR7281, Bioénergétique et Ingénierie des protéines, 13402 Marseille, France
| | - Miguel A. De la Rosa
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
| | - Irene Díaz-Moreno
- Institute for Chemical Research (IIQ), Scientific Research Centre “Isla de la Cartuja” (cicCartuja), University of Seville and CSIC, Avda. Américo Vespucio, 49, 41092 Seville, Spain
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9
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Nenasheva VV, Makarova IV, Stepanenko EA, Antonov SA, Novosadova EV, Narsullaeva AR, Kozikova LV, Polteva EA, Sleptsova LA, Shcherbatova NA, Khaidarova NV, Andreeva LE, Tarantul VZ. Human TAF-Iα promotes oncogenic transformation via enhancement of cell proliferation and suppression of apoptosis. In Vitro Cell Dev Biol Anim 2021; 57:531-538. [PMID: 34021475 DOI: 10.1007/s11626-021-00572-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/29/2021] [Indexed: 11/24/2022]
Abstract
Template activating factor-I (TAF-I) is a multifunctional protein involved in various biological processes including the inhibition of histone acetylation, DNA replication, cell cycle regulation, and oncogenesis. Two main TAF-I isoforms with different N-termini, TAF-Iα and TAF-Iβ (SET), are expressed in cells. There are numerous data about functional properties of TAF-Iβ, whereas the effects of TAF-Iα remain largely unexplored. Here, we employed focus formation and cell proliferation assays, TUNEL staining, cytological analysis, and RT-qPCR to compare the effects of human TAF-Iα and TAF-Iβ genes, transiently expressed in Rat2 cells and in Misgurnus fossilis loaches. We found that both TAF-I isoforms possessed equal oncogenic potential in these systems. Furthermore, an overexpression of human TAF-Iα and TAF-Iβ in Rat2 cells promoted their proliferation. Accordingly, the mitotic index was increased in the transgenic loaches expressing human TAF-Iα or TAF-Iβ. TUNEL assay as well as downregulation of p53 gene and upregulation of bcl-2 gene in these transgenic loaches demonstrated that both isoforms suppressed apoptosis. Thus, TAF-Iα isoform exerts the same oncogenic potential as TAF-Iβ, likely by suppressing the apoptosis and promoting cell proliferation.
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Affiliation(s)
- Valentina V Nenasheva
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia.
| | - Irina V Makarova
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Ekaterina A Stepanenko
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Stanislav A Antonov
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Ekaterina V Novosadova
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Anastasia R Narsullaeva
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Larisa V Kozikova
- Russian Research Institute of Farm Animal Genetics and Breeding - Branch of the L. K. Ernst Federal Science Center for Animal Husbandry, St. Petersburg, 196601, Russia
| | - Ekaterina A Polteva
- Russian Research Institute of Farm Animal Genetics and Breeding - Branch of the L. K. Ernst Federal Science Center for Animal Husbandry, St. Petersburg, 196601, Russia
| | - Lyudmila A Sleptsova
- Faculty of Biology, Department of Embryology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Natalya A Shcherbatova
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Nella V Khaidarova
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Lyudmila E Andreeva
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Vyacheslav Z Tarantul
- Department of Viral and Cellular Molecular Genetics, Institute of Molecular Genetics of National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
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10
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Distribution of SET/I2PP2A protein in gastrointestinal tissues. PLoS One 2019; 14:e0222845. [PMID: 31557212 PMCID: PMC6762106 DOI: 10.1371/journal.pone.0222845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 09/09/2019] [Indexed: 11/21/2022] Open
Abstract
SET (also called I2PP2A and TIF-1) is a multi-functional protein that regulates a variety of cell signaling including nucleosome assembly, histone binding, and tumorigenesis. Elevated SET protein levels are observed in various human tumors, and are correlated with poor prognosis and drug-resistance. We recently reported that SET protein levels in cancer cells were positively correlated with poor prognosis of gastric cancer patients. Using immunohistochemistry, SET protein was observed not only in cancer cells, but also in some interstitial cells. However, the tissue distribution of SET has not been investigated. Here we performed co-immunofluorescent staining to characterize SET protein distribution in gastrointestinal tissues. We found that even though the positive rate is much lower than epithelial cells, SET protein is also expressed in non-epithelial cells, such as monocytes/macrophages, neural cells, myofibroblasts, and smooth muscle cells. Our results indicate an extensive role of SET in a variety of cell types.
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11
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Qu Q, Zhang Q, Yang L, Chen Y, Liu H. SET binding to Sgo1 inhibits Sgo1-cohesin interactions and promotes chromosome segregation. J Cell Biol 2019; 218:2514-2528. [PMID: 31227592 PMCID: PMC6683731 DOI: 10.1083/jcb.201810096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 03/29/2019] [Accepted: 05/15/2019] [Indexed: 12/28/2022] Open
Abstract
At anaphase onset, Sgo1 function of cohesion protection must be disabled to allow timely chromosome segregation, but how this is achieved is not fully understood. Here, we show that SET, a known PP2A inhibitor, directly binds to a domain in Sgo1 in close proximity to the cohesin-binding motif. The Sgo1-cohesin binding can be disrupted by SET in a dose-dependent manner in vitro as well as by SET overexpression in cells, suggesting that SET is also an inhibitor to the Sgo1-cohesin binding. Furthermore, the SET binding-deficient Sgo1 mutant fully supports centromeric cohesion protection but delays chromosome segregation, suggesting that the SET-Sgo1 binding is required for timely chromosome segregation. Moreover, overexpression of SET WT, not the Sgo1 binding-deficient mutant, exacerbates the occurrence of cohesion fatigue in MG132-arrested cells. Conversely, SET depletion delays it. Thus, we propose that a major function of SET during mitosis is to disrupt the Sgo1-cohesin interaction, thereby promoting centromeric cohesion de-protection and timely chromosome segregation at anaphase onset.
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Affiliation(s)
- Qianhui Qu
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Qian Zhang
- Department of Biochemistry and Molecular Biology and Tulane Aging Center, Tulane University Health Science Center, New Orleans, LA
| | - Lu Yang
- Department of Biochemistry and Molecular Biology and Tulane Aging Center, Tulane University Health Science Center, New Orleans, LA
| | - Yujue Chen
- Department of Biochemistry and Molecular Biology and Tulane Aging Center, Tulane University Health Science Center, New Orleans, LA
| | - Hong Liu
- Department of Biochemistry and Molecular Biology and Tulane Aging Center, Tulane University Health Science Center, New Orleans, LA
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12
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SET protein accumulation prevents cell death in head and neck squamous cell carcinoma through regulation of redox state and autophagy. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:623-637. [DOI: 10.1016/j.bbamcr.2019.01.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 01/06/2019] [Accepted: 01/08/2019] [Indexed: 12/29/2022]
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13
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De Palma RM, Parnham SR, Li Y, Oaks JJ, Peterson YK, Szulc ZM, Roth BM, Xing Y, Ogretmen B. The NMR-based characterization of the FTY720-SET complex reveals an alternative mechanism for the attenuation of the inhibitory SET-PP2A interaction. FASEB J 2019; 33:7647-7666. [PMID: 30917007 DOI: 10.1096/fj.201802264r] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The su(var)3-9, enhancer of zeste, trithorax (SET)/inhibitor 2 of protein phosphatase 2A (PP2A) oncoprotein binds and inhibits PP2A, composed of various isoforms of scaffolding, regulatory, and catalytic subunits. Targeting SET with a sphingolipid analog drug fingolimod (FTY720) or ceramide leads to the reactivation of tumor suppressor PP2A. However, molecular details of the SET-FTY720 or SET-ceramide, and mechanism of FTY720-dependent PP2A activation, remain unknown. Here, we report the first in solution examination of the SET-FTY720 or SET-ceramide complexes by NMR spectroscopy. FTY720-ceramide binding resulted in chemical shifts of residues residing at the N terminus of SET, preventing its dimerization or oligomerization. This then released SET from PP2ACα, resulting in PP2A activation, while monomeric SET remained associated with the B56γ. Our data also suggest that the PP2A holoenzyme, composed of PP2A-Aβ, PP2A-B56γ, and PP2ACα subunits, is selectively activated in response to the formation of the SET-FTY720 complex in A549 cells. Various PP2A-associated downstream effector proteins in the presence or absence of FTY720 were then identified by stable isotope labeling with amino cells in cell culture, including tumor suppressor nonmuscle myosin IIA. Attenuation of FTY720-SET association by point mutations of residues that are involved in FTY720 binding or dephosphorylation of SET at Serine 171, enhanced SET oligomerization and the formation of the SET-PP2A inhibitory complex, leading to resistance to FTY720-dependent PP2A activation.-De Palma, R. M., Parnham, S. R., Li, Y., Oaks, J. J., Peterson, Y. K., Szulc, Z. M., Roth, B. M., Xing, Y., Ogretmen, B. The NMR-based characterization of the FTY720-SET complex reveals an alternative mechanism for the attenuation of the inhibitory SET-PP2A interaction.
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Affiliation(s)
- Ryan M De Palma
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Stuart R Parnham
- Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Yitong Li
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | | | - Yuri K Peterson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Zdzislaw M Szulc
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Braden M Roth
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Yongna Xing
- McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Besim Ogretmen
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.,Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina, USA
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14
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Elgenaidi IS, Spiers JP. Regulation of the phosphoprotein phosphatase 2A system and its modulation during oxidative stress: A potential therapeutic target? Pharmacol Ther 2019; 198:68-89. [PMID: 30797822 DOI: 10.1016/j.pharmthera.2019.02.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 02/15/2019] [Indexed: 02/06/2023]
Abstract
Phosphoprotein phosphatases are of growing interest in the pathophysiology of many diseases and are often the neglected partner of protein kinases. One family member, PP2A, accounts for dephosphorylation of ~55-70% of all serine/threonine phosphosites. Interestingly, dysregulation of kinase signalling is a hallmark of many diseases in which an increase in oxidative stress is also noted. With this in mind, we assess the evidence to support oxidative stress-mediated regulation of the PP2A system In this article, we first present an overview of the PP2A system before providing an analysis of the regulation of PP2A by endogenous inhibitors, post translational modification, and miRNA. Next, a detailed critique of data implicating reactive oxygen species, ischaemia, ischaemia-reperfusion, and hypoxia in regulating the PP2A holoenzyme and associated regulators is presented. Finally, the pharmacological targeting of PP2A, its endogenous inhibitors, and enzymes responsible for its post-translational modification are covered. There is extensive evidence that oxidative stress modulates multiple components of the PP2A system, however, most of the data pertains to the catalytic subunit of PP2A. Irrespective of the underlying aetiology, free radical-mediated attenuation of PP2A activity is an emerging theme. However, in many instances, a dichotomy exists, which requires clarification and mechanistic insight. Nevertheless, this raises the possibility that pharmacological activation of PP2A, either through small molecule activators of PP2A or CIP2A/SET antagonists may be beneficial in modulating the cellular response to oxidative stress. A better understanding of which, will have wide ranging implications for cancer, heart disease and inflammatory conditions.
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Affiliation(s)
- I S Elgenaidi
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland
| | - J P Spiers
- Department of Pharmacology and Therapeutics, Trinity College Dublin, Ireland.
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15
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Brander DM, Friedman DR, Volkheimer AD, Christensen DJ, Rassenti LZ, Kipps TJ, Guadalupe E, Chen Y, Zhang D, Wang X, Davis C, Owzar K, Weinberg JB. SET alpha and SET beta mRNA isoforms in chronic lymphocytic leukaemia. Br J Haematol 2018; 184:605-615. [PMID: 30443898 DOI: 10.1111/bjh.15677] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 09/04/2018] [Indexed: 01/01/2023]
Abstract
Alteration in RNA splicing is implicated in carcinogenesis and progression. Mutations in spliceosome genes and alternative splicing of other genes have been noted in chronic lymphocytic leukaemia (CLL), a common B cell malignancy with heterogeneous outcomes. We previously demonstrated that differences in the amount of SET oncoprotein (a physiological inhibitor of the serine/threonine phosphatase, PP2A) is associated with clinical aggressiveness in patients with CLL. It is unknown if alternative splicing of gene transcripts regulating kinases and phosphatases affects disease pathobiology and CLL progression. We show here for the first time that mRNA levels of the alternatively spliced SET isoforms, SETA and SETB (SETα and SETβ), significantly correlate with disease severity (overall survival and time-to-first-treatment) in CLL patients. In addition, we demonstrate that relative increase of SETA to SETB mRNA can discriminate patients with a more aggressive disease course within the otherwise favourable CLL risk classifications of IGHV mutated and favourable hierarchical fluorescence in situ hybridisation groups. We validate our finding by showing comparable relationships of SET mRNA with disease outcomes using samples from an independent CLL cohort from a separate institution. These findings indicate that alternative splicing of SET, and potentially other signalling cascade molecules, influences CLL biology and patient outcomes.
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Affiliation(s)
- Danielle M Brander
- Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Durham, NC, USA
| | - Daphne R Friedman
- Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Durham, NC, USA.,Durham VA Medical Center, Durham, NC, USA
| | | | | | - Laura Z Rassenti
- University of California San Diego Moores Cancer Center, San Diego, CA, USA
| | - Thomas J Kipps
- University of California San Diego Moores Cancer Center, San Diego, CA, USA
| | | | - Youwei Chen
- Duke University Medical Center, Durham, NC, USA
| | - Dadong Zhang
- Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Durham, NC, USA
| | - Xi Wang
- Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Durham, NC, USA
| | | | - Kouros Owzar
- Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Durham, NC, USA
| | - J Brice Weinberg
- Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Durham, NC, USA.,Durham VA Medical Center, Durham, NC, USA
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16
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SET Overexpression is Associated with Worse Recurrence-Free Survival in Patients with Primary Breast Cancer Receiving Adjuvant Tamoxifen Treatment. J Clin Med 2018; 7:jcm7090245. [PMID: 30154367 PMCID: PMC6162815 DOI: 10.3390/jcm7090245] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 08/23/2018] [Accepted: 08/24/2018] [Indexed: 12/21/2022] Open
Abstract
Adjuvant tamoxifen reduces the recurrence rate of estrogen receptor (ER)-positive breast cancer. Previous in vitro studies have suggested that tamoxifen can affect the cancerous inhibitor of protein phosphatase 2A (CIP2A)/protein phosphatase 2A (PP2A)/phosphorylation Akt (pAkt) signaling in ER-negative breast cancer cells. In addition to CIP2A, SET nuclear proto-oncogene (SET) oncoprotein is another intrinsic inhibitor of PP2A, participating in cancer progression. In the current study, we explored the clinical significance of SET, CIP2A, PP2A, and Akt in patients with ER-positive breast cancer receiving adjuvant tamoxifen. A total of 218 primary breast cancer patients receiving adjuvant tamoxifen with a median follow-up of 106 months were analyzed, of which 17 (7.8%) experienced recurrence or metastasis. In an immunohistochemical (IHC) stain, SET overexpression was independently associated with worse recurrence-free survival (RFS) (hazard ratio = 3.72, 95% confidence interval 1.26–10.94, p = 0.017). In silico analysis revealed mRNA expressions of SET, PPP2CA, and AKT1 significantly correlated with worse RFS. In vitro, SET overexpression reduced tamoxifen-induced antitumor effects and drove luciferase activity in an Estrogen receptor element (ERE)-dependent manner. In conclusion, SET is a prognostic biomarker in patients with primary ER-positive breast cancer receiving adjuvant tamoxifen and may contribute to the failure of the tamoxifen treatment by modulating the ER signaling. Our study warrants further investigation into the potential role of SET in ER-positive breast cancer.
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17
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Enjoji S, Yabe R, Tsuji S, Yoshimura K, Kawasaki H, Sakurai M, Sakai Y, Takenouchi H, Yoshino S, Hazama S, Nagano H, Oshima H, Oshima M, Vitek MP, Matsuura T, Hippo Y, Usui T, Ohama T, Sato K. Stemness Is Enhanced in Gastric Cancer by a SET/PP2A/E2F1 Axis. Mol Cancer Res 2018; 16:554-563. [PMID: 29330298 DOI: 10.1158/1541-7786.mcr-17-0393] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/10/2017] [Accepted: 12/13/2017] [Indexed: 11/16/2022]
Abstract
Gastric cancer is the fifth most common malignancy and the third leading cause of cancer-related deaths worldwide. Chemotherapies against gastric cancer often fail, with cancer recurrence due potentially to the persistence of cancer stem cells. This unique subpopulation of cells in tumors possesses the ability to self-renew and dedifferentiate. These cancer stem cells are critical for initiation, maintenance, metastasis, and relapse of cancers; however, the molecular mechanisms supporting cancer stemness remain largely unknown. Increased kinase and decreased phosphatase activity are hallmarks of oncogenic signaling. Protein phosphatase 2A (PP2A) functions as a tumor-suppressor enzyme, and elevated levels of SET/I2PP2A, an endogenous PP2A protein inhibitor, are correlated with poor prognosis of several human cancers. Here, it was determined that SET expression was elevated in tumor tissue in a gastric cancer mouse model system, and SET expression was positively correlated with poor survival of human gastric cancer patients. Mechanistically, SET knockdown decreased E2F1 levels and suppressed the stemness of cancer cell lines. Immunoprecipitations show SET associated with the PP2A-B56 complex, and the B56 subunit interacted with the E2F1 transcription factor. Treatment of gastric cancer cells with the SET-targeting drug OP449 increased PP2A activity, decreased E2F1 protein levels, and suppressed stemness of cancer cells. These data indicate that a SET/PP2A/E2F1 axis regulates cancer cell stemness and is a potential target for gastric cancer therapy.Implications: This study highlights the oncogenic role of SET/I2PP2A in gastric cancer and suggests that SET maintains cancer cell stemness by suppressing PP2A activity and stabilizing E2F1. Mol Cancer Res; 16(3); 554-63. ©2018 AACR.
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Affiliation(s)
- Shuhei Enjoji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Shunya Tsuji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Kazuhiro Yoshimura
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Hideyoshi Kawasaki
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Masashi Sakurai
- Laboratory of Veterinary Pathology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Yusuke Sakai
- Laboratory of Veterinary Pathology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Hiroko Takenouchi
- Department of Gastroenterological, Breast and Endocrine Surgery, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
| | | | - Shoichi Hazama
- Department of Gastroenterological, Breast and Endocrine Surgery, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
| | - Hiroaki Nagano
- Department of Gastroenterological, Breast and Endocrine Surgery, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan
| | - Hiroko Oshima
- Division of Genetics, Cancer Research Institute, Kanazawa University, Kanazawa, Japan
| | - Masanobu Oshima
- Division of Genetics, Cancer Research Institute, Kanazawa University, Kanazawa, Japan
| | - Michael P Vitek
- Department of Neurology, Duke University Medical Center, Durham, North Carolina.,Oncotide Pharmaceuticals, Inc., Research Triangle Park, North Carolina
| | - Tetsuya Matsuura
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Kanagawa, Japan
| | | | - Tatsuya Usui
- Laboratory of Veterinary Toxicology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Takashi Ohama
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan.
| | - Koichi Sato
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
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18
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Kake S, Tsuji S, Enjoji S, Hanasaki S, Hayase H, Yabe R, Tanaka Y, Nakagawa T, Liu HP, Chang SC, Usui T, Ohama T, Sato K. The role of SET/I2PP2A in canine mammary tumors. Sci Rep 2017; 7:4279. [PMID: 28655918 PMCID: PMC5487328 DOI: 10.1038/s41598-017-04291-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 05/12/2017] [Indexed: 01/27/2023] Open
Abstract
Canine mammary tumor is the most common neoplasm in female dogs, and it has generated considerable attention as a translational model for human breast cancer. Ser/Thr protein phosphatase 2A (PP2A) plays a critical role as a tumor suppressor, and SET/I2PP2A, the endogenous inhibitory protein of PP2A, binds directly to PP2A and suppresses its phosphatase activity. Here, we investigated the role of SET in the tumorigenic growth in canine mammary tumor as well as in the sensitivity of tumors to existing therapeutics. Elevated protein levels of SET were observed in advanced-stage of canine mammary tumor tissues of dogs compared with paired normal tissues. Knockdown of SET expression in a canine mammary tumor cell line CIP-m led to increased PP2A activity and decreased cell proliferation, colony formation, and in vivo tumor growth. We observed suppression of mTOR, β-catenin, and NFκB signaling by SET knockdown. The sensitivity of CIP-m cells to doxorubicin was decreased by SET knockdown, while SET knockdown in CIP-m cells did not affect sensitivity to 4-OH-tamoxifen, carboplatin, bortezomib, and X-ray radiation. These data suggest that SET plays important roles in the tumor progression of a subset of canine mammary tumor by suppressing PP2A activity and enhancing mTOR, β-catenin, and NFκB signaling.
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Affiliation(s)
- Satoru Kake
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
- Department of Comparative Animal Science, College of Life Science, Kurashiki University of Science and The Arts, Okayama, Japan
| | - Shunya Tsuji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Shuhei Enjoji
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Sayaka Hanasaki
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Hiroshi Hayase
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Yuiko Tanaka
- The Laboratory of Veterinary Surgery and the Veterinary Medical Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Takayuki Nakagawa
- The Laboratory of Veterinary Surgery and the Veterinary Medical Center, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Hao-Ping Liu
- Department of Veterinary Medicine, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan
| | - Shih-Chieh Chang
- Department of Veterinary Medicine, Veterinary Medical Teaching Hospital, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan
| | - Tatsuya Usui
- Laboratory of Veterinary Toxicology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
| | - Takashi Ohama
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan.
| | - Koichi Sato
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Japan
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19
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Kajitani K, Kato K, Nagata K. Histone H1 chaperone activity of TAF-I is regulated by its subtype-dependent intramolecular interaction. Genes Cells 2017; 22:334-347. [PMID: 28251751 DOI: 10.1111/gtc.12478] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 01/14/2017] [Indexed: 11/29/2022]
Abstract
Linker histone H1 is involved in the regulation of gene activity through the maintenance of higher-order chromatin structure. Previously, we have shown that template activating factor-I (TAF-I or protein SET) is involved in linker histone H1 dynamics as a histone H1 chaperone. In human and murine cells, two TAF-I subtypes exist, namely TAF-Iα and TAF-Iβ. TAF-I has a highly acidic amino acid cluster in its C-terminal region and forms homo- or heterodimers through its dimerization domain. Both dimer formation and the C-terminal region of TAF-I are essential for the histone chaperone activity. TAF-Iα exhibits less histone chaperone activity compared with TAF-Iβ even though TAF-Iα and β differ only in their N-terminal regions. However, it is unclear how subtype-specific TAF-I activities are regulated. Here, we have shown that the N-terminal region of TAF-Iα autoinhibits its histone chaperone activity via intramolecular interaction with its C-terminal region. When the interaction between the N- and C-terminal regions of TAF-Iα is disrupted, TAF-Iα shows a histone chaperone activity similar to that of TAF-Iβ. Taken together, these results provide mechanistic insights into the concept that fine tuning of TAF-I histone H1 chaperone activity relies on the subtype compositions of the TAF-I dimer.
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Affiliation(s)
- Kaori Kajitani
- Department of Infection Biology, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8575, Japan.,University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8575, Japan
| | - Kohsuke Kato
- Department of Infection Biology, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8575, Japan.,University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8575, Japan
| | - Kyosuke Nagata
- University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8575, Japan
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20
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Sangodkar J, Farrington C, McClinch K, Galsky MD, Kastrinsky DB, Narla G. All roads lead to PP2A: exploiting the therapeutic potential of this phosphatase. FEBS J 2016; 283:1004-24. [PMID: 26507691 PMCID: PMC4803620 DOI: 10.1111/febs.13573] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/29/2015] [Accepted: 10/21/2015] [Indexed: 12/22/2022]
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase involved in the regulation of many cellular processes. A confirmed tumor suppressor protein, PP2A is genetically altered or functionally inactivated in many cancers highlighting a need for its therapeutic reactivation. In this review we discuss recent literature on PP2A: the elucidation of its structure and the functions of its subunits, and the identification of molecular lesions and post-translational modifications leading to its dysregulation in cancer. A final section will discuss the proteins and small molecules that modulate PP2A and how these might be used to target dysregulated forms of PP2A to treat cancers and other diseases.
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Affiliation(s)
- Jaya Sangodkar
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mt. Sinai, New York, NY, USA
| | - Caroline Farrington
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Kimberly McClinch
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Matthew D. Galsky
- Department of Hematology and Medical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - David B. Kastrinsky
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Goutham Narla
- Department of Medicine and Institute for Transformative Molecular Medicine, Case Western Reserve University, Cleveland, OH, USA
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21
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D’Souza C, Henriques ST, Wang CK, Cheneval O, Chan LY, Bokil NJ, Sweet MJ, Craik DJ. Using the MCoTI-II Cyclotide Scaffold To Design a Stable Cyclic Peptide Antagonist of SET, a Protein Overexpressed in Human Cancer. Biochemistry 2016; 55:396-405. [DOI: 10.1021/acs.biochem.5b00529] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Charlotte D’Souza
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - Sónia Troeira Henriques
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - Conan K. Wang
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - Olivier Cheneval
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - Lai Yue Chan
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - Nilesh J. Bokil
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - Matthew J. Sweet
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
| | - David J. Craik
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland Australia, 4072
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Yu A, Snowhite I, Vendrame F, Rosenzwajg M, Klatzmann D, Pugliese A, Malek TR. Selective IL-2 responsiveness of regulatory T cells through multiple intrinsic mechanisms supports the use of low-dose IL-2 therapy in type 1 diabetes. Diabetes 2015; 64:2172-83. [PMID: 25576057 DOI: 10.2337/db14-1322] [Citation(s) in RCA: 147] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 01/05/2015] [Indexed: 12/13/2022]
Abstract
Low-dose interleukin-2 (IL-2) inhibited unwanted immune responses in several clinical settings and is currently being tested in patients with type 1 diabetes (T1D). Low-dose IL-2 selectively targets regulatory T cells (Tregs), but the mechanisms underlying this selectivity are poorly understood. We show that IL-2-dependent STAT5 activation in Tregs from healthy individuals and patients with T1D occurred at an ∼10-fold lower concentration of IL-2 than that required by T memory (TM) cells or by in vitro-activated T cells. This selective Treg responsiveness is explained by their higher expression of IL-2 receptor subunit α (IL-2Rα) and γ chain and also endogenous serine/threonine phosphatase protein phosphates 1 and/or 2A activity. Genome-wide profiling identified an IL-2-dependent transcriptome in human Tregs. Quantitative assessment of selected targets indicated that most were optimally activated by a 100-fold lower concentration of IL-2 in Tregs versus CD4(+) TM cells. Two such targets were selectively increased in Tregs from T1D patients undergoing low-dose IL-2 therapy. Thus, human Tregs possess an IL-2-dependent transcriptional amplification mechanism that widens their selective responses to low IL-2. Our findings support a model where low-dose IL-2 selectively activates Tregs to broadly induce their IL-2/IL-2R gene program and provide a molecular underpinning for low-dose IL-2 therapy to enhance Tregs for immune tolerance in T1D.
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Affiliation(s)
- Aixin Yu
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL
| | - Isaac Snowhite
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Francesco Vendrame
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
| | - Michelle Rosenzwajg
- Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, Biotherapy (CIC-BTi) and Inflammation-Immunopathology-Biotherapy Department (I2B), Paris, France Sorbonne Université, Université Pierre et Marie Curie Univ Paris 06, Unité Mixte de Recherche (UMR)-S 959, Immunology-Immunopathology-Immunotherapy (I3), Paris, France INSERM, UMR-S 959, Immunology-Immunopathology-Immunotherapy (I3), Paris, France
| | - David Klatzmann
- Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, Biotherapy (CIC-BTi) and Inflammation-Immunopathology-Biotherapy Department (I2B), Paris, France Sorbonne Université, Université Pierre et Marie Curie Univ Paris 06, Unité Mixte de Recherche (UMR)-S 959, Immunology-Immunopathology-Immunotherapy (I3), Paris, France INSERM, UMR-S 959, Immunology-Immunopathology-Immunotherapy (I3), Paris, France
| | - Alberto Pugliese
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL Department of Medicine, Miller School of Medicine, University of Miami, Miami, FL
| | - Thomas R Malek
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL
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Trakhtenberg EF, Morkin MI, Patel KH, Fernandez SG, Sang A, Shaw P, Liu X, Wang Y, Mlacker GM, Gao H, Velmeshev D, Dombrowski SM, Vitek MP, Goldberg JL. The N-terminal Set-β Protein Isoform Induces Neuronal Death. J Biol Chem 2015; 290:13417-26. [PMID: 25833944 DOI: 10.1074/jbc.m114.633883] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Indexed: 11/06/2022] Open
Abstract
Set-β protein plays different roles in neurons, but the diversity of Set-β neuronal isoforms and their functions have not been characterized. The expression and subcellular localization of Set-β are altered in Alzheimer disease, cleavage of Set-β leads to neuronal death after stroke, and the full-length Set-β regulates retinal ganglion cell (RGC) and hippocampal neuron axon growth and regeneration in a subcellular localization-dependent manner. Here we used various biochemical approaches to investigate Set-β isoforms and their role in the CNS, using the same type of neurons, RGCs, across studies. We found multiple alternatively spliced isoforms expressed from the Set locus in purified RGCs. Set transcripts containing the Set-β-specific exon were the most highly expressed isoforms. We also identified a novel, alternatively spliced Set-β transcript lacking the nuclear localization signal and demonstrated that the full-length (∼39-kDa) Set-β is localized predominantly in the nucleus, whereas a shorter (∼25-kDa) Set-β isoform is localized predominantly in the cytoplasm. Finally, we show that an N-terminal Set-β cleavage product can induce neuronal death.
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Affiliation(s)
- Ephraim F Trakhtenberg
- From the Neuroscience Program and Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and
| | - Melina I Morkin
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and the Shiley Eye Center, University of California San Diego, La Jolla, California 92093
| | - Karan H Patel
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and
| | | | - Alan Sang
- the Shiley Eye Center, University of California San Diego, La Jolla, California 92093
| | - Peter Shaw
- the Shiley Eye Center, University of California San Diego, La Jolla, California 92093
| | - Xiongfei Liu
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and
| | - Yan Wang
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and the Shiley Eye Center, University of California San Diego, La Jolla, California 92093
| | - Gregory M Mlacker
- Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and
| | - Han Gao
- From the Neuroscience Program and
| | - Dmitry Velmeshev
- Molecular and Cellular Pharmacology Program,University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Susan M Dombrowski
- Genomatix Software, Ann Arbor, Michigan 48108, the Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Michael P Vitek
- Oncotide Pharmaceuticals Inc., Durham, North Carolina 27709, and the Department of Neurology, Duke University Medical Center, Durham, North Carolina 27708
| | - Jeffrey L Goldberg
- From the Neuroscience Program and Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, and the Shiley Eye Center, University of California San Diego, La Jolla, California 92093,
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MicroRNA-9 regulates steroid-resistant airway hyperresponsiveness by reducing protein phosphatase 2A activity. J Allergy Clin Immunol 2015; 136:462-73. [PMID: 25772595 DOI: 10.1016/j.jaci.2014.11.044] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 11/25/2014] [Accepted: 11/26/2014] [Indexed: 12/16/2022]
Abstract
BACKGROUND Steroid-resistant asthma is a major clinical problem that is linked to activation of innate immune cells. Levels of IFN-γ and LPS are often increased in these patients. Cooperative signaling between IFN-γ/LPS induces macrophage-dependent steroid-resistant airway hyperresponsiveness (AHR) in mouse models. MicroRNAs (miRs) are small noncoding RNAs that regulate the function of innate immune cells by controlling mRNA stability and translation. Their role in regulating glucocorticoid responsiveness and AHR remains unexplored. OBJECTIVE IFN-γ and LPS synergistically increase the expression of miR-9 in macrophages and lung tissue, suggesting a role in the mechanisms of steroid resistance. Here we demonstrate the role of miR-9 in IFN-γ/LPS-induced inhibition of dexamethasone (DEX) signaling in macrophages and in induction of steroid-resistant AHR. METHODS MiRNA-9 expression was assessed by means of quantitative RT-PCR. Putative miR-9 targets were determined in silico and confirmed in luciferase reporter assays. miR-9 function was inhibited with sequence-specific antagomirs. The efficacy of DEX was assessed by quantifying glucocorticoid receptor (GR) cellular localization, protein phosphatase 2A (PP2A) activity, and AHR. RESULTS Exposure of pulmonary macrophages to IFN-γ/LPS synergistically induced miR-9 expression; reduced levels of its target transcript, protein phosphatase 2 regulatory subunit B (B56) δ isoform; attenuated PP2A activity; and inhibited DEX-induced GR nuclear translocation. Inhibition of miR-9 increased both PP2A activity and GR nuclear translocation in macrophages and restored steroid sensitivity in multiple models of steroid-resistant AHR. Pharmacologic activation of PP2A restored DEX efficacy and inhibited AHR. MiR-9 expression was increased in sputum of patients with neutrophilic but not those with eosinophilic asthma. CONCLUSION MiR-9 regulates GR signaling and steroid-resistant AHR. Targeting miR-9 function might be a novel approach for the treatment of steroid-resistant asthma.
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25
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Oaks J, Ogretmen B. Regulation of PP2A by Sphingolipid Metabolism and Signaling. Front Oncol 2015; 4:388. [PMID: 25642418 PMCID: PMC4295541 DOI: 10.3389/fonc.2014.00388] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 12/27/2014] [Indexed: 12/21/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is a serine/threonine phosphatase that is a primary regulator of cellular proliferation through targeting of proliferative kinases, cell cycle regulators, and apoptosis inhibitors. It is through the regulation of these regulatory elements that gives PP2A tumor suppressor functions. In addition to mutations on the regulatory subunits, the phosphatase/tumor suppressing activity of PP2A is also inhibited in several cancer types due to overexpression or modification of the endogenous PP2A inhibitors such as SET/I2PP2A. This review focuses on the current literature regarding the interactions between the lipid signaling molecules, selectively sphingolipids, and the PP2A inhibitor SET for the regulation of PP2A, and the therapeutic potential of sphingolipids as PP2A activators for tumor suppression via targeting SET oncoprotein.
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Affiliation(s)
- Joshua Oaks
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina , Charleston, SC , USA
| | - Besim Ogretmen
- Department of Biochemistry and Molecular Biology, Hollings Cancer Center, Medical University of South Carolina , Charleston, SC , USA
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26
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Haesen D, Sents W, Lemaire K, Hoorne Y, Janssens V. The Basic Biology of PP2A in Hematologic Cells and Malignancies. Front Oncol 2014; 4:347. [PMID: 25566494 PMCID: PMC4263090 DOI: 10.3389/fonc.2014.00347] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 11/20/2014] [Indexed: 12/30/2022] Open
Abstract
Reversible protein phosphorylation plays a crucial role in regulating cell signaling. In normal cells, phosphoregulation is tightly controlled by a network of protein kinases counterbalanced by several protein phosphatases. Deregulation of this delicate balance is widely recognized as a central mechanism by which cells escape external and internal self-limiting signals, eventually resulting in malignant transformation. A large fraction of hematologic malignancies is characterized by constitutive or unrestrained activation of oncogenic kinases. This is in part achieved by activating mutations, chromosomal rearrangements, or constitutive activation of upstream kinase regulators, in part by inactivation of their anti-oncogenic phosphatase counterparts. Protein phosphatase 2A (PP2A) represents a large family of cellular serine/threonine phosphatases with suspected tumor suppressive functions. In this review, we highlight our current knowledge about the complex structure and biology of these phosphatases in hematologic cells, thereby providing the rationale behind their diverse signaling functions. Eventually, this basic knowledge is a key to truly understand the tumor suppressive role of PP2A in leukemogenesis and to allow further rational development of therapeutic strategies targeting PP2A.
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Affiliation(s)
- Dorien Haesen
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Ward Sents
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Katleen Lemaire
- Gene Expression Unit, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Yana Hoorne
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
| | - Veerle Janssens
- Laboratory of Protein Phosphorylation and Proteomics, Department Cellular and Molecular Medicine, University of Leuven , Leuven , Belgium
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27
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Regulating Set-β's Subcellular Localization Toggles Its Function between Inhibiting and Promoting Axon Growth and Regeneration. J Neurosci 2014; 34:7361-74. [PMID: 24849368 DOI: 10.1523/jneurosci.3658-13.2014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The failure of the CNS neurons to regenerate axons after injury or stroke is a major clinical problem. Transcriptional regulators like Set-β are well positioned to regulate intrinsic axon regeneration capacity, which declines developmentally in maturing CNS neurons. Set-β also functions at cellular membranes and its subcellular localization is disrupted in Alzheimer's disease, but many of its biological mechanisms have not been explored in neurons. We found that Set-β was upregulated postnatally in CNS neurons, and was primarily localized to the nucleus but was also detected in the cytoplasm and adjacent to the plasma membrane. Remarkably, nuclear Set-β suppressed, whereas Set-β localized to cytoplasmic membranes promoted neurite growth in rodent retinal ganglion cells and hippocampal neurons. Mimicking serine 9 phosphorylation, as found in Alzheimer's disease brains, delayed nuclear import and furthermore blocked the ability of nuclear Set-β to suppress neurite growth. We also present data on gene regulation and protein binding partner recruitment by Set-β in primary neurons, raising the hypothesis that nuclear Set-β may preferentially regulate gene expression whereas Set-β at cytoplasmic membranes may regulate unique cofactors, including PP2A, which we show also regulates axon growth in vitro. Finally, increasing recruitment of Set-β to cellular membranes promoted adult rat optic nerve axon regeneration after injury in vivo. Thus, Set-β differentially regulates axon growth and regeneration depending on subcellular localization and phosphorylation.
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28
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Upregulation of SET expression by BACE1 and its implications in Down syndrome. Mol Neurobiol 2014; 51:781-90. [PMID: 24935721 DOI: 10.1007/s12035-014-8782-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 06/09/2014] [Indexed: 01/18/2023]
Abstract
Down syndrome (DS) is one of the most common genetic diseases. Patients with DS display growth delay and intellectual disabilities and develop Alzheimer's disease (AD) neuropathology after middle age, including neuritic plaques and neurofibrillary tangles. Beta-site amyloid β precursor protein (APP) cleaving enzyme 1 (BACE1), essential for Aβ production and neuritic plaque formation, is elevated in DS patients. However, its homolog, β-site APP cleaving enzyme 2 (BACE2), functions as θ-secretase and plays a differential role in plaque formation. In this study, by using Two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (2D SDS-PAGE) and LC-MS/MS proteomic profiling analysis, we found that the SET oncogene protein (SET) expression was associated with BACE1 but not BACE2. SET protein was increased in BACE1 overexpressing cells and was markedly reduced in the BACE1 knockout mice. We found that the overexpression of BACE1 or SET significantly inhibited cell proliferation. Moreover, knockdown of SET in BACE1 overexpression cells significantly rescued BACE1-induced cell growth suppression. Furthermore, both BACE1 and SET protein levels were increased in Down syndrome patients. It suggests that BACE1 overexpression-induced SET upregulation may contribute to growth delay and cognitive impairment in DS patients. Our work provides a new insight that BACE1 overexpression not only promotes neuritic plaque formation but may also potentiate neurodegeneration mediated by SET elevation in Alzheimer-associated dementia in DS.
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29
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Yabe R, Fujiwara N, Mizuno T, Usui T, Ohama T, Sato K. Characterization of SET/I2PP2A isoforms in dogs. J Vet Med Sci 2014; 76:1235-40. [PMID: 24897959 DOI: 10.1292/jvms.14-0209] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
SET is an endogenous protein phosphatase 2A (PP2A) inhibitor and is associated with a poor prognosis in human leukemia. Previously, we reported increased SET protein levels in canine lymphoma cell lines and the potential therapeutic application of SET antagonists in canine lymphoma. Here, we found that canine cells express several isoforms of the SET protein. We cloned 4 isoforms of SET, named SETα, β, γ and δ. Genomic BLAST showed that the SET genes are located on chromosomes X, 7, 1 and 8, respectively. An immunofluorescent study showed nuclear localization of SETα and β, and nuclear and cytosolic localization of SETγ and δ. We confirmed that SETα and β possess the ability to associate with PP2A. Our data reveal the existence of unique SET isoforms that should be taken into account in SET-targeting drug development studies in dogs.
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Affiliation(s)
- Ryotaro Yabe
- Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi 753-8515, Japan
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30
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Effect of FTY720 on the SET-PP2A complex in acute myeloid leukemia; SET binding drugs have antagonistic activity. Leukemia 2014; 28:1915-8. [PMID: 24781014 DOI: 10.1038/leu.2014.141] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Antagonistic activities of the immunomodulator and PP2A-activating drug FTY720 (Fingolimod, Gilenya) in Jak2-driven hematologic malignancies. Blood 2013; 122:1923-34. [PMID: 23926298 DOI: 10.1182/blood-2013-03-492181] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
FTY720 (Fingolimod, Gilenya) is a sphingosine analog used as an immunosuppressant in multiple sclerosis patients. FTY720 is also a potent protein phosphatase 2A (PP2A)-activating drug (PAD). PP2A is a tumor suppressor found inactivated in different types of cancer. We show here that PP2A is inactive in polycythemia vera (PV) and other myeloproliferative neoplasms characterized by the expression of the transforming Jak2(V617F) oncogene. PP2A inactivation occurs in a Jak2(V617F) dose/kinase-dependent manner through the PI-3Kγ-PKC-induced phosphorylation of the PP2A inhibitor SET. Genetic or PAD-mediated PP2A reactivation induces Jak2(V617F) inactivation/downregulation and impairs clonogenic potential of Jak2(V617F) cell lines and PV but not normal CD34(+) progenitors. Likewise, FTY720 decreases leukemic allelic burden, reduces splenomegaly, and significantly increases survival of Jak2(V617F) leukemic mice without adverse effects. Mechanistically, we show that in Jak2(V617F) cells, FTY720 antileukemic activity requires neither FTY720 phosphorylation (FTY720-P) nor SET dimerization or ceramide induction but depends on interaction with SET K209. Moreover, we show that Jak2(V617F) also utilizes an alternative sphingosine kinase-1-mediated pathway to inhibit PP2A and that FTY720-P, acting as a sphingosine-1-phosphate-receptor-1 agonist, elicits signals leading to the Jak2-PI-3Kγ-PKC-SET-mediated PP2A inhibition. Thus, PADs (eg, FTY720) represent suitable therapeutic alternatives for Jak2(V617F) MPNs.
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Irie A, Harada K, Araki N, Nishimura Y. Phosphorylation of SET protein at Ser171 by protein kinase D2 diminishes its inhibitory effect on protein phosphatase 2A. PLoS One 2012; 7:e51242. [PMID: 23251465 PMCID: PMC3522678 DOI: 10.1371/journal.pone.0051242] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 11/01/2012] [Indexed: 12/30/2022] Open
Abstract
We previously reported that protein kinase D2 (PKD2) in T cells is promptly activated after T-cell receptor (TCR) stimulation and involved in the activation of interleukin-2 promoter and T cell death, and that one of its candidate substrate is SET protein, a natural inhibitor for protein phosphatase 2A (PP2A). In this study, we investigated the target amino acid residues of SET phosphorylated by PKD2 and the effects of phosphorylation of SET on PP2A phosphatase activity. In vitro kinase assay using various recombinant SET mutants having Ser/Thr to Ala substitutions revealed that Ser171 of SET is one of the sites phosphorylated by PKD2. Recombinant SET with phosphorylation-mimic Ser171 to Glu substitution reduced its inhibitory effects on PP2A phosphatase activity compared with Ser171 to Ala substituted or wild-type SET. In addition, knockdown of PKD2 in Jurkat cells by RNAi or treatment of human CD4(+) T cell clone with the PKD2 inhibitor Gö6976 resulted in reduced PP2A activity after TCR-stimulation judged from phosphorylation status of Tyr307 of the catalytic subunit of PP2A. These results suggest that PKD2 is involved in the regulation of PP2A activity in activated T cells through phosphorylation of Ser171 of SET.
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Affiliation(s)
- Atsushi Irie
- Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan
| | - Kumiko Harada
- Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan
| | - Norie Araki
- Department of Tumor Genetics and Biology, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan
| | - Yasuharu Nishimura
- Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan
- * E-mail:
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Hong WX, Yang L, Chen M, Yang X, Ren X, Fang S, Ye J, Huang H, Peng C, Zhou L, Huang X, Yang F, Wu D, Zhuang Z, Liu J. Proteomic analysis of trichloroethylene-induced alterations in expression, distribution, and interactions of SET/TAF-Iα and two SET/TAF-Iα-binding proteins, eEF1A1 and eEF1A2, in hepatic L-02 cells. Toxicol Appl Pharmacol 2012; 263:259-72. [DOI: 10.1016/j.taap.2012.06.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 06/24/2012] [Accepted: 06/25/2012] [Indexed: 12/01/2022]
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Bíró J, Farkas I, Domoki M, Otvös K, Bottka S, Dombrádi V, Fehér A. The histone phosphatase inhibitory property of plant nucleosome assembly protein-related proteins (NRPs). PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2012; 52:162-168. [PMID: 22285370 DOI: 10.1016/j.plaphy.2011.12.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/31/2011] [Indexed: 05/31/2023]
Abstract
SET/I(2)(PP2A), a member of the family of nucleosome assembly proteins (NAPs), has been previously described as a multifunctional protein inhibiting protein phosphatase 2A (PP2A)-mediated histone H3((pSer10)) dephosphorylation during the heat shock response in animal cells. In the present work we demonstrate that its plant orthologs, designated as NAP-related proteins (NRPs), have a similar in vitro biochemical activity and interact with PP2A and histone H3((pSer10))in vivo. Although heat shock gene promoters were found to be associated with histone H3((pSer10))-marked chromatin following a high temperature treatment, heat shock gene expression was not affected in NRP-deficient mutant Arabidopsis thaliana (L.) plantlets. These observations indicate that NRPs are potential regulators of histone dephosphorylation in plants, but they are dispensable for gene expression reorganization in response to heat shock.
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Affiliation(s)
- Judit Bíró
- Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, Temesvári krt. 62, H-6726 Szeged, Hungary
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35
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Ichijo T, Chrousos GP, Kino T. Activated glucocorticoid receptor interacts with the INHAT component Set/TAF-Ibeta and releases it from a glucocorticoid-responsive gene promoter, relieving repression: implications for the pathogenesis of glucocorticoid resistance in acute undifferentiated leukemia with Set-Can translocation. Mol Cell Endocrinol 2008; 283:19-31. [PMID: 18096310 PMCID: PMC2350211 DOI: 10.1016/j.mce.2007.10.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Accepted: 10/26/2007] [Indexed: 02/04/2023]
Abstract
Set/template-activating factor (TAF)-Ibeta, part of the Set-Can oncogene product found in acute undifferentiated leukemia, is a component of the inhibitor of acetyltransferases (INHAT) complex. Set/TAF-Ibeta interacted with the DNA-binding domain of the glucocorticoid receptor (GR) in yeast two-hybrid screening, and repressed GR-induced transcriptional activity of a chromatin-integrated glucocorticoid-responsive and a natural promoter. Set/TAF-Ibeta was co-precipitated with glucocorticoid response elements (GREs) of these promoters in the absence of dexamethasone, while addition of the hormone caused dissociation of Set/TAF-Ibeta from and attraction of the p160-type coactivator GRIP1 to the promoter GREs. Set-Can fusion protein, on the other hand, did not interact with GR, was constitutively co-precipitated with GREs and suppressed GRIP1-induced enhancement of GR transcriptional activity and histone acetylation. Thus, Set/TAF-Ibeta acts as a ligand-activated GR-responsive transcriptional repressor, while Set-Can does not retain physiologic responsiveness to ligand-bound GR, possibly contributing to the poor responsiveness of Set-Can-harboring leukemic cells to glucocorticoids.
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MESH Headings
- Animals
- Chromatin Immunoprecipitation
- Chromosomal Proteins, Non-Histone/genetics
- Chromosomal Proteins, Non-Histone/metabolism
- DNA-Binding Proteins
- Drug Resistance, Neoplasm/drug effects
- Gene Expression Regulation, Neoplastic/drug effects
- Glucocorticoids/pharmacology
- HCT116 Cells
- Histone Acetyltransferases/metabolism
- Histone Chaperones
- Humans
- Leukemia/pathology
- Ligands
- Models, Genetic
- Nuclear Proteins/metabolism
- Oncogene Proteins, Fusion/metabolism
- Phosphoproteins/metabolism
- Promoter Regions, Genetic/genetics
- Protein Binding/drug effects
- Protein Structure, Tertiary
- Rats
- Receptors, Glucocorticoid/chemistry
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/metabolism
- Repressor Proteins/metabolism
- Response Elements
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription, Genetic/drug effects
- Translocation, Genetic/drug effects
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Affiliation(s)
- Takamasa Ichijo
- Section on Pediatric Endocrinology, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - George P. Chrousos
- Section on Pediatric Endocrinology, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
- First Department of Pediatrics, Athens University Medical School, 11527 Athens, Greece
| | - Tomoshige Kino
- Section on Pediatric Endocrinology, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
- * Address correspondence and requests for materials and reprints to: Tomoshige Kino, M.D., Ph.D. Section on Pediatric Endocrinology, Reproductive Biology and Medicine Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bldg. 10, Clinical Research Center, Rm. 1-3140, 10 Center Drive MSC 1109, Bethesda, MD 20892-1109, USA, Phone: 301-496-6417, Fax: 301-402-0884, E-mail:
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Urbanowski MD, Ilkow CS, Hobman TC. Modulation of signaling pathways by RNA virus capsid proteins. Cell Signal 2008; 20:1227-36. [PMID: 18258415 PMCID: PMC7127581 DOI: 10.1016/j.cellsig.2007.12.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Accepted: 12/18/2007] [Indexed: 01/16/2023]
Abstract
Capsid proteins are structural components of virus particles. They are nucleic acid-binding proteins whose main recognized function is to package viral genomes into protective structures called nucleocapsids. Research over the last 10 years indicates that in addition to their role as genome guardians, viral capsid proteins modulate host cell signaling networks. Disruption or alteration of intracellular signaling pathways by viral capsids may benefit replication of the virus by affecting innate immunity and in some cases, may underlie disease progression. In this review, we describe how the capsid proteins from medically relevant RNA viruses interact with host cell signaling pathways.
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Affiliation(s)
| | - Carolina S. Ilkow
- Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7
| | - Tom C. Hobman
- Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7
- Department of Medical Microbiology & Immunology, University of Alberta, Edmonton, Canada T6G 2H7
- Corresponding author. Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7. Tel.: +1 780 492 6485; fax: +1 780 492 0450.
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Hunt TA, Urbanowski MD, Kakani K, Law LMJ, Brinton MA, Hobman TC. Interactions between the West Nile virus capsid protein and the host cell-encoded phosphatase inhibitor, I2PP2A. Cell Microbiol 2007; 9:2756-66. [PMID: 17868381 DOI: 10.1111/j.1462-5822.2007.01046.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The West Nile virus (WNV) capsid protein functions in virus assembly to package genomic RNA into nucleocapsid structures. It is becoming clear, that in addition to their structural roles, capsid proteins of RNA viruses have non-structural functions. For example, the WNV capsid protein has been implicated as a pathogenic determinant. Presumably, many, if not all, of the non-structural functions of this protein involve interactions with host cell-encoded proteins. In the present study, we used affinity purification to isolate human proteins that bind to the WNV capsid protein. One of the capsid binding proteins is I(2)(PP2A), a previously characterized inhibitor of the serine/threonine phosphatase PP2A. Mapping studies revealed that capsid binding site overlaps with the region of I(2)(PP2A) that is required for inhibition of PP2A activity. Moreover, expression of the WNV capsid protein resulted in significantly increased PP2A activity and expected downstream events, such as inhibition of AP1-dependent transcription. Infected cells treated with I(2)(PP2A)-specific siRNAs produced less infectious virus than control siRNA-transfected cells, but this difference was minimal. Together, our data indicate that interactions between WNV capsid and I(2)(PP2A) result in increased PP2A activity. Given the central role of this phosphatase in cellular physiology, capsid/I(2)(PP2A) interactions may yet prove to be important for viral pathogenesis.
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Affiliation(s)
- Tracey A Hunt
- Department of Cell Biology, University of Alberta, 5-14 Medical Sciences Building, Edmonton, AB T6G 2H7, Canada
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38
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Kato K, Miyaji-Yamaguchi M, Okuwaki M, Nagata K. Histone acetylation-independent transcription stimulation by a histone chaperone. Nucleic Acids Res 2006; 35:705-15. [PMID: 17179179 PMCID: PMC1807960 DOI: 10.1093/nar/gkl1077] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Histone chaperones are thought to be important for maintaining the physiological activity of histones; however, their exact roles are not fully understood. The physiological function of template activating factor (TAF)-I, one of the histone chaperones, also remains unclear; however, its biochemical properties have been well studied. By performing microarray analyses, we found that TAF-I stimulates the transcription of a sub-set of genes. The transcription of endogenous genes that was up-regulated by TAF-I was found to be additively stimulated by histone acetylation. On performing an experiment with a cell line containing a model gene integrated into the chromosome, TAF-I was found to stimulate the model gene transcription in a histone chaperone activity-dependent manner additively with histone acetylation. TAF-I bound to the core histones and remodeled the chromatin structure independent of the N-terminal histone tail and its acetylation level in vitro. These results suggest that TAF-I remodel the chromatin structure through its interaction with the core domain of the histones, including the histone fold, and this mechanism is independent of the histone acetylation status.
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Affiliation(s)
| | | | | | - Kyosuke Nagata
- To whom correspondence should be addressed. Tel: +81 29 853 3233; Fax: +81 29 853 3233;
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39
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Chohan MO, Khatoon S, Iqbal IG, Iqbal K. Involvement of I2PP2A in the abnormal hyperphosphorylation of tau and its reversal by Memantine. FEBS Lett 2006; 580:3973-9. [PMID: 16806196 DOI: 10.1016/j.febslet.2006.06.021] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 06/02/2006] [Accepted: 06/02/2006] [Indexed: 11/22/2022]
Abstract
The activity of protein phosphatase (PP)-2A, which regulates tau phosphorylation, is compromised in Alzheimer disease brain. Here we show that the transient transfection of PC12 cells with inhibitor-2 (I2PP2A) of PP2A causes abnormal hyperphosphorylation of tau at Ser396/Ser404 and Ser262/Ser356. This hyperphosphorylation of tau is observed only when a sub-cellular shift of I2PP2A takes place from the nucleus to the cytoplasm and is accompanied by cleavage of I2PP2A into a 20 kDa fragment. Memantine, an un-competitive inhibitor of N-methyl-D-aspartate receptors, inhibits this abnormal phosphorylation of tau and cell death and prevents the I2PP2A-induced inhibition of PP2A activity in vitro. These findings demonstrate novel mechanisms by which I2PP2A regulates the intracellular activity of PP2A and phosphorylation of tau, and by which Memantine modulates PP2A signaling and inhibits neurofibrillary degeneration.
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Affiliation(s)
- Muhammad Omar Chohan
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314-6399, USA
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40
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Anazawa Y, Nakagawa H, Furihara M, Ashida S, Tamura K, Yoshioka H, Shuin T, Fujioka T, Katagiri T, Nakamura Y. PCOTH, a novel gene overexpressed in prostate cancers, promotes prostate cancer cell growth through phosphorylation of oncoprotein TAF-Ibeta/SET. Cancer Res 2005; 65:4578-86. [PMID: 15930275 DOI: 10.1158/0008-5472.can-04-4564] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Through genome-wide cDNA microarray analysis coupled with microdissection of prostate cancer cells, we identified a novel gene, prostate collagen triple helix (PCOTH), showing overexpression in prostate cancer cells and its precursor cells, prostatic intraepithelial neoplasia (PIN). Immunohistochemical analysis using polyclonal anti-PCOTH antibody confirmed elevated expression of PCOTH, a 100-amino-acid protein containing collagen triple-helix repeats, in prostate cancer cells and PINs. Knocking down PCOTH expression by small interfering RNA (siRNA) resulted in drastic attenuation of prostate cancer cell growth, and concordantly, LNCaP derivative cells that were designed to constitutively express exogenous PCOTH showed higher growth rate than LNCaP cells transfected with mock vector, suggesting the growth-promoting effect of PCOTH on prostate cancer cell. To investigate the biological mechanisms of this growth-promoting effect, we applied two-dimensional differential gel electrophoresis (2D-DIGE) to analyze the phospho-protein fractions in LNCaP cells transfected with PCOTH. We found that the phosphorylation level of oncoprotein TAF-Ibeta/SET was significantly elevated in LNCaP cells transfected with PCOTH than control LNCaP cells, and these findings were confirmed by Western blotting and in-gel kinase assay. Furthermore, knockdown of endogenous TAF-Ibeta expression by siRNA also attenuated viability of prostate cancer cells as well. These findings suggest that PCOTH is involved in growth and survival of prostate cancer cells thorough, in parts, the TAF-Ibeta pathway, and that this molecule should be a promising target for development of new therapeutic strategies for prostate cancers.
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Affiliation(s)
- Yoshio Anazawa
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, University of Tokyo, Tokyo, Japan
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41
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Kandilci A, Grosveld GC. SET-induced calcium signaling and MAPK/ERK pathway activation mediate dendritic cell-like differentiation of U937 cells. Leukemia 2005; 19:1439-45. [PMID: 15931263 DOI: 10.1038/sj.leu.2403826] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Human SET, a target of chromosomal translocation in human leukemia encodes a highly conserved, ubiquitously expressed, nuclear phosphoprotein. SET mediates many functions including chromatin remodeling, transcription, apoptosis and cell cycle control. We report that overexpression of SET directs differentiation of the human promonocytic cell line U937 along the dendritic cell (DC) pathway, as cells display typical morphologic changes associated with DC fate and express the DC surface markers CD11b and CD86. Differentiation occurs via a calcium-dependent mechanism involving the CaMKII and MAPK/ERK pathways. Similar responses are elicited by interferon-gamma (IFN-gamma) treatment with the distinction that IFN-gamma signaling activates the DNA-binding activity of STAT1 whereas SET overexpression does not. In addition, unlike IFN-gamma signaling, SET generated stress-induced p38/MAPK activity. Interestingly, IFN-gamma treatment transiently upregulated endogenous SET in a dose-dependent manner. These results suggest that SET is part of both IFN-gamma-mediated and stress-mediated cellular responses and that SET induces cell differentiation via calcium and MAPK/ERK pathways.
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Affiliation(s)
- A Kandilci
- Department of Genetics and Tumor Cell Biology, St Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105, USA
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42
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Tanimukai H, Grundke-Iqbal I, Iqbal K. Up-regulation of inhibitors of protein phosphatase-2A in Alzheimer's disease. THE AMERICAN JOURNAL OF PATHOLOGY 2005; 166:1761-71. [PMID: 15920161 PMCID: PMC1602412 DOI: 10.1016/s0002-9440(10)62486-8] [Citation(s) in RCA: 171] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/03/2005] [Indexed: 11/23/2022]
Abstract
The activity of protein phosphatase-2A (PP2A) is compromised and is believed to be a cause of the abnormal hyperphosphorylation of tau in Alzheimer's disease (AD) brain. We investigated in AD the role of the two known endogenous PP2A inhibitors, called I1(PP2A) and I2(PP2A), which regulate the intracellular activity of PP2A in mammalian tissues. We found a significant increase in the neocortical levels of I1(PP2A) and I2(PP2A) in AD as compared to control cases by in situ hybridization. The immunohistochemical studies revealed that I2(PP2A) was translocated from neuronal nuclei to cytoplasm in AD. The 39-kd full-length I2(PP2A) was selectively cleaved into an approximately 20-kd fragment in AD brain cytosol. Digestion of the recombinant human I2(PP2A) with AD brain extract showed an increase in the generation of the approximately 20 kd and other fragments of the inhibitor as compared to control brain extract. Double-immunohistochemical studies revealed co-localization of PP2A with PP2A inhibitors in neuronal cytoplasm and co-localization of the inhibitors with abnormally hyperphosphorylated tau. These studies suggest the possible involvement of I1(PP2A) and I2(PP2A) in the abnormal hyperphosphorylation of tau in AD.
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Affiliation(s)
- Hitoshi Tanimukai
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island, New York 10314-6399, USA
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43
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Gamble MJ, Erdjument-Bromage H, Tempst P, Freedman LP, Fisher RP. The histone chaperone TAF-I/SET/INHAT is required for transcription in vitro of chromatin templates. Mol Cell Biol 2005; 25:797-807. [PMID: 15632079 PMCID: PMC543418 DOI: 10.1128/mcb.25.2.797-807.2005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To uncover factors required for transcription by RNA polymerase II on chromatin, we fractionated a mammalian cell nuclear extract. We identified the histone chaperone TAF-I (also known as INHAT [inhibitor of histone acetyltransferase]), which was previously proposed to repress transcription, as a potent activator of chromatin transcription responsive to the vitamin D3 receptor or to Gal4-VP16. TAF-I associates with chromatin in vitro and can substitute for the related protein NAP-1 in assembling chromatin onto cloned DNA templates in cooperation with the remodeling enzyme ATP-dependent chromatin assembly factor (ACF). The chromatin assembly and transcriptional activation functions are distinct, however, and can be dissociated temporally. Efficient transcription of chromatin assembled with TAF-I still requires the presence of TAF-I during the polymerization reaction. Conversely, TAF-I cannot stimulate transcript elongation when added after the other factors necessary for assembly of a preinitiation complex on naked DNA. Thus, TAF-I is required to facilitate transcription at a step after chromatin assembly but before transcript elongation.
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Affiliation(s)
- Matthew J Gamble
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., New York, NY 10021, USA
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44
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Tsujio I, Zaidi T, Xu J, Kotula L, Grundke-Iqbal I, Iqbal K. Inhibitors of protein phosphatase-2A from human brain structures, immunocytological localization and activities towards dephosphorylation of the Alzheimer type hyperphosphorylated tau. FEBS Lett 2005; 579:363-72. [PMID: 15642345 DOI: 10.1016/j.febslet.2004.11.097] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2004] [Revised: 11/10/2004] [Accepted: 11/30/2004] [Indexed: 10/26/2022]
Abstract
Protein phosphatase (PP)-2A, which regulates the phosphorylation of tau, is regulated by two endogenous inhibitor proteins, I(1)(PP2A) and I(2)(PP2A), in mammalian tissues. Here, we report the cloning of I(1)(PP2A) and I(2)(PP2A) from human brain, and show that in PC12 cells and in I(1)(PP2A)-GFP or I(2)(PP2A)-GFP transfected NIH3T3 and human neural progenitor cells, I(1)(PP2A) is localized mostly in the cell cytoplasm and I(2)(PP2A) mostly in the nucleus. The recombinant I(1)(PP-2A) and I(2)(PP-2A) inhibit PP-2A activity towards hyperphosphorylated tau in vitro; the dephosphorylation of the hyperphosphorylated tau at specific sites is selectively inhibited. Overexpression of I(1)(PP2A) as well as I(2)(PP2A) results in tau hyperphosphorylation and degeneration of PC 12 cells.
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Affiliation(s)
- Ichiro Tsujio
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314-6399, USA
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45
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Kumar RN, Radhakrishnan R, Ha JH, Dhanasekaran N. Proteome Analysis of NIH3T3 Cells Transformed by Activated Gα12: Regulation of Leukemia-Associated Protein SET. J Proteome Res 2004; 3:1177-83. [PMID: 15595726 DOI: 10.1021/pr049896n] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Galpha(12), the alpha-subunit of the G12 family of heterotrimeric G proteins is involved in the regulation of cell proliferation and neoplastic transformation. GTPase-deficient, constitutively activated mutant of Galpha(12) (Galpha(12)Q229L or Galpha(12)QL) has been previously shown to induce oncogenic transformation of NIH3T3 cells promoting serum- and anchorage-independent growth. Reduced growth-factor dependent, autonomous cell growth forms a critical defining point at which a normal cell turns into an oncogenic one. To identify the underlying mechanism involved in such growth-factor/serum independent growth of Galpha(12)QL-transformed NIH3T3, we carried out a two-dimensional differential proteome analysis of Galpha(12)QL-transformed NIH3T3 cells and cells expressing vector control. This analysis revealed a total of 22 protein-spots whose expression was altered by more than 3-folds. Two of these spots were identified by MALDI-MS analysis as proliferating cell nuclear antigen (PCNA) and myeloid-leukemia-associated SET protein. The increased expressions of these proteins in Galpha(12)QL cells were validated by immunoblot analysis. Furthermore, transient transfection studies with NIH3T3 cells indicated that the expression of activated Galpha(12) readily increased the expression of SET protein by 24 h. As SET has been previously reported to be an inhibitor of phosphatase PP2A, the nuclear phosphatase activity was monitored in cells expressing activated Galpha(12). Our results indicate that the nuclear phosphatase activity is inhibited by greater than 50% in Galpha(12)QL cells compared to vector control cells. Thus, our results from differential proteome analysis presented here report for the first time a role for SET in Galpha(12)-mediated signaling pathways and a role for Galpha(12) in the regulation of the leukemia-associated SET-protein expression.
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Affiliation(s)
- Rashmi N Kumar
- Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA
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46
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Tanimukai H, Grundke-Iqbal I, Iqbal K. Inhibitors of protein phosphatase-2A: topography and subcellular localization. ACTA ACUST UNITED AC 2004; 126:146-56. [PMID: 15249138 DOI: 10.1016/j.molbrainres.2004.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2004] [Indexed: 11/27/2022]
Abstract
The mRNA and protein expressions of I1(PP2A) and I2(PP2A), the two inhibitors of protein phosphatase 2A (PP2A) were investigated in adult rat brain. The rat brain and human brain inhibitors showed similar molecular weights by Western blots. The cDNA probes for human brain I1(PP2A) and I2(PP2A) readily hybridized with the corresponding mRNAs of rat brain inhibitors in Northern blots. We detected 3.7 and 2.1 kb transcripts of I1(PP2A) and 2.9 and 2.0 kb transcripts of I2(PP2A) in rat brain. In situ hybridization revealed that the mRNAs of the two inhibitors were mainly localized in neurons. Strong expression of both I1(PP2A) and I2(PP2A) mRNAs were observed in the olfactory bulb, hippocampal pyramidal and dentate granule cell layers, and cerebellar Purkinje cell, granular and molecular layers. Moderate expression of I1(PP2A) and I2(PP2A) mRNAs were observed in the cerebral cortex, caudate putamen, thalamus, hypothalamus, amygdala and pontine nucleus. The expression of I1(PP2A) and I2(PP2A) and as well as of PP-2A was also investigated by immunohistochemistry using antibodies to each protein. The distribution patterns of the two inhibitor proteins were similar to those of their corresponding mRNAs and to the expression of PP-2A. While PP-2A was localized to neuronal perikarya, I1(PP2A) was observed both in the neuronal cytoplasm and the nucleus. I2(PP2A) had mainly nuclear localization but it could also be seen in the neuronal cytoplasm. All three proteins were also expressed in the neuropil. These studies suggest that PP-2A activity is probably regulated by I1(PP2A) and I2(PP2A) in the adult mammalian central nervous system, and that these inhibitors are conserved between rat and human brains.
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Affiliation(s)
- Hitoshi Tanimukai
- New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY, 10314, USA
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47
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Wang W, Yang X, Kawai T, López de Silanes I, Mazan-Mamczarz K, Chen P, Chook YM, Quensel C, Köhler M, Gorospe M. AMP-activated protein kinase-regulated phosphorylation and acetylation of importin alpha1: involvement in the nuclear import of RNA-binding protein HuR. J Biol Chem 2004; 279:48376-88. [PMID: 15342649 DOI: 10.1074/jbc.m409014200] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nuclear import of HuR, a shuttling RNA-binding protein, is associated with reduced stability of its target mRNAs. Increased function of the AMP-activated protein kinase (AMPK), an enzyme involved in responding to metabolic stress, was recently shown to reduce the cytoplasmic levels of HuR. Here, we provide evidence that importin alpha1, an adaptor protein involved in nuclear import, contributes to the nuclear import of HuR through two AMPK-modulated mechanisms. First, AMPK triggered the acetylation of importin alpha1 on Lys(22), a process dependent on the acetylase activity of p300. Second, AMPK phosphorylated importin alpha1 on Ser(105). Accordingly, expression of importin alpha1 proteins bearing K22R or S105A mutations failed to mediate the nuclear import of HuR in intact cells. Our results point to importin alpha1 as a critical downstream target of AMPK and key mediator of AMPK-triggered HuR nuclear import.
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Affiliation(s)
- Wengong Wang
- Laboratory of Cellular and Molecular Biology, NIA Intramural Research Program, National Institutes of Health, Baltimore, Maryland 21224, USA
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48
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Saito S, Miyaji-Yamaguchi M, Nagata K. Aberrant intracellular localization of SET-CAN fusion protein, associated with a leukemia, disorganizes nuclear export. Int J Cancer 2004; 111:501-7. [PMID: 15239126 DOI: 10.1002/ijc.20296] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The SET-CAN fusion gene is the product of a chromosomal rearrangement found on 9q34 associated with an acute undifferentiated leukemia. SET-CAN encodes an almost complete SET protein fused to the C-terminal two-thirds of CAN. SET is also known as TAF-Ibeta, a histone chaperone and intracellular inhibitor of protein phosphatase 2A, whereas CAN is identical to Nup214, a nucleoporin protein. To obtain insight into the leukemogenic function of SET/TAF-Ibeta-CAN/Nup214, we have examined its subcellular localization. Immunofluorescence analyses showed that SET/TAF-Ibeta and CAN/Nup214 are found in the nucleus and the nuclear envelope, respectively, whereas the majority of SET/TAF-Ibeta-CAN/Nup214 is localized in the nucleus. SET/TAF-Ibeta-CAN/Nup214 interacted with hCRM1, one of the nuclear export factors, and caused aberrant intracellular localization of hCRM1. In cells expressing SET/TAF-Ibeta-CAN/Nup214, a protein containing a nuclear export signal accumulated in the nucleus. The export of this protein was partially restored by overexpression of hCRM1. These results suggest that aberrantly localized molecules associated with SET/TAF-Ibeta-CAN/Nup214 may be involved in oncogenesis.
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Affiliation(s)
- Shoko Saito
- Department of Infection Biology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Japan
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49
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Kandilci A, Mientjes E, Grosveld G. Effects of SET and SET-CAN on the differentiation of the human promonocytic cell line U937. Leukemia 2004; 18:337-40. [PMID: 14671643 DOI: 10.1038/sj.leu.2403227] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2003] [Accepted: 08/25/2003] [Indexed: 11/08/2022]
Abstract
Human SET encodes a nuclear phosphoprotein with a highly acidic carboxyl-terminus, forming a SET-CAN fusion gene in a patient with acute undifferentiated leukemia. SET is highly conserved between species and is ubiquitously expressed, suggesting a widespread biological role. Even though SET is involved in chromatin remodeling and transcriptional activation, its precise role in hematopoietic cells and the contribution of SET-CAN to leukemogenesis remains unknown. We determined the effect of tetracycline-regulatable expression of SET, a deletion mutant of SET, and SET-CAN on the human promonocytic cell line U937T. The expression of SET and SET-CAN inhibited proliferation of these cells. SET accomplishes this through the induction of the differentiation program, an effect that depends on the presence of its acidic domain. SET-CAN most likely inhibits growth by interfering with hCRM1, but it also partially blocks differentiation. Our results are the first demonstration of a potential role of SET in hematopoietic differentiation.
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Affiliation(s)
- A Kandilci
- Department of Genetics, St Jude Children's Research Hospital, Memphis, TN 38105, USA
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50
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Ohkuni K, Okuda A, Kikuchi A. Yeast Nap1-Binding Protein Nbp2p Is Required for Mitotic Growth at High Temperatures and for Cell Wall Integrity. Genetics 2003; 165:517-29. [PMID: 14573466 PMCID: PMC1462787 DOI: 10.1093/genetics/165.2.517] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AbstractNbp2p is a Nap1-binding protein in Saccharomyces cerevisiae identified by its interaction with Nap1 by a two-hybrid system. NBP2 encodes a novel protein consisting of 236 amino acids with a Src homology 3 (SH3) domain. We showed that NBP2 functions to promote mitotic cell growth at high temperatures and cell wall integrity. Loss of Nbp2 results in cell death at high temperatures and in sensitivity to calcofluor white. Cell death at high temperature is thought not to be due to a weakened cell wall. Additionally, we have isolated several type-2C serine threonine protein phosphatases (PTCs) as multicopy suppressors and MAP kinase-kinase (MAPKK), related to the yeast PKC MAPK pathway, as deletion suppressors of the nbp2Δ mutant. Screening for deletion suppressors is a new genetic approach to identify and characterize additional proteins in the Nbp2-dependent pathway. Genetic analyses suggested that Ptc1, which interacts with Nbp2 by the two-hybrid system, acts downstream of Nbp2 and that cells lacking the function of Nbp2 prefer to lose Mkk1, but the PKC MAPK pathway itself is indispensable when Nbp2 is deleted at high temperature.
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Affiliation(s)
- Kentaro Ohkuni
- Laboratory of Medical Mycology, Research Institute for Disease Mechanism and Control, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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