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Marasini S, Mugisho OO, Swift S, Read H, Rupenthal ID, Dean SJ, Craig JP. Effect of therapeutic UVC on corneal DNA: Safety assessment for potential keratitis treatment. Ocul Surf 2021; 20:130-138. [PMID: 33610742 DOI: 10.1016/j.jtos.2021.02.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 01/28/2021] [Accepted: 02/13/2021] [Indexed: 12/23/2022]
Abstract
PURPOSE Antimicrobial ultraviolet C (UVC) has proven efficacy in vitro against keratitis isolates and has potential to treat corneal infection if safety can be confirmed. METHOD Safety of 265 nm, 1.93 mW/cm2 intensity UVC (15-300 s exposures) was investigated in vitro via cyclobutane pyrimidine dimer (CPD) formation in DNA of human cultured corneal epithelial cells; ex vivo, by evaluating UVC transmissibility as a function of porcine corneal thickness; and in vivo, by evaluating CPD induction in the mouse cornea following UVC exposure. RESULTS A single exposure of 15 s UVC did not induce significant CPD formation (0.92 ± 1.45%) in vitro relative to untreated control (p = 0.93) whereas 300 s exposure caused extensive CPD formation (86.8 ± 13.73%; p < 0.0001). Cumulative exposure to 15 s UVC daily for 3 days induced more CPD (14.6 ± 8.2%) than a single equivalent 45 s exposure (8.3 ± 4.0%) (p < 0.001) but levels returned to baseline within 72 h (p = 0.29), indicating highly efficient DNA repair. Ex vivo, UVC transmission decreased sharply with increasing corneal thickness, confirming UVC effects are limited to the superficial corneal layers. In vivo evaluations demonstrated no detectable CPD after three consecutive daily 15 s UVC exposures, whereas a single 300 s exposure induced extensive CPD formation in superficial corneal epithelium. CONCLUSION Up to three daily doses of 15 s UVC, in vivo, appear safe with respect to CPD formation. Ongoing research exploring UVC as a possible treatment for microbial keratitis is warranted.
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Affiliation(s)
- Sanjay Marasini
- Ocular Surface Laboratory, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand
| | - Odunayo O Mugisho
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand
| | - Simon Swift
- Department of Molecular Medicine and Pathology, The University of Auckland, New Zealand
| | - Hannah Read
- Department of Molecular Medicine and Pathology, The University of Auckland, New Zealand
| | - Ilva D Rupenthal
- Buchanan Ocular Therapeutics Unit, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand
| | - Simon J Dean
- Ocular Surface Laboratory, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand
| | - Jennifer P Craig
- Ocular Surface Laboratory, Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand.
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2
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Kamada T, Une Y, Matsui K, Fuma S, Ikeda T, Okamoto M. Cloning of Hynobius lichenatus (Tohoku hynobiid salamander) p53 and analysis of its expression in response to radiation. BMC Genet 2020; 21:53. [PMID: 32434469 PMCID: PMC7238597 DOI: 10.1186/s12863-020-00856-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 05/11/2020] [Indexed: 11/28/2022] Open
Abstract
Background Caudata species such as salamanders are easily affected by environmental changes, which can drastically reduce their population. The effects of acute X-rays and chronic γ-irradiation on Hynobius lichenatus, the Japanese Tohoku hynobiid salamander, are known. However, the expression of radiation-inducible genes, such as the DNA-damage checkpoint response gene p53, has not been analyzed in H. lichenatus. This has not occurred because there is no established method for mRNA quantification in H. lichenatus due to a lack of information on available nucleotide sequences corresponding to both radiation-inducible genes and endogenous control genes such as ACTB (β-actin). Results In this study, we aimed to evaluate the effects of radiation on gene expression in H. lichenatus. Using RNA extracted from irradiated salamanders, we performed rapid amplification of cDNA ends (RACE) and cloned H. lichenatus β-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and p53. We confirmed that the cloned cDNAs were able to synthesize salamander proteins by western blotting after transfection into cultured HEK293 cells. Proliferation assays using HEK293 cells stably expressing H. lichenatus p53 protein showed that this protein has antiproliferative effects, similar to that of mammalian p53. Furthermore, RT-qPCR analysis using gene-specific primers revealed that p53 mRNA expression in H. lichenatus was upregulated upon exposure to radiation. Conclusion Our results suggest that H. lichenatus p53 protein take an important role in regulating the cellular responses to various stimuli as mammalian p53 does. Furthermore, our study provides novel data to select appropriate primers to analyze internal control mRNA expression in H. lichenatus and to evaluate p53 expression as a marker of radiation and environmental stimuli.
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Affiliation(s)
- Toshiki Kamada
- Laboratory of Veterinary Immunology, Department of Veterinary Medicine, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Yumi Une
- Laboratory of Veterinary Pathology, Faculty of Veterinary Medicine, Imabari campus, Okayama University of Science, 1-3 Ikoinooka, Imabari, Ehime, 794-8555, Japan
| | - Kumi Matsui
- Laboratory of Veterinary Physiology 1, Department of Veterinary Medicine, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Shoichi Fuma
- Department of Radioecology and Fukushima Project, Center for Advanced Radiation Emergency Medicine, Quantum Medical Science Directorate, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Teruo Ikeda
- Laboratory of Veterinary Immunology, Department of Veterinary Medicine, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan
| | - Mariko Okamoto
- Laboratory of Veterinary Immunology, Department of Veterinary Medicine, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa, 252-5201, Japan.
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Seshacharyulu P, Baine MJ, Souchek JJ, Menning M, Kaur S, Yan Y, Ouellette MM, Jain M, Lin C, Batra SK. Biological determinants of radioresistance and their remediation in pancreatic cancer. Biochim Biophys Acta Rev Cancer 2017; 1868:69-92. [PMID: 28249796 PMCID: PMC5548591 DOI: 10.1016/j.bbcan.2017.02.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/16/2017] [Accepted: 02/17/2017] [Indexed: 12/17/2022]
Abstract
Despite recent advances in radiotherapy, a majority of patients diagnosed with pancreatic cancer (PC) do not achieve objective responses due to the existence of intrinsic and acquired radioresistance. Identification of molecular mechanisms that compromise the efficacy of radiation therapy and targeting these pathways is paramount for improving radiation response in PC patients. In this review, we have summarized molecular mechanisms associated with the radio-resistant phenotype of PC. Briefly, we discuss the reversible and irreversible biological consequences of radiotherapy, such as DNA damage and DNA repair, mechanisms of cancer cell survival and radiation-induced apoptosis following radiotherapy. We further describe various small molecule inhibitors and molecular targeting agents currently being tested in preclinical and clinical studies as potential radiosensitizers for PC. Notably, we draw attention towards the confounding effects of cancer stem cells, immune system, and the tumor microenvironment in the context of PC radioresistance and radiosensitization. Finally, we discuss the need for examining selective radioprotectors in light of the emerging evidence on radiation toxicity to non-target tissue associated with PC radiotherapy.
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Affiliation(s)
- Parthasarathy Seshacharyulu
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Michael J Baine
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Joshua J Souchek
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Melanie Menning
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Sukhwinder Kaur
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Ying Yan
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Michel M. Ouellette
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Maneesh Jain
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Chi Lin
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Surinder K. Batra
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
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4
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Takeuchi S, Matsuda T, Ono R, Tsujimoto M, Nishigori C. Mitotic genes are transcriptionally upregulated in the fibroblast irradiated with very low doses of UV-C. Sci Rep 2016; 6:29233. [PMID: 27378355 PMCID: PMC4932599 DOI: 10.1038/srep29233] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 06/14/2016] [Indexed: 12/19/2022] Open
Abstract
Ultraviolet (UV) radiation induces a variety of biological effects, including DNA damage response and cell signaling pathways. We performed transcriptome analysis using microarray in human primary cultured fibroblasts irradiated with UV-C (0.5 or 5 J/m2) and harvested at 4 or 12 h following UV exposure. All transcript data were analyzed by comparison with the corresponding results in non-irradiated (control) cells. The number of genes with significantly altered expression (≥2-fold difference relative to the control) is higher in the sample irradiated with high dose of UV, suggesting that gene expression was UV dose-dependent. Pathway analysis on the upregulated genes at 12 h indicates that the expression of some cell cycle-related genes was predominantly induced irrespective of UV-dose. Interestingly, almost all the genes with significant altered expression were cell cycle-related genes designated as ‘Mitotic Genes’, which function in the spindle assembly checkpoint. Therefore, even a low dose of UV could affect the transcriptional profile.
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Affiliation(s)
- Seiji Takeuchi
- Division of Dermatology, Department of Internal Related, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuou-ku, Kobe 650-0017, Japan
| | - Toshiro Matsuda
- Kindai University Atomic Energy Research Institute, 3-4-1 Kowakae, Higashiosaka City, Osaka 577-8502, Japan
| | - Ryusuke Ono
- Division of Dermatology, Department of Internal Related, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuou-ku, Kobe 650-0017, Japan
| | - Mariko Tsujimoto
- Division of Dermatology, Department of Internal Related, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuou-ku, Kobe 650-0017, Japan
| | - Chikako Nishigori
- Division of Dermatology, Department of Internal Related, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuou-ku, Kobe 650-0017, Japan
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5
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Su W, Hopkins S, Nesser NK, Sopher B, Silvestroni A, Ammanuel S, Jayadev S, Möller T, Weinstein J, Garden GA. The p53 transcription factor modulates microglia behavior through microRNA-dependent regulation of c-Maf. THE JOURNAL OF IMMUNOLOGY 2013; 192:358-66. [PMID: 24319262 DOI: 10.4049/jimmunol.1301397] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Neuroinflammation occurs in acute and chronic CNS injury, including stroke, traumatic brain injury, and neurodegenerative diseases. Microglia are specialized resident myeloid cells that mediate CNS innate immune responses. Disease-relevant stimuli, such as reactive oxygen species (ROS), can influence microglia activation. Previously, we observed that p53, a ROS-responsive transcription factor, modulates microglia behaviors in vitro and in vivo, promoting proinflammatory functions and suppressing downregulation of the inflammatory response and tissue repair. In this article we describe a novel mechanism by which p53 modulates the functional differentiation of microglia both in vitro and in vivo. Adult microglia from p53-deficient mice have increased expression of the anti-inflammatory transcription factor c-Maf. To determine how p53 negatively regulates c-Maf, we examined the impact of p53 on known c-Maf regulators. MiR-155 is a microRNA that targets c-Maf. We observed that cytokine-induced expression of miR-155 was suppressed in p53-deficient microglia. Furthermore, Twist2, a transcriptional activator of c-Maf, is increased in p53-deficient microglia. We identified recognition sites in the 3' untranslated region of Twist2 mRNA that are predicted to interact with two p53-dependent microRNAs: miR-34a and miR-145. In this article, we demonstrate that miR-34a and -145 are regulated by p53 and negatively regulate Twist2 and c-Maf expression in microglia and the RAW macrophage cell line. Taken together, these findings support the hypothesis that p53 activation induced by local ROS or accumulated DNA damage influences microglia functions and that one specific molecular target of p53 in microglia is c-Maf.
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Affiliation(s)
- Wei Su
- Department of Neurology, University of Washington, Seattle, WA 98195
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6
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McFeat GD, Allinson SL, McMillan TJ. Characterisation of the p53-mediated cellular responses evoked in primary mouse cells following exposure to ultraviolet radiation. PLoS One 2013; 8:e75800. [PMID: 24098727 PMCID: PMC3786933 DOI: 10.1371/journal.pone.0075800] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 08/20/2013] [Indexed: 12/24/2022] Open
Abstract
Exposure to ultraviolet (UV) light can cause significant damage to mammalian cells and, although the spectrum of damage produced varies with the wavelength of UV, all parts of the UV spectrum are recognised as being detrimental to human health. Characterising the cellular response to different wavelengths of UV therefore remains an important aim so that risks and their moderation can be evaluated, in particular in relation to the initiation of skin cancer. The p53 tumour suppressor protein is central to the cellular response that protects the genome from damage by external agents such as UV, thus reducing the risk of tumorigenesis. In response to a variety of DNA damaging agents including UV light, wild-type p53 plays a role in mediating cell-cycle arrest, facilitating apoptosis and stimulating repair processes, all of which prevent the propagation of potentially mutagenic defects. In this study we examined the induction of p53 protein and its influence on the survival of primary mouse fibroblasts exposed to different wavelengths of UV light. UVC was found to elevate p53 protein and its sequence specific DNA binding capacity. Unexpectedly, UVA treatment failed to induce p53 protein accumulation or sequence specific DNA binding. Despite this, UVA exposure of wild-type cells induced a p53 dependent G1 cell cycle arrest followed by a wave of p53 dependent apoptosis, peaking 12 hours post-insult. Thus, it is demonstrated that the elements of the p53 cellular response evoked by exposure to UV radiation are wavelength dependent. Furthermore, the interrelationship between various endpoints is complex and not easily predictable. This has important implications not only for understanding the mode of action of p53 but also for the use of molecular endpoints in quantifying exposure to different wavelengths of UV in the context of human health protection.
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Affiliation(s)
- Gillian D. McFeat
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster, United Kingdom
| | - Sarah L. Allinson
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster, United Kingdom
| | - Trevor J. McMillan
- Division of Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster, United Kingdom
- * E-mail:
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7
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Mouret S, Favier A, Beani JC, Leccia MT. Differential p53-mediated responses to solar-simulated radiation in human papillomavirus type 16-infected keratinocytes. Exp Dermatol 2007; 16:476-84. [PMID: 17518987 DOI: 10.1111/j.1600-0625.2007.00560.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In immunocompromised patients, cooperative effects of human papillomavirus (HPV) and ultraviolet (UV) radiation have been postulated in the development of non-melanoma skin cancers. The tumor suppressor p53 is a key component of the cellular response to genotoxic agents, such as UV radiation. We have previously demonstrated that in HPV16-infected cells, a higher E6* level was associated with a higher resistance to UV and oxidative stress. Using the two same SKv cell lines, the aim of the present study was to investigate p53 and p21 expression and cell death in HPV-infected keratinocytes in response to UV irradiation and to determine the role of HPV oncoprotein levels on the p53-mediated cellular response. We demonstrated that the weakly E6*-expressing level SKv-e cell line presented both higher cytotoxicity and apoptosis to UV. This high sensitivity was associated with both p53 and p21 nuclear accumulation, while a high E6* level and resistance were associated with no p53 accumulation and a p21 nuclear down-regulation after UV. Moreover, in SKv-e cell line, p21 promoter activation was p53 dependent. Our results suggest that an alteration and/or a modulation of the p53-p21 pathway in response to UV could be determinant for HPV-infected keratinocyte survival and HPV-associated carcinogenic process.
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Affiliation(s)
- Stéphane Mouret
- Laboratoire Oligoéléments et Résistance au Stress Oxydant induit par les Xénobiotiques (ORSOX; EA UJF, LRC7 CEA 8M), Université Joseph Fourier, UFR de Médecine et Pharmacie, La Tronche, France
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8
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Abstract
Cell cycle is one of the most complex processes in the life of a dividing cell. It involves numerous regulatory proteins, which direct the cell through a specific sequence of events for the production of two daughter cells. Cyclin-dependent kinases (cdks), which complex with the cyclin proteins, are the main players in the cell cycle. They can regulate the progression of the cells through different stages regulated by several proteins including p53, p21(WAF1), p19, p16, and cdc25. Downstream targets of cyclin-cdk complexes include pRB and E2F. A cell cycle can be altered to the advantage of many viral agents, most notably polyomaviruses, papillomaviruses, adenoviruses, and retroviruses. In addition, viral protein R (Vpr) is a protein encoded by the human immunodeficiency virus type 1 (HIV-1). HIV-1, the causative agent of acquired immunodeficiency syndrome (AIDS), is a member of the lentivirus class of retroviruses. This accessory protein plays an important role in the regulation of the cell cycle by causing G(2) arrest and affecting cell cycle regulators. Vpr prevents infected cells from proliferating, and collaborates with the matrix protein (MA) to enable HIV-1 to enter the nucleus of nondividing cells. Studies from different labs including ours showed that Vpr affects the functions of cell cycle proteins, including p53 and p21(WAF1). Thus, the replication of HIV-1, and ultimately its pathogenesis, are intrinsically tied to cell-cycle control.
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Affiliation(s)
- Shohreh Amini
- Center for Neurovirology and Cancer Biology, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA
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9
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Gentile M, Latonen L, Laiho M. Cell cycle arrest and apoptosis provoked by UV radiation-induced DNA damage are transcriptionally highly divergent responses. Nucleic Acids Res 2003; 31:4779-90. [PMID: 12907719 PMCID: PMC169943 DOI: 10.1093/nar/gkg675] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
DNA damage caused by UV radiation initiates cellular recovery mechanisms, which involve activation of DNA damage response pathways, cell cycle arrest and apoptosis. To assess cellular transcriptional responses to UVC-induced DNA damage we compared time course responses of human skin fibroblasts to low and high doses of UVC radiation known to induce a transient cellular replicative arrest or apoptosis, respectively. UVC radiation elicited >3-fold changes in 460 out of 12,000 transcripts and 89% of these represented downregulated transcripts. Only 5% of the regulated genes were common to both low and high doses of radiation. Cells inflicted with a low dose of UVC exhibited transcription profiles demonstrating transient regulation followed by recovery, whereas the responses were persistent after the high dose. A detailed clustering analysis and functional classification of the targets implied regulation of biologically divergent responses and suggested involvement of transcriptional and translational machinery, inflammatory, anti-proliferative and anti-angiogenic responses. The data support the notion that UVC radiation induces prominent, dose-dependent downregulation of transcription. However, the data strongly suggest that transcriptional repression is also target gene selective. Furthermore, the results demonstrate that dose-dependent induction of cell cycle arrest and apoptosis by UVC radiation are transcriptionally highly distinct responses.
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Affiliation(s)
- Massimiliano Gentile
- Haartman Institute, University of Helsinki and Helsinki University Central Hospital, FIN-00014 Helsinki, Finland
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10
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Schultz LB, Chehab NH, Malikzay A, DiTullio RA, Stavridi ES, Halazonetis TD. The DNA damage checkpoint and human cancer. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 65:489-98. [PMID: 12760066 DOI: 10.1101/sqb.2000.65.489] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- L B Schultz
- Wistar Institute, Graduate Program in Biomedical Sciences, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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11
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Latonen L, Kurki S, Pitkänen K, Laiho M. p53 and MDM2 are regulated by PI-3-kinases on multiple levels under stress induced by UV radiation and proteasome dysfunction. Cell Signal 2003; 15:95-102. [PMID: 12401524 DOI: 10.1016/s0898-6568(02)00044-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
p53 is a key stress responsive cellular component. It is negatively regulated by MDM2, which is also its transcriptional target. Here we have studied the involvement of phosphatidylinositol-3-kinases (PI-3-kinase) in the regulation of p53-MDM2 pathway following cellular stress induced by UV damage and proteasomal downregulation. We show that p53 stabilized both by proteasome inhibition and UV damage is transcriptionally active. However, p53 in proteasomally downregulated cells differs from UV-stabilized p53 in its interaction with MDM2, posttranslational modifications and subnuclear localization. It is known that members of PI-3-kinase family are able to directly phosphorylate p53 and MDM2. We show that these kinases regulate p53 accumulation after UV radiation, but accumulation of MDM2 after proteasome inhibition. Both proteins have earlier been shown to translocate into nucleoli after downregulation of the proteasome. We found this effect to be dependent on PI-3-kinase activity but not on any suggested PI-3-kinase phosphorylation site on MDM2. In conclusion, we show here that PI-3-kinases regulate p53-MDM2 pathway on multiple, earlier unknown levels.
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Affiliation(s)
- Leena Latonen
- Department of Virology, Haartman Institute, University of Helsinki and Helsinki University Central Hospital, PO Box 63, FIN-00014 Helsinki, Finland
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12
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Buzek J, Latonen L, Kurki S, Peltonen K, Laiho M. Redox state of tumor suppressor p53 regulates its sequence-specific DNA binding in DNA-damaged cells by cysteine 277. Nucleic Acids Res 2002; 30:2340-8. [PMID: 12034820 PMCID: PMC117181 DOI: 10.1093/nar/30.11.2340] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2002] [Revised: 04/04/2002] [Accepted: 04/04/2002] [Indexed: 11/12/2022] Open
Abstract
Using a bio-oligo pull-down DNA-binding assay we investigated the binding capacity of endogenous, DNA damage-induced p53 in human diploid fibroblasts to several p53-responsive elements (REs) present in p53-regulated genes. During the course of p53 accumulation, we observed a decrease in p53 binding to the GADD45 but not to the p21(WAF1/CIP1) RE. Using mutated GADD45 sequences we show that this change is dependent on the presence of cytosines at position 3 in RE pentamers and on the p53 redox state. Site-directed mutagenesis experiments demonstrated that Cys277 (a residue directly contacting base 3 in a RE pentamer) is critical for differential regulation of GADD45 in DNA-damaged cells. These data represent a novel mechanism for differential affinity of p53 to distinct REs.
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Affiliation(s)
- Jiri Buzek
- Department of Virology, Haartman Institute, and Molecular Cancer Biology Program, Biomedicum Helsinki, University of Helsinki and Helsinki University Central Hospital Laboratory Diagnostics, PO Box 63, FIN-00014 Helsinki, Finland
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13
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Houser S, Koshlatyi S, Lu T, Gopen T, Bargonetti J. Camptothecin and Zeocin can increase p53 levels during all cell cycle stages. Biochem Biophys Res Commun 2001; 289:998-1009. [PMID: 11741290 DOI: 10.1006/bbrc.2001.6073] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ability of DNA damage to stabilize p53 in all cell cycle stages has not been examined in actively growing cells. The chemotherapeutic drug camptothecin is a topoisomerase I poison. Zeocin is a member of the bleomycin/phleomycin family of antibiotics, known to bind DNA. Both increase the level of p53 albeit by different mechanisms. We have utilized centrifugal elutriation to separate exponentially growing ML-1 cells (containing wild-type p53) into cell cycle fractions and have subsequently treated these cells with the two drugs. We provide evidence that both drugs can mediate an increase in p53 protein levels independent of the cell cycle stage. The p53 induced by both drugs was able to bind to DNA; however, only the p53 induced by camptothecin was phosphorylated at serine-392. This is the first demonstration that camptothecin and Zeocin can differentially signal for increased levels of modified p53 during all stages of the cell cycle.
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Affiliation(s)
- S Houser
- Institute for Biomolecular Structure and Function, Department of Biological Sciences, Hunter College and Graduate School, City University of New York, 695 Park Avenue, New York 10021, USA
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14
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Latonen L, Taya Y, Laiho M. UV-radiation induces dose-dependent regulation of p53 response and modulates p53-HDM2 interaction in human fibroblasts. Oncogene 2001; 20:6784-93. [PMID: 11709713 DOI: 10.1038/sj.onc.1204883] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2001] [Revised: 07/17/2001] [Accepted: 08/01/2001] [Indexed: 12/11/2022]
Abstract
We address here the effects of increasing fluencies of UV-radiation on stability, modifications, activity and HDM2-interactions of endogenous p53 tumor suppressor and on cellular damage response of human diploid fibroblasts. Low amounts of UVB/C-radiation induced a transient cell cycle arrest of the cells which correlated with rapid but transient increase in p53 levels. In contrast, high UV-fluency caused cell apoptosis and a slower but sustained increase in p53. Regulation of p53 target genes was highly dependent on the radiation dose used. Whereas low doses induced p21/Cip1/Waf1 and HDM2, high doses induced only GADD45 and BAX increasing the BAX:BCL-2 ratio. The levels of HDM2, a negative regulator of p53, increased only by the low dose of UVC and p53-HDM2 association was promoted. In the absence of HDM2-induction after the high dose of UV-radiation p53-HDM2-interaction was promoted, but HDM2 failed to downregulate p53. p53 site-specific modifications (Ser15, Ser33, Ser37, Lys382) varied kinetically and were dependent on the fluency of the radiation used. Maximal phosphorylation of p53 on Ser15 and Ser33 correlated with increased levels of HDM2-free p53. The results suggest that regulation of p53 and HDM2 by UV-radiation is highly dose-dependent and contributes to the outcome of the cellular response.
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Affiliation(s)
- L Latonen
- Haartman Institute, Department of Virology, University of Helsinki, PO Box 63, FIN-00014 Helsinki, Finland
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15
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Affiliation(s)
- E S Hickman
- European Institute of Oncology, Department of Experimental Oncology, Via Ripamonti 435, Milano 20141, Italy
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16
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Nagasawa M, Gelfand EW, Lucas JJ. Accumulation of high levels of the p53 and p130 growth-suppressing proteins in cell lines stably over-expressing cyclin-dependent kinase 6 (cdk6). Oncogene 2001; 20:2889-99. [PMID: 11420701 DOI: 10.1038/sj.onc.1204396] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/1998] [Revised: 02/07/2001] [Accepted: 02/13/2001] [Indexed: 11/09/2022]
Abstract
Cyclin-dependent kinase 6(cdk6) is present in randomly proliferating cultures of 3T3 cells but has little detectable enzymatic activity. Significant activity is detected only during a short period in early G1 phase. To examine the possible functions of cdk6 in 3T3 cells, lines stably over-expressing cdk6 were constructed and compared to normal 3T3 cells or cell lines with reduced cdk6 levels due to expression of a dominant-negative form of the protein. Over-expression of cdk6 in cells, which led to high levels of activity even in proliferating cultures, had dramatic effects. Cell lines stably over-expressing wild-type cdk6 had a markedly reduced growth rate compared to parental 3T3 cells or lines expressing a dominant-negative form of cdk6. They also over-produced the p53 and p130 proteins and had increased sensitivity to UV-irradiation. Irradiation resulted in accumulation of the Bax protein and rapid cell death. Levels of p53 and p130 proteins were down-regulated and the growth rate of the cells was increased by introduction of the dominant-negative form of cdk6 into cells over-expressing cdk6, indicating that cdk6 is involved in the overproduction of p53 and p130. The results suggest that cdk6, through regulation of growth-suppressing molecules, may play a role in halting cellular growth when proliferation is inappropriate.
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Affiliation(s)
- M Nagasawa
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, Colorado, CO 80206, USA
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17
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Jaks V, Jõers A, Kristjuhan A, Maimets T. p53 protein accumulation in addition to the transactivation activity is required for p53-dependent cell cycle arrest after treatment of cells with camptothecin. Oncogene 2001; 20:1212-9. [PMID: 11313865 DOI: 10.1038/sj.onc.1204232] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2000] [Revised: 12/21/2000] [Accepted: 01/03/2001] [Indexed: 11/09/2022]
Abstract
In this study we characterize the connections between p53-dependent G1 cell cycle arrest, transcriptional activation of the protein and the increase of its intracellular steady-state concentration. Several cell lines expressing wild-type p53 protein were treated with increasing concentrations of DNA-damaging drug camptothecin. Lower doses of the drug caused transcriptional activation of p53, but no accumulation of the protein was detected. Only after a certain threshold dose of camptothecin does the amount of the protein rapidly increase and reach its plateau levels. The threshold dose was different for different cell lines, but the general non-linear profile was similar. Increase of p53 level was accompanied by additional transcriptional activation of some p53 target genes (i.e. waf1), but not the others (mdm2). We demonstrate here that transcriptional activation of p53 after the treatment of camptothecin is not sufficient to cause p53-dependent G1 cell cycle arrest. The latter is observable only after the increase of steady-state level of p53. Low drug concentrations, although accompanied by transcriptional activation of p53, do not cause either p53 protein accumulation nor cell cycle arrest at G1. We propose a model for p53 acting as a part of cellular sensor system detecting the severity of DNA damage.
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Affiliation(s)
- V Jaks
- Department of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia23, Tartu, 51010, Estonia
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18
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Collavin L, Monte M, Verardo R, Pfleger C, Schneider C. Cell-cycle regulation of the p53-inducible gene B99. FEBS Lett 2000; 481:57-62. [PMID: 10984615 DOI: 10.1016/s0014-5793(00)01969-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
B99 is a p53-inducible gene whose accumulation upon p53 activation is restricted to late S/G2 cells. Here we have analyzed B99 regulation during the cell cycle in murine cells with or without functional p53. We report that B99 accumulates in late S/G2 phase, is phosphorylated in mitosis, and disappears in G1 phase, regardless of the status of p53. As a complement to this observation, we show that B99 is not induced by p53 in quiescent cells. Therefore, B99 expression is modulated both by cell-cycle regulatory mechanisms and by p53, and p53 can increase the cellular levels of B99 only during the window of the cell cycle when it is normally expressed. On the basis of these observations we rename B99 Gtse-1 (G-two- and S-phase-expressed).
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Affiliation(s)
- L Collavin
- Laboratorio Nazionale Consorzio Interuniversitario Biotechnologie, Trieste, Italy
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19
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Katoh I, Aisaki KI, Kurata SI, Ikawa S, Ikawa Y. p51A (TAp63gamma), a p53 homolog, accumulates in response to DNA damage for cell regulation. Oncogene 2000; 19:3126-30. [PMID: 10871867 DOI: 10.1038/sj.onc.1203644] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
p51A, or TAp63gamma, a translation product of gene p51, or p63, was identified as a homolog of p53 in its primary structure and transactivating function. p53 plays a decision-making role in inducing either cell cycle arrest or apoptosis in response to DNA damage, and thereby preserves genome integrity of living cells. To compare the biological activities between p51A and p53, cell lines with low-level, constitutive expression of each protein were obtained by cDNA transfection of mouse erythroleukemic cells. Production of p51A with an apparent molecular mass of 57-kilodalton (kD) accompanied induction of p21waf1 and appearance of hemoglobin-producing cells. After DNA-damaging treatment either with ultraviolet light (UV) irradiation or with actinomycin D, the p51A protein accumulated in time courses corresponding to those of wild-type p53, and caused an increase in the hemoglobin-positive cell count. In contrast, p53-accumulated cells underwent apoptosis without exhibiting the feature of erythroid differentiation. The mode of p21waf1 and Bax-alpha upregulations varied between p51A- and p53-expressing cells and between the types of DNA damage. These results suggest the possibility that p51A induces differentiation under genotoxic circumstances. There may be cellular factors that control p51A protein stability and transactivating ability.
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Affiliation(s)
- I Katoh
- Department of Retroviral Regulation, Medical Research Division, Tokyo Medical and Dental University, Tokyo 113-8519, Japan
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20
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Chehab NH, Malikzay A, Appel M, Halazonetis TD. Chk2/hCds1 functions as a DNA damage checkpoint in G1 by stabilizing p53. Genes Dev 2000. [DOI: 10.1101/gad.14.3.278] [Citation(s) in RCA: 335] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Chk2/hcds1, the human homolog of theSaccharomyces cerevisiae RAD53/SPK1 andSchizosaccharomyces pombe cds1 DNA damage checkpoint genes, encodes a protein kinase that is post-translationally modified after DNA damage. Like its yeast homologs, the Chk2/hCds1 protein phosphorylates Cdc25C in vitro, suggesting that it arrests cells in G2 in response to DNA damage. We expressed Chk2/hCds1 in human cells and analyzed their cell cycle profile. Wild-type, but not catalytically inactive, Chk2/hCds1 led to G1 arrest after DNA damage. The arrest was inhibited by cotransfection of a dominant-negative p53 mutant, indicating that Chk2/hCds1 acted upstream of p53. In vitro, Chk2/hCds1 phosphorylated p53 on Ser-20 and dissociated preformed complexes of p53 with Mdm2, a protein that targets p53 for degradation. In vivo, ectopic expression of wild-type Chk2/hCds1 led to increased p53 stabilization after DNA damage, whereas expression of a dominant-negative Chk2/hCds1 mutant abrogated both phosphorylation of p53 on Ser-20 and p53 stabilization. Thus, in response to DNA damage, Chk2/hCds1 stabilizes the p53 tumor suppressor protein leading to cell cycle arrest in G1.
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21
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Chehab NH, Malikzay A, Appel M, Halazonetis TD. Chk2/hCds1 functions as a DNA damage checkpoint in G(1) by stabilizing p53. Genes Dev 2000; 14:278-88. [PMID: 10673500 PMCID: PMC316357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Chk2/hcds1, the human homolog of the Saccharomyces cerevisiae RAD53/SPK1 and Schizosaccharomyces pombe cds1 DNA damage checkpoint genes, encodes a protein kinase that is post-translationally modified after DNA damage. Like its yeast homologs, the Chk2/hCds1 protein phosphorylates Cdc25C in vitro, suggesting that it arrests cells in G(2) in response to DNA damage. We expressed Chk2/hCds1 in human cells and analyzed their cell cycle profile. Wild-type, but not catalytically inactive, Chk2/hCds1 led to G(1) arrest after DNA damage. The arrest was inhibited by cotransfection of a dominant-negative p53 mutant, indicating that Chk2/hCds1 acted upstream of p53. In vitro, Chk2/hCds1 phosphorylated p53 on Ser-20 and dissociated preformed complexes of p53 with Mdm2, a protein that targets p53 for degradation. In vivo, ectopic expression of wild-type Chk2/hCds1 led to increased p53 stabilization after DNA damage, whereas expression of a dominant-negative Chk2/hCds1 mutant abrogated both phosphorylation of p53 on Ser-20 and p53 stabilization. Thus, in response to DNA damage, Chk2/hCds1 stabilizes the p53 tumor suppressor protein leading to cell cycle arrest in G(1).
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Affiliation(s)
- N H Chehab
- Department of Molecular Genetics, The Wistar Institute, Philadelphia, Pennsylvania 19104, USA
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22
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Chehab NH, Malikzay A, Stavridi ES, Halazonetis TD. Phosphorylation of Ser-20 mediates stabilization of human p53 in response to DNA damage. Proc Natl Acad Sci U S A 1999; 96:13777-82. [PMID: 10570149 PMCID: PMC24141 DOI: 10.1073/pnas.96.24.13777] [Citation(s) in RCA: 438] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Stabilization of p53 in response to DNA damage is caused by its dissociation from Mdm2, a protein that targets p53 for degradation in the proteasome. Dissociation of p53 from Mdm2 could be caused by DNA damage-induced p53 posttranslational modifications. The ATM and ATR kinases, whose activation in response to ionizing radiation (IR) and UV light, respectively, is required for p53 stabilization, directly phosphorylate p53 on Ser-15. However, phosphorylation of Ser-15 is critical for the apoptotic activity of p53 and not for p53 stabilization. Thus, whether any p53 modifications, and which, underlie disruption of the p53-Mdm2 complex after DNA damage remains to be determined. We analyzed the IR- and UV light-induced stabilization of p53 proteins with substitutions of Ser known to be posttranslationally modified after DNA damage. Substitution of Ser-20 was sufficient to abrogate p53 stabilization in response to both IR and UV light. Furthermore, both IR and UV light induced phosphorylation of p53 on Ser-20, which involved the majority of nuclear p53 protein and weakened the interaction of p53 with Mdm2 in vitro. ATM and ATR cannot phosphorylate p53 on Ser-20. We therefore propose that ATM and ATR activate an, as yet unidentified, kinase that stabilizes p53 by phosphorylating it on Ser-20.
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Affiliation(s)
- N H Chehab
- Department of Molecular Genetics, The Wistar Institute, Philadelphia, PA 19104, USA
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23
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Kivinen L, Tsubari M, Haapajärvi T, Datto MB, Wang XF, Laiho M. Ras induces p21Cip1/Waf1 cyclin kinase inhibitor transcriptionally through Sp1-binding sites. Oncogene 1999; 18:6252-61. [PMID: 10597223 DOI: 10.1038/sj.onc.1203000] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
p21Cip1/Waf1 cyclin-dependent kinase inhibitor (p21) is inducible by Raf and mitogen-activated protein kinase kinase (MAPKK), but the level of regulation is unknown. We show here by conditional and transient Ras-expression models that Ras induces p21. Induction of p21 in conditionally Ras-expressing cells is posttranscriptional utilizing mitogen-activated protein kinase (MAPK) pathway. Transient, high-level Ras-expression induces transcriptional activation of p21 mediated by a GC-rich region in p21 promoter -83-54 bp relative to the transcription initiation site containing binding sites for Sp1-family transcription factors. Mutation of either Sp1-binding site 2 or 4 in this region decreases the magnitude of induction of promoter activity by Ras, but only the simultaneous mutation of both sites abolishes fully the induction. Electrophoretic mobility shift assays using an oligonucleotide corresponding to Sp1-binding site 2 indicate that both Sp1 and Sp3 transcription factors bind to this region. The results demonstrate that the central cytosolic growth regulator Ras is a potent transcriptional and posttranscriptional inducer of the nuclear growth inhibitor p21.
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Affiliation(s)
- L Kivinen
- Haartman Institute, Department of Virology, University of Helsinki, Finland
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24
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Kachnic LA, Wu B, Wunsch H, Mekeel KL, DeFrank JS, Tang W, Powell SN. The ability of p53 to activate downstream genes p21(WAF1/cip1) and MDM2, and cell cycle arrest following DNA damage is delayed and attenuated in scid cells deficient in the DNA-dependent protein kinase. J Biol Chem 1999; 274:13111-7. [PMID: 10224064 DOI: 10.1074/jbc.274.19.13111] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
scid mouse embryonic fibroblasts are deficient in DNA-dependent protein kinase activity due to a mutation in the C-terminal domain of the catalytic subunit (DNA-PKcs). When exposed to ionizing radiation, the increase in levels of p53 was the same as in normal mouse embryonic fibroblasts. However, the rise in p21(WAF1/cip1) and mdm2 was found to be delayed and attenuated, which correlated in time with delayed onset of G1/S arrest by flow cytometric analysis. The p53-dependent G1 checkpoint was not eliminated: inactivation of p53 by the E6 protein in scid cells resulted in the complete loss of detectable G1/S arrest after DNA damage. Immunofluorescence analysis of normal cells revealed p53 to be localized predominantly within the cytoplasm prior to irradiation and then translocate to the nucleus after irradiation. In contrast, scid cells show abnormal accumulation of p53 in the nucleus independent of irradiation, which was confirmed by immunoblot analysis of nuclear lysates. Taken together, these data suggest that loss of DNA-PK activity appears to attenuate the kinetics of p53 to activate downstream genes, implying that DNA-PK plays a role in post-translational modification of p53, without affecting the increase in levels of p53 in response to DNA damage.
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Affiliation(s)
- L A Kachnic
- Laboratory of Molecular and Cellular Radiation Biology, Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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25
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Haapajärvi T, Kivinen L, Heiskanen A, des Bordes C, Datto MB, Wang XF, Laiho M. UV radiation is a transcriptional inducer of p21(Cip1/Waf1) cyclin-kinase inhibitor in a p53-independent manner. Exp Cell Res 1999; 248:272-9. [PMID: 10094833 DOI: 10.1006/excr.1999.4403] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
p53 target genes p21(Cip1/Waf1) cyclin-kinase inhibitor (p21 CKI), GADD45, bax, and cyclin G and genes affecting the redox state of the cells are implicated in p53 damage control responses. In order to attribute their functions and dependency of p53 in UV-damaged cells we undertook an analysis of UVC responses of fibroblasts derived from p53 knock-out mice. UVC radiation efficiently and rapidly inhibited DNA replication in both p53 -/- and +/+ cells. The arrest was persistent in p53 -/- fibroblasts and cells underwent apoptosis, whereas p53 +/+ cells recovered and reentered the cycle. Protein and mRNA analyses of p21 expression showed that it was induced up to sixfold with similar kinetics both in the presence and in the absence of p53. However, high doses of UV abrogated the p21 response in p53 -/- cells, whereas it was maintained in cells with normal p53. UVC radiation transcriptionally activated p21 expression as demonstrated by luciferase reporter assays using deletion constructs of the p21 promoter. The promoter assays further confirmed the independency of p53-binding sites in the activation and linked UV-responsive transcriptional regulation of p21 to two Sp1 consensus binding sites within -61 bp of the transcription initiation site. A weaker regulation was mediated by elements between -1300 to -500 bp relative to the transcription initiation site. The results suggest that in fibroblasts UVC radiation is a rapid and efficient inducer of p21 expression also in a p53-independent manner.
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Affiliation(s)
- T Haapajärvi
- Department of Virology, University of Helsinki, Haartmaninkatu 3, Helsinki, FIN-00014, Finland
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26
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Sakaguchi K, Herrera JE, Saito S, Miki T, Bustin M, Vassilev A, Anderson CW, Appella E. DNA damage activates p53 through a phosphorylation-acetylation cascade. Genes Dev 1998; 12:2831-41. [PMID: 9744860 PMCID: PMC317174 DOI: 10.1101/gad.12.18.2831] [Citation(s) in RCA: 921] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Activation of p53-mediated transcription is a critical cellular response to DNA damage. p53 stability and site-specific DNA-binding activity and, therefore, transcriptional activity, are modulated by post-translational modifications including phosphorylation and acetylation. Here we show that p53 is acetylated in vitro at separate sites by two different histone acetyltransferases (HATs), the coactivators p300 and PCAF. p300 acetylates Lys-382 in the carboxy-terminal region of p53, whereas PCAF acetylates Lys-320 in the nuclear localization signal. Acetylations at either site enhance sequence-specific DNA binding. Using a polyclonal antisera specific for p53 that is phosphorylated or acetylated at specific residues, we show that Lys-382 of human p53 becomes acetylated and Ser-33 and Ser-37 become phosphorylated in vivo after exposing cells to UV light or ionizing radiation. In vitro, amino-terminal p53 peptides phosphorylated at Ser-33 and/or at Ser-37 differentially inhibited p53 acetylation by each HAT. These results suggest that DNA damage enhances p53 activity as a transcription factor in part through carboxy-terminal acetylation that, in turn, is directed by amino-terminal phosphorylation.
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Affiliation(s)
- K Sakaguchi
- Laboratory of Cell Biology, National Cancer Institute (NCI), National Institutes of Health, Bethesda, Maryland 20892, USA
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27
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Waterman MJ, Stavridi ES, Waterman JL, Halazonetis TD. ATM-dependent activation of p53 involves dephosphorylation and association with 14-3-3 proteins. Nat Genet 1998; 19:175-8. [PMID: 9620776 DOI: 10.1038/542] [Citation(s) in RCA: 361] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The p53 tumour-suppressor protein is a sequence-specific DNA-binding transcription factor that induces cell cycle arrest or apoptosis in response to genotoxic stress. Activation of p53 by DNA-damaging agents is critical for eliminating cells with damaged genomic DNA and underlies the apoptotic response of human cancers treated with ionizing radiation (IR) and radiomimetic drugs. The molecular mechanisms by which DNA damage activates p53 have not been elucidated. Both the levels of p53 protein and its affinity for specific DNA sequences increase in response to genotoxic stress. In vitro, the affinity of p53 for DNA is regulated by its carboxy-terminus. We therefore examined whether this region of p53 is targeted by DNA-damage signalling pathways in vivo. In nonirradiated cells, serines 376 and 378 of p53 were phosphorylated. IR led to dephosphorylation of Ser376, creating a consensus binding site for 14-3-3 proteins and leading to association of p53 with 14-3-3. In turn, this increased the affinity of p53 for sequence-specific DNA. Consistent with the lack of p53 activation by IR in ataxia telangiectasia (AT; refs 14,15), neither Ser376 dephosphorylation, nor the interaction of p53 with 14-3-3 proteins occurred in AT cells.
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Affiliation(s)
- M J Waterman
- Department of Molecular Genetics, The Wistar Institute, Philadelphia, Pennsylvania 19104-4268, USA
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