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Lu WY, Bird TG, Boulter L, Tsuchiya A, Cole AM, Hay T, Guest RV, Wojtacha D, Man TY, Mackinnon A, Ridgway RA, Kendall T, Williams MJ, Jamieson T, Raven A, Hay DC, Iredale JP, Clarke AR, Sansom OJ, Forbes SJ. Hepatic progenitor cells of biliary origin with liver repopulation capacity. Nat Cell Biol 2015; 17:971-983. [PMID: 26192438 PMCID: PMC4612439 DOI: 10.1038/ncb3203] [Citation(s) in RCA: 332] [Impact Index Per Article: 36.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 06/09/2015] [Indexed: 12/13/2022]
Abstract
Hepatocytes and cholangiocytes self-renew following liver injury. Following severe injury hepatocytes are increasingly senescent, but whether hepatic progenitor cells (HPCs) then contribute to liver regeneration is unclear. Here, we describe a mouse model where the E3 ubiquitin ligase Mdm2 is inducibly deleted in more than 98% of hepatocytes, causing apoptosis, necrosis and senescence with nearly all hepatocytes expressing p21. This results in florid HPC activation, which is necessary for survival, followed by complete, functional liver reconstitution. HPCs isolated from genetically normal mice, using cell surface markers, were highly expandable and phenotypically stable in vitro. These HPCs were transplanted into adult mouse livers where hepatocyte Mdm2 was repeatedly deleted, creating a non-competitive repopulation assay. Transplanted HPCs contributed significantly to restoration of liver parenchyma, regenerating hepatocytes and biliary epithelia, highlighting their in vivo lineage potency. HPCs are therefore a potential future alternative to hepatocyte or liver transplantation for liver disease.
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Affiliation(s)
- Wei-Yu Lu
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Thomas G Bird
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Luke Boulter
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, Edinburgh, EH4 2XU
| | - Atsunori Tsuchiya
- Division of Gastroenterology and Hepatology, Graduate School of Medical and Dental Science, Niigata University, Niigata, Japan
| | - Alicia M Cole
- The CRUK Beatson Institute for Cancer Research, Switchback Road, Bearsden, Glasgow, G61 1BD
| | - Trevor Hay
- European Cancer Stem Cell Research Institute, Cardiff School of Biosciences, CF24 4HQ
| | - Rachel V Guest
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Davina Wojtacha
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Tak Yung Man
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Alison Mackinnon
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Rachel A Ridgway
- The CRUK Beatson Institute for Cancer Research, Switchback Road, Bearsden, Glasgow, G61 1BD
| | - Timothy Kendall
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, Edinburgh, EH4 2XU
| | - Michael J Williams
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - Thomas Jamieson
- The CRUK Beatson Institute for Cancer Research, Switchback Road, Bearsden, Glasgow, G61 1BD
| | - Alex Raven
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - David C Hay
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
| | - John P Iredale
- MRC Centre for Inflammation Research, Queen's Medical Research Institute, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Alan R Clarke
- European Cancer Stem Cell Research Institute, Cardiff School of Biosciences, CF24 4HQ
| | - Owen J Sansom
- The CRUK Beatson Institute for Cancer Research, Switchback Road, Bearsden, Glasgow, G61 1BD
| | - Stuart J Forbes
- MRC Centre for Regenerative Medicine, 5 Little France Drive, Edinburgh, EH16 4UU
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2
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Lai CY, Tsai AC, Chen MC, Chang LH, Sun HL, Chang YL, Chen CC, Teng CM, Pan SL. Aciculatin induces p53-dependent apoptosis via MDM2 depletion in human cancer cells in vitro and in vivo. PLoS One 2012; 7:e42192. [PMID: 22912688 PMCID: PMC3418269 DOI: 10.1371/journal.pone.0042192] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 07/04/2012] [Indexed: 12/27/2022] Open
Abstract
Aciculatin, a natural compound extracted from the medicinal herb Chrysopogon aciculatus, shows potent anti-cancer potency. This study is the first to prove that aciculatin induces cell death in human cancer cells and HCT116 mouse xenografts due to G1 arrest and subsequent apoptosis. The primary reason for cell cycle arrest and cell death was p53 accumulation followed by increased p21 level, dephosphorylation of Rb protein, PUMA expression, and induction of apoptotic signals such as cleavage of caspase-9, caspase-3, and PARP. We demonstrated that p53 allele-null (-/-) (p53-KO) HCT116 cells were more resistant to aciculatin than cells with wild-type p53 (+/+). The same result was achieved by knocking down p53 with siRNA in p53 wild-type cells, indicating that p53 plays a crucial role in aciculatin-induced apoptosis. Although DNA damage is the most common event leading to p53 activation, we found only weak evidence of DNA damage after aciculatin treatment. Interestingly, the aciculatin-induced downregulation of MDM2, an important negative regulator of p53, contributed to p53 accumulation. The anti-cancer activity and importance of p53 after aciculatin treatment were also confirmed in the HCT116 xenograft models. Collectively, these results indicate that aciculatin treatment induces cell cycle arrest and apoptosis via inhibition of MDM2 expression, thereby inducing p53 accumulation without significant DNA damage and genome toxicity.
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Affiliation(s)
- Chin-Yu Lai
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - An-Chi Tsai
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan Town, Taiwan
| | - Mei-Chuan Chen
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Li-Hsun Chang
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Hui-Lung Sun
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ya-Ling Chang
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chien-Chih Chen
- Department of Biotechnology, Hungkuang University, Taichung, Taiwan
| | - Che-Ming Teng
- Pharmacological Institute, College of Medicine, National Taiwan University, Taipei, Taiwan
- * E-mail: (CMT); (SLP)
| | - Shiow-Lin Pan
- Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes, Zhunan Town, Taiwan
- * E-mail: (CMT); (SLP)
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Liu G, Terzian T, Xiong S, Van Pelt CS, Audiffred A, Box NF, Lozano G. The p53-Mdm2 network in progenitor cell expansion during mouse postnatal development. J Pathol 2008; 213:360-8. [PMID: 17893884 DOI: 10.1002/path.2238] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Mdm2, an E3 ubiquitin ligase, negatively regulates the tumour suppressor p53. Loss of Mdm2 in mice results in p53-dependent apoptosis and embryonic lethality. This phenotype was rescued by the p53(515C) allele, which encodes an apoptosis-deficient p53R172P protein. However, these mice died within 2 weeks of birth, due to a severe impairment of progenitor cell expansion during postnatal haematopoiesis and cerebellar development, leading to p53-dependent cell cycle arrest. Loss of Mdm2 led to phosphorylation of the p53R172P protein, p53R172P stability and activation of the cell cycle inhibitor p21 in proliferating cells, but not in differentiated cells, in multiple tissue compartments. Proliferating cells of epithelial origin were not affected. The haematopoietic and neural defects were alleviated in mice lacking Mdm2 and containing one p53(515C) and one p53-null allele, but spermatogenesis was arrested. These findings establish a crucial role for the p53-Mdm2 network in regulating proliferation and progenitor expansion in many cell lineages and have important implications for the use of drugs that aim to disrupt the p53-Mdm2 interaction.
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Affiliation(s)
- G Liu
- Department of Cancer Genetics, University of Texas M D Anderson Cancer Center, Houston, TX 77030, USA.
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4
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Itahana K, Mao H, Jin A, Itahana Y, Clegg HV, Lindström MS, Bhat KP, Godfrey VL, Evan GI, Zhang Y. Targeted inactivation of Mdm2 RING finger E3 ubiquitin ligase activity in the mouse reveals mechanistic insights into p53 regulation. Cancer Cell 2007; 12:355-66. [PMID: 17936560 DOI: 10.1016/j.ccr.2007.09.007] [Citation(s) in RCA: 193] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Revised: 06/22/2007] [Accepted: 09/04/2007] [Indexed: 12/15/2022]
Abstract
It is believed that Mdm2 suppresses p53 in two ways: transcriptional inhibition by direct binding, and degradation via its E3 ligase activity. To study these functions physiologically, we generated mice bearing a single-residue substitution (C462A) abolishing the E3 function without affecting p53 binding. Unexpectedly, homozygous mutant mice died before E7.5, and deletion of p53 rescued the lethality. Furthermore, reintroducing a switchable p53 by crossing with p53ER(TAM) mice surprisingly demonstrated that the mutant Mdm2(C462A) was rapidly degraded in a manner indistinguishable from that of the wild-type Mdm2. Hence, our data indicate that (1) the Mdm2-p53 physical interaction, without Mdm2-mediated p53 ubiquitination, cannot control p53 activity sufficiently to allow early mouse embryonic development, and (2) Mdm2's E3 function is not required for Mdm2 degradation.
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Affiliation(s)
- Koji Itahana
- Department of Radiation Oncology, School of Medicine, the University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7512, USA
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Abstract
Current evidence shows that cardiomyocyte apoptosis plays a central role in the pathogenesis of myocardial disease and that reactive oxygen species is critically responsible for mediating cardiomyocyte apoptosis in both ischemia-reperfusion injury and dilated cardiomyopathy. ARC (Apoptosis Repressor with Caspase recruitment domain) is an anti-apoptotic protein that is found abundantly in terminally differentiated cells such as cardiomyocytes. The ARC knock-out mouse developed larger infarct in response to ischemia-reperfusion and transitioned more rapidly and severely to dilated cardiomyopathy following aortic constriction. In addition, ARC protein levels are decreased in human dilated cardiomyopathy and when cardiomyocytes are exposed to oxidative stress in vitro, but the mechanisms regulating ARC protein levels are not known. Here we show that degradation of ARC is dependent on the p53-induced ubiquitin E3 ligase, MDM2. Oxidative stress reduced ARC levels and up-regulated MDM2. MDM2 directly accelerated ARC protein turnover via ubiquitination and proteasomal-dependent degradation. This activity requires a functioning MDM2 ring finger domain because the MDM2(C464A) mutant was unable to direct ARC degradation. Furthermore, ARC degradation requires MDM2, because MDM2 knock-out fibroblasts showed defective ARC degradation that could be rescued by MDM2. Proteasomal inhibitors rescued both MDM2 and H(2)O(2)-induced degradation of ARC and inhibited cardiomyocyte apoptosis. Dilated cardiomyopathic hearts from mice that have undergone transverse aortic banding have increased MDM2 levels associated with decreased ARC levels. We conclude that MDM2 is a critical regulator of ARC levels in cardiomyocytes. Prevention of MDM2-induced degradation of ARC represents a potential therapeutic target to prevent cardiomyocyte apoptosis.
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Affiliation(s)
- Roger S-Y Foo
- Division of Cardiovascular Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QQ, United Kingdom.
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Ringshausen I, O'Shea CC, Finch AJ, Swigart LB, Evan GI. Mdm2 is critically and continuously required to suppress lethal p53 activity in vivo. Cancer Cell 2006; 10:501-14. [PMID: 17157790 DOI: 10.1016/j.ccr.2006.10.010] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Revised: 06/16/2006] [Accepted: 10/06/2006] [Indexed: 01/25/2023]
Abstract
There is currently much interest in the idea of restoring p53 activity in tumor cells by inhibiting Hdm2/Mdm2. However, it has remained unclear whether this would also activate p53 in normal cells. Using a switchable endogenous p53 mouse model, which allows rapid and reversible toggling of p53 status between wild-type and null states, we show that p53 is spontaneously active in all tested tissues of mdm2-deficient mice, triggering fatal pathologies that include ablation of classically radiosensitive tissues. In apoptosis-resistant tissues, spontaneous unbuffered p53 activity triggers profound inhibition of cell proliferation. Such acute spontaneous p53 activity occurs in the absence of any detectable p53 posttranslational modification, DNA damage, or p19ARF signaling and triggers rapid p53 degradation.
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Affiliation(s)
- Ingo Ringshausen
- Cancer Research Institute and Department of Cellular and Molecular Pharmacology, Comprehensive Cancer Center, University of California, San Francisco, San Francisco, California 94143, USA
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7
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Lee MH, Lee SW, Lee EJ, Choi SJ, Chung SS, Lee JI, Cho JM, Seol JH, Baek SH, Kim KI, Chiba T, Tanaka K, Bang OS, Chung CH. SUMO-specific protease SUSP4 positively regulates p53 by promoting Mdm2 self-ubiquitination. Nat Cell Biol 2006; 8:1424-31. [PMID: 17086174 DOI: 10.1038/ncb1512] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Accepted: 10/09/2006] [Indexed: 11/09/2022]
Abstract
The p53 tumour suppressor has a key role in the control of cell growth and differentiation, and in the maintenance of genome integrity. p53 is kept labile under normal conditions, but in response to stresses, such as DNA damage, it accumulates in the nucleus for induction of cell-cycle arrest, DNA repair or apoptosis. Mdm2 is an ubiquitin ligase that promotes p53 ubiquitination and degradation. Mdm2 is also self-ubiquitinated and degraded. Here, we identified a novel cascade for the increase in p53 level in response to DNA damage. A new SUMO-specific protease, SUSP4, removed SUMO-1 from Mdm2 and this desumoylation led to promotion of Mdm2 self-ubiquitination, resulting in p53 stabilization. Moreover, SUSP4 competed with p53 for binding to Mdm2, also resulting in p53 stabilization. Overexpression of SUSP4 inhibited cell growth, whereas knockdown of susp4 by RNA interference (RNAi) promoted of cell growth. UV damage induced SUSP4 expression, leading to an increase in p53 levels in parallel with a decrease in Mdm2 levels. These findings establish a new mechanism for the elevation of cellular p53 levels in response to UV damage.
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Affiliation(s)
- Moon Hee Lee
- NRL of Protein Biochemistry, School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
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8
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Salcedo A, Mayor F, Penela P. Mdm2 is involved in the ubiquitination and degradation of G-protein-coupled receptor kinase 2. EMBO J 2006; 25:4752-62. [PMID: 17006543 PMCID: PMC1618114 DOI: 10.1038/sj.emboj.7601351] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 08/23/2006] [Indexed: 11/09/2022] Open
Abstract
G-protein-coupled receptor kinase 2 (GRK2) is a central regulator of G-protein-coupled receptor signaling. We report that Mdm2, an E3-ubiquitin ligase involved in the control of cell growth and apoptosis, plays a key role in GRK2 degradation. Mdm2 and GRK2 association is enhanced by beta(2)-adrenergic receptor stimulation and beta-arrestin. Increased Mdm2 expression accelerates GRK2 proteolysis and promotes kinase ubiquitination at defined residues, whereas GRK2 turnover is markedly impaired in Mdm2-deficient cells. Moreover, we find that activation of the PI3K/Akt pathway by insulin-like growth factor-1 alters Mdm2-mediated GRK2 degradation, leading to enhanced GRK2 stability and increased kinase levels. These data put forward a novel mechanism for controlling GRK2 expression in physiological and pathological conditions.
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Affiliation(s)
- Alicia Salcedo
- Departamento de Biología Molecular and Centro de Biología Molecular ‘Severo Ochoa', Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Federico Mayor
- Departamento de Biología Molecular and Centro de Biología Molecular ‘Severo Ochoa', Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
- Departamento de Biología Molecular and Centro de Biología Molecular ‘Severo Ochoa', Consejo Superior de Investigaciones Científicas- Universidad Autónoma de Madrid, 28049 Madrid, Spain. Tel.: +34 91 497 4865; Fax: +34 91 497 4799; E-mail:
| | - Petronila Penela
- Departamento de Biología Molecular and Centro de Biología Molecular ‘Severo Ochoa', Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
- Departamento de Biología Molecular and Centro de Biología Molecular ‘Severo Ochoa', Consejo Superior de Investigaciones Científicas- Universidad Autónoma de Madrid, 28049 Madrid, Spain. Tel.: +34 91 497 4865; Fax: +34 91 497 4799; E-mail:
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9
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Toledo F, Krummel KA, Lee CJ, Liu CW, Rodewald LW, Tang M, Wahl GM. A mouse p53 mutant lacking the proline-rich domain rescues Mdm4 deficiency and provides insight into the Mdm2-Mdm4-p53 regulatory network. Cancer Cell 2006; 9:273-85. [PMID: 16616333 DOI: 10.1016/j.ccr.2006.03.014] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 02/27/2006] [Accepted: 03/13/2006] [Indexed: 01/21/2023]
Abstract
The mechanisms by which Mdm2 and Mdm4 (MdmX) regulate p53 remain controversial. We generated a mouse encoding p53 lacking the proline-rich domain (p53DeltaP). p53DeltaP exhibited increased sensitivity to Mdm2-dependent degradation and decreased transactivation capacity, correlating with deficient cell cycle arrest and reduced apoptotic responses. p53DeltaP induced lethality in Mdm2-/- embryos, but not in Mdm4-/- embryos. Mdm4 loss did not alter Mdm2 stability but significantly increased p53DeltaP transactivation to partially restore cycle control. In contrast, decreasing Mdm2 levels increased p53DeltaP levels without altering p53DeltaP transactivation. Thus, Mdm4 regulates p53 activity, while Mdm2 mainly controls p53 stability. Furthermore, Mdm4 loss dramatically improved p53DeltaP-mediated suppression of oncogene-induced tumors, emphasizing the importance of targeting Mdm4 in chemotherapies designed to activate p53.
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Affiliation(s)
- Franck Toledo
- The Salk Institute for Biological Studies, Gene Expression Laboratory, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
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Francoz S, Froment P, Bogaerts S, De Clercq S, Maetens M, Doumont G, Bellefroid E, Marine JC. Mdm4 and Mdm2 cooperate to inhibit p53 activity in proliferating and quiescent cells in vivo. Proc Natl Acad Sci U S A 2006; 103:3232-7. [PMID: 16492744 PMCID: PMC1413884 DOI: 10.1073/pnas.0508476103] [Citation(s) in RCA: 189] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The Mdm2 and Mdm4 oncoproteins are key negative regulators of the p53 tumor suppressor. However, their physiological contributions to the regulation of p53 stability and activity remain highly controversial. Here, we combined a p53 knock-in allele, in which p53 is silenced by a transcriptional stop element flanked by loxP sites, with the mdm2- and mdm4-null alleles. This approach allows Cre-mediated conditional p53 expression in tissues in vivo and cells in vitro lacking Mdm2, Mdm4, or both. Using this strategy, we show that Mdm2 and Mdm4 are essential in a nonredundant manner for preventing p53 activity in the same cell type, irrespective of the proliferation/differentiation status of the cells. Although Mdm2 prevents accumulation of the p53 protein, Mdm4 contributes to the overall inhibition of p53 activity independent of Mdm2. We propose a model in which Mdm2 is critical for the regulation of p53 levels and Mdm4 is critical for the fine-tuning of p53 transcriptional activity, both proteins acting synergistically to keep p53 in check.
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Affiliation(s)
- Sarah Francoz
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
- Laboratory of Molecular Embryology, Free University of Brussels, B-6041 Gosselies, Belgium
| | - Pascal Froment
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
| | - Sven Bogaerts
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
| | - Sarah De Clercq
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
| | - Marion Maetens
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
- Laboratory of Molecular Embryology, Free University of Brussels, B-6041 Gosselies, Belgium
| | - Gilles Doumont
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
| | - Eric Bellefroid
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
- Laboratory of Molecular Embryology, Free University of Brussels, B-6041 Gosselies, Belgium
| | - Jean-Christophe Marine
- Laboratory for Molecular Cancer Biology, Flanders Interuniversity Institute for Biotechnology, University of Ghent, B-9052 Ghent, Belgium; and
- To whom correspondence should be addressed at:
Laboratory for Molecular Cancer Biology, VIB, Technologiepark, 927, B-9052 Ghent, Belgium E-mail:
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11
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Xiong S, Van Pelt CS, Elizondo-Fraire AC, Liu G, Lozano G. Synergistic roles of Mdm2 and Mdm4 for p53 inhibition in central nervous system development. Proc Natl Acad Sci U S A 2006; 103:3226-31. [PMID: 16492743 PMCID: PMC1413885 DOI: 10.1073/pnas.0508500103] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Loss of Mdm2 or Mdm4 leads to embryo lethal phenotypes that are p53-dependent. To determine whether Mdm2 and Mdm4 inhibit p53 function redundantly in a more restricted cell type, conditional alleles were crossed to a neuronal specific Cre transgene to delete Mdm2 and Mdm4 in the CNS. Mice lacking Mdm2 in the CNS developed hydranencephaly at embryonic day 12.5 due to apoptosis, whereas Mdm4 deletion showed a proencephaly phenotype at embryonic day 17.5 because of cell cycle arrest and apoptosis. The deletion of both genes, strikingly, contributed to an even earlier and more severe CNS phenotype. Additionally, Mdm2 and Mdm4 had a gene dosage effect, because loss of three of the four Mdm alleles also showed a more accelerated CNS phenotype than deletion of either gene alone. All phenotypes were rescued by deletion of p53. Thus, these in vivo data demonstrate the importance of Mdm4 independent of Mdm2 in inhibition of p53.
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Affiliation(s)
| | - Carolyn S. Van Pelt
- Veterinary Medicine and Surgery, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030
| | | | - Geng Liu
- Departments of *Molecular Genetics and
| | - Guillermina Lozano
- Departments of *Molecular Genetics and
- To whom correspondence should be addressed. E-mail:
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12
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MacDuff DA, Neuberger MS, Harris RS. MDM2 can interact with the C-terminus of AID but it is inessential for antibody diversification in DT40 B cells. Mol Immunol 2005; 43:1099-108. [PMID: 16122802 DOI: 10.1016/j.molimm.2005.07.024] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Indexed: 01/10/2023]
Abstract
Activation-induced deaminase (AID) is essential for immunoglobulin gene diversification by the distinct processes of class switch recombination, somatic hypermutation and gene conversion. Most evidence indicates that AID triggers these reactions through the direct deamination of cytosine residues in the DNA. However, AID is predominantly cytoplasmic and the mechanism that directs it to the immunoglobulin loci remains elusive. Like its homolog APOBEC1, which requires at least one additional factor to efficiently edit APOB RNA, other proteins are likely to be required for the proper targeting of AID to the immunoglobulin loci. Here, we show that AID can interact with MDM2, an oncoprotein that shuttles between the nucleus and the cytoplasm and targets p53 for nuclear export and degradation. This interaction mapped to the carboxy-terminal region of AID that harbors a nuclear export sequence, suggesting that MDM2 may be involved in the nucleo-cytoplasmic trafficking of AID. We therefore assessed the role of MDM2 in immunoglobulin gene diversification by disrupting MDM2 in DT40, an avian B cell line that constitutively undergoes AID-dependent immunoglobulin gene diversification. The subcellular localization of AID was unaffected in MDM2-deficient DT40 cells. However, slight hyper-and hypo-conversion phenotypes were caused by MDM2-abrogation and overexpression, respectively. These observations suggested that MDM2 has the capacity to negatively regulate AID. Intriguingly, the same carboxy-terminal residues of AID were recently shown to be inessential for somatic hypermutation and immunoglobulin gene conversion but they were strictly required for class switch recombination.
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Affiliation(s)
- Donna A MacDuff
- University of Minnesota, Department of Biochemistry, Minneapolis, MN 55455, USA
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