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Tao Y, Dai L, Liang W, Li X, Lyu Y, Li J, Li Z, Shi Z, Liang X, Zhou S, Fu X, Hu W, Wang X. Advancements and perspectives of RBX2 as a molecular hallmark in cancer. Gene 2024; 892:147864. [PMID: 37820940 DOI: 10.1016/j.gene.2023.147864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 09/18/2023] [Accepted: 09/29/2023] [Indexed: 10/13/2023]
Abstract
Cancer is a challenging issue for human health. One of the key methods to address this issue is by comprehending the molecular causes of tumors and creating medications that target those causes. RBX2 (RING box protein 2), also known as ROC2 (Regulator of Cullins 2), RNF7 (RING Finger Protein 7), or SAG (Sensitive to Apoptosis Gene) is a key component of the Cullin-RING-type E3 ubiquitin ligases (CRLs) and overexpressed in various human cancers. RBX2 is a potential drug target, the expression of which correlates with tumor staging, grading, and prognosis analysis. Through a synergistically biological interaction with Kras mutation in preclinical models, RBX2 accelerated the progression of skin cancer, pancreatic cancer, and lung cancer. In accordance, the aberrant expression of RBX2 will lead to dysregulation of many signaling pathways, which is crucial for tumor initiation and growth. However, the impact of RBX2 on tumors also intriguingly demonstrates a spatial reliance manner. In this review, we summarized the current understanding of RBX2 in multiple cancer types and suggested a significant potential of RBX2 as a therapeutic target.
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Affiliation(s)
- Yiran Tao
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China; Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Lirui Dai
- Department of Neurosurgery, Pituitary Adenoma Multidisciplinary Center, West China Hospital of Sichuan University, Chengdu 610041, Sichuan, China
| | - Wulong Liang
- Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Xiang Li
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China; Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Yuan Lyu
- Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China; Medical Research Center, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, PR China; Institute of Neuroscience, Zhengzhou University, Zhengzhou, Henan 450052, PR China
| | - Junqi Li
- Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China; Medical Research Center, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, PR China; Institute of Neuroscience, Zhengzhou University, Zhengzhou, Henan 450052, PR China
| | - Zian Li
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China; Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Zimin Shi
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China; Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Xianyin Liang
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China; Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Shaolong Zhou
- Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Xudong Fu
- Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Weihua Hu
- Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China
| | - Xinjun Wang
- Department of Neurosurgery, The Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China; Henan International Joint Laboratory of Glioma Metabolism and Microenvironment Research, Zhengzhou, Henan, PR China.
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Wińska P, Sobiepanek A, Pawlak K, Staniszewska M, Cieśla J. Phosphorylation of Thymidylate Synthase and Dihydrofolate Reductase in Cancer Cells and the Effect of CK2α Silencing. Int J Mol Sci 2023; 24:ijms24033023. [PMID: 36769342 PMCID: PMC9917831 DOI: 10.3390/ijms24033023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 01/30/2023] [Accepted: 02/01/2023] [Indexed: 02/08/2023] Open
Abstract
Our previous research suggests an important regulatory role of CK2-mediated phosphorylation of enzymes involved in the thymidylate biosynthesis cycle, i.e., thymidylate synthase (TS), dihydrofolate reductase (DHFR), and serine hydroxymethyltransferase (SHMT). The aim of this study was to show whether silencing of the CK2α gene affects TS and DHFR expression in A-549 cells. Additionally, we attempted to identify the endogenous kinases that phosphorylate TS and DHFR in CCRF-CEM and A-549 cells. We used immunodetection, immunofluorescence/confocal analyses, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), in-gel kinase assay, and mass spectrometry analysis. Our results demonstrate that silencing of the CK2α gene in lung adenocarcinoma cells significantly increases both TS and DHFR expression and affects their cellular distribution. Additionally, we show for the first time that both TS and DHFR are very likely phosphorylated by endogenous CK2 in two types of cancer cells, i.e., acute lymphoblastic leukaemia and lung adenocarcinoma. Moreover, our studies indicate that DHFR is phosphorylated intracellularly by CK2 to a greater extent in leukaemia cells than in lung adenocarcinoma cells. Interestingly, in-gel kinase assay results indicate that the CK2α' isoform was more active than the CK2α subunit. Our results confirm the previous studies concerning the physiological relevance of CK2-mediated phosphorylation of TS and DHFR.
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Affiliation(s)
- Patrycja Wińska
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland
- Correspondence: (P.W.); (M.S.); Tel.: +48-222-345-573 (P.W.); +48-606-438-241 (M.S.)
| | - Anna Sobiepanek
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland
| | - Katarzyna Pawlak
- Chair of Analytical Chemistry, Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland
| | - Monika Staniszewska
- Centre for Advanced Materials and Technologies, Warsaw University of Technology, Poleczki 19, 02-822 Warsaw, Poland
- Correspondence: (P.W.); (M.S.); Tel.: +48-222-345-573 (P.W.); +48-606-438-241 (M.S.)
| | - Joanna Cieśla
- Chair of Drug and Cosmetics Biotechnology, Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland
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Yang KM, Kim K. Protein kinase CK2 modulation of pyruvate kinase M isoforms augments the Warburg effect in cancer cells. J Cell Biochem 2018; 119:8501-8510. [PMID: 30015359 DOI: 10.1002/jcb.27078] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 04/26/2018] [Indexed: 12/31/2022]
Abstract
Protein kinase CK2 is active in cancer cells. Previously, we reported that increased CK2 activity could induce epithelial mesenchymal transition of cancer cells. CK2 also induced epithelial mesenchymal transition in colon cancer cell lines such as HT29 and SW620, and the transitioned cells (CK2α cells) became more proliferative than the controls. We assumed that CK2 could affect cancer cell growth by modulating their energy metabolism. Here, we examined the molecular effects of CK2 on the glucose metabolism of cancer cells. We found that CK2α cells consumed more glucose and produced more lactate than control cells did. An XF glycolysis stress test showed that aerobic glycolysis was augmented up to the cancer cell's maximal glycolytic capacity in CK2α cells. Molecular analysis revealed that pyruvate kinase M1 was downregulated and pyruvate kinase M2 was nuclear localized in CK2α cells. Consequently, the expression and activity of lactate dehydrogenase A (LDHA) were upregulated. Treatment with FX11-a specific LDHA inhibitor-or clustered regularly interspaced short palindromic repeats (CRISPR)-mediated knockout of LDHA inhibited the CK2-driven proliferation of cancer cells. We conclude that CK2 augments the Warburg effect, resulting in increased proliferation of cancer cells.
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Affiliation(s)
- Kyung Mi Yang
- Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul, Korea
| | - Kunhong Kim
- Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, Seoul, Korea.,Integrated Genomic Research Center for Metabolic Regulation, Seodaemun-gu, Seoul, Korea
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Klein S, Meng R, Montenarh M, Götz C. The Phosphorylation of PDX-1 by Protein Kinase CK2 Is Crucial for Its Stability. Pharmaceuticals (Basel) 2016; 10:ph10010002. [PMID: 28036027 PMCID: PMC5374406 DOI: 10.3390/ph10010002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 12/20/2016] [Accepted: 12/23/2016] [Indexed: 12/14/2022] Open
Abstract
The homeodomain protein PDX-1 is a critical regulator of pancreatic development and insulin production in pancreatic β-cells. We have recently shown that PDX-1 is a substrate of protein kinase CK2; a multifunctional protein kinase which is implicated in the regulation of various cellular aspects, such as differentiation, proliferation, and survival. The CK2 phosphorylation site of PDX-1 is located within the binding region of the E3 ubiquitin ligase adaptor protein PCIF1. To study the interaction between PDX-1 and PCIF1 we used immunofluorescence analysis, co-immunoprecipitation, GST-pull-down studies, and proximity ligation assay (PLA). For the analysis of the stability of PDX-1 we performed a cycloheximide chase. We used PDX-1 in its wild-type form as well as phosphomutants of the CK2 phosphorylation site. In pancreatic β-cells PDX-1 binds to PCIF1. The phosphorylation of PDX-1 by CK2 increases the ratio of PCIF1 bound to PDX-1. The stability of PDX-1 is extended in the absence of CK2 phosphorylation. Our results identified protein kinase CK2 as new important modulator of the stability of PDX-1.
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Affiliation(s)
- Sabrina Klein
- Medical Biochemistry and Molecular Biology, Saarland University, 66424 Homburg, Germany.
| | - Rui Meng
- Medical Biochemistry and Molecular Biology, Saarland University, 66424 Homburg, Germany.
- Cancer Center of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 156 Wujiadun, Hankou, Wuhan 430045, China.
| | - Mathias Montenarh
- Medical Biochemistry and Molecular Biology, Saarland University, 66424 Homburg, Germany.
| | - Claudia Götz
- Medical Biochemistry and Molecular Biology, Saarland University, 66424 Homburg, Germany.
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Li H, Tan M, Jia L, Wei D, Zhao Y, Chen G, Xu J, Zhao L, Thomas D, Beer DG, Sun Y. Inactivation of SAG/RBX2 E3 ubiquitin ligase suppresses KrasG12D-driven lung tumorigenesis. J Clin Invest 2014; 124:835-46. [PMID: 24430184 PMCID: PMC3904615 DOI: 10.1172/jci70297] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Accepted: 11/07/2013] [Indexed: 12/20/2022] Open
Abstract
Cullin-RING ligases (CRLs) are a family of E3 ubiquitin ligase complexes that rely on either RING-box 1 (RBX1) or sensitive to apoptosis gene (SAG), also known as RBX2, for activity. RBX1 and SAG are both overexpressed in human lung cancer; however, their contribution to patient survival and lung tumorigenesis is unknown. Here, we report that overexpression of SAG, but not RBX1, correlates with poor patient prognosis and more advanced disease. We found that SAG is overexpressed in murine KrasG12D-driven lung tumors and that Sag deletion suppressed lung tumorigenesis and extended murine life span. Using cultured lung cancer cells, we showed that SAG knockdown suppressed growth and survival, inactivated both NF-κB and mTOR pathways, and resulted in accumulation of tumor suppressor substrates, including p21, p27, NOXA, and BIM. Importantly, growth suppression by SAG knockdown was partially rescued by simultaneous knockdown of p21 or the mTOR inhibitor DEPTOR. Treatment with MLN4924, a small molecule inhibitor of CRL E3s, also inhibited the formation of KrasG12D-induced lung tumors through a similar mechanism involving inactivation of NF-κB and mTOR and accumulation of tumor suppressor substrates. Together, our results demonstrate that Sag is a Kras-cooperating oncogene that promotes lung tumorigenesis and suggest that targeting SAG-CRL E3 ligases may be an effective therapeutic approach for Kras-driven lung cancers.
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Affiliation(s)
- Hua Li
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Mingjia Tan
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Lijun Jia
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Dongping Wei
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Yongchao Zhao
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Guoan Chen
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Jie Xu
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Lili Zhao
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Dafydd Thomas
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - David G. Beer
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Yi Sun
- Division of Radiation and Cancer Biology, Department of Radiation Oncology,
Thoracic Surgery, Department of Surgery,
Department of Biostatistics, and
Department of Pathology and Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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Sun Y, Li H. Functional characterization of SAG/RBX2/ROC2/RNF7, an antioxidant protein and an E3 ubiquitin ligase. Protein Cell 2012; 4:103-16. [PMID: 23136067 DOI: 10.1007/s13238-012-2105-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Accepted: 10/09/2012] [Indexed: 01/28/2023] Open
Abstract
SAG (Sensitive to Apoptosis Gene), also known as RBX2 (RING box protein 2), ROC2 (Regulator of Cullins 2), or RNF7 (RING Finger Protein 7), was originally cloned in our laboratory as a redox inducible antioxidant protein and later characterized as the second member of the RBX/ROC RING component of the SCF (SKP1-CUL-F-box Proteins) E3 ubiquitin ligase. When acting alone, SAG scavenges oxygen radicals by forming inter- and intra-molecular disulfide bonds, whereas by forming a complex with other components of the SCF E3 ligase, SAG promotes ubiquitination and degradation of a number of protein substrates, including c-JUN, DEPTOR, HIF-1α, IκBα, NF1, NOXA, p27, and procaspase-3, thus regulating various signaling pathways and biological processes. Specifically, SAG protects cells from apoptosis, confers radioresistance, and plays an essential and non-redundant role in mouse embryogenesis and vasculogenesis. Furthermore, stress-inducible SAG is overexpressed in a number of human cancers and SAG overexpression correlates with poor patient prognosis. Finally, SAG transgenic expression in epidermis causes an early stage inhibition, but later stage promotion, of skin tumorigenesis triggered by DMBA/TPA. Given its major role in promoting targeted degradation of tumor suppressive proteins, leading to apoptosis suppression and accelerated tumorigenesis, SAG E3 ligase appears to be an attractive anticancer target.
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Affiliation(s)
- Yi Sun
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B Medical Science-I, 1301 Catherine Street, Ann Arbor, MI 48109, USA.
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Chen F, Wang H, He H, Song L, Wu J, Gao Y, Liu X, He C, Yang H, Chen L, Wang L, Li G, Li Y, Kaplan DE, Zhong J. Short hairpin RNA-mediated silencing of bovine rotavirus NSP4 gene prevents diarrhoea in suckling mice. J Gen Virol 2010; 92:945-51. [PMID: 21148273 DOI: 10.1099/vir.0.027680-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
While RNA interference (RNAi) has been widely used to study rotavirus gene function in vitro, the potential therapeutic role for RNAi in vivo has not been explored. To this end, we constructed two recombinant lentiviral vectors containing short hairpin RNA (shRNA) against non-structural protein-4 (NSP4) of bovine rotavirus (BRV), RNAi-351 and RNAi-492. RNAi-351 and RNAi-492 strongly suppressed the transient expression of a FLAG-tagged NSP4 fusion protein in 293T cells. In BRV-susceptible MA104 cells, RNAi-492 more potently silenced NSP4 mRNA than RNAi-351 and combination of the two shRNAs almost completely silenced viral NSP4 gene expression. While 100% of suckling mice exposed to BRV and control shRNA developed severe diarrhoea, no suckling mice exposed to BRV in the presence of RNAi-492 or a combination of RNAi-492/RNAi-351 developed severe diarrhoea, and only 20 and 3.3% developed mild diarrhoea, respectively. In addition, RNAi-492 and RNAi-351 markedly abrogated rotaviral replication in MA104 cells and significantly inhibited BRV replication in mouse pups. These results indicated that shRNAs silencing NSP4 gene had substantial antiviral properties and inhibited replication of BRV in a sequence-specific manner that may have clinical application.
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Affiliation(s)
- Fangyuan Chen
- Dairy Cattle Research Center, Shandong Academy of Agricultural Sciences, Jinan 250100, PR China
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Tan M, Zhu Y, Kovacev J, Zhao Y, Pan ZQ, Spitz DR, Sun Y. Disruption of Sag/Rbx2/Roc2 induces radiosensitization by increasing ROS levels and blocking NF-kappaB activation in mouse embryonic stem cells. Free Radic Biol Med 2010; 49:976-83. [PMID: 20638939 PMCID: PMC2921456 DOI: 10.1016/j.freeradbiomed.2010.05.030] [Citation(s) in RCA: 29] [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: 03/31/2010] [Revised: 05/19/2010] [Accepted: 05/28/2010] [Indexed: 01/16/2023]
Abstract
SAG (sensitive to apoptosis gene; also known as RBX2 or ROC2) is a dual-function protein with antioxidant activity when acting alone or E3 ligase activity when complexed with other components of SCF (Skp1, cullins, F-box proteins) E3 ubiquitin ligases. SAG acts as a survival protein to inhibit apoptosis induced by a variety of stresses. Our recent work showed that SAG siRNA silencing sensitized cancer cells to radiation but the mechanism responsible remains elusive. Here we report that complete elimination of Sag expression via a gene-trapping strategy significantly sensitized mouse embryonic stem (ES) cells to radiation, with a sensitizing enhancement rate of 1.5-1.6. Radiosensitization was associated with increased steady-state levels of intracellular ROS (including superoxide) 24h after irradiation as well as enhancement of radiation-induced apoptosis. Furthermore, Sag elimination abrogated IkappaBalpha degradation leading to inhibition of NF-kappaB activation. Further detailed analysis revealed that IkappaBalpha is a direct substrate of SAG-SCF(beta-TrCP) E3 ubiquitin ligase. Taken together, these results support the hypothesis that Sag elimination via gene disruption sensitizes ES cells to radiation-induced cell killing by mechanisms that involve increased steady-state levels of ROS and decreased activation of NF-kappaB.
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Affiliation(s)
- Mingjia Tan
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109
| | - Yueming Zhu
- Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, The University of Iowa, Iowa City, IA 52242
| | - Jordan Kovacev
- Department of Oncological Sciences, 1425 Madison Avenue, Room 15-26, Mount Sinai School of Medicine, New York, NY 10029
| | - Yongchao Zhao
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109
| | - Zhen-Qiang Pan
- Department of Oncological Sciences, 1425 Madison Avenue, Room 15-26, Mount Sinai School of Medicine, New York, NY 10029
| | - Douglas R. Spitz
- Free Radical and Radiation Biology Program, Department of Radiation Oncology, Holden Comprehensive Cancer Center, The University of Iowa, Iowa City, IA 52242
| | - Yi Sun
- Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109
- Corresponding author: Tel. 734-615-1989, Fax 734-647-9654;
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Immunolocalization of phospho-Arg-directed protein kinase-substrate in hypoxic kidneys using in vivo cryotechnique. Med Mol Morphol 2009; 42:24-31. [DOI: 10.1007/s00795-008-0430-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 11/28/2008] [Indexed: 01/15/2023]
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Park HJ, Zheng H, Kulkarni D, Kerrigan J, Pungaliya P, Saleem A, Rubin EH. Identification of phosphorylation sites of TOPORS and a role for serine 98 in the regulation of ubiquitin but not SUMO E3 ligase activity. Biochemistry 2009; 47:13887-96. [PMID: 19053840 DOI: 10.1021/bi801904q] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
TOPORS is the first example of a protein that possesses both ubiquitin and SUMO E3 ligase activity. The ubiquitination activity maps to a conserved RING domain in the N-terminal region of the protein, which is not required for sumoylation activity. Similar to other E3 ligases, it is likely that the ubiquitin and sumoylation activities of TOPORS are regulated by post-translational modifications. Therefore, we employed mass spectrometry to identify post-translational modifications of TOPORS. Several putative phosphorylated regions were identified in conserved regions of the protein. We investigated the role of phosphorylation of serine 98, which is adjacent to the RING domain, in both cells and in vitro. Mutation of serine 98 to aspartic acid resulted in an increase in the ubiquitin ligase activity of TOPORS both in cells and in vitro. In addition, this mutation increased the binding of TOPORS to the E2 enzyme UbcH5a both in vitro and in cells. Conversely, a phospho-deficient mutant (S98A) exhibited little change in ubiquitin ligase activity compared to wild-type TOPORS, both in cells and in vitro. Neither of the mutants affected the localization of TOPORS to punctate nuclear regions. In addition, neither mutant affected the SUMO ligase activity of TOPORS in cells or in vitro. Molecular modeling studies support a role for serine 98 in regulating TOPORS-E2 interactions. Our findings indicate that phosphorylation of serine 98 regulates the ubiquitin but not the SUMO ligase activity of TOPORS, consistent with a potential binary switch function for TOPORS in protein ubiquitination versus sumoylation.
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Affiliation(s)
- Hye-Jin Park
- Departments of Pharmacology and Medicine, The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 195 Little Albany Street, New Brunswick, New Jersey 08901, USA
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Regulation of peptide import through phosphorylation of Ubr1, the ubiquitin ligase of the N-end rule pathway. Proc Natl Acad Sci U S A 2008; 105:19188-93. [PMID: 19033468 DOI: 10.1073/pnas.0808891105] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Substrates of the N-end rule pathway include proteins with destabilizing N-terminal residues. These residues are recognized by E3 ubiquitin ligases called N-recognins. Ubr1 is the N-recognin of the yeast Saccharomyces cerevisiae. Extracellular amino acids or short peptides up-regulate the peptide transporter gene PTR2, thereby increasing the capacity of a cell to import peptides. Cup9 is a transcriptional repressor that down-regulates PTR2. The induction of PTR2 by peptides or amino acids involves accelerated degradation of Cup9 by the N-end rule pathway. We report here that the Ubr1 N-recognin, which conditionally targets Cup9 for degradation, is phosphorylated in vivo at multiple sites, including Ser(300) and Tyr(277). We also show that the type-I casein kinases Yck1 and Yck2 phosphorylate Ubr1 on Ser(300), and thereby make possible ("prime") the subsequent (presumably sequential) phosphorylations of Ubr1 on Ser(296), Ser(292), Thr(288), and Tyr(277) by Mck1, a kinase of the glycogen synthase kinase 3 (Gsk3) family. Phosphorylation of Ubr1 on Tyr(277) by Mck1 is a previously undescribed example of a cascade-based tyrosine phosphorylation by a Gsk3-type kinase outside of autophosphorylation. We show that the Yck1/Yck2-mediated phosphorylation of Ubr1 on Ser(300) plays a major role in the control of peptide import by the N-end rule pathway. In contrast to phosphorylation on Ser(300), the subsequent (primed) phosphorylations, including the one on Tyr(277), have at most minor effects on the known properties of Ubr1, including regulation of peptide import. Thus, a biological role of the rest of Ubr1 phosphorylation cascade remains to be identified.
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Ahmad KA, Wang G, Unger G, Slaton J, Ahmed K. Protein kinase CK2--a key suppressor of apoptosis. ACTA ACUST UNITED AC 2008; 48:179-87. [PMID: 18492491 DOI: 10.1016/j.advenzreg.2008.04.002] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Kashif A Ahmad
- Cellular and Molecular Biochemistry Research Laboratory (151), V.A. Medical Center, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55417, USA.
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