1
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Crespo R, Ne E, Reinders J, Meier JI, Li C, Jansen S, Górska A, Koçer S, Kan TW, Doff W, Dekkers D, Demmers J, Palstra RJ, Rao S, Mahmoudi T. PCID2 dysregulates transcription and viral RNA processing to promote HIV-1 latency. iScience 2024; 27:109152. [PMID: 38384833 PMCID: PMC10879814 DOI: 10.1016/j.isci.2024.109152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 12/06/2023] [Accepted: 02/01/2024] [Indexed: 02/23/2024] Open
Abstract
HIV-1 latency results from tightly regulated molecular processes that act at distinct steps of HIV-1 gene expression. Here, we characterize PCI domain-containing 2 (PCID2) protein, a subunit of the transcription and export complex 2 (TREX2) complex, to enforce transcriptional repression and post-transcriptional blocks to HIV-1 gene expression during latency. PCID2 bound the latent HIV-1 LTR (long terminal repeat) and repressed transcription initiation during latency. Depletion of PCID2 remodeled the chromatin landscape at the HIV-1 promoter and resulted in transcriptional activation and latency reversal. Immunoprecipitation coupled to mass spectrometry identified PCID2-interacting proteins to include negative viral RNA (vRNA) splicing regulators, and PCID2 depletion resulted in over-splicing of intron-containing vRNA in cell lines and primary cells obtained from PWH. MCM3AP and DSS1, two other RNA-binding TREX2 complex subunits, also inhibit transcription initiation and vRNA alternative splicing during latency. Thus, PCID2 is a novel HIV-1 latency-promoting factor, which in context of the TREX2 sub-complex PCID2-DSS1-MCM3AP blocks transcription and dysregulates vRNA processing.
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Affiliation(s)
- Raquel Crespo
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Enrico Ne
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Julian Reinders
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Jenny I.J. Meier
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Chengcheng Li
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Sanne Jansen
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Alicja Górska
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Selin Koçer
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Tsung Wai Kan
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
- Department of Pathology, Erasmus University Medical Center, Rotterdam, the Netherlands
- Department of Urology, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Wouter Doff
- Proteomics Center, Erasmus University Medical Center, Ee679a PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Dick Dekkers
- Proteomics Center, Erasmus University Medical Center, Ee679a PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Jeroen Demmers
- Proteomics Center, Erasmus University Medical Center, Ee679a PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Robert-Jan Palstra
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
- Department of Pathology, Erasmus University Medical Center, Rotterdam, the Netherlands
- Department of Urology, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Shringar Rao
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
| | - Tokameh Mahmoudi
- Department of Biochemistry, Erasmus University Medical Center, Ee622 PO Box 2040, 3000 CA Rotterdam, the Netherlands
- Department of Pathology, Erasmus University Medical Center, Rotterdam, the Netherlands
- Department of Urology, Erasmus University Medical Center, Rotterdam, the Netherlands
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2
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Sakai Y, Kuwahara K. Carcinogenesis caused by transcription-coupled DNA damage through GANP and other components of the TREX-2 complex. Pathol Int 2024; 74:103-118. [PMID: 38411330 DOI: 10.1111/pin.13415] [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: 08/27/2023] [Revised: 02/05/2024] [Accepted: 02/10/2024] [Indexed: 02/28/2024]
Abstract
Perturbation of genes is important for somatic hypermutation to increase antibody affinity during B-cell immunity; however, it may also promote carcinogenesis. Previous studies have revealed that transcription is an important process that can induce DNA damage and genomic instability. Transciption-export-2 (TREX-2) complex, which regulates messenger RNA (mRNA) nuclear export, has been studied in the budding yeast Saccharomyces cerevisiae; however, recent studies have started investigating the molecular function of the mammalian TREX-2 complex. The central molecule in the TREX-2 complex, that is, germinal center-associated nuclear protein (GANP), is closely associated with antibody affinity maturation as well as cancer etiology. In this review, we focus on carcinogenesis, lymphomagenesis, and teratomagenesis caused by transcription-coupled DNA damage through GANP and other components of the TREX-2 complex. We review the basic machinery of mRNA nuclear export and transcription-coupled DNA damage. We then briefly describe the immunological relationship between GANP and the affinity maturation of antibodies. Finally, we illustrate that the aberrant expression of the components of the TREX-2 complex, especially GANP, is associated with the etiology of various solid tumors, lymphomas, and testicular teratoma. These components serve as reliable predictors of cancer prognosis and response to chemotherapy.
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Affiliation(s)
- Yasuhiro Sakai
- Department of Tumor Pathology, Hamamatsu University School of Medicine, Shizuoka, Japan
- Department of Joint Research Laboratory of Clinical Medicine, Fujita Health University School of Medicine, Aichi, Japan
| | - Kazuhiko Kuwahara
- Department of Diagnostic Pathology, Kindai University Hospital, Osaka, Japan
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3
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Dobish KK, Wittorf KJ, Swenson SA, Bean DC, Gavile CM, Woods NT, Ghosal G, Hyde RK, Buckley SM. FBXO21 mediated degradation of p85α regulates proliferation and survival of acute myeloid leukemia. Leukemia 2023; 37:2197-2208. [PMID: 37689825 PMCID: PMC10624613 DOI: 10.1038/s41375-023-02020-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/18/2023] [Accepted: 08/31/2023] [Indexed: 09/11/2023]
Abstract
Acute myeloid leukemia (AML) is a heterogeneous disease characterized by clonal expansion of myeloid blasts in the bone marrow (BM). Despite advances in therapy, the prognosis for AML patients remains poor, and there is a need to identify novel molecular pathways regulating tumor cell survival and proliferation. F-box ubiquitin E3 ligase, FBXO21, has low expression in AML, but expression correlates with survival in AML patients and patients with higher expression have poorer outcomes. Silencing FBXO21 in human-derived AML cell lines and primary patient samples leads to differentiation, inhibition of tumor progression, and sensitization to chemotherapy agents. Additionally, knockdown of FBXO21 leads to up-regulation of cytokine signaling pathways. Through a mass spectrometry-based proteomic analysis of FBXO21 in AML, we identified that FBXO21 ubiquitylates p85α, a regulatory subunit of the phosphoinositide 3-kinase (PI3K) pathway, for degradation resulting in decreased PI3K signaling, dimerization of free p85α and ERK activation. These findings reveal the ubiquitin E3 ligase, FBXO21, plays a critical role in regulating AML pathogenesis, specifically through alterations in PI3K via regulation of p85α protein stability.
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Affiliation(s)
- Kasidy K Dobish
- Department of Internal Medicine, Division of Hematology & Hematopoietic Malignancies, University of Utah, Salt Lake City, UT, USA
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, USA
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Karli J Wittorf
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, USA
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - Samantha A Swenson
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Dalton C Bean
- Department of Internal Medicine, Division of Hematology & Hematopoietic Malignancies, University of Utah, Salt Lake City, UT, USA
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
- Department of Oncological Sciences, University of Utah, Salt Lake City, USA
| | - Catherine M Gavile
- Department of Internal Medicine, Division of Hematology & Hematopoietic Malignancies, University of Utah, Salt Lake City, UT, USA
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA
| | - Nicholas T Woods
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, USA
| | - Gargi Ghosal
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE, USA
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
| | - R Katherine Hyde
- Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE, USA
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Shannon M Buckley
- Department of Internal Medicine, Division of Hematology & Hematopoietic Malignancies, University of Utah, Salt Lake City, UT, USA.
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT, USA.
- Department of Oncological Sciences, University of Utah, Salt Lake City, USA.
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4
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Wittorf KJ, Weber KK, Swenson SA, Buckley SM. Ubiquitin E3 ligase FBXO21 regulates cytokine-mediated signaling pathways, but is dispensable for steady-state hematopoiesis. Exp Hematol 2022; 114:33-42.e3. [PMID: 35987460 DOI: 10.1016/j.exphem.2022.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 08/03/2022] [Accepted: 08/04/2022] [Indexed: 11/24/2022]
Abstract
Hematopoietic cell fate decisions such as self-renewal and differentiation are highly regulated through multiple molecular pathways. One pathway, the ubiquitin proteasome system (UPS), controls protein levels by tagging them with polyubiquitin chains and promoting their degradation through the proteasome. Ubiquitin E3 ligases serve as the substrate-recognition component of the UPS. By investigating the FBOX family of E3 ligases, we discovered that Fbxo21 was highly expressed in the hematopoietic stem and progenitor cell (HSPC) population, and exhibited low to no expression in mature myeloid populations. To determine the role of FBXO21 on HSPC maintenance, self-renewal, and differentiation, we generated shRNAs against FBXO21 and a hematopoiesis-specific Fbxo21 conditional knockout (cKO) mouse model. We found that silencing FBXO21 in HSPCs led to a loss in colony formation and an increase in cell differentiation in vitro. Additionally, stressing the HSPC populations in our Fbxo21 cKO mouse with 5-fluorouracil injections resulted in a decrease in survival, despite these populations exhibiting minimal alterations during steady-state hematopoiesis. Although FBXO21 has previously been proposed to regulate cytokine signaling via ASK and p38, our results indicate that depletion of FBXO21 led to altered ERK signaling in vitro. Together, these findings suggest ubiquitin E3 ligase FBXO21 regulates HSPCs through cytokine-mediated pathways.
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Affiliation(s)
- Karli J Wittorf
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE; Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE
| | - Kasidy K Weber
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE; Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE
| | - Samantha A Swenson
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE; Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE
| | - Shannon M Buckley
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE; Fred and Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE.
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5
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Beisang DJ, Smith K, Yang L, Benyumov A, Gilbertsen A, Herrera J, Lock E, Racila E, Forster C, Sandri BJ, Henke CA, Bitterman PB. Single-cell RNA sequencing reveals that lung mesenchymal progenitor cells in IPF exhibit pathological features early in their differentiation trajectory. Sci Rep 2020; 10:11162. [PMID: 32636398 PMCID: PMC7341888 DOI: 10.1038/s41598-020-66630-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 05/06/2020] [Indexed: 12/12/2022] Open
Abstract
In Idiopathic Pulmonary Fibrosis (IPF), there is unrelenting scarring of the lung mediated by pathological mesenchymal progenitor cells (MPCs) that manifest autonomous fibrogenicity in xenograft models. To determine where along their differentiation trajectory IPF MPCs acquire fibrogenic properties, we analyzed the transcriptome of 335 MPCs isolated from the lungs of 3 control and 3 IPF patients at the single-cell level. Using transcriptional entropy as a metric for differentiated state, we found that the least differentiated IPF MPCs displayed the largest differences in their transcriptional profile compared to control MPCs. To validate entropy as a surrogate for differentiated state functionally, we identified increased CD44 as a characteristic of the most entropic IPF MPCs. Using FACS to stratify IPF MPCs based on CD44 expression, we determined that CD44hi IPF MPCs manifested an increased capacity for anchorage-independent colony formation compared to CD44lo IPF MPCs. To validate our analysis morphologically, we used two differentially expressed genes distinguishing IPF MPCs from control (CD44, cell surface; and MARCKS, intracellular). In IPF lung tissue, pathological MPCs resided in the highly cellular perimeter region of the fibroblastic focus. Our data support the concept that IPF fibroblasts acquire a cell-autonomous pathological phenotype early in their differentiation trajectory.
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Affiliation(s)
- Daniel J Beisang
- University of Minnesota, Department of Pediatrics, Division of Pediatric Pulmonology, Minneapolis, USA
| | - Karen Smith
- University of Minnesota, Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Minneapolis, USA
| | - Libang Yang
- University of Minnesota, Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Minneapolis, USA
| | - Alexey Benyumov
- University of Minnesota, Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Minneapolis, USA
| | - Adam Gilbertsen
- University of Minnesota, Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Minneapolis, USA
| | - Jeremy Herrera
- University of Manchester, School of Biological Sciences, Division of Cell Matrix Biology & Regenerative Medicine, Manchester, United Kingdom
| | - Eric Lock
- University of Minnesota, School of Public Health, Division of Biostatistics, Minneapolis, USA
| | - Emilian Racila
- University of Minnesota, Department of Laboratory Medicine and Pathology, Minneapolis, USA
| | - Colleen Forster
- University of Minnesota, Clinical and Translational Science Institute, Minneapolis, USA
| | - Brian J Sandri
- University of Minnesota, Department of Pediatrics, Division of Neonatology, Minneapolis, USA
| | - Craig A Henke
- University of Minnesota, Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Minneapolis, USA
| | - Peter B Bitterman
- University of Minnesota, Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Minneapolis, USA.
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6
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de Dieuleveult M, Miotto B. Ubiquitin Dynamics in Stem Cell Biology: Current Challenges and Perspectives. Bioessays 2020; 42:e1900129. [PMID: 31967345 DOI: 10.1002/bies.201900129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 12/18/2019] [Indexed: 11/09/2022]
Abstract
Ubiquitination plays a central role in the regulation of stem cell self-renewal, propagation, and differentiation. In this review, the functions of ubiquitin dynamics in a myriad of cellular processes, acting along side the pluripotency network, to regulate embryonic stem cell identity are highlighted. The implication of deubiquitinases (DUBs) and E3 Ubiquitin (Ub) ligases in cellular functions beyond protein degradation is reported, including key functions in the regulation of mRNA stability, protein translation, and intra-cellular trafficking; and how it affects cell metabolism, the micro-environment, and chromatin organization is discussed. Finally, unsolved issues in the field are emphasized and will need to be tackled in order to fully understand the contribution of ubiquitin dynamics to stem cell self-renewal and differentiation.
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Affiliation(s)
- Maud de Dieuleveult
- Université de Paris, Institut Cochin, INSERM, U1016, CNRS, UMR8104, F-75014, Paris, France
| | - Benoit Miotto
- Université de Paris, Institut Cochin, INSERM, U1016, CNRS, UMR8104, F-75014, Paris, France
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7
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Fu X, Ding B, Wang C, Chen C, Wang J, Fei X, Xu R. EID1 plays a crucial role in proliferation of neural stem cell. Biochem Biophys Res Commun 2019; 512:763-769. [PMID: 30926163 DOI: 10.1016/j.bbrc.2019.03.138] [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: 03/18/2019] [Accepted: 03/20/2019] [Indexed: 11/19/2022]
Abstract
EP300-interacting inhibitor of differentiation 1 (Eid1) regulates differentiation, transcription and acetyltransferase activity. But the main function of Eid1 in the brain is still unclear. To better understand this issue, we generated Eid1-knockout (Eid1-KO) mice. We found poorer learning and memory ability, and smaller volume of neonatal telencephalon in Eid1-KO group than wild-type (WT). Bioinformatics implied that Eid1 may directly regulate cell proliferation. We then isolated neural stem cells (NSCs) and discovered a slower proliferation rate in Eid1-KO NSCs. Moreover, based on bioinformatics results, we investigated the expression of phosphatidylinositol 3-kinase (PI3K)/AKT/GSK3β pathway by Western blotting assay, which showed attenuated in Eid1-KO group. Our data proved the first comprehensive report of Eid1 regulating NSCs proliferation via PI3K/AKT/GSK3β pathway, and provide a foundation for the role of EID1 in the brain.
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Affiliation(s)
- Xiaojun Fu
- Medical School of Chinese PLA & General Hospital of Chinese PLA, Beijing, PR China
| | - Boyun Ding
- Stem Cell Research Center, Neurosurgery Institute of PLA Army, Beijing, PR China
| | - Chongwu Wang
- Stem Cell Research Center, Neurosurgery Institute of PLA Army, Beijing, PR China
| | - Chen Chen
- Stem Cell Research Center, Neurosurgery Institute of PLA Army, Beijing, PR China
| | - Ji Wang
- Stem Cell Research Center, Neurosurgery Institute of PLA Army, Beijing, PR China
| | - Xiaowei Fei
- Stem Cell Research Center, Neurosurgery Institute of PLA Army, Beijing, PR China
| | - Ruxiang Xu
- Medical School of Chinese PLA & General Hospital of Chinese PLA, Beijing, PR China; Stem Cell Research Center, Neurosurgery Institute of PLA Army, Beijing, PR China.
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8
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Ye B, Liu B, Hao L, Zhu X, Yang L, Wang S, Xia P, Du Y, Meng S, Huang G, Qin X, Wang Y, Yan X, Li C, Hao J, Zhu P, He L, Tian Y, Fan Z. Klf4 glutamylation is required for cell reprogramming and early embryonic development in mice. Nat Commun 2018; 9:1261. [PMID: 29593216 PMCID: PMC5871780 DOI: 10.1038/s41467-018-03008-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 01/10/2018] [Indexed: 12/20/2022] Open
Abstract
Temporal and spatial-specific regulation of pluripotency networks is largely dependent on the precise modifications of core transcription factors. Misregulation of glutamylation is implicated in severe physiological abnormalities. However, how glutamylation regulates cell reprogramming and pluripotency networks remains elusive. Here we show that cytosolic carboxypeptidases 1 (CCP1) or CCP6 deficiency substantially promotes induced pluripotent cell (iPSC) induction and pluripotency of embryonic stem cells (ESCs). Klf4 polyglutamylation at Glu381 by tubulin tyrosine ligase-like 4 (TTLL4) and TTLL1 during cell reprogramming impedes its lysine 48-linked ubiquitination and sustains Klf4 stability. Klf4-E381A knockin mice display impaired blastocyst development and embryonic lethality. Deletion of TTLL4 or TTLL1 abrogates cell reprogramming and early embryogenesis. Thus, Klf4 polyglutamylation plays a critical role in the regulation of cell reprogramming and pluripotency maintenance. Embryonic stem cell pluripotency depends upon precise regulation by a core transcription network. Here the authors show that polyglutamylation mediated stabilization of the transcription factor Klf4 by TTLL1 and TTLL4 promotes reprogramming, pluripotency and preimplantation embryonic development.
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Affiliation(s)
- Buqing Ye
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Benyu Liu
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Lu Hao
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoxiao Zhu
- Laboratory Animal Center, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Liuliu Yang
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shuo Wang
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Pengyan Xia
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Ying Du
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Shu Meng
- Laboratory Animal Center, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Guanling Huang
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiwen Qin
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yanying Wang
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Xinlong Yan
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Chong Li
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Junfeng Hao
- Laboratory Animal Center, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Pingping Zhu
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Luyun He
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yong Tian
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Zusen Fan
- Key Laboratory of Infection and Immunity of CAS, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
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9
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Ye B, Liu B, Yang L, Zhu X, Zhang D, Wu W, Zhu P, Wang Y, Wang S, Xia P, Du Y, Meng S, Huang G, Wu J, Chen R, Tian Y, Fan Z. LncKdm2b controls self-renewal of embryonic stem cells via activating expression of transcription factor Zbtb3. EMBO J 2018. [PMID: 29535137 DOI: 10.15252/embj.201797174] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Divergent long noncoding RNAs (lncRNAs) represent a major lncRNA biotype in mouse and human genomes. The biological and molecular functions of the divergent lncRNAs remain largely unknown. Here, we show that lncKdm2b, a divergent lncRNA for Kdm2b gene, is conserved among five mammalian species and highly expressed in embryonic stem cells (ESCs) and early embryos. LncKdm2b knockout impairs ESC self-renewal and causes early embryonic lethality. LncKdm2b can activate Zbtb3 by promoting the assembly and ATPase activity of Snf2-related CREBBP activator protein (SRCAP) complex in trans Zbtb3 potentiates the ESC self-renewal in a Nanog-dependent manner. Finally, Zbtb3 deficiency impairs the ESC self-renewal and early embryonic development. Therefore, our findings reveal that lncRNAs may represent an additional layer of the regulation of ESC self-renewal and early embryogenesis.
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Affiliation(s)
- Buqing Ye
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Benyu Liu
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Liuliu Yang
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xiaoxiao Zhu
- Laboratory Animal Center, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Dongdong Zhang
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Wei Wu
- University of Chinese Academy of Sciences, Beijing, China.,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Pingping Zhu
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yanying Wang
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Shuo Wang
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Pengyan Xia
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Ying Du
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Shu Meng
- Laboratory Animal Center, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Guanling Huang
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Jiayi Wu
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Runsheng Chen
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yong Tian
- University of Chinese Academy of Sciences, Beijing, China .,Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Zusen Fan
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China .,University of Chinese Academy of Sciences, Beijing, China
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10
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Suppression of SRCAP chromatin remodelling complex and restriction of lymphoid lineage commitment by Pcid2. Nat Commun 2017; 8:1518. [PMID: 29138493 PMCID: PMC5686073 DOI: 10.1038/s41467-017-01788-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Accepted: 10/16/2017] [Indexed: 12/31/2022] Open
Abstract
Lymphoid lineage commitment is an important process in haematopoiesis, which forms the immune system to protect the host from pathogen invasion. However, how multipotent progenitors (MPP) switch into common lymphoid progenitors (CLP) or common myeloid progenitors (CMP) during this process remains elusive. Here we show that PCI domain-containing protein 2 (Pcid2) is highly expressed in MPPs. Pcid2 deletion in the haematopoietic system causes skewed lymphoid lineage specification. In MPPs, Pcid2 interacts with the Zinc finger HIT-type containing 1 (ZNHIT1) to block Snf2-related CREBBP activator protein (SRCAP) activity and prevents the deposition of histone variant H2A.Z and transcription factor PU.1 to key lymphoid fate regulator genes. Furthermore, Znhit1 deletion also abrogates H2A/H2A.Z exchange in MPPs. Thus Pcid2 controls lymphoid lineage commitment through the regulation of SRCAP remodelling activity.
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11
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Sakaguchi N, Maeda K. Germinal Center B-Cell-Associated Nuclear Protein (GANP) Involved in RNA Metabolism for B Cell Maturation. Adv Immunol 2016; 131:135-86. [PMID: 27235683 DOI: 10.1016/bs.ai.2016.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Germinal center B-cell-associated nuclear protein (GANP) is upregulated in germinal center B cells against T-cell-dependent antigens in mice and humans. In mice, GANP depletion in B cells impairs antibody affinity maturation. Conversely, its transgenic overexpression augments the generation of high-affinity antigen-specific B cells. GANP associates with AID in the cytoplasm, shepherds AID into the nucleus, and augments its access to the rearranged immunoglobulin (Ig) variable (V) region of the genome in B cells, thereby precipitating the somatic hypermutation of V region genes. GANP is also upregulated in human CD4(+) T cells and is associated with APOBEC3G (A3G). GANP interacts with A3G and escorts it to the virion cores to potentiate its antiretroviral activity by inactivating HIV-1 genomic cDNA. Thus, GANP is characterized as a cofactor associated with AID/APOBEC cytidine deaminase family molecules in generating diversity of the IgV region of the genome and genetic alterations of exogenously introduced viral targets. GANP, encoded by human chromosome 21, as well as its mouse equivalent on chromosome 10, contains a region homologous to Saccharomyces Sac3 that was characterized as a component of the transcription/export 2 (TREX-2) complex and was predicted to be involved in RNA export and metabolism in mammalian cells. The metabolism of RNA during its maturation, from the transcription site at the chromosome within the nucleus to the cytoplasmic translation apparatus, needs to be elaborated with regard to acquired and innate immunity. In this review, we summarize the current knowledge on GANP as a component of TREX-2 in mammalian cells.
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Affiliation(s)
- N Sakaguchi
- WPI Immunology Frontier Research Center (IFReC), Osaka University, Suita, Osaka, Japan; Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
| | - K Maeda
- WPI Immunology Frontier Research Center (IFReC), Osaka University, Suita, Osaka, Japan; Laboratory of Host Defense, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
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12
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Zhang C, Li X, Adelmant G, Dobbins J, Geisen C, Oser MG, Wucherpfenning KW, Marto JA, Kaelin WG. Peptidic degron in EID1 is recognized by an SCF E3 ligase complex containing the orphan F-box protein FBXO21. Proc Natl Acad Sci U S A 2015; 112:15372-7. [PMID: 26631746 PMCID: PMC4687553 DOI: 10.1073/pnas.1522006112] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
EP300-interacting inhibitor of differentiation 1 (EID1) belongs to a protein family implicated in the control of transcription, differentiation, DNA repair, and chromosomal maintenance. EID1 has a very short half-life, especially in G0 cells. We discovered that EID1 contains a peptidic, modular degron that is necessary and sufficient for its polyubiquitylation and proteasomal degradation. We found that this degron is recognized by an Skp1, Cullin, and F-box (SCF)-containing ubiquitin ligase complex that uses the F-box Only Protein 21 (FBXO21) as its substrate recognition subunit. SCF(FBXO21) polyubiquitylates EID1 both in vitro and in vivo and is required for the efficient degradation of EID1 in both cycling and quiescent cells. The EID1 degron partially overlaps with its retinoblastoma tumor suppressor protein-binding domain and is congruent with a previously defined melanoma-associated antigen-binding motif shared by EID family members, suggesting that binding to retinoblastoma tumor suppressor and melanoma-associated antigen family proteins could affect the polyubiquitylation and turnover of EID family members in cells.
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Affiliation(s)
- Cuiyan Zhang
- Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215
| | - Xiaotong Li
- State Key Laboratory for Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Guillaume Adelmant
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215
| | - Jessica Dobbins
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02215
| | - Christoph Geisen
- Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215; Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Matthew G Oser
- Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215
| | - Kai W Wucherpfenning
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02215
| | - Jarrod A Marto
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, MA 02215; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215
| | - William G Kaelin
- Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215; Howard Hughes Medical Institute, Chevy Chase, MD 20815
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13
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Chen X, Du Z, Li X, Wang L, Wang F, Shi W, Hao A. Protein Palmitoylation Regulates Neural Stem Cell Differentiation by Modulation of EID1 Activity. Mol Neurobiol 2015; 53:5722-36. [PMID: 26497028 DOI: 10.1007/s12035-015-9481-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/08/2015] [Indexed: 01/13/2023]
Abstract
The functional significance of palmitoylation in the switch between self-renewal and differentiation of neural stem cells (NSCs) is not well defined, and the underlying mechanisms of protein palmitoylation are not well understood. Here, mouse NSCs were used as a model system and cell behavior was monitored in the presence of the protein palmitoylation inhibitor 2-bromopalmitate (2BRO). Our data show that 2BRO impaired the differentiation of NSCs into both neurons and glia and impaired NSC cell cycle exit. Moreover, the results show that palmitoylation modified E1A-like inhibitor of differentiation one (EID1) and this modification regulated EID1 degradation and CREB-binding protein (CBP)/p300 histone acetyltransferase activity at the switch between self-renewal and differentiation of NSCs. Our results extended the cellular role of palmitoylation, suggesting that it acts as a regulator in the acetylation-dependent gene expression network, and established the epigenetic regulatory function of palmitoylation in the switch between maintenance of multipotency and differentiation in NSCs.
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Affiliation(s)
- Xueran Chen
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China.,Center of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, No. 350, Shushan Hu Road, Hefei, Anhui, 230031, People's Republic of China
| | - Zhaoxia Du
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Xian Li
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Liyan Wang
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Fuwu Wang
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Wei Shi
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China
| | - Aijun Hao
- Key Laboratory of the Ministry of Education for Experimental Teratology, Shandong Provincial Key Laboratory of Mental Disorders, Department of Histology and Embryology, Shandong University School of Medicine, No. 44, Wenhua Xi Road, Jinan, Shandong, 250012, People's Republic of China.
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14
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Randle SJ, Laman H. F-box protein interactions with the hallmark pathways in cancer. Semin Cancer Biol 2015; 36:3-17. [PMID: 26416465 DOI: 10.1016/j.semcancer.2015.09.013] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 09/18/2015] [Accepted: 09/23/2015] [Indexed: 12/24/2022]
Abstract
F-box proteins (FBP) are the substrate specifying subunit of Skp1-Cul1-FBP (SCF)-type E3 ubiquitin ligases and are responsible for directing the ubiquitination of numerous proteins essential for cellular function. Due to their ability to regulate the expression and activity of oncogenes and tumour suppressor genes, FBPs themselves play important roles in cancer development and progression. In this review, we provide a comprehensive overview of FBPs and their targets in relation to their interaction with the hallmarks of cancer cell biology, including the regulation of proliferation, epigenetics, migration and invasion, metabolism, angiogenesis, cell death and DNA damage responses. Each cancer hallmark is revealed to have multiple FBPs which converge on common signalling hubs or response pathways. We also highlight the complex regulatory interplay between SCF-type ligases and other ubiquitin ligases. We suggest six highly interconnected FBPs affecting multiple cancer hallmarks, which may prove sensible candidates for therapeutic intervention.
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Affiliation(s)
- Suzanne J Randle
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
| | - Heike Laman
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom.
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15
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Zhu P, Wang Y, He L, Huang G, Du Y, Zhang G, Yan X, Xia P, Ye B, Wang S, Hao L, Wu J, Fan Z. ZIC2-dependent OCT4 activation drives self-renewal of human liver cancer stem cells. J Clin Invest 2015; 125:3795-808. [PMID: 26426078 DOI: 10.1172/jci81979] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 07/23/2015] [Indexed: 12/25/2022] Open
Abstract
Liver cancer stem cells (CSCs) have been identified and shown to have self-renewal and differentiation properties; however, the biology of these hepatic CSCs remains largely unknown. Here, we analyzed transcriptome gene expression profiles of liver CSCs and non-CSCs from hepatocellular carcinoma (HCC) cells lines and found that the transcription factor (TF) ZIC2 is highly expressed in liver CSCs. ZIC2 was required for the self-renewal maintenance of liver CSCs, as ZIC2 depletion reduced sphere formation and xenograft tumor growth in mice. We determined that ZIC2 acts upstream of the TF OCT4 and that ZIC2 recruits the nuclear remodeling factor (NURF) complex to the OCT4 promoter, thereby initiating OCT4 activation. In HCC patients, expression levels of the NURF complex were consistent with clinical severity and prognosis. Moreover, ZIC2 and OCT4 levels positively correlated to the clinicopathological stages of HCC patients. Altogether, our results indicate that levels of ZIC2, OCT4, and the NURF complex can be detected and used for diagnosis and prognosis prediction of HCC patients. Moreover, these factors may be potential therapeutic targets for eradicating liver CSCs.
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16
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A comprehensive method for detecting ubiquitinated substrates using TR-TUBE. Proc Natl Acad Sci U S A 2015; 112:4630-5. [PMID: 25827227 DOI: 10.1073/pnas.1422313112] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The identification of substrates for ubiquitin ligases has remained challenging, because most substrates are either immediately degraded by the proteasome or processed by deubiquitinating enzymes (DUBs) to remove polyubiquitin. Although a methodology that enables detection of ubiquitinated proteins using ubiquitin Lys-ε-Gly-Gly (diGly) remnant antibodies and MS has been developed, it is still insufficient for identification and characterization of the ubiquitin-modified proteome in cells overexpressing a particular ubiquitin ligase. Here, we show that exogenously expressed trypsin-resistant tandem ubiquitin-binding entity(ies) (TR-TUBE) protect polyubiquitin chains on substrates from DUBs and circumvent proteasome-mediated degradation in cells. TR-TUBE effectively associated with substrates ubiquitinated by an exogenously overexpressed ubiquitin ligase, allowing detection of the specific activity of the ubiquitin ligase and isolation of its substrates. Although the diGly antibody enabled effective identification of ubiquitinated proteins in cells, overexpression of an ubiquitin ligase and treatment with a proteasome inhibitor did not increase the level of diGly peptides specific for the ligase relative to the background level of diGly peptides, probably due to deubiquitination. By contrast, in TR-TUBE-expressing cells, the level of substrate-derived diGly peptides produced by the overexpressed ubiquitin ligase was significantly elevated. We developed a method for identifying the substrates of specific ubiquitin ligases using two enrichment strategies, TR-TUBE and diGly remnant antibodies, coupled with MS. Using this method, we identified target substrates of FBXO21, an uncharacterized F-box protein.
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