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Lafita-Navarro MC, Conacci-Sorrell M. Nucleolar stress: From development to cancer. Semin Cell Dev Biol 2023; 136:64-74. [PMID: 35410715 PMCID: PMC9883801 DOI: 10.1016/j.semcdb.2022.04.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/29/2022] [Accepted: 04/02/2022] [Indexed: 02/06/2023]
Abstract
The nucleolus is a large nuclear membraneless organelle responsible for ribosome biogenesis. Ribosomes are cytoplasmic macromolecular complexes comprising RNA and proteins that link amino acids together to form new proteins. The biogenesis of ribosomes is an intricate multistep process that involves the transcription of ribosomal DNA (rDNA), the processing of ribosomal RNA (rRNA), and the assembly of rRNA with ribosomal proteins to form active ribosomes. Nearly all steps necessary for ribosome production and maturation occur in the nucleolus. Nucleolar shape, size, and number are directly linked to ribosome biogenesis. Errors in the steps of ribosomal biogenesis are sensed by the nucleolus causing global alterations in nucleolar function and morphology. This phenomenon, known as nucleolar stress, can lead to molecular changes such as stabilization of p53, which in turn activates cell cycle arrest or apoptosis. In this review, we discuss recent work on the association of nucleolar stress with degenerative diseases and developmental defects. In addition, we highlight the importance of de novo nucleotide biosynthesis for the enhanced nucleolar activity of cancer cells and discuss targeting nucleotide biosynthesis as a strategy to activate nucleolar stress to specifically target cancer cells.
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Affiliation(s)
- M Carmen Lafita-Navarro
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Maralice Conacci-Sorrell
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA; Hamon Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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Deciphering the Role of p53 and TAp73 in Neuroblastoma: From Pathogenesis to Treatment. Cancers (Basel) 2022; 14:cancers14246212. [PMID: 36551697 PMCID: PMC9777536 DOI: 10.3390/cancers14246212] [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: 11/04/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Neuroblastoma (NB) is an embryonic cancer that develops from neural crest stem cells, being one of the most common malignancies in children. The clinical manifestation of this disease is highly variable, ranging from spontaneous regression to increased aggressiveness, which makes it a major therapeutic challenge in pediatric oncology. The p53 family proteins p53 and TAp73 play a key role in protecting cells against genomic instability and malignant transformation. However, in NB, their activities are commonly inhibited by interacting proteins such as murine double minute (MDM)2 and MDMX, mutant p53, ΔNp73, Itch, and Aurora kinase A. The interplay between the p53/TAp73 pathway and N-MYC, a known biomarker of poor prognosis and drug resistance in NB, also proves to be decisive in the pathogenesis of this tumor. More recently, a strong crosstalk between microRNAs (miRNAs) and p53/TAp73 has been established, which has been the focused of great attention because of its potential for developing new therapeutic strategies. Collectively, this review provides an updated overview about the critical role of the p53/TAp73 pathway in the pathogenesis of NB, highlighting encouraging clues for the advance of alternative NB targeted therapies.
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Ding L, Zhang Z, Zhao C, Chen L, Chen Z, Zhang J, Liu Y, Nie Y, He Y, Liao K, Zhang X. Ribosomal L1 domain-containing protein 1 coordinates with HDM2 to negatively regulate p53 in human colorectal Cancer cells. J Exp Clin Cancer Res 2021; 40:245. [PMID: 34362424 PMCID: PMC8344204 DOI: 10.1186/s13046-021-02057-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 07/31/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Ribosomal L1 domain-containing protein 1 (RSL1D1) is a nucleolar protein that is essential in cell proliferation. In the current opinion, RSL1D1 translocates to the nucleoplasm under nucleolar stress and inhibits the E3 ligase activity of HDM2 via direct interaction, thereby leading to stabilization of p53. METHODS Gene knockdown was achieved in HCT116p53+/+, HCT116p53-/-, and HCT-8 human colorectal cancer (CRC) cells by siRNA transfection. A lentiviral expression system was used to establish cell strains overexpressing genes of interest. The mRNA and protein levels in cells were evaluated by qRT-PCR and western blot analyses. Cell proliferation, cell cycle, and cell apoptosis were determined by MTT, PI staining, and Annexin V-FITC/PI double staining assays, respectively. The level of ubiquitinated p53 protein was assessed by IP. The protein-RNA interaction was investigated by RIP. The subcellular localization of proteins of interest was determined by IFA. Protein-protein interaction was investigated by GST-pulldown, BiFC, and co-IP assays. The therapeutic efficacy of RSL1D1 silencing on tumor growth was evaluated in HCT116 tumor-bearing nude mice. RESULTS RSL1D1 distributed throughout the nucleus in human CRC cells. Silencing of RSL1D1 gene induced cell cycle arrest at G1/S and cell apoptosis in a p53-dependent manner. RSL1D1 directly interacted with and recruited p53 to HDM2 to form a ternary RSL1D1/HDM2/p53 protein complex and thereby enhanced p53 ubiquitination and degradation, leading to a decrease in the protein level of p53. Destruction of the ternary complex increased the level of p53 protein. RSL1D1 also indirectly decreased the protein level of p53 by stabilizing HDM2 mRNA. Consequently, the negative regulation of p53 by RSL1D1 facilitated cell proliferation and survival and downregulation of RSL1D1 remarkably inhibited the growth of HCT116p53+/+ tumors in a nude mouse model. CONCLUSION We report, for the first time, that RSL1D1 is a novel negative regulator of p53 in human CRC cells and more importantly, a potential molecular target for anticancer drug development.
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Affiliation(s)
- Li Ding
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Zhiping Zhang
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Chenhong Zhao
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Lei Chen
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Zhiqiang Chen
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Jie Zhang
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Yaxian Liu
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Yesen Nie
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Yanzhi He
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Kai Liao
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China
| | - Xinyue Zhang
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, 225009, Jiangsu, China. .,Joint International Research Laboratory of Agriculture & Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, Jiangsu, China. .,Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Agriculture of China, Yangzhou University (26116120), Yangzhou, 225009, Jiangsu, China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, Jiangsu, China.
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4
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Bruer M, Reinhardt D, Welte K, Thakur BK. Insights into the limitations of transient expression systems for the functional study of p53 acetylation site and oncogenic mutants. Biochem Biophys Res Commun 2020; 524:990-995. [PMID: 32061389 DOI: 10.1016/j.bbrc.2020.02.002] [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: 01/20/2020] [Accepted: 02/02/2020] [Indexed: 10/25/2022]
Abstract
Tumor suppressor protein p53 protects cells against malignant transformation mostly through transcriptional activation. Lysine acetylation is required to mediate activation of p53. The protein displays eight lysine residues and their evolutionary conservation argues for an essential role. The aim of this study was to investigate the significance of individual acetylation sites in mediating p53 functions. Differences in intracellular localization, protein expression levels, and transcriptional activity were investigated by overexpressing acetylation-deficient p53 variants in the colon carcinoma-derived p53 knock-out cell line HCT 116 p53(-/-). We found that not all lysine residues are equally capable of promoting p53's functions. Individual amino acid mutations or combinations thereof led to altered p53 expression levels, intracellular distribution, or transcriptional transactivation capacity, as compared to the wild-type protein. However, we observed that the choice of protein tag and expression vector could significantly alter obtained results on certain aspects of p53 function.
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Affiliation(s)
- Marius Bruer
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Dirk Reinhardt
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany
| | - Karl Welte
- Molecular Hematopoiesis, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover, Germany
| | - Basant Kumar Thakur
- Department of Pediatric Hematology/Oncology, Hannover Medical School, Carl-Neuberg-Straße 1, 30625, Hannover, Germany.
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Ducker C, Chow LKY, Saxton J, Handwerger J, McGregor A, Strahl T, Layfield R, Shaw PE. De-ubiquitination of ELK-1 by USP17 potentiates mitogenic gene expression and cell proliferation. Nucleic Acids Res 2019; 47:4495-4508. [PMID: 30854565 PMCID: PMC6511843 DOI: 10.1093/nar/gkz166] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 02/26/2019] [Accepted: 03/01/2019] [Indexed: 01/06/2023] Open
Abstract
ELK-1 is a transcription factor involved in ERK-induced cellular proliferation. Here, we show that its transcriptional activity is modulated by ubiquitination at lysine 35 (K35). The level of ubiquitinated ELK-1 rises in mitogen-deprived cells and falls upon mitogen stimulation or oncogene expression. Ectopic expression of USP17, a cell cycle-dependent deubiquitinase, decreases ELK-1 ubiquitination and up-regulates ELK-1 target-genes with a concomitant increase in cyclin D1 expression. In contrast, USP17 depletion attenuates ELK-1-dependent gene expression and slows cell proliferation. The reduced rate of proliferation upon USP17 depletion appears to be a direct effect of ELK-1 ubiquitination because it is rescued by an ELK-1(K35R) mutant refractory to ubiquitination. Overall, our results show that ubiquitination of ELK-1 at K35, and its reversal by USP17, are important mechanisms in the regulation of nuclear ERK signalling and cellular proliferation. Our findings will be relevant for tumours that exhibit elevated USP17 expression and suggest a new target for intervention.
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Affiliation(s)
- Charles Ducker
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Leo Kam Yuen Chow
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Janice Saxton
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Jürgen Handwerger
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Alexander McGregor
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Thomas Strahl
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Robert Layfield
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
| | - Peter E Shaw
- Transcription and Molecular Signalling Laboratory, School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
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Park JH, Li J, Starost MF, Liu C, Zhuang J, Chen J, Achatz MI, Kang JG, Wang PY, Savage SA, Hwang PM. Mouse Homolog of the Human TP53 R337H Mutation Reveals Its Role in Tumorigenesis. Cancer Res 2018; 78:5375-5383. [PMID: 30042151 PMCID: PMC6139041 DOI: 10.1158/0008-5472.can-18-0016] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 05/27/2018] [Accepted: 07/12/2018] [Indexed: 01/07/2023]
Abstract
Inheritance of germline mutations in the tumor suppressor gene TP53 causes Li-Fraumeni syndrome (LFS), a cancer predisposition disorder. The arginine to histidine substitution at amino acid position 337 of p53 (R337H) is a founder mutation highly prevalent in southern and southeastern Brazil and is considered an LFS mutation. Although this mutation is of significant clinical interest, its role in tumorigenesis using animal models has not been described. Here, we generate a knockin mouse model containing the homologous R337H mutation (mouse R334H). De novo tumorigenesis was not significantly increased in either heterozygous (p53334R/H ) or homozygous (p53334H/H ) p53 R334H knockin mice compared with wild-type mice. However, susceptibility to diethylnitrosamine (DEN)-induced liver carcinogenesis was increased in a mutant allele dose-dependent manner. In parallel, p53334H/H mice exposed to DEN exhibited increased DNA damage but decreased cell-cycle regulation in the liver. Oligomerization of p53, which is required for transactivation of target genes, was reduced in R334H liver, consistent with its decreased nuclear activity compared with wild-type. By modeling a TP53 mutation in mice that has relatively weak cancer penetrance, this study provides in vivo evidence that the human R337H mutation can compromise p53 activity and promote tumorigenesis.Significance: A germline mutation in the oligomerization domain of p53 decreases its transactivation potential and renders mice susceptible to carcinogen-induced liver tumorigenesis. Cancer Res; 78(18); 5375-83. ©2018 AACR.
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Affiliation(s)
- Ji-Hoon Park
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland
| | - Jie Li
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland
| | | | - Chengyu Liu
- Transgenic Core, NHLBI, NIH, Bethesda, Maryland
| | - Jie Zhuang
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland
| | - Jichun Chen
- Hematology Branch, NHLBI, NIH, Bethesda, Maryland
| | - Maria I Achatz
- Division of Cancer Epidemiology and Genetics, Clinical Genetics Branch, National Cancer Institute, Rockville, Maryland
- Centro de Oncologia, Hospital Sírio-Libanês, São Paulo, Brazil
| | - Ju-Gyeong Kang
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland
| | - Ping-Yuan Wang
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland
| | - Sharon A Savage
- Division of Cancer Epidemiology and Genetics, Clinical Genetics Branch, National Cancer Institute, Rockville, Maryland
| | - Paul M Hwang
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, Maryland.
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7
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Garziera M, Cecchin E, Canzonieri V, Sorio R, Giorda G, Scalone S, De Mattia E, Roncato R, Gagno S, Poletto E, Romanato L, Sartor F, Polesel J, Toffoli G. Identification of Novel Somatic TP53 Mutations in Patients with High-Grade Serous Ovarian Cancer (HGSOC) Using Next-Generation Sequencing (NGS). Int J Mol Sci 2018; 19:ijms19051510. [PMID: 29783665 PMCID: PMC5983728 DOI: 10.3390/ijms19051510] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 04/26/2018] [Accepted: 05/16/2018] [Indexed: 02/07/2023] Open
Abstract
Somatic mutations in TP53 are a hallmark of high-grade serous ovarian cancer (HGSOC), although their prognostic and predictive value as markers is not well defined. Next-generation sequencing (NGS) can identify novel mutations with high sensitivity, that may be repurposed as potential druggable anti-cancer targets and aid in therapeutic decisions. Here, a commercial NGS cancer panel comprising 26 genes, including TP53, was used to identify new genetic markers of platinum resistance and patient prognosis in a retrospective set of patients diagnosed with epithelial ovarian cancer. Six novel TP53 somatic mutations in untreated tumors from six distinct patients diagnosed with HGSOC were identified: TP53 c.728_739delTGGGCGGCATGA (p.Met243_Met247del, in-frame insertion or deletion (INDEL); TP53 c.795_809delGGGACGGAACAGCTT (p.Gly266_Phe270del, in-frame INDEL); TP53 c.826_827GC>AT (p.Ala276Ile, missense); TP53 c.1022insT (p.Arg342Profs*5, frameshift INDEL); TP53 c.1180delT (p.Ter394Aspfs*28, frameshift INDEL); and TP53 c.573insT (p.Gln192Serfs*17, frameshift INDEL). Novel TP53 variants were validated by classical sequencing methods and their impact on protein expression in tumors explored by immunohistochemistry. Further insights into the potential functional effect of the mutations were obtained by different in silico approaches, bioinformatics tools, and structural modeling. This discovery of previously unreported TP53 somatic mutations provides an opportunity to translate NGS technology into personalized medicine and identify new potential targets for therapeutic applications.
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Affiliation(s)
- Marica Garziera
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Erika Cecchin
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Vincenzo Canzonieri
- Pathology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Roberto Sorio
- Medical Oncology Unit C, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Giorgio Giorda
- Gynecological Oncology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Simona Scalone
- Medical Oncology Unit C, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Elena De Mattia
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Rossana Roncato
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Sara Gagno
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Elena Poletto
- Medical Oncology Department, Azienda Sanitaria Universitaria Integrata di Udine, via Pozzuolo 330, 33100 Udine (UD), Italy.
| | - Loredana Romanato
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Franca Sartor
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Jerry Polesel
- Unit of Cancer Epidemiology, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
| | - Giuseppe Toffoli
- Experimental and Clinical Pharmacology Unit, CRO Aviano-National Cancer Institute, IRCCS, via F. Gallini 2, 33081 Aviano (PN), Italy.
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8
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Carr MI, Jones SN. Regulation of the Mdm2-p53 signaling axis in the DNA damage response and tumorigenesis. Transl Cancer Res 2016; 5:707-724. [PMID: 28690977 PMCID: PMC5501481 DOI: 10.21037/tcr.2016.11.75] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The p53 tumor suppressor acts as a guardian of the genome in mammalian cells undergoing DNA double strand breaks induced by a various forms of cell stress, including inappropriate growth signals or ionizing radiation. Following damage, p53 protein levels become greatly elevated in cells and p53 functions primarily as a transcription factor to regulate the expression a wide variety of genes that coordinate this DNA damage response. In cells undergoing high amounts of DNA damage, p53 can promote apoptosis, whereas in cells undergoing less damage, p53 promotes senescence or transient cell growth arrest and the expression of genes involved in DNA repair, depending upon the cell type and level of damage. Failure of the damaged cell to undergo growth arrest or apoptosis, or to respond to the DNA damage by other p53-coordinated mechanisms, can lead to inappropriate cell growth and tumorigenesis. In cells that have successfully responded to genetic damage, the amount of p53 present in the cell must return to basal levels in order for the cell to resume normal growth and function. Although regulation of p53 levels and function is coordinated by many proteins, it is now widely accepted that the master regulator of p53 is Mdm2. In this review, we discuss the role(s) of p53 in the DNA damage response and in tumor suppression, and how post-translational modification of Mdm2 regulates the Mdm2-p53 signaling axis to govern p53 activities in the cell.
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Affiliation(s)
- Michael I Carr
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
| | - Stephen N Jones
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655, USA
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9
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D'Allard DL, Liu JM. Toward RNA Repair of Diamond Blackfan Anemia Hematopoietic Stem Cells. Hum Gene Ther 2016; 27:792-801. [PMID: 27550323 DOI: 10.1089/hum.2016.081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Diamond blackfan anemia (DBA) is a well-known inherited bone marrow failure syndrome mostly caused by mutations in ribosomal protein (RP) genes but also rarely in the hematopoietic transcription factor gene, GATA1, or TSR2, a ribosomal protein (Rps26) chaperone gene. About 25% of patients have heterozygous mutations in the RPS19 gene, which leads to haploinsufficiency of Rps19 protein in most cases. However, some RPS19 missense mutations appear to act in a dominant negative fashion. DBA typically leads to a hypoplastic anemia that becomes apparent during the first year of life, and standard treatment includes steroids or red blood cell transfusions, each modality having attendant side effects. The only curative therapy is allogeneic stem-cell transplantation, but this option is limited to patients with a histocompatible donor. DBA-mutant embryonic, induced pluripotent, and hematopoietic stem cells all exhibit growth abnormalities that can be corrected by DNA gene transfer, suggesting the possibility of ex vivo autologous gene therapy. The authors have been interested in the application of spliceosome-mediated mRNA trans-splicing (SMaRT) technology to RNA repair of DBA stem cells. Compared with gene replacement or other RNA re-programming approaches, SMaRT has several potential advantages. First, delivery of the entire normal cDNA is unnecessary, thus minimizing the overall size of the construct for packaging into a viral delivery vector. Second, RNA transcription of the corrected gene relies on the cell's endogenous transcriptional, processing, and regulatory machinery, thereby ensuring faithful and contextual expression. Third, RNA trans-splicing employs the endogenous spliceosome enzymatic machinery present in nearly all cells. Fourth, RNA trans-splicing converts mutant transcripts into therapeutically useful mRNA, and thus may be capable of treating disorders caused by dominant negative mutations. This review critically assesses prospects for both gene and RNA repair in DBA stem cells.
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Affiliation(s)
- Diane L D'Allard
- Les Nelkin Memorial Pediatric Oncology Laboratory, The Feinstein Institute for Medical Research , Manhasset, New York
| | - Johnson M Liu
- Les Nelkin Memorial Pediatric Oncology Laboratory, The Feinstein Institute for Medical Research , Manhasset, New York
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10
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Laptenko O, Shiff I, Freed-Pastor W, Zupnick A, Mattia M, Freulich E, Shamir I, Kadouri N, Kahan T, Manfredi J, Simon I, Prives C. The p53 C terminus controls site-specific DNA binding and promotes structural changes within the central DNA binding domain. Mol Cell 2016; 57:1034-1046. [PMID: 25794615 DOI: 10.1016/j.molcel.2015.02.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/23/2014] [Accepted: 02/06/2015] [Indexed: 11/19/2022]
Abstract
DNA binding by numerous transcription factors including the p53 tumor suppressor protein constitutes a vital early step in transcriptional activation. While the role of the central core DNA binding domain (DBD) of p53 in site-specific DNA binding has been established, the contribution of the sequence-independent C-terminal domain (CTD) is still not well understood. We investigated the DNA-binding properties of a series of p53 CTD variants using a combination of in vitro biochemical analyses and in vivo binding experiments. Our results provide several unanticipated and interconnected findings. First, the CTD enables DNA binding in a sequence-dependent manner that is drastically altered by either its modification or deletion. Second, dependence on the CTD correlates with the extent to which the p53 binding site deviates from the canonical consensus sequence. Third, the CTD enables stable formation of p53-DNA complexes to divergent binding sites via DNA-induced conformational changes within the DBD itself.
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Affiliation(s)
- Oleg Laptenko
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Idit Shiff
- Department of Microbiology and Molecular Genetics, Hebrew University Medical School, IMRIC, Jerusalem 91120, Israel
| | - Will Freed-Pastor
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Andrew Zupnick
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Melissa Mattia
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Ella Freulich
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Inbal Shamir
- Department of Microbiology and Molecular Genetics, Hebrew University Medical School, IMRIC, Jerusalem 91120, Israel
| | - Noam Kadouri
- Department of Microbiology and Molecular Genetics, Hebrew University Medical School, IMRIC, Jerusalem 91120, Israel
| | - Tamar Kahan
- Department of Microbiology and Molecular Genetics, Hebrew University Medical School, IMRIC, Jerusalem 91120, Israel
| | - James Manfredi
- Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Itamar Simon
- Department of Microbiology and Molecular Genetics, Hebrew University Medical School, IMRIC, Jerusalem 91120, Israel.
| | - Carol Prives
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
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Huang EY, Wang FS, Chen YM, Chen YF, Wang CC, Lin IH, Huang YJ, Yang KD. Amifostine alleviates radiation-induced lethal small bowel damage via promotion of 14-3-3σ-mediated nuclear p53 accumulation. Oncotarget 2015; 5:9756-69. [PMID: 25230151 PMCID: PMC4259435 DOI: 10.18632/oncotarget.2386] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Amifostine (AM) is a radioprotector that scavenges free radicals and is used in patients undergoing radiotherapy. p53 has long been implicated in cell cycle arrest for cellular repair after radiation exposure. We therefore investigated the protective p53-dependent mechanism of AM on small bowel damage after lethal whole-abdominal irradiation (WAI). AM increased both the survival rate of rats and crypt survival following lethal 18 Gy WAI. The p53 inhibitor PFT-α compromised AM-mediated effects when administered prior to AM administration. AM significantly increased clonogenic survival in IEC-6 cells expressing wild type p53 but not in p53 knockdown cells. AM significantly increased p53 nuclear accumulation and p53 tetramer expression before irradiation through the inhibition of p53 degradation. AM inhibited p53 interactions with MDM2 but enhanced p53 interactions with 14-3-3σ. Knockdown of 14-3-3σ also compromised the effect of AM on clonogenic survival and p53 nuclear accumulation in IEC-6 cells. For the first time, our data reveal that AM alleviates lethal small bowel damage through the induction of 14-3-3σ and subsequent accumulation of p53. Enhancement of the p53/14-3-3σ interaction results in p53 tetramerization in the nucleus that rescues lethal small bowel damage.
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Affiliation(s)
- Eng-Yen Huang
- Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Niao-Sung District, Kaohsiung 833, Taiwan. Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taiwan. School of Traditional Chinese Medicine, Chang Gung University College of Medicine, Taiwan
| | - Feng-Sheng Wang
- Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taiwan. Department of Medical Research, Niao-Sung District, Kaohsiung 833, Taiwan. Center for Laboratory Animals, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Niao-Sung District, Kaohsiung 833, Taiwan
| | - Yu-Min Chen
- Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Niao-Sung District, Kaohsiung 833, Taiwan
| | - Yi-Fan Chen
- Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Niao-Sung District, Kaohsiung 833, Taiwan
| | - Chung-Chi Wang
- Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Niao-Sung District, Kaohsiung 833, Taiwan
| | - I-Hui Lin
- Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Niao-Sung District, Kaohsiung 833, Taiwan
| | - Yu-Jie Huang
- Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Niao-Sung District, Kaohsiung 833, Taiwan
| | - Kuender D Yang
- Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taiwan. Department of Medical Research, Show Chwan Memorial Hospital in Chang Bing, Chang Bing Industrial Center, Lu-Kang, Changhua 505, Taiwan. Institute of Clinical Medicine, National Yang Ming University, Taiwan
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12
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Rodríguez JA. Interplay between nuclear transport and ubiquitin/SUMO modifications in the regulation of cancer-related proteins. Semin Cancer Biol 2014; 27:11-9. [DOI: 10.1016/j.semcancer.2014.03.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 03/22/2014] [Accepted: 03/25/2014] [Indexed: 11/25/2022]
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13
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Vlatković N, Boyd MT, Rubbi CP. Nucleolar control of p53: a cellular Achilles' heel and a target for cancer therapy. Cell Mol Life Sci 2014; 71:771-91. [PMID: 23685903 PMCID: PMC11113510 DOI: 10.1007/s00018-013-1361-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 04/07/2013] [Accepted: 04/30/2013] [Indexed: 02/07/2023]
Abstract
Nucleoli perform a crucial cell function, ribosome biogenesis, and of critical relevance to the subject of this review, they are also extremely sensitive to cellular stresses, which can cause loss of function and/or associated structural disruption. In recent years, we have learned that cells take advantage of this stress sensitivity of nucleoli, using them as stress sensors. One major protein regulated by this role of nucleoli is the tumor suppressor p53, which is activated in response to diverse cellular injuries in order to exert its onco-protective effects. Here we discuss a model of nucleolar regulation of p53, which proposes that key steps in the promotion of p53 degradation by the ubiquitin ligase MDM2 occur in nucleoli, thus providing an explanation for the observed link between nucleolar disruption and p53 stability. We review current evidence for this compartmentalization in p53 homeostasis and highlight current limitations of the model. Interestingly, a number of current chemotherapeutic agents capable of inducing a p53 response are likely to do so by targeting nucleolar functions and these compounds may serve to inform further improved therapeutic targeting of nucleoli.
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Affiliation(s)
- Nikolina Vlatković
- Cancer Research Centre, University of Liverpool, 200 London Rd, Liverpool, L3 9TA UK
| | - Mark T. Boyd
- Cancer Research Centre, University of Liverpool, 200 London Rd, Liverpool, L3 9TA UK
| | - Carlos P. Rubbi
- Cancer Research Centre, University of Liverpool, 200 London Rd, Liverpool, L3 9TA UK
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14
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Wiech M, Olszewski MB, Tracz-Gaszewska Z, Wawrzynow B, Zylicz M, Zylicz A. Molecular mechanism of mutant p53 stabilization: the role of HSP70 and MDM2. PLoS One 2012; 7:e51426. [PMID: 23251530 PMCID: PMC3520893 DOI: 10.1371/journal.pone.0051426] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 10/29/2012] [Indexed: 12/12/2022] Open
Abstract
Numerous p53 missense mutations possess gain-of-function activities. Studies in mouse models have demonstrated that the stabilization of p53 R172H (R175H in human) mutant protein, by currently unknown factors, is a prerequisite for its oncogenic gain-of-function phenotype such as tumour progression and metastasis. Here we show that MDM2-dependent ubiquitination and degradation of p53 R175H mutant protein in mouse embryonic fibroblasts is partially inhibited by increasing concentration of heat shock protein 70 (HSP70/HSPA1-A). These phenomena correlate well with the appearance of HSP70-dependent folding intermediates in the form of dynamic cytoplasmic spots containing aggregate-prone p53 R175H and several molecular chaperones. We propose that a transient but recurrent interaction with HSP70 may lead to an increase in mutant p53 protein half-life. In the presence of MDM2 these pseudoaggregates can form stable amyloid-like structures, which occasionally merge into an aggresome. Interestingly, formation of folding intermediates is not observed in the presence of HSC70/HSPA8, the dominant-negative K71S variant of HSP70 or HSP70 inhibitor. In cancer cells, where endogenous HSP70 levels are already elevated, mutant p53 protein forms nuclear aggregates without the addition of exogenous HSP70. Aggregates containing p53 are also visible under conditions where p53 is partially unfolded: 37°C for temperature-sensitive variant p53 V143A and 42°C for wild-type p53. Refolding kinetics of p53 indicate that HSP70 causes transient exposure of p53 aggregate-prone domain(s). We propose that formation of HSP70- and MDM2-dependent protein coaggregates in tumours with high levels of these two proteins could be one of the mechanisms by which mutant p53 is stabilized. Moreover, sequestration of p73 tumour suppressor protein by these nuclear aggregates may lead to gain-of-function phenotypes.
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Affiliation(s)
- Milena Wiech
- Department of Molecular Biology, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
- The Nencki Institute of Experimental Biology, PAS, Warsaw, Poland
| | - Maciej B. Olszewski
- Department of Molecular Biology, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Zuzanna Tracz-Gaszewska
- Department of Molecular Biology, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
- The Institute of Biochemistry and Biophysics, PAS, Warsaw, Poland
| | - Bartosz Wawrzynow
- Department of Molecular Biology, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Maciej Zylicz
- Department of Molecular Biology, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Alicja Zylicz
- Department of Molecular Biology, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
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15
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Muscolini M, Montagni E, Palermo V, Di Agostino S, Gu W, Abdelmoula-Souissi S, Mazzoni C, Blandino G, Tuosto L. The cancer-associated K351N mutation affects the ubiquitination and the translocation to mitochondria of p53 protein. J Biol Chem 2011; 286:39693-702. [PMID: 21953469 PMCID: PMC3220532 DOI: 10.1074/jbc.m111.279539] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Revised: 09/27/2011] [Indexed: 12/17/2022] Open
Abstract
Stress-induced monoubiquitination of p53 is a crucial event for the nuclear-cytoplasm-mitochondria trafficking and transcription-independent pro-apoptotic functions of p53. Although an intact ubiquitination pathway and a functional nuclear export sequence are required for p53 nuclear export, the role of specific residues within this region in regulating both processes remains largely unknown. Here we characterize the mechanisms accounting for the nuclear accumulation of a new point mutation (Lys-351 to Asn) in the nuclear export sequence of p53 identified in a cisplatin-resistant ovarian carcinoma cell line (A2780 CIS). We found that K351N substitution abrogates the monoubiquitination of p53 induced by both Mdm2 and MSL2 E3-ligases. As a consequence, cells expressing p53 K351N mutant showed defects in cisplatin-induced translocation of p53 to mitochondria, Bax oligomerization, and mitochondrial membrane depolarization. These data identify K351N as a critical mutation of p53 that contributes to the development and maintenance of resistance to cisplatin.
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Affiliation(s)
- Michela Muscolini
- From the Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biology and Biotechnology, Sapienza University, 00185-Rome, Italy
| | - Elisa Montagni
- From the Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biology and Biotechnology, Sapienza University, 00185-Rome, Italy
| | - Vanessa Palermo
- From the Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biology and Biotechnology, Sapienza University, 00185-Rome, Italy
| | - Silvia Di Agostino
- the Translational Oncogenomic Unit, Via Elio Chianesi, Istituto Regina Elena-IFO, 00144-Rome, Italy
| | - Wei Gu
- the Institute for Cancer Genetics and Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York 10027, and
| | | | - Cristina Mazzoni
- From the Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biology and Biotechnology, Sapienza University, 00185-Rome, Italy
| | - Giovanni Blandino
- the Translational Oncogenomic Unit, Via Elio Chianesi, Istituto Regina Elena-IFO, 00144-Rome, Italy
| | - Loretta Tuosto
- From the Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biology and Biotechnology, Sapienza University, 00185-Rome, Italy
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16
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David Y, Ternette N, Edelmann MJ, Ziv T, Gayer B, Sertchook R, Dadon Y, Kessler BM, Navon A. E3 ligases determine ubiquitination site and conjugate type by enforcing specificity on E2 enzymes. J Biol Chem 2011; 286:44104-44115. [PMID: 21965653 DOI: 10.1074/jbc.m111.234559] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ubiquitin-conjugating enzymes (E2s) have a dominant role in determining which of the seven lysine residues of ubiquitin is used for polyubiquitination. Here we show that tethering of a substrate to an E2 enzyme in the absence of an E3 ubiquitin ligase is sufficient to promote its ubiquitination, whereas the type of the ubiquitin conjugates and the identity of the target lysine on the substrate are promiscuous. In contrast, when an E3 enzyme is introduced, a clear decision between mono- and polyubiquitination is made, and the conjugation type as well as the identity of the target lysine residue on the substrate becomes highly specific. These features of the E3 can be further regulated by auxiliary factors as exemplified by MDMX (Murine Double Minute X). In fact, we show that this interactor reconfigures MDM2-dependent ubiquitination of p53. Based on several model systems, we propose that although interaction with an E2 is sufficient to promote substrate ubiquitination the E3 molds the reaction into a specific, physiologically relevant protein modification.
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Affiliation(s)
- Yael David
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Nicola Ternette
- The Henry Wellcome Building for Molecular Physiology, Nuffield Department of Clinical Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Mariola J Edelmann
- The Henry Wellcome Building for Molecular Physiology, Nuffield Department of Clinical Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Tamar Ziv
- Smoler Proteomics Center, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - Batya Gayer
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Rotem Sertchook
- Faculty of Biochemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yakir Dadon
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Benedikt M Kessler
- The Henry Wellcome Building for Molecular Physiology, Nuffield Department of Clinical Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, United Kingdom
| | - Ami Navon
- Department of Biological Regulation, The Weizmann Institute of Science, Rehovot 76100, Israel.
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17
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Stindt MH, Carter S, Vigneron AM, Ryan KM, Vousden KH. MDM2 promotes SUMO-2/3 modification of p53 to modulate transcriptional activity. Cell Cycle 2011; 10:3176-88. [PMID: 21900752 PMCID: PMC3218624 DOI: 10.4161/cc.10.18.17436] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 07/28/2011] [Accepted: 07/28/2011] [Indexed: 01/02/2023] Open
Abstract
The tumor suppressor p53 is extensively regulated by post-translational modification, including modification by the small ubiquitin-related modifier SUMO. We show here that MDM2, previously shown to promote ubiquitin, Nedd8 and SUMO-1 modification of p53, can also enhance conjugation of endogenous SUMO-2/3 to p53. Sumoylation activity requires p53-MDM2 binding but does not depend on an intact RING finger. Both ARF and L11 can promote SUMO-2/3 conjugation of p53. However, unlike the previously described SUMO-1 conjugation of p53 by an MDM2-ARF complex, this activity does not depend on the ability of MDM2 to relocalize to the nucleolus. Interestingly, the SUMO consensus is not conserved in mouse p53, which is therefore not modified by SUMO-2/3. Finally, we show that conjugation of SUMO-2/3 to p53 correlates with a reduction of both activation and repression of a subset of p53-target genes.
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18
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Hu R, Peng G, Dai H, Breuer EK, Stemke-Hale K, Li K, Gonzalez-Angulo AM, Mills GB, Lin SY. ZNF668 functions as a tumor suppressor by regulating p53 stability and function in breast cancer. Cancer Res 2011; 71:6524-34. [PMID: 21852383 DOI: 10.1158/0008-5472.can-11-0853] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Genome-wide sequencing studies in breast cancer have recently identified frequent mutations in the zinc finger protein 668 (ZNF668), the function of which is undefined. Here, we report that ZNF668 is a nucleolar protein that physically interacts with and regulates p53 and its negative regulator MDM2. Through MDM2 binding, ZNF668 regulated autoubiquitination of MDM2 and its ability to mediate p53 ubiquitination and degradation. ZNF668 deficiency also impaired DNA damage-induced stabilization of p53. RNA interference-mediated knockdown of ZNF668 was sufficient to transform normal mammary epithelial cells. ZNF668 effectively suppressed breast cancer cell proliferation in vitro and tumorigenicity in vivo. Taken together, our studies identify ZNF668 as a novel breast tumor suppressor gene that functions in regulating p53 stability.
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Affiliation(s)
- Ruozhen Hu
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77054, USA
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19
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Ozaki T, Kubo N, Nakagawara A. p73-Binding Partners and Their Functional Significance. INTERNATIONAL JOURNAL OF PROTEOMICS 2011; 2010:283863. [PMID: 22084676 PMCID: PMC3195385 DOI: 10.1155/2010/283863] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 10/26/2010] [Indexed: 12/21/2022]
Abstract
p73 is one of the tumor-suppressor p53 family of nuclear transcription factor. As expected from the structural similarity between p53 and p73, p73 has a tumor-suppressive function. However, p73 was rarely mutated in human primary tumors. Under normal physiological conditions, p73 is kept at an extremely low level to allow cells normal growth. In response to a certain subset of DNA damages, p73 is induced dramatically and transactivates an overlapping set of p53-target genes implicated in the promotion of cell cycle arrest and/or apoptotic cell death. Cells undergo cell cycle arrest and/or apoptotic cell death depending on the type and strength of DNA damages. p73 is regulated largely through the posttranslational modifications such as phosphorylation and acetylation. These chemical modifications are tightly linked to direct protein-protein interactions. In the present paper, the authors describe the functional significance of the protein-protein interactions in the regulation of proapoptotic p73.
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Affiliation(s)
- Toshinori Ozaki
- Laboratory of Anti-tumor Research, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan
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20
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Yakovlev VA, Bayden AS, Graves PR, Kellogg GE, Mikkelsen RB. Nitration of the tumor suppressor protein p53 at tyrosine 327 promotes p53 oligomerization and activation. Biochemistry 2010; 49:5331-9. [PMID: 20499882 DOI: 10.1021/bi100564w] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Previous studies demonstrate that nitric oxide (NO) promotes p53 transcriptional activity by a classical DNA damage responsive mechanism involving activation of ATM/ATR and phosphorylation of p53. These studies intentionally used high doses of NO donors to achieve the maximum DNA damage. However, lower concentrations of NO donors also stimulate rapid and unequivocal nuclear retention of p53 but apparently do not require ATM/ATR-dependent p53 phosphorylation or total p53 protein accumulation. To identify possible mechanisms for p53 activation at low NO levels, the role of Tyr nitration in p53 activation was evaluated. Low concentrations of the NO donor, DETA NONOate (<200 microM), exclusively nitrate Tyr327 within the tetramerization domain promoting p53 oligomerization, nuclear accumulation, and increased DNA-binding activity without p53 Ser15 phosphorylation. Molecular modeling indicates that nitration of one Tyr327 stabilizes the dimer by about 2.67 kcal mol(-1). Significant quantitative and qualitative differences in the patterns of p53-target gene modulation by low (50 microM), non-DNA-damaging and high (500 microM), DNA-damaging NO donor concentrations were shown. These results demonstrate a new posttranslational mechanism for modulating p53 transcriptional activity responsive to low NO concentrations and independent of DNA damage signaling.
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Affiliation(s)
- Vasily A Yakovlev
- Department of Radiation Oncology, Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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21
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Nguyen KV. Human p53 and Hdm2: Cloning and Construction of Expression Plasmid. ANAL LETT 2010. [DOI: 10.1080/00032710903327530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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22
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Mdmx enhances p53 ubiquitination by altering the substrate preference of the Mdm2 ubiquitin ligase. FEBS Lett 2009; 583:2710-4. [DOI: 10.1016/j.febslet.2009.07.021] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 06/26/2009] [Accepted: 07/13/2009] [Indexed: 11/22/2022]
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23
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Ohtsubo C, Shiokawa D, Kodama M, Gaiddon C, Nakagama H, Jochemsen AG, Taya Y, Okamoto K. Cytoplasmic tethering is involved in synergistic inhibition of p53 by Mdmx and Mdm2. Cancer Sci 2009; 100:1291-9. [PMID: 19432880 PMCID: PMC11159218 DOI: 10.1111/j.1349-7006.2009.01180.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 03/24/2009] [Accepted: 03/25/2009] [Indexed: 01/28/2023] Open
Abstract
The mdm2 and mdmx oncogenes play essential yet nonredundant roles in synergistic inactivatiosn of p53. However, the biochemical mechanism by which Mdmx synergizes with Mdm2 to inhibit p53 function remains obscure. Here we demonstrate that, using nonphosphorylatable mutants of Mdmx, the cooperative inhibition of p53 by Mdmx and Mdm2 was associated with cytoplasmic localization of p53, and with an increase of the interaction of Mdmx to p53 and Mdm2 in the cytoplasm. In addition, the Mdmx mutant cooperates with Mdm2 to induce ubiquitination of p53 at C-terminal lysine residues, and the integrity of the C-terminal lysines was partly required for the cooperative inhibition. The expression of subcellular localization mutants of Mdmx revealed that subcellular localization of Mdmx dictated p53 localization, and that cytoplasmic Mdmx tethered p53 in the cytoplasm and efficiently inhibited p53 activity. RNAi-mediated inhibition of Mdmx or introduction of the nuclear localization mutant of Mdmx reduced cytoplasmic retention of p53 in neuroblastoma cells, in which cytoplasmic sequestration of p53 is involved in its inactivation. Our data indicate that cytoplasmic tethering of p53 mediated by Mdmx contributes to p53 inactivation in some types of cancer cells.
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Affiliation(s)
- Chihiro Ohtsubo
- Radiobiology Division, National Cancer Center Research Institute, Tokyo, Japan
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24
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Wang F, Marshall CB, Yamamoto K, Li GY, Plevin MJ, You H, Mak TW, Ikura M. Biochemical and Structural Characterization of an Intramolecular Interaction in FOXO3a and Its Binding with p53. J Mol Biol 2008; 384:590-603. [DOI: 10.1016/j.jmb.2008.09.025] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Revised: 08/23/2008] [Accepted: 09/02/2008] [Indexed: 11/26/2022]
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25
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Kruse JP, Gu W. MSL2 promotes Mdm2-independent cytoplasmic localization of p53. J Biol Chem 2008; 284:3250-3263. [PMID: 19033443 DOI: 10.1074/jbc.m805658200] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Although it was originally thought of as a passive way to block the nuclear function of p53, accumulating evidence suggests that cytoplasmic localization of p53 plays an active role in p53-mediated functions such as apoptosis and autophagy. Previous studies by us and others demonstrated that Mdm2-mediated p53 ubiquitination induces both degradation and cytoplasmic localization. Here we describe MSL2, a novel E3 ligase for p53 that promotes ubiquitin-dependent cytoplasmic p53 localization. Unlike Mdm2 or most other p53 E3 ligases, MSL2-mediated p53 ubiquitination does not affect the stability of p53. Moreover, the MSL2-mediated effect on p53 is Mdm2-independent. Thus, our study identifies an important ubiquitin-ligase for modulating p53 subcellular localization.
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Affiliation(s)
- Jan-Philipp Kruse
- Institute for Cancer Genetics and Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York 10032
| | - Wei Gu
- Institute for Cancer Genetics and Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
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26
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Liu B, Chen Y, St Clair DK. ROS and p53: a versatile partnership. Free Radic Biol Med 2008; 44:1529-35. [PMID: 18275858 PMCID: PMC2359898 DOI: 10.1016/j.freeradbiomed.2008.01.011] [Citation(s) in RCA: 624] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 11/12/2007] [Accepted: 01/14/2008] [Indexed: 01/18/2023]
Abstract
The tumor suppressor protein p53 is a redox-active transcription factor that organizes and directs cellular responses in the face of a variety of stresses that lead to genomic instability. One of the most important questions in the study of p53 is how selective transactivation of certain p53 target genes is achieved. Reactive oxygen species (ROS), generated by cells as products or by-products, can function either as signaling molecules or as cellular toxicants. Cellular generation of ROS is central to redox signaling. Recent studies have revealed that each cellular concentration and distribution of p53 has a distinct cellular function and that ROS act as both an upstream signal that triggers p53 activation and a downstream factor that mediates apoptosis. Here, we examine the newly discovered role of p53 in regulating cellular ROS generation and how ROS modulate selective transactivation of p53 target genes. The focus is on interlinks between ROS and p53.
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Affiliation(s)
- Bin Liu
- Graduate Center for Toxicology, University of Kentucky, Lexington, KY 40506, USA
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27
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Foo RSY, Nam YJ, Ostreicher MJ, Metzl MD, Whelan RS, Peng CF, Ashton AW, Fu W, Mani K, Chin SF, Provenzano E, Ellis I, Figg N, Pinder S, Bennett MR, Caldas C, Kitsis RN. Regulation of p53 tetramerization and nuclear export by ARC. Proc Natl Acad Sci U S A 2007; 104:20826-31. [PMID: 18087040 PMCID: PMC2409226 DOI: 10.1073/pnas.0710017104] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Indexed: 11/18/2022] Open
Abstract
Inactivation of the transcription factor p53 is central to carcinogenesis. Yet only approximately one-half of cancers have p53 loss-of-function mutations. Here, we demonstrate a mechanism for p53 inactivation by apoptosis repressor with caspase recruitment domain (ARC), a protein induced in multiple cancer cells. The direct binding in the nucleus of ARC to the p53 tetramerization domain inhibits p53 tetramerization. This exposes a nuclear export signal in p53, triggering Crm1-dependent relocation of p53 to the cytoplasm. Knockdown of endogenous ARC in breast cancer cells results in spontaneous tetramerization of endogenous p53, accumulation of p53 in the nucleus, and activation of endogenous p53 target genes. In primary human breast cancers with nuclear ARC, p53 is almost always WT. Conversely, nearly all breast cancers with mutant p53 lack nuclear ARC. We conclude that nuclear ARC is induced in cancer cells and negatively regulates p53.
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Affiliation(s)
- Roger S.-Y. Foo
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
- Departments of Medicine
| | - Young-Jae Nam
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Marc Jason Ostreicher
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Mark D. Metzl
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Russell S. Whelan
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Chang-Fu Peng
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Anthony W. Ashton
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Weimin Fu
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Kartik Mani
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
| | | | - Elena Provenzano
- Pathology, University of Cambridge, Cambridge CB2 2QQ, United Kingdom; and
| | - Ian Ellis
- Department of Histopathology, Nottingham City Hospital, Nottingham NG5 1PB, United Kingdom
| | | | - Sarah Pinder
- Pathology, University of Cambridge, Cambridge CB2 2QQ, United Kingdom; and
| | | | | | - Richard N. Kitsis
- *Departments of Medicine and Cell Biology, Cardiovascular Research Center, and Cancer Center, Albert Einstein College of Medicine, Bronx, NY 10461
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28
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Abstract
While wild-type p53 is normally a rapidly degraded protein, mutant forms of p53 are stabilized and accumulate to high levels in tumor cells. In this study, we show that mutant and wild-type p53 proteins are ubiquitinated and degraded through overlapping but distinct pathways. While Mdm2 can drive the degradation of both mutant and wild-type p53, our data suggest that the ability of Mdm2 to function as a ubiquitin ligase is less important in the degradation of mutant p53, which is heavily ubiquitinated in an Mdm2-independent manner. Our initial attempts to identify ubiquitin ligases that are responsible for the ubiquitination of mutant p53 have suggested a role for the chaperone-associated ubiquitin ligase CHIP (C terminus of Hsc70-interacting protein), although other unidentified ubiquitin ligases also appear to contribute. The contribution of Mdm2 to the degradation of mutant p53 may reflect the ability of Mdm2 to deliver the ubiquitinated mutant p53 to the proteasome.
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Affiliation(s)
- Natalia Lukashchuk
- The Beatson Institute for Cancer Research, Switchback Rd., Glasgow G61 1BD, United Kingdom
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29
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Wahl GM. Mouse bites dogma: how mouse models are changing our views of how P53 is regulated in vivo. Cell Death Differ 2007; 13:973-83. [PMID: 16575406 DOI: 10.1038/sj.cdd.4401911] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
P53 is a transcription factor that can cause cells to be eliminated by apoptosis or senescent-like arrest upon its activation by irreparable genetic damage, excessively expressed oncogenes, or a broad spectrum of other stresses. As P53 executes life and death decisions, its activity must be stringently regulated, which implies that it is not likely to be controlled by a simple regulatory mechanism involving a binary on-off switch. This brief review will summarize a subset of the new information presented at the 10th P53 workshop in Dunedin, New Zealand in November 2004 as well as very recent publications that provide new insights into the molecular regulators of P53. Data emerging from mouse models provide a fundamentally different view of how P53 is regulated than suggested by more traditional in vitro approaches. The differences between cell culture and mouse models demonstrate the importance of preserving stoichiometric relationships between P53 and its various regulators to obtain an accurate view of the relevant molecular mechanisms that control P53 activity.
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Affiliation(s)
- G M Wahl
- Salk Institute for Biological Studies, Gene Expression Laboratory, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA.
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30
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Abstract
Over the years, p53 has been shown to sit at the centre of an increasingly complex web of incoming stress signals and outgoing effector pathways. The number and diversity of stress signals that lead to p53 activation illustrates the breadth of p53's remit - responding to a wide variety of potentially oncogenic insults to prevent tumour development. Interestingly, different stress signals can use different and independent pathways to activate p53, and there is some evidence that different stress signals can mediate different responses. How each of the responses to p53 contributes to inhibition of malignant progression is beginning to be clarified, with the hope that identification of responses that are key to tumour suppression will allow a more focused and effective search for new therapeutic targets. In this review, we will highlight some recently identified roles for p53 in tumour suppression, and discuss some of the numerous mechanisms through which p53 can be regulated and activated.
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Affiliation(s)
- H F Horn
- The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Glasgow, UK
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31
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Becker K, Marchenko ND, Maurice M, Moll UM. Hyperubiquitylation of wild-type p53 contributes to cytoplasmic sequestration in neuroblastoma. Cell Death Differ 2007; 14:1350-60. [PMID: 17380154 DOI: 10.1038/sj.cdd.4402126] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Neuroblastoma (NB) is the most common solid malignancy in childhood and its prognosis is still generally poor. In contrast to many other cancers, mutations of the p53 tumor suppressor are rare. Instead, significant cytosolic sequestration of wtp53 is one of several mechanisms that attenuate p53 function in this cancer. Here, we report that aberrant p53 hyperubiquitylation contributes to p53 cytoplasmic sequestration in NB. NB lines constitutively harbor an elevated portion of wtp53 as stable ubiquitylated species confined to the cytoplasm. p53 hyperubiquitylation is not due to dysregulation by Hdm2 or proteasomal dysfunction. Instead, the defect lies in p53 regulation by HAUSP, a major p53-deubiquitylating enzyme. In contrast to non-NB cancer cells with nuclear p53 and normal ubiquitylation, p53 from NB cells shows impaired HAUSP interaction. Conversely, interference with p53 hyperubiquitylation in NB cells by Nutlin 3a or by a C-terminal p53 peptide (aa 305-393) results in p53 relocalization from the cytoplasm to the nucleus, and in case of Nutlin, in reactivation of p53's transcriptional and apoptotic functions. Moreover, nutlin and camptothecin act synergistically in inducing NB cell apoptosis. Hence, this study strengthens the rationale for targeting p53 deubiquitylation by drugs like Nutlin as a promising new strategy in NB therapy.
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Affiliation(s)
- K Becker
- Department of Pathology, State University of New York at Stony Brook, Stony Brook, NY, USA
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32
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Nie L, Sasaki M, Maki CG. Regulation of p53 nuclear export through sequential changes in conformation and ubiquitination. J Biol Chem 2007; 282:14616-25. [PMID: 17371868 DOI: 10.1074/jbc.m610515200] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Wild-type p53 is a conformationally labile protein that undergoes nuclear-cytoplasmic shuttling. MDM2-mediated ubiquitination promotes p53 nuclear export by exposing or activating a nuclear export signal (NES) in the C terminus of p53. We observed that cancer-derived p53s with a mutant (primary antibody 1620-/pAb240+) conformation localized in the cytoplasm to a greater extent and displayed increased susceptibility to ubiquitination than p53s with a more wild-type (primary antibody 1620+/pAb240-) conformation. The cytoplasmic localization of mutant p53s required the C-terminal NES and an intact ubiquitination pathway. Mutant p53 ubiquitination occurred at lysines in both the DNA-binding domain (DBD) and C terminus. Interestingly, Lys to Arg mutations that inhibited ubiquitination restored nuclear localization to mutant p53 but had no apparent effect on p53 conformation. Further studies revealed that wild-type p53, like mutant p53, is ubiquitinated by MDM2 in both the DBD and C terminus and that ubiquitination in both regions contributes to its nuclear export. MDM2 binding can induce a conformational change in wild-type p53, but this conformational change is insufficient to promote p53 nuclear export in the absence of MDM2 ubiquitination activity. Taken together, these results support a stepwise model for mutant and wild-type p53 nuclear export. In this model, the conformational change induced by either the cancer-derived mutation or MDM2 binding precedes p53 ubiquitination. The addition of ubiquitin to DBD and C-terminal lysines then promotes nuclear export via the C-terminal NES.
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Affiliation(s)
- Linghu Nie
- Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60637, USA
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33
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Carter S, Bischof O, Dejean A, Vousden KH. C-terminal modifications regulate MDM2 dissociation and nuclear export of p53. Nat Cell Biol 2007; 9:428-35. [PMID: 17369817 DOI: 10.1038/ncb1562] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Accepted: 02/15/2007] [Indexed: 01/15/2023]
Abstract
p53 functions to prevent malignant progression, in part by inhibiting proliferation or inducing the death of potential tumour cells. One of the most important regulators of p53 is MDM2, a RING domain E3 ligase that ubiquitinates p53, leading to both proteasomal degradation and relocation of p53 from the nucleus to the cytoplasm. Previous studies have suggested that although polyubiquitination is required for degradation, monoubiquitination of p53 is sufficient for nuclear export. Using a p53-ubiquitin fusion protein we show that ubiquitination contributes to two steps before export: exposure of a carboxy-terminal nuclear export sequence (NES), and dissociation of MDM2. Monoubiquitination can directly promote further modifications of p53 with ubiquitin-like proteins and MDM2 promotes the interaction of the SUMO E3 ligase PIASy with p53, enhancing both sumoylation and nuclear export. Our results suggest that modifications such as sumoylation can regulate the strength of the p53-MDM2 interaction and participate in driving the export of p53.
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Affiliation(s)
- Stephanie Carter
- The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
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34
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Garat CV, Fankell D, Erickson PF, Reusch JEB, Bauer NN, McMurtry IF, Klemm DJ. Platelet-derived growth factor BB induces nuclear export and proteasomal degradation of CREB via phosphatidylinositol 3-kinase/Akt signaling in pulmonary artery smooth muscle cells. Mol Cell Biol 2006; 26:4934-48. [PMID: 16782881 PMCID: PMC1489168 DOI: 10.1128/mcb.02477-05] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Revised: 02/01/2006] [Accepted: 04/14/2006] [Indexed: 01/05/2023] Open
Abstract
Cyclic AMP response element binding protein (CREB) content is diminished in smooth muscle cells (SMCs) in remodeled pulmonary arteries from animals with pulmonary hypertension and in the SMC layers of atherogenic systemic arteries and cardiomyocytes from hypertensive individuals. Loss of CREB can be induced in cultured SMCs by chronic exposure to hypoxia or platelet-derived growth factor BB (PDGF-BB). Here we investigated the signaling pathways and mechanisms by which PDGF elicits depletion of SMC CREB. Chronic PDGF treatment increased CREB ubiquitination in SMCs, while treatment of SMCs with the proteasome inhibitor lactacystin prevented decreases in CREB content. The nuclear export inhibitor leptomycin B also prevented depletion of SMC CREB alone or in combination with lactacystin. Subsequent studies showed that PDGF activated extracellular signal-regulated kinase, Jun N-terminal protein kinase, and phosphatidylinositol 3 (PI3)-kinase pathways in SMCs. Inhibition of these pathways blocked SMC proliferation in response to PDGF, but only inhibition of PI3-kinase or its effector, Akt, blocked PDGF-induced CREB loss. Finally, chimeric proteins containing enhanced cyan fluorescent protein linked to wild-type CREB or CREB molecules with mutations in several recognized phosphorylation sites were introduced into SMCs. PDGF treatment reduced the levels of each of these chimeric proteins except for one containing mutations in adjacent serine residues (serines 103 and 107), suggesting that CREB loss was dependent on CREB phosphorylation at these sites. We conclude that PDGF stimulates nuclear export and proteasomal degradation of CREB in SMCs via PI3-kinase/Akt signaling. These results indicate that in addition to direct phosphorylation, proteolysis and intracellular localization are key mechanisms regulating CREB content and activity in SMCs.
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Affiliation(s)
- Chrystelle V Garat
- Cardiovascular Pulmonary Research, University of Colorado Health Sciences Center, 4200 East Ninth Ave., Campus Box B-133, Denver, CO 80262, USA
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35
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Utama B, Shen YH, Mitchell BM, Makagiansar IT, Gan Y, Muthuswamy R, Duraisamy S, Martin D, Wang X, Zhang MX, Wang J, Wang J, Vercellotti GM, Gu W, Wang XL. Mechanisms for human cytomegalovirus-induced cytoplasmic p53 sequestration in endothelial cells. J Cell Sci 2006; 119:2457-67. [PMID: 16720642 DOI: 10.1242/jcs.02974] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human cytomegalovirus (HCMV) infection results in endothelial dysfunction, typically known as dysregulated apoptosis, and aberrant expression and sub-cellular localization of p53, a tumor suppressor that accumulates at the late stage of infection. In this study, we examined three hypotheses that could be responsible for HCMV-induced cytoplasmic p53 accumulation at the later stage of infection: hyperactive nuclear export, cytoplasmic p53 tethering and delayed p53 degradation. Leptomycin B treatment, a nuclear export inhibitor, was unable to reduce cytoplasmic p53, thereby eliminating the hyperactive nuclear export mechanism. The findings that nascent p53 still entered nuclei after the nuclear export inhibition indicated that cytoplasmic tethering may play a minor role. Cytoplasmic p53 was still observed after the translation activities were blocked by cycloheximide. There was more than an eight-fold increase in the cytoplasmic p53 half-life with abnormal p53 ubiquitination. Taken together, these results suggest that delayed degradation could be responsible for the cytoplasmic p53 accumulation. The general slow-down of the proteasomal activity and the dysregulated p53 ubiquitination process at the later stage of infection could contribute to the reduced cytoplasmic p53 degradation and might be relevant to dysregulated endothelial apoptosis. The HCMV-induced changes in p53 dynamics could contribute to endothelial dysfunction.
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Affiliation(s)
- Budi Utama
- Division of Cardiothoracic Surgery, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX 77030, USA
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36
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Shin YC, Nakamura H, Liang X, Feng P, Chang H, Kowalik TF, Jung JU. Inhibition of the ATM/p53 signal transduction pathway by Kaposi's sarcoma-associated herpesvirus interferon regulatory factor 1. J Virol 2006; 80:2257-66. [PMID: 16474133 PMCID: PMC1395370 DOI: 10.1128/jvi.80.5.2257-2266.2006] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Accepted: 12/05/2005] [Indexed: 12/21/2022] Open
Abstract
Infected cells recognize viral replication as a DNA damage stress and elicit the ataxia telangiectasia-mutated (ATM)/p53-mediated DNA damage response signal transduction pathway as part of the host surveillance mechanisms, which ultimately induces the irreversible cell cycle arrest and apoptosis. Viruses have evolved a variety of mechanisms to counteract this host intracellular innate immunity. Kaposi's sarcoma-associated herpesvirus (KSHV) viral interferon regulatory factor 1 (vIRF1) interacts with the cellular p53 tumor suppressor through its central DNA binding domain, and this interaction inhibits transcriptional activation of p53. Here, we further demonstrate that KSHV vIRF1 downregulates the total p53 protein level by facilitating its proteasome-mediated degradation. Detailed biochemical study showed that vIRF1 interacted with cellular ATM kinase through its carboxyl-terminal transactivation domain and that this interaction blocked the activation of ATM kinase activity induced by DNA damage stress. As a consequence, vIRF1 expression greatly reduced the level of serine 15 phosphorylation of p53, resulting in an increase of p53 ubiquitination and thereby a decrease of its protein stability. These results indicate that KSHV vIRF1 comprehensively compromises an ATM/p53-mediated DNA damage response checkpoint by targeting both upstream ATM kinase and downstream p53 tumor suppressor, which might circumvent host growth surveillance and facilitate viral replication in infected cells.
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Affiliation(s)
- Young C Shin
- Department of Microbiology and Molecular Genetics and Tumor Virology Division, New England Primate Research Center, Harvard Medical School, Southborough, MA 01772, USA
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37
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Chan WM, Mak MC, Fung TK, Lau A, Siu WY, Poon RYC. Ubiquitination of p53 at multiple sites in the DNA-binding domain. Mol Cancer Res 2006; 4:15-25. [PMID: 16446403 DOI: 10.1158/1541-7786.mcr-05-0097] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The tumor suppressor p53 is negatively regulated by the ubiquitin ligase MDM2. The MDM2 recognition site is at the NH2-terminal region of p53, but the positions of the actual ubiquitination acceptor sites are less well defined. Lysine residues at the COOH-terminal region of p53 are implicated as sites for ubiquitination and other post-translational modifications. Unexpectedly, we found that substitution of the COOH-terminal lysine residues did not diminish MDM2-mediated ubiquitination. Ubiquitination was not abolished even after the entire COOH-terminal regulatory region was removed. Using a method involving in vitro proteolytic cleavage at specific sites after ubiquitination, we found that p53 was ubiquitinated at the NH2-terminal portion of the protein. The lysine residue within the transactivation domain is probably not essential for ubiquitination, as substitution with an arginine did not affect MDM2 binding or ubiquitination. In contrast, several conserved lysine residues in the DNA-binding domain are critical for p53 ubiquitination. Removal of the DNA-binding domain reduced ubiquitination and increased the stability of p53. These data provide evidence that in addition to the COOH-terminal residues, p53 may also be ubiquitinated at sites in the DNA-binding domain.
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Affiliation(s)
- Wan Mui Chan
- Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
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38
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Derheimer FA, Chang CW, Ljungman M. Transcription inhibition: a potential strategy for cancer therapeutics. Eur J Cancer 2005; 41:2569-76. [PMID: 16213135 DOI: 10.1016/j.ejca.2005.08.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Interference with transcription triggers a stress response leading to the induction of the tumour suppressor p53. If transcription is not restored within a certain time frame cells may undergo apoptosis in a p53-dependent and independent manner. The mechanisms by which blockage of transcription induces apoptosis may involve diminished levels of anti-apoptotic factors, inappropriate accumulation of proteins in the nucleus, accumulation of p53 at mitochondria or complications during replication. Many chemotherapeutic agents currently used in the clinic interfere with transcription and this interference may contribute to their anti-cancer activities. Future efforts should be directed towards exploring whether interference of transcription could be used as an anti-cancer therapeutic strategy.
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Affiliation(s)
- Frederick A Derheimer
- Department of Radiation Oncology, Division of Radiation and Cancer Biology, University of Michigan Comprehensive Cancer Center, Ann Arbor, MI 48109, USA
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39
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Oberst A, Rossi M, Salomoni P, Pandolfi PP, Oren M, Melino G, Bernassola F. Regulation of the p73 protein stability and degradation. Biochem Biophys Res Commun 2005; 331:707-12. [PMID: 15865926 DOI: 10.1016/j.bbrc.2005.03.158] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Indexed: 10/25/2022]
Abstract
p73, a homologue to the tumor suppressor gene p53, is involved in tumorigenesis, though its specific role remains unclear. The gene has two distinct promoters which allow the formation of two protein isoforms with opposite effects: full-length transactivating (TA) p73 shows pro-apoptotic effects, while the shorter DeltaNp73, which lacks the N-terminal transactivating domain, has an evident anti-apoptotic function. Unlike p53, the p73 gene is rarely mutated in human cancers. However, alterations in the relative levels of TA and DeltaNp73 have been shown to correlate with prognosis in several human cancers, suggesting that the fine regulation of these two isoforms is of pivotal importance in controlling proliferation and cell death. Much effort is currently focused on the elucidation of the mechanisms that differentially control TA and DeltaNp73 activity and protein stability, a process complicated by the finding that both proteins are regulated by a similar suite of complex post-translational modifications that include ubiquitination, sequential phosphorylation, prolyl-isomerization, recruitment into the PML-nuclear body (PML-NB), and acetylation. Here we shall consider the main regulatory partners of p73, with particular attention to the recently discovered Itch- and Nedd8-mediated degradation pathways, along with the emerging roles of PML, p38 MAP kinase, Pin1, and p300 in p73 transcriptional activation, and possible mechanisms for the differential regulation of the TAp73 and DeltaNp73 isoforms.
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Affiliation(s)
- Andrew Oberst
- IDI-IRCCS Biochemistry Lab, c/o Department of Experimental Medicine, University of Rome Tor Vergata, Rome 00133, Italy
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40
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Yang Y, Ludwig RL, Jensen JP, Pierre SA, Medaglia MV, Davydov IV, Safiran YJ, Oberoi P, Kenten JH, Phillips AC, Weissman AM, Vousden KH. Small molecule inhibitors of HDM2 ubiquitin ligase activity stabilize and activate p53 in cells. Cancer Cell 2005; 7:547-59. [PMID: 15950904 DOI: 10.1016/j.ccr.2005.04.029] [Citation(s) in RCA: 246] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 03/02/2005] [Accepted: 04/21/2005] [Indexed: 12/13/2022]
Abstract
The p53 tumor suppressor protein is regulated by its interaction with HDM2, which serves as a ubiquitin ligase (E3) to target p53 for degradation. We have identified a family of small molecules (HLI98) that inhibits HDM2's E3 activity. These compounds show some specificity for HDM2 in vitro, although at higher concentrations effects on unrelated RING and HECT domain E3s are detectable, which could be due, at least in part, to effects on E2-ubiquitin thiol-ester levels. In cells, the compounds allow the stabilization of p53 and HDM2 and activation of p53-dependent transcription and apoptosis, although other p53-independent toxicity was also observed.
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Affiliation(s)
- Yili Yang
- Laboratory of Protein Dynamics and Signaling, Center for Cancer Research, National Cancer Institute at Frederick, NIH, 1050 Boyles Street, Frederick, MD 21702, USA
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41
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Weber HO, Ludwig RL, Morrison D, Kotlyarov A, Gaestel M, Vousden KH. HDM2 phosphorylation by MAPKAP kinase 2. Oncogene 2005; 24:1965-72. [PMID: 15688025 DOI: 10.1038/sj.onc.1208389] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
p53 stability is regulated by HDM2, a RING domain protein that acts as an E3 ligase to ubiquitinate p53 and target its degradation. Phosphorylation of HDM2 on serine 166 by AKT has been shown to enhance HDM2 activity and promote the degradation of p53. Here, we show that MAPKAP kinase 2 (MK2) can phosphorylate HDM2 on serine 157 and 166 in vitro. Treatment of cells with anisomycin, which activates MK2, also results in phosphorylation of HDM2 on serine 157 and 166 in vivo. Mutation of the MK2 phosphorylation sites in HDM2 to aspartic acid renders HDM2 slightly more active in the degradation of p53, and mouse cells deficient for MK2 show reduced Mdm2 phosphorylation and elevated levels of p53 protein. Together, our results suggest that MK2 may act to dampen the extent and duration of the p53 response.
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Affiliation(s)
- Hans Oliver Weber
- The Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Glasgow, G61 1BD, UK
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42
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Walther RF, Atlas E, Carrigan A, Rouleau Y, Edgecombe A, Visentin L, Lamprecht C, Addicks GC, Haché RJG, Lefebvre YA. A Serine/Threonine-rich Motif Is One of Three Nuclear Localization Signals That Determine Unidirectional Transport of the Mineralocorticoid Receptor to the Nucleus. J Biol Chem 2005; 280:17549-61. [PMID: 15737989 DOI: 10.1074/jbc.m501548200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mineralocorticoid receptor (MR) is a tightly regulated nuclear hormone receptor that selectively transmits corticosteroid signals. Steroid treatment transforms MR from a transcriptionally inert state, in which it is distributed equally between the nucleus and cytoplasm, to an active completely nuclear transcription factor. We report here that MR is an atypical nuclear hormone receptor that moves unidirectionally from the cytoplasm to the nucleus. We show that nuclear import of MR is controlled through three nuclear localization signals (NLSs) of distinct types. Nuclear localization of naive MR was mediated primarily through a novel serine/threonine-rich NLS (NL0) in the receptor N terminus. Specific amino acid substitutions that mimicked phosphorylation selectively enhanced or repressed NL0 activity, highlighting the potential for active regulation of this new type of NLS. The second NLS (NL2) within the ligand-binding domain also lacks a recognizable basic motif. Nuclear transfer through this signal was strictly dependent on steroid agonist, but was independent of the interaction of MR with coactivator proteins. The third MR NLS (NL1) is a bipartite basic motif localized to the C terminus of the MR DNA-binding domain with properties distinct from those of NL1 of the closely related glucocorticoid receptor. NL1 acted in concert with NL0 and NL2 to stimulate nuclear uptake of the agonist-treated receptor, but also directed the complete nuclear localization of MR in response to treatment with steroid antagonist. These results present MR as a nuclear hormone receptor whose unidirectional transfer to the nucleus may be regulated through multiple pathways.
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Affiliation(s)
- Rhian F Walther
- Department of Medicine and Biochemistry, Graduate Program in Biochemistry, Ottawa Health Research Institute, Ottawa Hospital, University of Ottawa, Ontario, Canada
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43
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Abstract
Cells induce the expression of DNA-repair enzymes, activate cell-cycle checkpoints and, under some circumstances, undergo apoptosis in response to DNA-damaging agents. The mechanisms by which these cellular responses are triggered are not well understood, but there is recent evidence that the transcription machinery might be used in DNA-damage surveillance and in triggering DNA-damage responses to suppress mutagenesis. Transcription might also act as a DNA-damage dosimeter where the severity of blockage determines whether or not to induce cell death. Could transcription therefore be a potential therapeutic target for anticancer strategies?
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Affiliation(s)
- Mats Ljungman
- Department of Radiation Oncology, Division of Radiation and Cancer Biology, University of Michigan Comprehensive Cancer Center, University of Michigan Medical School, University of Michigan, Ann Arbor, Michigan 48109-0936, USA.
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44
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Poulin DL, Kung AL, DeCaprio JA. p53 targets simian virus 40 large T antigen for acetylation by CBP. J Virol 2004; 78:8245-53. [PMID: 15254196 PMCID: PMC446111 DOI: 10.1128/jvi.78.15.8245-8253.2004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Simian virus 40 (SV40) large T antigen (T Ag) interacts with the tumor suppressor p53 and the transcriptional coactivators CBP and p300. Binding of these cellular proteins in a ternary complex has been implicated in T Ag-mediated transformation. It has been suggested that the ability of CBP/p300 to modulate p53 function underlies p53's regulation of cell proliferation and tumorigenesis. In this study, we provide further evidence that CBP activity may be mediated through its synergistic action with p53. We demonstrate that SV40 T Ag is acetylated in vivo in a p53-dependent manner and T Ag acetylation is largely mediated by CBP. The acetylation of T Ag is dependent on its interaction with p53 and on p53's interaction with CBP. We have mapped the site of acetylation on T Ag to the C-terminal lysine residue 697. This acetylation site is conserved between the T antigens of the human polyomaviruses JC and BK, which are also known to interact with p53. We show that both JC and BK T antigens are also acetylated at corresponding sites in vivo. While other proteins are known to be acetylated by CBP/p300, none are known to depend on p53 for acetylation. T Ag acetylation may provide a regulatory mechanism for T Ag binding to a cellular factor or play a role in another aspect of T Ag function.
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Affiliation(s)
- Danielle L Poulin
- Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA 02115, USA
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Abstract
Ubiquitin (Ub)-protein conjugation represents a novel means of posttranscriptional modification in a proteolysis-dependent or -independent manner. E3 Ub ligases play a key role in governing the cascade of Ub transfer reactions by recognizing and catalyzing Ub conjugation to specific protein substrates. The E3s, which can be generally classified into HECT-type and RING-type families, are involved in the regulation of many aspects of the immune system, including the development, activation, and differentiation of lymphocytes, T cell-tolerance induction, antigen presentation, immune evasion, and virus budding. E3-promoted ubiquitination affects a wide array of biological processes, such as receptor downmodulation, signal transduction, protein processing or translocation, protein-protein interaction, and gene transcription, in addition to proteasome-mediated degradation. Deficiency or mutation of some of the E3s like Cbl, Cbl-b, or Itch, causes abnormal immune responses such as autoimmunity, malignancy, and inflammation. This review discusses our current understanding of E3 Ub ligases in both innate and adaptive immunity. Such knowledge may facilitate the development of novel therapeutic approaches for immunological diseases.
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Affiliation(s)
- Yun-Cai Liu
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
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Jefford CE, Feki A, Harb J, Krause KH, Irminger-Finger I. Nuclear-cytoplasmic translocation of BARD1 is linked to its apoptotic activity. Oncogene 2004; 23:3509-20. [PMID: 15077185 DOI: 10.1038/sj.onc.1207427] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The tumor suppressor protein BARD1 plays a dual role in response to genotoxic stress: DNA repair as a BARD1-BRCA1 heterodimer and induction of apoptosis in a BRCA1-independent manner. We have constructed a series of BARD1 deletion mutants and analysed their cellular distribution and capacity to induce apoptosis. As opposed to previous studies suggesting an exclusively nuclear localization of BARD1, we found, both in tissues and cell cultures, nuclear and cytoplasmic localization of BARD1. Enhanced cytoplasmic localization of BARD1, as well as appearance of a 67 kDa C-terminal proteolytic cleavage product, coincided with apoptosis. BARD1 translocates to the nucleus independently of BRCA1. For recruitment to nuclear dots, however, the BRCA1-interacting RING finger domain is required but not sufficient. Protein levels of N-terminal RING finger deletion mutants were much higher than those of full-length BARD1, despite comparable mRNA levels, suggesting that the N-terminal region comprising the RING finger is important for BARD1 degradation. Sequences required for apoptosis induction were mapped between the ankyrin repeats and the BRCT domains coinciding with two known cancer-associated missense mutations. We suggest that nuclear and cytoplasmic localization of BARD1 reflect its dual function and that the increased cytoplasmic localization of BARD1 is associated with apoptosis.
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Affiliation(s)
- Charles Edward Jefford
- Biology of Aging Laboratory, Department of Geriatrics, University of Geneva, 1225 Geneva, Switzerland
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47
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Jensik PJ, Huggenvik JI, Collard MW. Identification of a nuclear export signal and protein interaction domains in deformed epidermal autoregulatory factor-1 (DEAF-1). J Biol Chem 2004; 279:32692-9. [PMID: 15161925 DOI: 10.1074/jbc.m400946200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Deformed epidermal autoregulatory factor-1 (DEAF-1) is a DNA-binding protein required for embryonic development and linked to clinical depression and suicidal behavior in humans. Although primarily nuclear, cytoplasmic localization of DEAF-1 has been observed, and this suggests the presence of a nuclear export signal (NES). Using a series of fluorescent fusion proteins, an NES with a novel spacing of leucines (LXLX(6)LLX(5)LX(2)L) was identified near the COOH-terminal MYND domain at amino acids 454-476. The NES was leptomycin B-sensitive and mutation of the leucine residues decreased or eliminated nuclear export activity. In vitro pull downs and an in vivo fluorescent protein interaction assay identified a DEAF-1/DEAF-1 protein interaction domain within the NES region. DNA binding had been previously mapped to a positively charged surface patch in the novel DNA binding fold called the "SAND" domain. A second protein-protein interaction domain was identified at amino acids 243-306 that contains the DNA-binding SAND domain and also an adjacent zinc binding motif and a monopartite nuclear localization signal (NLS). Deletion of these adjacent sequences or mutation of the conserved cysteines or histidine in the zinc binding motif not only inhibits protein interaction but also eliminates DNA binding, demonstrating that DEAF-1 protein-protein interaction is required for DNA recognition. The identification of an NES and NLS provides a basis for the control of DEAF-1 subcellular localization and function, whereas the requirement of protein-protein interaction by the SAND domain appears to be unique among this class of transcription factors.
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Affiliation(s)
- Philip J Jensik
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, USA
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48
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Xia L, Paik A, Li JJ. p53 activation in chronic radiation-treated breast cancer cells: regulation of MDM2/p14ARF. Cancer Res 2004; 64:221-8. [PMID: 14729628 DOI: 10.1158/0008-5472.can-03-0969] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Mammalian cells chronically exposed to ionizing radiation (IR) induce stress response with a tolerance to the subsequent cytotoxicity of IR. Although p53 is well documented in IR response, the signaling network causing p53 activation in chronic IR remains to be identified. Using breast carcinoma MCF+FIR cells that showed a transient radioresistance after exposure chronically to fractionated IR (FIR), the present study shows that the basal DNA binding and transcriptional activity of p53 was elevated by FIR. p53-controlled luciferase activity was strikingly induced ( approximately 7.9-fold) with little enhancement of p53/DNA binding activity ( approximately 1.3-fold). The phosphorylated p53 (Thr 55) was increased in the cytoplasm and nucleus of MCF+FIR but not in the sham-FIR control cells. On the contrary, the sham-FIR control MCF-7 cells showed a low p53 luciferase transcription ( approximately 3-fold) but a striking enhancement of p53/DNA binding (12-fold) after 5 Gy of IR. To determine the signaling elements regulating p53 activity, DNA microarray of MCF+FIR using sham-FIR MCF-7 cells as a reference demonstrated that the mRNA of p21, MDM2, and p14ARF was up-regulated. Time course Western blot analysis, however, showed no difference in p21 induction. In contrast, MDM2 that was absent in control cells and was predominantly induced by IR was not induced in MCF+FIR cells. In agreement with MDM2 inhibition, MDM2-inhibitory protein p14ARF was increased in MCF+FIR cells. In summary, these results demonstrate that up-regulation of p14ARF paralleled with MDM2 inhibition contributes to p53 accumulation in the nucleus and causes a high responsiveness of p53 in chronic IR-treated breast cancer cells.
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Affiliation(s)
- Liqun Xia
- Radiation Biology, Division of Radiation Oncology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California 91010, USA
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49
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Affiliation(s)
- Lan Xu
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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50
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Luo J, Li M, Tang Y, Laszkowska M, Roeder RG, Gu W. Acetylation of p53 augments its site-specific DNA binding both in vitro and in vivo. Proc Natl Acad Sci U S A 2004; 101:2259-64. [PMID: 14982997 PMCID: PMC356938 DOI: 10.1073/pnas.0308762101] [Citation(s) in RCA: 325] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
p53 promotes tumor suppression through its ability to function as a transcriptional factor and is activated by posttranslational modifications that include acetylation. Our earlier study demonstrated that p53 acetylation can enhance its sequence-specific DNA binding in vitro, and this notion was later confirmed in several other studies. However, a recent study has reported that in vitro acetylation of p53 fails to stimulate its DNA binding to large DNA fragments, raising an important issue that requires further investigation. Here, we show that unacetylated p53 is able to bind weakly to its consensus site within the context of large DNA fragments, although it completely fails to bind the same site within short oligonucleotide probes. Strikingly, by using highly purified and fully acetylated p53 proteins obtained from cells, we show that acetylation of the C-terminal domain can dramatically enhance site-specific DNA binding on both short oligonucleotide probes and long DNA fragments. Moreover, endogenous p53 apparently can be fully acetylated in response to DNA damage when both histone deacetylase complex 1 (HDAC1)- and Sir2-mediated deacetylation are inhibited, indicating dynamic p53 acetylation and deacetylation events during the DNA damage response. Finally, we also show that acetylation of endogenous p53 indeed significantly augments its ability to bind an endogenous target gene and that p53 acetylation levels correlate well with p53-mediated transcriptional activation in vivo. Thus, our results clarify some of the confusion surrounding acetylation-mediated effects on p53 binding to DNA and suggest that acetylation of p53 in vivo may contribute, at least in part, to its transcriptional activation functions.
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Affiliation(s)
- Jianyuan Luo
- Institute for Cancer Genetics and Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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