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Elabd S, Pauletto E, Solozobova V, Eickhoff N, Padrao N, Zwart W, Blattner C. TRIM25 targets p300 for degradation. Life Sci Alliance 2023; 6:e202301980. [PMID: 37770115 PMCID: PMC10539465 DOI: 10.26508/lsa.202301980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 09/18/2023] [Accepted: 09/19/2023] [Indexed: 10/01/2023] Open
Abstract
p300 is an important transcriptional co-factor. By stimulating the transfer of acetyl residues onto histones and several key transcription factors, p300 enhances transcriptional initiation and impacts cellular processes including cell proliferation and cell division. Despite its importance for cellular homeostasis, its regulation is poorly understood. We show that TRIM25, a member of the TRIM protein family, targets p300 for proteasomal degradation. However, despite TRIM25's RING domain and E3 activity, degradation of p300 by TRIM25 is independent of TRIM25-mediated p300 ubiquitination. Instead, TRIM25 promotes the interaction of p300 with dynein, which ensures a microtubule-dependent transport of p300 to cellular proteasomes. Through mediating p300 degradation, TRIM25 affects p300-dependent gene expression.
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Affiliation(s)
- Seham Elabd
- Institute for Biological and Chemical Systems - Biological Information Processing, Karlsruhe, Germany
- https://ror.org/00mzz1w90 Human Physiology Department, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Eleonora Pauletto
- Institute for Biological and Chemical Systems - Biological Information Processing, Karlsruhe, Germany
| | - Valeria Solozobova
- Institute for Biological and Chemical Systems - Biological Information Processing, Karlsruhe, Germany
| | - Nils Eickhoff
- Division of Oncogenomics, Oncode Institute, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Nuno Padrao
- Division of Oncogenomics, Oncode Institute, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Wilbert Zwart
- Division of Oncogenomics, Oncode Institute, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Christine Blattner
- Institute for Biological and Chemical Systems - Biological Information Processing, Karlsruhe, Germany
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2
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Aranda S, Alcaine-Colet A, Ballaré C, Blanco E, Mocavini I, Sparavier A, Vizán P, Borràs E, Sabidó E, Di Croce L. Thymine DNA glycosylase regulates cell-cycle-driven p53 transcriptional control in pluripotent cells. Mol Cell 2023:S1097-2765(23)00517-8. [PMID: 37506700 DOI: 10.1016/j.molcel.2023.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/11/2023] [Accepted: 07/05/2023] [Indexed: 07/30/2023]
Abstract
Cell cycle progression is linked to transcriptome dynamics and variations in the response of pluripotent cells to differentiation cues, mostly through unknown determinants. Here, we characterized the cell-cycle-associated transcriptome and proteome of mouse embryonic stem cells (mESCs) in naive ground state. We found that the thymine DNA glycosylase (TDG) is a cell-cycle-regulated co-factor of the tumor suppressor p53. Furthermore, TDG and p53 co-bind ESC-specific cis-regulatory elements and thereby control transcription of p53-dependent genes during self-renewal. We determined that the dynamic expression of TDG is required to promote the cell-cycle-associated transcriptional heterogeneity. Moreover, we demonstrated that transient depletion of TDG influences cell fate decisions during the early differentiation of mESCs. Our findings reveal an unanticipated role of TDG in promoting molecular heterogeneity during the cell cycle and highlight the central role of protein dynamics for the temporal control of cell fate during development.
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Affiliation(s)
- Sergi Aranda
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain.
| | - Anna Alcaine-Colet
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
| | - Cecilia Ballaré
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
| | - Enrique Blanco
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
| | - Ivano Mocavini
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain
| | | | - Pedro Vizán
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain; Blanquerna School of Health Science, Universitat Ramon Llull, Barcelona 08025, Spain
| | - Eva Borràs
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Eduard Sabidó
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Luciano Di Croce
- Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain; ICREA, Pg. Lluis Companys 23, Barcelona 08010, Spain.
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3
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Isbel L, Iskar M, Durdu S, Weiss J, Grand RS, Hietter-Pfeiffer E, Kozicka Z, Michael AK, Burger L, Thomä NH, Schübeler D. Readout of histone methylation by Trim24 locally restricts chromatin opening by p53. Nat Struct Mol Biol 2023:10.1038/s41594-023-01021-8. [PMID: 37386214 DOI: 10.1038/s41594-023-01021-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 05/15/2023] [Indexed: 07/01/2023]
Abstract
The genomic binding sites of the transcription factor (TF) and tumor suppressor p53 are unusually diverse with regard to their chromatin features, including histone modifications, raising the possibility that the local chromatin environment can contextualize p53 regulation. Here, we show that epigenetic characteristics of closed chromatin, such as DNA methylation, do not influence the binding of p53 across the genome. Instead, the ability of p53 to open chromatin and activate its target genes is locally restricted by its cofactor Trim24. Trim24 binds to both p53 and unmethylated histone 3 lysine 4 (H3K4), thereby preferentially localizing to those p53 sites that reside in closed chromatin, whereas it is deterred from accessible chromatin by H3K4 methylation. The presence of Trim24 increases cell viability upon stress and enables p53 to affect gene expression as a function of the local chromatin state. These findings link H3K4 methylation to p53 function and illustrate how specificity in chromatin can be achieved, not by TF-intrinsic sensitivity to histone modifications, but by employing chromatin-sensitive cofactors that locally modulate TF function.
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Affiliation(s)
- Luke Isbel
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Murat Iskar
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Sevi Durdu
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Joscha Weiss
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Faculty of Sciences, University of Basel, Basel, Switzerland
| | - Ralph S Grand
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Zentrum für Molekulare Biologie der Universität Heidelberg, Heidelberg, Germany
| | - Eric Hietter-Pfeiffer
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Faculty of Sciences, University of Basel, Basel, Switzerland
| | - Zuzanna Kozicka
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Faculty of Sciences, University of Basel, Basel, Switzerland
| | - Alicia K Michael
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Biozentrum, University of Basel, Basel, Switzerland
| | - Lukas Burger
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Swiss Institute of Bioinformatics, Basel, Switzerland
| | - Nicolas H Thomä
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Dirk Schübeler
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
- Faculty of Sciences, University of Basel, Basel, Switzerland.
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4
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Tichy ED. Specialized Circuitry of Embryonic Stem Cells Promotes Genomic Integrity. Crit Rev Oncog 2023; 27:1-15. [PMID: 36734869 DOI: 10.1615/critrevoncog.2022042332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Embryonic stem cells (ESCs) give rise to all cell types of the organism. Given the importance of these cells in this process, ESCs must employ robust mechanisms to protect genomic integrity or risk catastrophic propagation of mutations throughout the organism. Should such an event occur in daughter cells that will eventually contribute to the germline, the overall species health could dramatically decline. This review describes several key mechanisms employed by ESCs that are unique to these cells, in order to maintain their genomic integrity. Additionally, the contributions of cell cycle regulators in modulating ESC differentiation, after DNA damage exposure, are also examined. Where data are available, findings reported in ESCs are extended to include observations described in induced pluripotent stem cells (IPSCs).
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Affiliation(s)
- Elisia D Tichy
- Department of Orthopaedic Surgery, Perelman School of Medicine, The University of Pennsylvania, 371 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104-6081
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5
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Kon N, Churchill M, Li H, Mukherjee S, Manfredi JJ, Gu W. Robust p53 Stabilization Is Dispensable for Its Activation and Tumor Suppressor Function. Cancer Res 2021; 81:935-944. [PMID: 33323382 PMCID: PMC8026563 DOI: 10.1158/0008-5472.can-20-1804] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 11/06/2020] [Accepted: 12/10/2020] [Indexed: 11/16/2022]
Abstract
p53 is a short-lived protein with low basal levels under normal homeostasis conditions. However, upon DNA damage, levels of p53 dramatically increase for its activation. Although robust stabilization of p53 serves as a "trademark" for DNA damage responses, the requirement for such dramatic protein stabilization in tumor suppression has not been well addressed. Here we generated a mutant p53KQ mouse where all the C-terminal domain lysine residues were mutated to glutamines (K to Q mutations at K367, K369, K370, K378, K379, K383, and K384) to mimic constitutive acetylation of the p53 C-terminus. Because of p53 activation, p53KQ/KQ mice were perinatal lethal, yet this lethality was averted in p53KQ/- mice, which displayed normal postnatal development. Nevertheless, p53KQ/- mice died prematurely due to anemia and hematopoiesis failure. Further analyses indicated that expression of the acetylation-mimicking p53 mutant in vivo induces activation of p53 targets in various tissues without obviously increasing p53 levels. In the well-established pancreatic ductal adenocarcinoma (PDAC) mouse model, expression of the acetylation-mimicking p53-mutant protein effectively suppressed K-Ras-induced PDAC development in the absence of robust p53 stabilization. Together, our results provide proof-of-principle evidence that p53-mediated transcriptional function and tumor suppression can be achieved independently of its robust stabilization and reveal an alternative approach to activate p53 function for therapeutic purposes. SIGNIFICANCE: Although robust p53 stabilization is critical for acute p53 responses such as DNA damage, this study underscores the important role of low basal p53 protein levels in p53 activation and tumor suppression.
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Affiliation(s)
- Ning Kon
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, New York, New York
| | - Michael Churchill
- Department of Medicine and Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, New York, New York
| | - Huan Li
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, New York, New York
| | - Siddhartha Mukherjee
- Department of Medicine and Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, New York, New York
| | - James J Manfredi
- Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Wei Gu
- Institute for Cancer Genetics, Department of Pathology and Cell Biology, and Herbert Irving Comprehensive Cancer Center, College of Physicians & Surgeons, Columbia University, New York, New York.
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6
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Pan M, Blattner C. Regulation of p53 by E3s. Cancers (Basel) 2021; 13:745. [PMID: 33670160 PMCID: PMC7916862 DOI: 10.3390/cancers13040745] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/15/2021] [Accepted: 02/05/2021] [Indexed: 12/18/2022] Open
Abstract
More than 40 years of research on p53 have given us tremendous knowledge about this protein. Today we know that p53 plays a role in different biological processes such as proliferation, invasion, pluripotency, metabolism, cell cycle control, ROS (reactive oxygen species) production, apoptosis, inflammation and autophagy. In the nucleus, p53 functions as a bona-fide transcription factor which activates and represses transcription of a number of target genes. In the cytoplasm, p53 can interact with proteins of the apoptotic machinery and by this also induces cell death. Despite being so important for the fate of the cell, expression levels of p53 are kept low in unstressed cells and the protein is largely inactive. The reason for the low expression level is that p53 is efficiently degraded by the ubiquitin-proteasome system and the vast inactivity of the tumor suppressor protein under normal growth conditions is due to the absence of activating and the presence of inactivating posttranslational modifications. E3s are important enzymes for these processes as they decorate p53 with ubiquitin and small ubiquitin-like proteins and by this control p53 degradation, stability and its subcellular localization. In this review, we provide an overview about E3s that target p53 and discuss the connection between p53, E3s and tumorigenesis.
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Affiliation(s)
| | - Christine Blattner
- Institute of Biological and Chemical Systems—Biological Information Processing, Karlsruhe Institute of Technology, PO-box 3640, 76021 Karlsruhe, Germany;
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7
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Cozene B, Antonucci I, Stuppia L. Activity of p53 in human amniotic fluid stem cells increases their potentiality as a candidate for stem cell therapy. Brain Circ 2019; 5:134-139. [PMID: 31620661 PMCID: PMC6785949 DOI: 10.4103/bc.bc_35_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 09/01/2019] [Accepted: 09/03/2019] [Indexed: 12/19/2022] Open
Abstract
The potential use of stem cells as a therapeutic treatment for many neurological disorders, such as stroke, has spiked an interest in their properties. Due to limitations of the present-day treatments, regenerative and protective therapies could prove very beneficial if a safe and effective treatment is identified. Using human amniotic fluid stem (hAFS) cells could theoretically provide both neuroprotective and regenerative properties to patients, and knowledge of p53's activity and function could be a key component in understanding the behavior and characteristics of these stem cells to harness their full potential. Many recent studies on p53 have provided new and valuable information that could give rise to new ideas for treatment options. More specifically, p53's activity inside hAFS cells lead them closer to becoming a potential therapeutic stem cell. Other neuroprotective treatments, such as hyperoxia and hypoxia sessions, are showing positive results. In combination, these data are helping to get closer to an effective treatment for neurological disorders.
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Affiliation(s)
- Blaise Cozene
- Department of Neurosurgery and Brain Repair, College of Medicine, University of South Florida Morsani, Tampa, FL, USA
| | - Ivana Antonucci
- Department of Psychological, Health and Territorial Sciences, Laboratory of Molecular Genetics, School of Medicine and Health Sciences, G. d'Annunzio University, Chieti-Pescara, Italy
| | - Liborio Stuppia
- Department of Psychological, Health and Territorial Sciences, Laboratory of Molecular Genetics, School of Medicine and Health Sciences, G. d'Annunzio University, Chieti-Pescara, Italy
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8
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Amniotic Fluid Cells, Stem Cells, and p53: Can We Stereotype p53 Functions? Int J Mol Sci 2019; 20:ijms20092236. [PMID: 31067653 PMCID: PMC6539965 DOI: 10.3390/ijms20092236] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 04/20/2019] [Accepted: 04/30/2019] [Indexed: 12/30/2022] Open
Abstract
In recent years, great interest has been devoted to finding alternative sources for human stem cells which can be easily isolated, ideally without raising ethical objections. These stem cells should furthermore have a high proliferation rate and the ability to differentiate into all three germ layers. Amniotic fluid, ordinarily discarded as medical waste, is potentially such a novel source of stem cells, and these amniotic fluid derived stem cells are currently gaining a lot of attention. However, further information will be required about the properties of these cells before they can be used for therapeutic purposes. For example, the risk of tumor formation after cell transplantation needs to be explored. The tumor suppressor protein p53, well known for its activity in controlling Cell Prolif.eration and cell death in differentiated cells, has more recently been found to be also active in amniotic fluid stem cells. In this review, we summarize the major findings about human amniotic fluid stem cells since their discovery, followed by a brief overview of the important role played by p53 in embryonic and adult stem cells. In addition, we explore what is known about p53 in amniotic fluid stem cells to date, and emphasize the need to investigate its role, particularly in the context of cell tumorigenicity.
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Rodrigues M, Antonucci I, Elabd S, Kancherla S, Marchisio M, Blattner C, Stuppia L. p53 Is Active in Human Amniotic Fluid Stem Cells. Stem Cells Dev 2018; 27:1507-1517. [PMID: 30044176 PMCID: PMC6209428 DOI: 10.1089/scd.2017.0254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Despite increasing interest in human amniotic fluid cells, very little is known about the regulation and function of p53 in this cell type. In this study, we show that undifferentiated human amniotic fluid cells express p53, yet at lower levels than in cancer cells. The p53 protein in amniotic fluid cells is mainly localized in the nuclei, however, its antiproliferative activity is compromised in these cells. Igf2, a maternal imprinted gene, and c-jun, a proto-oncogene, are regulated by p53 in these cells. DNA damage leads to an increase in p53 abundance in human amniotic fluid cells and to transcriptional activation of its target genes. Interestingly, cell differentiation toward the neural lineage leads to p53 induction as differentiation progresses.
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Affiliation(s)
- Melissa Rodrigues
- Laboratory of Molecular Genetics, Department of Psychological, Health and Territorial Sciences, School of Medicine and Health Sciences, G. d' Annunzio University, Chieti-Pescara, Italy
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Ivana Antonucci
- Laboratory of Molecular Genetics, Department of Psychological, Health and Territorial Sciences, School of Medicine and Health Sciences, G. d' Annunzio University, Chieti-Pescara, Italy
- Centre of Aging Science and Translational Medicine (Ce.S.I.-Me.T.), G. d'Annunzio University, Chieti-Pescara, Italy
| | - Seham Elabd
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Karlsruhe, Germany
- Department of Human Physiology, Medical Research Institute, Alexandria University, Alexandria, Egypt
| | - Shilpa Kancherla
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Marco Marchisio
- Centre of Aging Science and Translational Medicine (Ce.S.I.-Me.T.), G. d'Annunzio University, Chieti-Pescara, Italy
- Department of Medicine and Aging Sciences, School of Medicine and Health Sciences, G. d' Annunzio University, Chieti-Pescara, Italy
| | - Christine Blattner
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Liborio Stuppia
- Laboratory of Molecular Genetics, Department of Psychological, Health and Territorial Sciences, School of Medicine and Health Sciences, G. d' Annunzio University, Chieti-Pescara, Italy
- Centre of Aging Science and Translational Medicine (Ce.S.I.-Me.T.), G. d'Annunzio University, Chieti-Pescara, Italy
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Wild-type p53 binds to MYC promoter G-quadruplex. Biosci Rep 2016; 36:BSR20160232. [PMID: 27634752 PMCID: PMC5064454 DOI: 10.1042/bsr20160232] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 09/15/2016] [Indexed: 12/19/2022] Open
Abstract
G-quadruplexes are four-stranded nucleic acid structures that are implicated in the regulation of transcription, translation and replication. Genome regions enriched in putative G-quadruplex motifs include telomeres and gene promoters. Tumour suppressor p53 plays a critical role in regulatory pathways leading to cell cycle arrest, DNA repair and apoptosis. In addition to transcriptional regulation mediated via sequence-specific DNA binding, p53 can selectively bind various non-B DNA structures. In the present study, wild-type p53 (wtp53) binding to G-quadruplex formed by MYC promoter nuclease hypersensitive element (NHE) III1 region was investigated. Wtp53 binding to MYC G-quadruplex is comparable to interaction with specific p53 consensus sequence (p53CON). Apart from the full-length wtp53, its isolated C-terminal region (aa 320-393) as well, is capable of high-affinity MYC G-quadruplex binding, suggesting its critical role in this type of interaction. Moreover, wtp53 binds to MYC promoter region containing putative G-quadruplex motif in two wtp53-expressing cell lines. The results suggest that wtp53 binding to G-quadruplexes can take part in transcriptional regulation of its target genes.
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11
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Histone modifications and p53 binding poise the p21 promoter for activation in human embryonic stem cells. Sci Rep 2016; 6:28112. [PMID: 27346849 PMCID: PMC4921813 DOI: 10.1038/srep28112] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 05/31/2016] [Indexed: 11/08/2022] Open
Abstract
The high proliferation rate of embryonic stem cells (ESCs) is thought to arise partly from very low expression of p21. However, how p21 is suppressed in ESCs has been unclear. We found that p53 binds to the p21 promoter in human ESCs (hESCs) as efficiently as in differentiated human mesenchymal stem cells, however it does not promote p21 transcription in hESCs. We observed an enrichment for both the repressive histone H3K27me3 and activating histone H3K4me3 chromatin marks at the p21 locus in hESCs, suggesting it is a suppressed, bivalent domain which overrides activation by p53. Reducing H3K27me3 methylation in hESCs rescued p21 expression, and ectopic expression of p21 in hESCs triggered their differentiation. Further, we uncovered a subset of bivalent promoters bound by p53 in hESCs that are similarly induced upon differentiation in a p53-dependent manner, whereas p53 promotes the transcription of other target genes which do not show an enrichment of H3K27me3 in ESCs. Our studies reveal a unique epigenetic strategy used by ESCs to poise undesired p53 target genes, thus balancing the maintenance of pluripotency in the undifferentiated state with a robust response to differentiation signals, while utilizing p53 activity to maintain genomic stability and homeostasis in ESCs.
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12
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Dewaele M, Tabaglio T, Willekens K, Bezzi M, Teo SX, Low DHP, Koh CM, Rambow F, Fiers M, Rogiers A, Radaelli E, Al-Haddawi M, Tan SY, Hermans E, Amant F, Yan H, Lakshmanan M, Koumar RC, Lim ST, Derheimer FA, Campbell RM, Bonday Z, Tergaonkar V, Shackleton M, Blattner C, Marine JC, Guccione E. Antisense oligonucleotide-mediated MDM4 exon 6 skipping impairs tumor growth. J Clin Invest 2016. [PMID: 26595814 DOI: 10.1172/jci82534.mdm4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023] Open
Abstract
MDM4 is a promising target for cancer therapy, as it is undetectable in most normal adult tissues but often upregulated in cancer cells to dampen p53 tumor-suppressor function. The mechanisms that underlie MDM4 upregulation in cancer cells are largely unknown. Here, we have shown that this key oncogenic event mainly depends on a specific alternative splicing switch. We determined that while a nonsense-mediated, decay-targeted isoform of MDM4 (MDM4-S) is produced in normal adult tissues as a result of exon 6 skipping, enhanced exon 6 inclusion leads to expression of full-length MDM4 in a large number of human cancers. Although this alternative splicing event is likely regulated by multiple splicing factors, we identified the SRSF3 oncoprotein as a key enhancer of exon 6 inclusion. In multiple human melanoma cell lines and in melanoma patient-derived xenograft (PDX) mouse models, antisense oligonucleotide-mediated (ASO-mediated) skipping of exon 6 decreased MDM4 abundance, inhibited melanoma growth, and enhanced sensitivity to MAPK-targeting therapeutics. Additionally, ASO-based MDM4 targeting reduced diffuse large B cell lymphoma PDX growth. As full-length MDM4 is enhanced in multiple human tumors, our data indicate that this strategy is applicable to a wide range of tumor types. We conclude that enhanced MDM4 exon 6 inclusion is a common oncogenic event and has potential as a clinically compatible therapeutic target.
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13
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Dewaele M, Tabaglio T, Willekens K, Bezzi M, Teo SX, Low DHP, Koh CM, Rambow F, Fiers M, Rogiers A, Radaelli E, Al-Haddawi M, Tan SY, Hermans E, Amant F, Yan H, Lakshmanan M, Koumar RC, Lim ST, Derheimer FA, Campbell RM, Bonday Z, Tergaonkar V, Shackleton M, Blattner C, Marine JC, Guccione E. Antisense oligonucleotide-mediated MDM4 exon 6 skipping impairs tumor growth. J Clin Invest 2015; 126:68-84. [PMID: 26595814 DOI: 10.1172/jci82534] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 10/09/2015] [Indexed: 12/27/2022] Open
Abstract
MDM4 is a promising target for cancer therapy, as it is undetectable in most normal adult tissues but often upregulated in cancer cells to dampen p53 tumor-suppressor function. The mechanisms that underlie MDM4 upregulation in cancer cells are largely unknown. Here, we have shown that this key oncogenic event mainly depends on a specific alternative splicing switch. We determined that while a nonsense-mediated, decay-targeted isoform of MDM4 (MDM4-S) is produced in normal adult tissues as a result of exon 6 skipping, enhanced exon 6 inclusion leads to expression of full-length MDM4 in a large number of human cancers. Although this alternative splicing event is likely regulated by multiple splicing factors, we identified the SRSF3 oncoprotein as a key enhancer of exon 6 inclusion. In multiple human melanoma cell lines and in melanoma patient-derived xenograft (PDX) mouse models, antisense oligonucleotide-mediated (ASO-mediated) skipping of exon 6 decreased MDM4 abundance, inhibited melanoma growth, and enhanced sensitivity to MAPK-targeting therapeutics. Additionally, ASO-based MDM4 targeting reduced diffuse large B cell lymphoma PDX growth. As full-length MDM4 is enhanced in multiple human tumors, our data indicate that this strategy is applicable to a wide range of tumor types. We conclude that enhanced MDM4 exon 6 inclusion is a common oncogenic event and has potential as a clinically compatible therapeutic target.
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