1
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Rozenberg JM, Zvereva S, Dalina A, Blatov I, Zubarev I, Luppov D, Bessmertnyi A, Romanishin A, Alsoulaiman L, Kumeiko V, Kagansky A, Melino G, Ganini C, Barlev NA. The p53 family member p73 in the regulation of cell stress response. Biol Direct 2021; 16:23. [PMID: 34749806 PMCID: PMC8577020 DOI: 10.1186/s13062-021-00307-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 10/12/2021] [Indexed: 12/14/2022] Open
Abstract
During oncogenesis, cells become unrestrictedly proliferative thereby altering the tissue homeostasis and resulting in subsequent hyperplasia. This process is paralleled by resumption of cell cycle, aberrant DNA repair and blunting the apoptotic program in response to DNA damage. In most human cancers these processes are associated with malfunctioning of tumor suppressor p53. Intriguingly, in some cases two other members of the p53 family of proteins, transcription factors p63 and p73, can compensate for loss of p53. Although both p63 and p73 can bind the same DNA sequences as p53 and their transcriptionally active isoforms are able to regulate the expression of p53-dependent genes, the strongest overlap with p53 functions was detected for p73. Surprisingly, unlike p53, the p73 is rarely lost or mutated in cancers. On the contrary, its inactive isoforms are often overexpressed in cancer. In this review, we discuss several lines of evidence that cancer cells develop various mechanisms to repress p73-mediated cell death. Moreover, p73 isoforms may promote cancer growth by enhancing an anti-oxidative response, the Warburg effect and by repressing senescence. Thus, we speculate that the role of p73 in tumorigenesis can be ambivalent and hence, requires new therapeutic strategies that would specifically repress the oncogenic functions of p73, while keeping its tumor suppressive properties intact.
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Affiliation(s)
- Julian M Rozenberg
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
| | - Svetlana Zvereva
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Aleksandra Dalina
- The Engelhardt Institute of Molecular Biology, Russian Academy of Science, Moscow, Russia
| | - Igor Blatov
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Ilya Zubarev
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Daniil Luppov
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | | | - Alexander Romanishin
- School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia.,School of Life Sciences, Immanuel Kant Baltic Federal University, Kaliningrad, Russia
| | - Lamak Alsoulaiman
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Vadim Kumeiko
- School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia
| | - Alexander Kagansky
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.,School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia
| | - Gerry Melino
- Department of Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Carlo Ganini
- Department of Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Nikolai A Barlev
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia. .,Institute of Cytology, Russian Academy of Science, Saint-Petersburg, Russia.
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2
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p73: From the p53 shadow to a major pharmacological target in anticancer therapy. Pharmacol Res 2020; 162:105245. [PMID: 33069756 DOI: 10.1016/j.phrs.2020.105245] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/30/2020] [Accepted: 10/02/2020] [Indexed: 02/06/2023]
Abstract
p73, along with p53 and p63, belongs to the p53 family of transcription factors. Besides the p53-like tumor suppressive activities, p73 has unique roles, namely in neuronal development and differentiation. In addition, the TP73 gene is rarely mutated in tumors. This makes p73 a highly appealing therapeutic target, particularly towards cancers with a null or disrupted p53 pathway. Distinct isoforms are transcribed from the TP73 locus either with (TAp73) and without (ΔNp73) the N-terminal transactivation domain. Conversely to TA tumor suppressors, ΔN proteins exhibit oncogenic properties by inhibiting p53 and TA protein functions. As such, p73 isoforms compose a puzzled and challenging regulatory pathway. This state-of-the-art review affords an update overview on p73 structure, biological functions and pharmacological regulation. Importantly, it addresses the relevance of p73 isoforms in carcinogenesis, highlighting their potential as drug targets in anticancer therapy. A critical discussion of major pharmacological approaches to promote p73 tumor suppressive activities, with relevant survival outcomes for cancer patients, is also provided.
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3
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Zhang YX, Pan WY, Chen J. p53 and its isoforms in DNA double-stranded break repair. J Zhejiang Univ Sci B 2019; 20:457-466. [PMID: 31090271 DOI: 10.1631/jzus.b1900167] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
DNA double-stranded break (DSB) is one of the most catastrophic damages of genotoxic insult. Inappropriate repair of DNA DSBs results in the loss of genetic information, mutation, and the generation of harmful genomic rearrangements, which predisposes an organism to immunodeficiency, neurological damage, and cancer. The tumor repressor p53 plays a key role in DNA damage response, and has been found to be mutated in 50% of human cancer. p53, p63, and p73 are three members of the p53 gene family. Recent discoveries have shown that human p53 gene encodes at least 12 isoforms. Different p53 members and isoforms play various roles in orchestrating DNA damage response to maintain genomic integrity. This review briefly explores the functions of p53 and its isoforms in DNA DSB repair.
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Affiliation(s)
- Yu-Xi Zhang
- MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Wen-Ya Pan
- MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Jun Chen
- MOE Key Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
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4
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Naseer F, Saleem M. Epigenetic modification in the expression of p73 p73 - epigenetic target for anticancer therapy. Oncol Rev 2019; 13:421. [PMID: 31410249 PMCID: PMC6661529 DOI: 10.4081/oncol.2019.421] [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: 03/14/2019] [Accepted: 06/10/2019] [Indexed: 11/22/2022] Open
Abstract
A p73 is a new member of p53 family of transcription factor, having two types. First is TAp73, transcriptionally active and expressed via upstream promoter as a tumor suppressor and vital apoptotic inductor, it also has a key role in cell cycle arrest/differentiation and Second is ΔNp73 that is transcriptionally inactive and expressed via downstream regulator as oncogenes. Both types are expressed in various isoforms, which originate from alternative splicing events at the C-terminus. Upon DNA damage, posttranslational modifications cause conformational changes in various amino acid residues via induction or inhibition of various proteins, which are present in the structural domains of p73. These modifications may cause up- or down-regulation of p73 expression levels, as well as alters the transcriptional activity and/or stability of the protein. In this review, we have made an effort to assemble all existing data regarding the role of p73, its modification and after effects in cancer.
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Affiliation(s)
- Faiza Naseer
- Shifa College of Pharmaceutical Sciences, Shifa Tameer e Millat University, Islamabad, Pakistan
| | - Mohammad Saleem
- Faculty of Pharmaceutical Sciences, Punjab University, Lahore, Pakistan
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5
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Wang Z, Førsund MS, Trope CG, Nesland JM, Holm R, Slipicevic A. Evaluation of CHK1 activation in vulvar squamous cell carcinoma and its potential as a therapeutic target in vitro. Cancer Med 2018; 7:3955-3964. [PMID: 29963769 PMCID: PMC6089182 DOI: 10.1002/cam4.1638] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 05/28/2018] [Accepted: 05/28/2018] [Indexed: 11/05/2022] Open
Abstract
CHK1 is an important regulator of the cell cycle and DNA damage response, and its altered expression has been identified in various tumors. Chk1 inhibitors are currently being evaluated as monotherapy and as potentiators of chemotherapy in clinical settings. However, to our knowledge, no previous study has investigated either the activation status or the therapeutic potential of CHK1 targeting in vulvar cancer. Therefore, we examined the expression status of activated CHK1 forms pCHK1Ser345, pCHK1Ser317, pCHK1Ser296, and pCHK1Ser280 in 294 vulvar squamous cell carcinomas (VSCC) using immunohistochemistry and analyzed their relationships with various clinicopathological variables and clinical outcome. To aid translation of preclinical studies, we also assessed cell sensitivity to the Chk1 inhibition in two vulvar cancer cell lines. Compared to the levels of pCHK1Ser345, pCHK1Ser317, pCHK1Ser296, and pCHK1Ser280 in normal vulvar squamous epithelium, high nuclear pCHK1Ser345 expression was found in 57% of vulvar carcinomas, whereas low nuclear pCHK1Ser317, pCHK1Ser296, and pCHK1Ser280 expressions were observed in 58%, 64%, and 40% of the cases, respectively. Low levels of pCHK1Ser317 and pCHK1Ser280 in the nucleus correlated significantly with advanced tumor behaviors and aggressive features. None of pCHK1Ser345, pCHK1Ser317, pCHK1Ser296, and pCHK1Ser280 forms were identified as prognostic factors. In vitro inhibition of CHK1 by small molecular inhibitors or siRNA reduced viability by inducing DNA damage and apoptosis of vulvar cancer cell lines. In summary, we conclude that cellular functions regulated by CHK1 are phosphorylation/localization‐dependent and deregulation of CHK1 function occurs in VSCC and might contribute to tumorigenesis. Targeting CHK1 might represent as a useful antitumor strategy for the subgroup of VSCC harboring p53 mutations.
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Affiliation(s)
- Zhihui Wang
- Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Mette S Førsund
- Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Claes G Trope
- Department of Obstetrics and Gynecology, The Norwegian Radium Hospital, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Jahn M Nesland
- Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital and University of Oslo, Oslo, Norway
| | - Ruth Holm
- Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Ana Slipicevic
- Department of Pathology, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
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6
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p73 coordinates with Δ133p53 to promote DNA double-strand break repair. Cell Death Differ 2018; 25:1063-1079. [PMID: 29511339 PMCID: PMC5988805 DOI: 10.1038/s41418-018-0085-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 01/18/2018] [Accepted: 02/07/2018] [Indexed: 12/16/2022] Open
Abstract
Tumour repressor p53 isoform Δ133p53 is a target gene of p53 and an antagonist of p53-mediated apoptotic activity. We recently demonstrated that Δ133p53 promotes DNA double-strand break (DSB) repair by upregulating transcription of the repair genes RAD51, LIG4 and RAD52 in a p53-independent manner. However, Δ133p53 lacks the transactivation domain of full-length p53, and the mechanism by which it exerts transcriptional activity independently of full-length p53 remains unclear. In this report, we describe the accumulation of high levels of both Δ133p53 and p73 (a p53 family member) at 24 h post γ-irradiation (hpi). Δ133p53 can form a complex with p73 upon γ-irradiation. The co-expression of Δ133p53 and p73, but not either protein alone, can significantly promote DNA DSB repair mechanisms, including homologous recombination (HR), non-homologous end joining (NHEJ) and single-strand annealing (SSA). p73 and Δ133p53 act synergistically to promote the expression of RAD51, LIG4 and RAD52 by joining together to bind to region containing a Δ133p53-responsive element (RE) and a p73-RE in the promoters of all three repair genes. In addition to its accumulation at 24 hpi, p73 protein expression also peaks at 4 hpi. The depletion of p73 not only reduces early-stage apoptotic frequency (4–6 hpi), but also significantly increases later-stage DNA DSB accumulation (48 hpi), leading to cell cycle arrest in the G2 phase and, ultimately, cell senescence. In summary, the apoptotic regulator p73 also coordinates with Δ133p53 to promote DNA DSB repair, and the loss of function of p73 in DNA DSB repair may underlie spontaneous and carcinogen-induced tumorigenesis in p73 knockout mice.
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7
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Zhang M, Zhang J, Yan W, Chen X. p73 expression is regulated by ribosomal protein RPL26 through mRNA translation and protein stability. Oncotarget 2018; 7:78255-78268. [PMID: 27825141 PMCID: PMC5346636 DOI: 10.18632/oncotarget.13126] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 10/15/2016] [Indexed: 12/20/2022] Open
Abstract
p73, a p53 family tumor suppressor, is regulated by multiple mechanisms, including transcription and mRNA and protein stability. However, whether p73 expression is regulated via mRNA translation has not been explored. To test this, we examined whether ribosomal protein 26 (RPL26) plays a role in p73 expression. Here, we showed that p73 expression is controlled by RPL26 via protein stability and mRNA translation. To examine whether MDM2 mediates RPL26 to regulate p73 protein stability, we generated multiple MDM2-knockout cell lines by CRISPR-cas9. We found that in the absence of MDM2, the half-life of p73 protein is markedly increased. Interestingly, we also found that RPL26 is still capable of regulating p73 expression, albeit to a lesser extent, in MDM2-KO cells compared to that in isogenic control cells, suggesting that RPL26 regulates p73 expression via multiple mechanisms. Indeed, we found that RPL26 is necessary for efficient assembly of polysomes on p73 mRNA and de novo synthesis of p73 protein. Consistently, we found that RPL26 directly binds to p73 3′ untranslated region (3′UTR) and that RPL26 is necessary for efficient expression of an eGFP reporter that carries p73 3′UTR. We also found that RPL26 interacts with cap-binding protein eIF4E and enhances the association of eIF4E with p73 mRNA, leading to increased p73 mRNA translation. Finally, we showed that knockdown of RPL26 promotes, whereas ectopic expression of RPL26 inhibits, cell growth in a TAp73-dependent manner. Together, our data indicate that RPL26 regulates p73 expression via two distinct mechanisms: protein stability and mRNA translation.
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Affiliation(s)
- Min Zhang
- College of Life Sciences and Technology, Huazhong Agricultural University, Wuhan, China.,Comparative Oncology Laboratory, Schools of Veterinary Medicine and Medicine, University of California at Davis, Davis, CA, USA
| | - Jin Zhang
- Comparative Oncology Laboratory, Schools of Veterinary Medicine and Medicine, University of California at Davis, Davis, CA, USA
| | - Wensheng Yan
- Comparative Oncology Laboratory, Schools of Veterinary Medicine and Medicine, University of California at Davis, Davis, CA, USA
| | - Xinbin Chen
- Comparative Oncology Laboratory, Schools of Veterinary Medicine and Medicine, University of California at Davis, Davis, CA, USA
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8
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Cai Q, Zeng S, Dai X, Wu J, Ma W. miR-504 promotes tumour growth and metastasis in human osteosarcoma by targeting TP53INP1. Oncol Rep 2017; 38:2993-3000. [PMID: 29048685 DOI: 10.3892/or.2017.5983] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 09/04/2017] [Indexed: 11/06/2022] Open
Abstract
An increasing number of studies have demonstrated that microRNAs participate in the development of osteosarcoma by acting as tumour suppressor or tumour-promoting genes. We investigated the role of miR-504 in the growth and metastasis of osteosarcoma. The expression of miR-504 in clinical osteosarcoma samples was higher than that in the adjacent normal tissue and correlated with tumour size and clinical stage. Tumour protein p53-inducible nuclear protein 1 (TP53INP1) was downregulated in the clinical osteosarcoma samples compared with the adjacent normal tissues and was consistently correlated with the clinical stage. The results of dual-luciferase reporter assay and western blot analysis demonstrated that the TP53INP1 gene is a direct target of miR-504. Altogether, the Cell Counting Kit-8 (CCK-8), the colony formation, the flow cytometry and the Transwell assay results demonstrated that miR-504 promoted osteosarcoma cell growth and metastasis in vitro. P73, P21, Bax, cleaved-caspase-3 and secreted protein acidic and rich in cysteine (SPARC) were associated with the suppressive role of miR-504/TP53INP1. The overexpression of miR-504 in osteosarcoma xenografts enhanced the tumour growth and increased the metastatic burden. Collectively, these results revealed that TP53INP1 is a target gene of miR-504 and that miR-504 enhances osteosarcoma growth and promotes distant metastases by targeting TP53INP1. Thus, miR-504/TP53INP1 may be associated with osteosarcoma size and clinical stage.
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Affiliation(s)
- Qingchun Cai
- Department of Orthopaedics, First Affiliated Hospital of the Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Sixiang Zeng
- Department of Orthopaedics, First Affiliated Hospital of the Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Xing Dai
- Department of Orthopaedics, First Affiliated Hospital of the Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Junlong Wu
- Department of Orthopaedics, First Affiliated Hospital of the Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
| | - Wei Ma
- Department of Orthopaedics, First Affiliated Hospital of the Medical College, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
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9
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Hu ZB, Liao XH, Xu ZY, Yang X, Dong C, Jin AM, Lu H. PLK2 phosphorylates and inhibits enriched TAp73 in human osteosarcoma cells. Cancer Med 2015; 5:74-87. [PMID: 26625870 PMCID: PMC4708894 DOI: 10.1002/cam4.558] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/12/2015] [Accepted: 09/14/2015] [Indexed: 01/01/2023] Open
Abstract
TAp73, a member of the p53 tumor suppressor family, can substitute for p53 function, especially in p53‐null and p53‐mutant cells. However, TAp73 enrichment and phosphorylation change its transcriptional activity. Previously, we found that the antitumor function of TAp73 was reactivated by dephosphorylation. Polo‐like kinase 2 (PLK2) plays an important role in bone development. Using a biological information database and phosphorylation prediction software, we hypothesized that PLK2 phosphorylates TAp73 and inhibits TAp73 function in osteosarcomas. Actually,we determined that PLK2 physically binds to and phosphorylates TAp73 when TAp73 protein abundance is up‐regulated by cisplatin. PLK2‐phosphorylated TAp73 at residue Ser48 within the TA domain; phosphorylation of TAp73 was abolished by mutating this residue. Moreover, PLK2 inhibition combined with cisplatin treatment in osteosarcoma Saos2 cells up‐regulated p21 and puma mRNA expression to a greater extent than cisplatin treatment alone. Inhibiting PLK2 in TAp73‐enriched Saos2 cells resulted in inhibited cell proliferation, increased apoptosis, G1 phase arrest, and decreased cell invasion. However, these changes did not occur in TAp73 knockdown Saos2 cells. In conclusion, these findings reveal a novel PLK2 function in the phosphorylation of TAp73, which prevents TAp73 activity in osteosarcoma cells. Thereby, this research provides an insight into the clinical treatment of malignant tumors overexpressing TAp73.
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Affiliation(s)
- Zheng Bo Hu
- Department of Orthopedics, Zhu Jiang Hospital of Southern Medical University, Guangzhou, Guangdong, 510280, China
| | - Xiao Hong Liao
- The State Key Laboratory of Respiratory Diseases, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, 510280, China
| | - Zun Ying Xu
- Department of Orthopedics, Zhu Jiang Hospital of Southern Medical University, Guangzhou, Guangdong, 510280, China
| | - Xiao Yang
- Department of Orthopedics, Zhu Jiang Hospital of Southern Medical University, Guangzhou, Guangdong, 510280, China
| | - Chao Dong
- Department of Orthopedics, Zhu Jiang Hospital of Southern Medical University, Guangzhou, Guangdong, 510280, China
| | - An Min Jin
- Department of Orthopedics, Zhu Jiang Hospital of Southern Medical University, Guangzhou, Guangdong, 510280, China
| | - Hai Lu
- Department of Orthopaedics, The Third Affiliated Hospital of Southern Medical University, Academy of Orthopedics, Guangzhou, Guangdong, 510665, China
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10
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Hu Z, Xu Z, Liao X, Yang X, Dong C, Luk K, Jin A, Lu H. Polo-like kinase 2 acting as a promoter in human tumor cells with an abundance of TAp73. Onco Targets Ther 2015; 8:3475-88. [PMID: 26640387 PMCID: PMC4662374 DOI: 10.2147/ott.s90302] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Background TAp73, a member of the p53 tumor suppressor family, is frequently overexpressed in malignant tumors in humans. TAp73 abundance and phosphorylation modification result in variations in transcriptional activity. In a previous study, we found that the antitumor function of TAp73 was reactivated by dephosphorylation in head and neck squamous cell carcinomas. Polo-like kinase 2 (PLK2) displayed a close relationship with the p53 family in affecting the fate of cells. Herein, we investigate the hypothesis that PLK2 phosphorylates TAp73 and inhibits TAp73 function. Materials and methods Head and neck squamous cell carcinoma cell lines and osteosarcoma cell lines were used as natural models of the different expression levels of TAp73. Phosphorylation predictor software Scansite 3.0 and the predictor GPS-polo 1.0 were used to analyze the phosphorylation sites. Coimmunoprecipitation, phosphor-tag Western blot, metabolic labeling, and indirect immunofluorescence assays were used to determine the interactions between PLK2 and TAp73. TAp73 activity was assessed by Western blot and reverse transcription polymerase chain reaction, which we used to detect P21 and PUMA, both downstream genes of TAp73. The physiological effects of PLK2 cross talk with TAp73 on cell cycle progress and apoptosis were observed by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assays. Results PLK2 binds to and phosphorylates TAp73. PLK2 phosphorylates TAp73 at residue Ser48 and prohibits TAp73 translocation to the nucleus. Additionally, PLK2 inhibition combined with a DNA-damaging drug upregulated p21 and PUMA mRNA expression to a greater extent than DNA-damaging drug treatment alone. Inhibiting PLK2 in TAp73-enriched cells strengthened the effects of the DNA-damaging drug on both G1 phase arrest and apoptosis. Pretreatment with TAp73-siRNA weakened these effects. Conclusion These findings reveal a novel PLK2 function (catalyzed phosphorylation of TAp73) which suppresses TAp73 functions. PLK2 promotes the survival of human tumor cells, a novel insight into the workings of malignant tumors characterized by TAp73 overexpression, and one that could speed the development of therapies.
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Affiliation(s)
- ZhengBo Hu
- Department of Orthopedics, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - ZunYing Xu
- Department of Orthopedics, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - XiaoHong Liao
- The State Key Laboratory of Respiratory Diseases, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Xiao Yang
- Department of Orthopedics, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Cao Dong
- Department of Orthopedics, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - KuaDi Luk
- Department of Orthopedics and Traumatology, The University of Hong Kong, Hong Kong, SAR, People's Republic of China
| | - AnMin Jin
- Department of Orthopedics, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Hai Lu
- Department of Orthopedics, the Third Affiliated Hospital of the Southern Medical University, Guangzhou, Guangdong, People's Republic of China ; Academy of Orthopedics, Guangdong Province, People's Republic of China
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Zhou X, Hao Q, Zhang Q, Liao JM, Ke JW, Liao P, Cao B, Lu H. Ribosomal proteins L11 and L5 activate TAp73 by overcoming MDM2 inhibition. Cell Death Differ 2014; 22:755-66. [PMID: 25301064 DOI: 10.1038/cdd.2014.167] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 09/09/2014] [Accepted: 09/10/2014] [Indexed: 01/08/2023] Open
Abstract
Over the past decade, a number of ribosomal proteins (RPs) have been found to have a role in activating the tumor suppressor p53 by directly binding to MDM2 and impeding its activity toward p53. Herein, we report that RPL5 and RPL11 can also enhance the transcriptional activity of a p53 homolog TAp73, but through a distinct mechanism. Interestingly, even though RPL5 and RPL11 were not shown to bind to p53, they were able to directly associate with the transactivation domain of TAp73 independently of MDM2 in response to RS. This association led to perturbation of the MDM2-TAp73 interaction, consequently preventing MDM2 from its association with TAp73 target gene promoters. Furthermore, ectopic expression of RPL5 or RPL11 markedly induced TAp73 transcriptional activity by antagonizing MDM2 suppression. Conversely, ablation of either of the RPs compromised TAp73 transcriptional activity, as evident by the reduction of p21 and Puma expression, in response to 5-fluorouracil (5-FU). Consistently, overexpression of RPL5 or RPL11 enhanced, but knockdown of either of them hampered, TAp73-mediated apoptosis. Intriguingly, simultaneous knockdown of TAp73 and either of the RPs was required for rescuing the 5-FU-triggered S-phase arrest of p53-null tumor cells. These results demonstrate a novel mechanism underlying the inhibition of tumor cell proliferation and growth by these two RPs via TAp73 activation.
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Affiliation(s)
- X Zhou
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
| | - Q Hao
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
| | - Q Zhang
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
| | - J-M Liao
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
| | - J-W Ke
- 1] Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA [2] Department of Laboratory Medicine; Jiangxi Children's Hospital, Nanchang, Jiangxi, China
| | - P Liao
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
| | - B Cao
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
| | - H Lu
- Department of Biochemistry & Molecular Biology, Tulane Cancer Center; Tulane University School of Medicine; New Orleans, Louisiana, USA
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12
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Wang M, Guo L, Wu Q, Zeng T, Lin Q, Qiao Y, Wang Q, Liu M, Zhang X, Ren L, Zhang S, Pei Y, Yin Z, Ding F, Wang HR. ATR/Chk1/Smurf1 pathway determines cell fate after DNA damage by controlling RhoB abundance. Nat Commun 2014; 5:4901. [PMID: 25249323 DOI: 10.1038/ncomms5901] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 08/02/2014] [Indexed: 11/09/2022] Open
Abstract
ATM- and RAD3-related (ATR)/Chk1 and ataxia-telangiectasia mutated (ATM)/Chk2 signalling pathways play critical roles in the DNA damage response. Here we report that the E3 ubiquitin ligase Smurf1 determines cell apoptosis rates downstream of DNA damage-induced ATR/Chk1 signalling by promoting degradation of RhoB, a small GTPase recognized as tumour suppressor by promoting death of transformed cells. We show that Smurf1 targets RhoB for degradation to control its abundance in the basal state. DNA damage caused by ultraviolet light or the alkylating agent methyl methanesulphonate strongly activates Chk1, leading to phosphorylation of Smurf1 that enhances its self-degradation, hence resulting in a RhoB accumulation to promote apoptosis. Suppressing RhoB levels by overexpressing Smurf1 or blocking Chk1-dependent Smurf1 self-degradation significantly inhibits apoptosis. Hence, our study unravels a novel ATR/Chk1/Smurf1/RhoB pathway that determines cell fate after DNA damage, and raises the possibility that aberrant upregulation of Smurf1 promotes tumorigenesis by excessively targeting RhoB for degradation.
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Affiliation(s)
- Meilin Wang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Lei Guo
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Qingang Wu
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Taoling Zeng
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Qi Lin
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Yikai Qiao
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Qun Wang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Mingdong Liu
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Xin Zhang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Lan Ren
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Sheng Zhang
- Department of Surgery, Zhongshan Hospital, Xiamen University, Xiamen, Fujian 361005, China
| | - Yihua Pei
- Central Laboratory, Zhongshan Hospital, Xiamen University, Xiamen, Fujian 361005, China
| | - Zhenyu Yin
- Department of Surgery, Zhongshan Hospital, Xiamen University, Xiamen, Fujian 361005, China
| | - Feng Ding
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China
| | - Hong-Rui Wang
- 1] State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361102, China [2] Shenzhen Research Institute of Xiamen University, Shenzhen, Guangdong 518057, China
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13
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Petsalaki E, Dandoulaki M, Morrice N, Zachos G. Chk1 protects against chromatin bridges by constitutively phosphorylating BLM serine 502 to inhibit BLM degradation. J Cell Sci 2014; 127:3902-8. [PMID: 25015292 DOI: 10.1242/jcs.155176] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Chromatin bridges represent incompletely segregated chromosomal DNA connecting the anaphase poles and can result in chromosome breakage. The Bloom's syndrome protein helicase (BLM, also known as BLMH) suppresses formation of chromatin bridges. Here, we show that cells deficient in checkpoint kinase 1 (Chk1, also known as CHEK1) exhibit higher frequency of chromatin bridges and reduced BLM protein levels compared to controls. Chk1 inhibition leads to BLM ubiquitylation and proteasomal degradation during interphase. Furthermore, Chk1 constitutively phosphorylates human BLM at serine 502 (S502) and phosphorylated BLM localises to chromatin bridges. Mutation of S502 to a non-phosphorylatable alanine residue (BLM-S502A) reduces the stability of BLM, whereas expression of a phospho-mimicking BLM-S502D, in which S502 is mutated to aspartic acid, stabilises BLM and prevents chromatin bridges in Chk1-deficient cells. In addition, wild-type but not BLM-S502D associates with cullin 3, and cullin 3 depletion rescues BLM accumulation and localisation to chromatin bridges after Chk1 inhibition. We propose that Chk1 phosphorylates BLM-S502 to inhibit cullin-3-mediated BLM degradation during interphase. These results suggest that Chk1 prevents deleterious anaphase bridges by stabilising BLM.
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Affiliation(s)
- Eleni Petsalaki
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion 70013, Greece
| | - Maria Dandoulaki
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion 70013, Greece
| | - Nick Morrice
- Beatson Institute for Cancer Research, Glasgow G61 1BD, UK
| | - George Zachos
- Department of Biology, University of Crete, Vassilika Vouton, Heraklion 70013, Greece
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14
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Costanzo A, Pediconi N, Narcisi A, Guerrieri F, Belloni L, Fausti F, Botti E, Levrero M. TP63 and TP73 in cancer, an unresolved "family" puzzle of complexity, redundancy and hierarchy. FEBS Lett 2014; 588:2590-9. [PMID: 24983500 DOI: 10.1016/j.febslet.2014.06.047] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 06/16/2014] [Accepted: 06/16/2014] [Indexed: 12/24/2022]
Abstract
TP53 belongs to a small gene family that includes, in mammals, two additional paralogs, TP63 and TP73. The p63 and p73 proteins are structurally and functionally similar to p53 and their activity as transcription factors is regulated by a wide repertoire of shared and unique post-translational modifications and interactions with regulatory cofactors. p63 and p73 have important functions in embryonic development and differentiation but are also involved in tumor suppression. The biology of p63 and p73 is complex since both TP63 and TP73 genes are transcribed into a variety of different isoforms that give rise to proteins with antagonistic properties, the TA-isoforms that act as tumor-suppressors and DN-isoforms that behave as proto-oncogenes. The p53 family as a whole behaves as a signaling "network" that integrates developmental, metabolic and stress signals to control cell metabolism, differentiation, longevity, proliferation and death. Despite the progress of our knowledge, the unresolved puzzle of complexity, redundancy and hierarchy in the p53 family continues to represent a formidable challenge.
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Affiliation(s)
- Antonio Costanzo
- Dermatology Unit, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sapienza University of Rome, Italy
| | - Natalia Pediconi
- Laboratory of Molecular Oncology, Department of Molecular Medicine, Sapienza University of Rome, Italy; Center for Life Nanosciences (CNLS) - IIT/Sapienza, Rome, Italy
| | - Alessandra Narcisi
- Dermatology Unit, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sapienza University of Rome, Italy
| | - Francesca Guerrieri
- Center for Life Nanosciences (CNLS) - IIT/Sapienza, Rome, Italy; Laboratory of Gene Expression, Department of Internal Medicine (DMISM), Sapienza University of Rome, Italy
| | - Laura Belloni
- Center for Life Nanosciences (CNLS) - IIT/Sapienza, Rome, Italy; Laboratory of Gene Expression, Department of Internal Medicine (DMISM), Sapienza University of Rome, Italy
| | - Francesca Fausti
- Dermatology Unit, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sapienza University of Rome, Italy
| | - Elisabetta Botti
- Dermatology Unit, Department of Neuroscience, Mental Health and Sensory Organs (NESMOS), Sapienza University of Rome, Italy
| | - Massimo Levrero
- Center for Life Nanosciences (CNLS) - IIT/Sapienza, Rome, Italy; Laboratory of Gene Expression, Department of Internal Medicine (DMISM), Sapienza University of Rome, Italy.
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15
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AMPK couples p73 with p53 in cell fate decision. Cell Death Differ 2014; 21:1451-9. [PMID: 24874608 DOI: 10.1038/cdd.2014.60] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 03/16/2014] [Accepted: 03/28/2014] [Indexed: 12/14/2022] Open
Abstract
The p53 family of proteins has an important role in determining cell fate in response to different types of stress, such as DNA damage, hypoxia, or oncogenic stress. In recent years, p53 has also been shown to respond to metabolic stress, and to be induced by the AMP-activated protein kinase (AMPK), a central cellular energy sensor. A bioinformatic analysis revealed three putative AMPK phopshorylation sites in p73, a p53 tumor suppressor paralog. In vitro and in vivo assays confirmed that AMPK phosphorylates p73 on a novel residue, S426. Following specific pharmacologic stimulation of AMPK in cells, p73 protein half-life was prolonged leading to p73 accumulation in the nucleus. We show that p73 escaped the E3 ligase Itch resulting in reduced p73 ubiquitination and proteasomal degradation. Furthermore, chronic activation of AMPK led to apoptosis that was p73 dependent, but only in p53-expressing cells. Surprisingly, we found that p73 was required for p53 stabilization and accumulation under AMPK activation, but was dispensable under DNA damage. Our findings couple p73 with p53 in determining cell fate under AMPK-induced metabolic stress.
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16
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Park GB, Choi Y, Kim YS, Lee HK, Kim D, Hur DY. Silencing of PKCη induces cycle arrest of EBV(+) B lymphoma cells by upregulating expression of p38-MAPK/TAp73/GADD45α and increases susceptibility to chemotherapeutic agents. Cancer Lett 2014; 350:5-14. [PMID: 24784886 DOI: 10.1016/j.canlet.2014.04.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 03/28/2014] [Accepted: 04/21/2014] [Indexed: 01/01/2023]
Abstract
PKCη is involved in proliferation, differentiation, and drug resistance. However, PKCη function in EBV(+) B lymphoma remains poorly understood. Gene silencing of PKCη through siRNA knockdown inhibited cellular proliferation, induced cell cycle arrest in G0/G1 and G2/M phases, and sensitized cells to chemotherapeutic drugs. Upon PKCη knockdown, expression levels of p21, GADD45α, and TAp73 were all increased, whereas expression levels of CDK2, CDK4, CDK6, cyclin E, cyclin B1, and cdc2 were all downregulated. PKCη silencing also activated p38-MAPK, which in turn contributed to the expression of cell cycle arrest-related molecules. These results suggest that siRNA-mediated silencing of PKCη can be a potent tool to complement existing chemotherapy regimens for treating EBV(+) B lymphoma.
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Affiliation(s)
- Ga Bin Park
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Yunock Choi
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Yeong-Seok Kim
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Hyun-Kyung Lee
- Department of Internal Medicine, Inje University Busan Paik Hospital, Busan 614-735, Republic of Korea
| | - Daejin Kim
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Dae Young Hur
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea.
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17
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Park GB, Kim YS, Kim D, Kim S, Lee HK, Cho DH, Lee WJ, Hur DY. Melphalan-induced apoptosis of EBV-transformed B cells through upregulation of TAp73 and XAF1 and nuclear import of XPA. THE JOURNAL OF IMMUNOLOGY 2013; 191:6281-91. [PMID: 24249729 DOI: 10.4049/jimmunol.1203442] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Melphalan (Mel) is widely used to treat patients with hematologic cancer, including multiple myeloma, but its mechanism of action in EBV-transformed B cells is poorly described. In this study, we demonstrate a novel mechanism by which transcriptionally active p73 (TAp73) induces translocation of X-linked inhibitor of apoptosis protein-associated factor 1 (XAF1) and xeroderma pigmentosum group A (XPA) during apoptosis caused by Mel treatment. We observed that Mel induced significant generation of reactive oxygen species (ROS) and subsequent apoptosis, as well as an early phosphorylation of p38 MAPK that preceded expression of the mitochondria membrane potential disruption-related molecules and the cleavage of caspases. In particular, Mel led to upregulation of TAp73, XAF1, and Puma and induced XPA nuclear import and translocation of Bax into mitochondria. Mel-induced apoptosis was inhibited by pretreatment with the ROS scavenger 4-amino-2,4-pyrrolidine-dicarboxylic acid (APDC) and the p38 MAPK inhibitor SB203580. We supposed that ROS generation might be the first event in Mel-induced apoptosis, because APDC blocked the increase in ROS, p38 MAPK, and TAp73, but SB203580 did not block ROS generation. Moreover, Mel elicited activation of ATR, and APDC inhibited phosphorylation of ATR but not SB203580. APDC and SB203580 completely blocked XPA and Bax translocation. We conclude that Mel promotes TAp73-mediated XAF1 and Puma expression via ROS generation and ATR/p38 MAPK pathway activation, thereby triggering apoptosis. Our results provide evidence of a novel alternate regulatory mechanism of TAp73 and reveal that Mel may be a therapeutic drug for curing EBV-related malignancies.
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Affiliation(s)
- Ga Bin Park
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
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18
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Zhang Y, Hunter T. Roles of Chk1 in cell biology and cancer therapy. Int J Cancer 2013; 134:1013-23. [PMID: 23613359 DOI: 10.1002/ijc.28226] [Citation(s) in RCA: 302] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/11/2013] [Indexed: 01/05/2023]
Abstract
The evolutionally conserved DNA damage response (DDR) and cell cycle checkpoints preserve genome integrity. Central to these genome surveillance pathways is a protein kinase, Chk1. DNA damage induces activation of Chk1, which then transduces the checkpoint signal and facilitates cell cycle arrest and DNA damage repair. Significant progress has been made recently toward our understanding of Chk1 regulation and its implications in cancer etiology and therapy. Specifically, a model that involves both spatiotemporal and conformational changes of proteins has been proposed for Chk1 activation. Further, emerging evidence suggests that Chk1 does not appear to be a tumor suppressor; instead, it promotes tumor growth and may contribute to anticancer therapy resistance. Recent data from our laboratory suggest that activating, but not inhibiting, Chk1 in the absence of chemotherapy might represent an innovative approach to suppress tumor growth. These findings suggest unique regulation of Chk1 in cell biology and cancer etiology, pointing to novel strategies for targeting Chk1 in cancer therapy.
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Affiliation(s)
- Youwei Zhang
- Department of Pharmacology, Case Comprehensive Cancer Center, School of Medicine, Case Western Reserve University, Cleveland, OH
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19
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Mendoza J, Sekiya M, Taniguchi T, Iijima KM, Wang R, Ando K. Global analysis of phosphorylation of tau by the checkpoint kinases Chk1 and Chk2 in vitro. J Proteome Res 2013; 12:2654-65. [PMID: 23550703 DOI: 10.1021/pr400008f] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Hyperphosphorylation of microtubule-associated protein tau is thought to contribute to Alzheimer's disease (AD) pathogenesis. We previously showed that DNA damage-activated cell cycle checkpoint kinases Chk1 and Chk2 phosphorylate tau at an AD-related site and enhance tau toxicity, suggesting potential roles of these kinases in AD. The purpose of this study is to systematically identify which sites in tau are directly phosphorylated by Chk1 and Chk2. Using recombinant human tau phosphorylated by Chk1 and Chk2 in vitro, we first analyzed tau phosphorylation at the AD-related sites by Western blot with phospho-tau-specific antibodies. Second, to globally identify phosphorylated sites in tau, liquid chromatography-tandem mass spectrometry (LC-MS(3)) was employed. These systematic analyses identified a total of 27 Ser/Thr residues as Chk1- or Chk2- target sites. None of them were proline-directed kinase targets. Many of these sites are located within the microtubule-binding domain and C-terminal domain, whose phosphorylation has been shown to reduce tau binding to microtubules and/or has been implicated in tau toxicity. Among these 27 sites, 13 sites have been identified to be phosphorylated in AD brains. Since DNA damage is accumulated in diseased brains, Chk1 and Chk2 may be involved in tau phosphorylation and toxicity in AD pathogenesis.
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Affiliation(s)
- Jhoana Mendoza
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, 1425 Madison Avenue, Box 1498, New York, New York 10029, United States
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20
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Patil M, Pabla N, Dong Z. Checkpoint kinase 1 in DNA damage response and cell cycle regulation. Cell Mol Life Sci 2013; 70:4009-21. [PMID: 23508805 DOI: 10.1007/s00018-013-1307-3] [Citation(s) in RCA: 190] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 01/28/2013] [Accepted: 02/18/2013] [Indexed: 12/19/2022]
Abstract
Originally identified as a mediator of DNA damage response (DDR), checkpoint kinase 1 (Chk1) has a broader role in checkpoint activation in DDR and normal cell cycle regulation. Chk1 activation involves phosphorylation at conserved sites. However, recent work has identified a splice variant of Chk1, which may regulate Chk1 in both DDR and normal cell cycle via molecular interaction. Upon activation, Chk1 phosphorylates a variety of substrate proteins, resulting in the activation of DNA damage checkpoints, cell cycle arrest, DNA repair, and/or cell death. Chk1 and its related signaling may be an effective therapeutic target in diseases such as cancer.
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Affiliation(s)
- Mallikarjun Patil
- Department of Cellular Biology and Anatomy, Georgia Regents University and Charlie Norwood VA Medical Center, 1459 Laney Walker Blvd., Augusta, GA, 30912, USA
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21
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Ho H, Aruri J, Kapadia R, Mehr H, White MA, Ganesan AK. RhoJ regulates melanoma chemoresistance by suppressing pathways that sense DNA damage. Cancer Res 2012; 72:5516-28. [PMID: 22971344 DOI: 10.1158/0008-5472.can-12-0775] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Melanomas resist conventional chemotherapeutics, in part, through intrinsic disrespect of apoptotic checkpoint activation. In this study, using an unbiased genome-wide RNA interference screen, we identified RhoJ and its effector PAK1, as key modulators of melanoma cell sensitivity to DNA damage. We find that RhoJ activates PAK1 in response to drug-induced DNA damage, which then uncouples ATR from its downstream effectors, ultimately resulting in a blunted DNA damage response (DDR). In addition, ATR suppression leads to the decreased phosphorylation of ATF2 and consequent increased expression of the melanocyte survival gene Sox10 resulting in a higher DDR threshold required to engage melanoma cell death. In the setting of normal melanocyte behavior, this regulatory relationship may facilitate appropriate epidermal melanization in response to UV-induced DNA damage. However, pathologic pathway activation during oncogenic transformation produces a tumor that is intrinsically resistant to chemotherapy and has the propensity to accumulate additional mutations. These findings identify DNA damage agents and pharmacologic inhibitors of RhoJ/PAK1 as novel synergistic agents that can be used to treat melanomas that are resistant to conventional chemotherapies.
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Affiliation(s)
- Hsiang Ho
- Department of Dermatology, University of California at Irvine, Irvine, California 92697, USA
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22
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Abstract
The transcription factor p73 is a member of the p53 family that can be expressed as at least 24 different isoforms with pro- or anti-apoptotic attributes. The TAp73 isoforms are expressed from an upstream promoter and are regarded as bona fide tumor suppressors; they can induce cell cycle arrest/apoptosis and protect against genomic instability. On the other hand, ΔNp73 isoforms lack the N-terminus transactivation domain; hence, cannot induce the expression of pro-apoptotic genes, but still can oligomerize with TAp73 or p53 to block their transcriptional activities. Therefore, the ratio of TAp73 isoforms to ΔNp73 isoforms is critical for the quality of the response to a genomic insult and needs to be delicately regulated at both transcriptional and post-translational level. In this review, we will summarize the current knowledge on the post-translational regulatory pathways involved to keep p73 protein under control. A comprehensive understanding of p73 post-translational modifications will be extremely useful for the development of new strategies for treating and preventing cancer.
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23
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Bisso A, Collavin L, Del Sal G. p73 as a pharmaceutical target for cancer therapy. Curr Pharm Des 2011; 17:578-90. [PMID: 21391908 PMCID: PMC3267157 DOI: 10.2174/138161211795222667] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 03/03/2011] [Indexed: 02/07/2023]
Abstract
About half of all human tumors contain an inactivating mutation of p53, while in the remaining tumors, the p53 pathway is frequently abrogated by alterations of other components of its signaling pathway. In humans, the p53 tumor suppressor is part of a small gene family that includes two other members, p73 and p63, structurally and functionally related to p53. Accumulating evidences indicate that all p53-family proteins function as molecular hubs of a highly interconnected signaling network that coordinates cell proliferation, differentiation and death in response to physiological inputs and oncogenic stress. Therefore, not only the p53-pathway but the entire “p53-family pathway” is a primary target for cancer drug development. In particular, the p53-related protein p73 has a crucial role in determining cellular responses to chemotherapy, and can vicariate p53 functions in triggering cell death after DNA damage in multiple experimental models. The biology and regulation of p73 is complex, since the TP73 gene incorporates both tumor-suppressive and proto-oncogenic functions. However, the p73 gene is rarely mutated in tumors, so appropriate pharmacological manipulation of the p73 pathway is a very promising approach for cancer therapy. Here we provide an overview of the principal mechanism of p73 regulation, and describe several examples of pharmacological tools that can induce p73 accumulation and function by acting on upstream p73 modulators or displacing inhibitory p73 interactors. A better understanding of how the p73 pathway works is mandatory to discover additional players intervening in this pathway and has important implications for the improvement of cancer treatment with the development of new molecules or with the reposition of currently available drugs.
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Affiliation(s)
- Andrea Bisso
- Laboratorio Nazionale CIB, AREA Science Park, Padriciano 99, Trieste, TS 34149, Italy
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24
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IkappaB kinase beta promotes cell survival by antagonizing p53 functions through DeltaNp73alpha phosphorylation and stabilization. Mol Cell Biol 2011; 31:2210-26. [PMID: 21482671 DOI: 10.1128/mcb.00964-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
ΔNp73α, a dominant-negative inhibitor of p53 and p73, exhibits antiapoptotic and transforming activity in in vitro models and is often found to be upregulated in human cancers. The mechanisms involved in the regulation of ΔNp73α protein levels in normal and cancer cells are poorly characterized. Here, we show that that IκB kinase beta (IKKβ) increases ΔNp73α protein stability independently of its ability to activate NF-κB. IKKβ associates with and phosphorylates ΔNp73α at serine 422 (S422), leading to its accumulation in the nucleus, where it binds and represses several p53-regulated genes. S422A mutation in ΔNp73α abolished IKKβ-mediated stabilization and inhibition of p53-regulated gene expression. Inhibition of IKKβ activity by chemical inhibitors, overexpression of dominant-negative mutants, or gene silencing by siRNA also resulted in ΔNp73α destabilization, which under these conditions was rapidly translocated into the cytoplasm and degraded by a calpain-mediated mechanism. We also present evidence for the IKKβ and ΔNp73α cross talk in cancer-derived cell lines and primary cancers. Our data unveil a new mechanism involved in the regulation of the p73 and p53 network.
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25
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Ozaki T, Kubo N, Nakagawara A. p73-Binding Partners and Their Functional Significance. INTERNATIONAL JOURNAL OF PROTEOMICS 2011; 2010:283863. [PMID: 22084676 PMCID: PMC3195385 DOI: 10.1155/2010/283863] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 10/26/2010] [Indexed: 12/21/2022]
Abstract
p73 is one of the tumor-suppressor p53 family of nuclear transcription factor. As expected from the structural similarity between p53 and p73, p73 has a tumor-suppressive function. However, p73 was rarely mutated in human primary tumors. Under normal physiological conditions, p73 is kept at an extremely low level to allow cells normal growth. In response to a certain subset of DNA damages, p73 is induced dramatically and transactivates an overlapping set of p53-target genes implicated in the promotion of cell cycle arrest and/or apoptotic cell death. Cells undergo cell cycle arrest and/or apoptotic cell death depending on the type and strength of DNA damages. p73 is regulated largely through the posttranslational modifications such as phosphorylation and acetylation. These chemical modifications are tightly linked to direct protein-protein interactions. In the present paper, the authors describe the functional significance of the protein-protein interactions in the regulation of proapoptotic p73.
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Affiliation(s)
- Toshinori Ozaki
- Laboratory of Anti-tumor Research, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan
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26
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Ozaki T, Nakagawara A. p53: the attractive tumor suppressor in the cancer research field. J Biomed Biotechnol 2010; 2011:603925. [PMID: 21188172 PMCID: PMC3004423 DOI: 10.1155/2011/603925] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 10/07/2010] [Indexed: 01/16/2023] Open
Abstract
p53 is one of the most studied tumor suppressors in the cancer research field. Of note, over 50% of human tumors carry loss of function mutations, and thus p53 has been considered to be a classical Knudson-type tumor suppressor. From the functional point of view, p53 is a nuclear transcription factor to transactivate a variety of its target genes implicated in the induction of cell cycle arrest, DNA repair, and apoptotic cell death. In response to cellular stresses such as DNA damage, p53 is activated and promotes cell cycle arrest followed by the replacement of DNA lesions and/or apoptotic cell death. Therefore, p53 is able to maintain the genomic integrity to prevent the accumulation of genetic alterations, and thus stands at a crossroad between cell survival and cell death. In this paper, we describe a variety of molecular mechanisms behind the regulation of p53.
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Affiliation(s)
- Toshinori Ozaki
- Laboratory of Anti-Tumor Research, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan
| | - Akira Nakagawara
- Laboratory of Innovative Cancer Therapeutics, Chiba Cancer Center Research Institute, 666-2 Nitona, Chuoh-ku, Chiba 260-8717, Japan
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27
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Chakraborty J, Banerjee S, Ray P, Hossain DMS, Bhattacharyya S, Adhikary A, Chattopadhyay S, Das T, Sa G. Gain of cellular adaptation due to prolonged p53 impairment leads to functional switchover from p53 to p73 during DNA damage in acute myeloid leukemia cells. J Biol Chem 2010; 285:33104-33112. [PMID: 20675383 PMCID: PMC2963387 DOI: 10.1074/jbc.m110.122705] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 06/15/2010] [Indexed: 12/29/2022] Open
Abstract
Tumor suppressor p53 plays the central role in regulating apoptosis in response to genotoxic stress. From an evolutionary perspective, the activity of p53 has to be backed up by other protein(s) in case of any functional impairment of this protein, to trigger DNA damage-induced apoptosis in cancer cells. We adopted multiple experimental approaches to demonstrate that in p53-impaired cancer cells, DNA damage caused accumulation of p53 paralogue p73 via Chk-1 that strongly impacted Bax expression and p53-independent apoptosis. On the contrary, when p53 function was restored by ectopic expression, Chk-2 induced p53 accumulation that in turn overshadowed p73 activity, suggesting an antagonistic interaction between p53 family members. To understand such interaction better, p53-expressing cells were impaired differentially for p53 activity. In wild-type p53-expressing cancer cells that were silenced for p53 for several generations, p73 was activated, whereas no such trend was observed when p53 was transiently silenced. Prolonged p53 interference, even in functional p53 settings, therefore, leads to the "gain of cellular adaptation" in a way that alters the cellular microenvironment in favor of p73 activation by altering p73-regulatory proteins, e.g. Chk1 activation and dominant negative p73 down-regulation. These findings not only unveil a hitherto unexplained mechanism underlying the functional switchover from p53 to p73, but also validate p73 as a promising and potential target for cancer therapy in the absence of functional p53.
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Affiliation(s)
- Juni Chakraborty
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Shuvomoy Banerjee
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Pallab Ray
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Dewan Md Sakib Hossain
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Sankar Bhattacharyya
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Arghya Adhikary
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Sreya Chattopadhyay
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Tanya Das
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India
| | - Gaurisankar Sa
- From the Division of Molecular Medicine, Bose Institute, P-1/12 CIT Scheme VII M, Kolkata 700 054, India.
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28
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Bruno T, Desantis A, Bossi G, Di Agostino S, Sorino C, De Nicola F, Iezzi S, Franchitto A, Benassi B, Galanti S, La Rosa F, Floridi A, Bellacosa A, Passananti C, Blandino G, Fanciulli M. Che-1 promotes tumor cell survival by sustaining mutant p53 transcription and inhibiting DNA damage response activation. Cancer Cell 2010; 18:122-34. [PMID: 20708154 DOI: 10.1016/j.ccr.2010.05.027] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 04/06/2010] [Accepted: 06/23/2010] [Indexed: 11/25/2022]
Abstract
Che-1 is a RNA polymerase II binding protein involved in the regulation of gene transcription and, in response to DNA damage, promotes p53 transcription. In this study, we investigated whether Che-1 regulates mutant p53 expression. We found that Che-1 is required for sustaining mutant p53 expression in several cancer cell lines, and that Che-1 depletion by siRNA induces apoptosis both in vitro and in vivo. Notably, loss of Che-1 activates DNA damage checkpoint response and induces transactivation of p73. Therefore, these findings underline the important role that Che-1 has in survival of cells expressing mutant p53.
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Affiliation(s)
- Tiziana Bruno
- Department of Therapeutic Programs Development, Regina Elena Cancer Institute, Rome, Italy
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29
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Wolter J, Angelini P, Irwin M. p53 family: Therapeutic targets in neuroblastoma. Future Oncol 2010; 6:429-44. [PMID: 20222799 DOI: 10.2217/fon.09.176] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Survival rates for metastatic neuroblastoma remain poor, despite significant increase in the intensity of therapy. Although it represents approximately 7% of pediatric cancer, neuroblastoma accounts for approximately 15% of childhood cancer deaths. Thus, novel approaches to enhance neuroblastoma chemotherapy sensitivity and prevent or bypass chemoresistance are required. Disruption of the p53 pathway is a common mechanism leading to defects in apoptosis in cancer cells. Increasing evidence suggests that the p53 pathway may be inactivated in neuroblastoma. Inactivation of the p53 pathway occurs most commonly at the time of relapse, and probably contributes to chemoresistance. The p53 family proteins, p73 and p63, can also induce apoptosis, and early studies suggest that p73 may be important in neuroblastoma pathogenesis and response to treatment. This article focuses on current therapies and novel drugs targeting p53 and p73 signaling pathways in neuroblastoma. Understanding the balance between the p53 family proteins in neuroblastoma and how their expression and activity are regulated will hopefully lead to the discovery of agents that target these pathways to induce neuroblastoma cell death, alone or in combination with chemotherapies.
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Affiliation(s)
- Jennifer Wolter
- Department of Medical Biophysics, University of Toronto, Hospital for Sick Children, ON, Canada
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30
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Collavin L, Lunardi A, Del Sal G. p53-family proteins and their regulators: hubs and spokes in tumor suppression. Cell Death Differ 2010; 17:901-11. [PMID: 20379196 DOI: 10.1038/cdd.2010.35] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The tumor suppressor p53 is a central hub in a molecular network controlling cell proliferation and death in response to potentially oncogenic conditions, and a wide array of covalent modifications and protein interactions modulate the nuclear and cytoplasmic activities of p53. The p53 relatives, p73 and p63, are entangled in the same regulatory network, being subject at least in part to the same modifications and interactions that convey signals on p53, and actively contributing to the resulting cellular output. The emerging picture is that of an interconnected pathway, in which all p53-family proteins are involved in the response to oncogenic stress and physiological inputs. Therefore, common and specific interactors of p53-family proteins can have a wide effect on function and dysfunction of this pathway. Many years of research have uncovered an impressive number of p53-interacting proteins, but much less is known about protein interactions of p63 and p73. Yet, many interactors may be shared by multiple p53-family proteins, with similar or different effects. In this study we review shared interactors of p53-family proteins with the aim to encourage research into this field; this knowledge promises to unveil regulatory elements that could be targeted by a new generation of molecules, and allow more efficient use of currently available drugs for cancer treatment.
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Affiliation(s)
- L Collavin
- Laboratorio Nazionale CIB, AREA Science Park, Trieste, Italy
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31
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Abstract
Emerging evidence indicates that suppression of protein kinase C (PKC) renders the susceptibility of cells expressing mutated ras to apoptosis. Although the effort has been made, the underlying molecular mechanisms are not fully understood. In this study, using small hairpin RNAs (shRNAs) or PKC inhibitor, we show that the concurrent suppression of PKC-alpha and beta induces cells ectopically expressing v-ras to undergo apoptosis. In this apoptotic process, PKC-delta is upregulated and translocated from the cytosol to the nucleus. The activated PKC-delta associates with and phosphorylates p73 to initiate apoptosis. In this apoptotic process, Akt seems to be downstream of oncogenic Ras. Moreover, overexpression of PKC-delta, without co-suppression of PKC-alpha and beta, is not apoptotic to the cells, suggesting that PKC-delta and PKC-alpha/beta function oppositely to facilitate cells harboring v-ras to survive. Thus, our study shows that PKC-alpha and beta are necessary for sustaining the homeostasis in cells containing a hyperactive Ras. The abrogation of these two isoforms switches on the p73-regulated apoptotic machinery through the activation of PKC-delta.
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32
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Liontos M, Niforou K, Velimezi G, Vougas K, Evangelou K, Apostolopoulou K, Vrtel R, Damalas A, Kontovazenitis P, Kotsinas A, Zoumpourlis V, Tsangaris GT, Kittas C, Ginsberg D, Halazonetis TD, Bartek J, Gorgoulis VG. Modulation of the E2F1-driven cancer cell fate by the DNA damage response machinery and potential novel E2F1 targets in osteosarcomas. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 175:376-91. [PMID: 19541929 PMCID: PMC2708823 DOI: 10.2353/ajpath.2009.081160] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/27/2009] [Indexed: 12/30/2022]
Abstract
Osteosarcoma is the most common primary bone cancer. Mutations of the RB gene represent the most frequent molecular defect in this malignancy. A major consequence of this alteration is that the activity of the key cell cycle regulator E2F1 is unleashed from the inhibitory effects of pRb. Studies in animal models and in human cancers have shown that deregulated E2F1 overexpression possesses either "oncogenic" or "oncosuppressor" properties, depending on the cellular context. To address this issue in osteosarcomas, we examined the status of E2F1 relative to cell proliferation and apoptosis in a clinical setting of human primary osteosarcomas and in E2F1-inducible osteosarcoma cell line models that are wild-type and deficient for p53. Collectively, our data demonstrated that high E2F1 levels exerted a growth-suppressing effect that relied on the integrity of the DNA damage response network. Surprisingly, induction of p73, an established E2F1 target, was also DNA damage response-dependent. Furthermore, a global proteome analysis associated with bioinformatics revealed novel E2F1-regulated genes and potential E2F1-driven signaling networks that could provide useful targets in challenging this aggressive neoplasm by innovative therapies.
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Affiliation(s)
- Michalis Liontos
- Department of Histology and Embryology, School of Medicine, University of Athens, Athens, Greece
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Sang M, Ando K, Okoshi R, Koida N, Li Y, Zhu Y, Shimozato O, Geng C, Shan B, Nakagawara A, Ozaki T. Plk3 inhibits pro-apoptotic activity of p73 through physical interaction and phosphorylation. Genes Cells 2009; 14:775-88. [PMID: 19490146 DOI: 10.1111/j.1365-2443.2009.01309.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Plk3, one of Polo-like kinase family members, is involved in the regulation of cell cycle progression and DNA damage response. In this study, we found that Plk3 inhibits pro-apoptotic activity of p73 through physical interaction and phosphorylation. During cisplatin (CDDP)-mediated apoptosis, Plk3 was transcriptionally induced, whereas its protein level was kept at basal level, suggesting that Plk3 might rapidly degrade in response to CDDP. Immunoprecipitation and in vitro pull-down experiments demonstrated that Plk3 interacts with p73. Luciferase reporter assays and RT-PCR experiments revealed that Plk3 inhibits p73-mediated transcriptional activity. Consistent with these results, pro-apoptotic activity of p73 was blocked by Plk3. Additionally, Plk3 decreased the stability of p73. Intriguingly, kinase-deficient Plk3 failed to inhibit p73 function, indicating that kinase activity of Plk3 is required for Plk3-mediated inhibition of p73. Indeed, in vitro kinase reaction showed that NH(2)-terminal portion of p73 is phosphorylated by Plk3. In accordance with these observations, knocking down of Plk3 increased the stability of p73 and promoted CDDP-mediated apoptosis in association with up-regulation of p73. Collectively, our present findings suggest that Plk3 plays an important role in the regulation of cell fate determination in response to DNA damage through the inhibition of p73.
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Affiliation(s)
- Meixiang Sang
- Division of Biochemistry, Chiba Cancer Center Research Institute, Chiba, Japan
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34
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Dong X, Jiao L, Li Y, Evans DB, Wang H, Hess KR, Abbruzzese JL, Li D. Significant associations of mismatch repair gene polymorphisms with clinical outcome of pancreatic cancer. J Clin Oncol 2009; 27:1592-9. [PMID: 19237629 DOI: 10.1200/jco.2008.20.1111] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
PURPOSE DNA mismatch repair (MMR) is critical in maintaining genomic stability and may modulate the cellular response to gemcitabine. We hypothesized that genetic variations in MMR may affect the clinical outcome of patients with pancreatic cancer. PATIENTS AND METHODS We evaluated 15 single-nucleotide polymorphisms (SNPs) of eight MMR genes in 154 patients with potentially resectable pancreatic adenocarcinoma who were enrolled onto phase II clinical trials for preoperative gemcitabine-based chemoradiotherapy from 1999 to 2006. Associations of genotypes with tumor response to therapy (change of tumor size by radiologic evaluation at restaging), margin-negative tumor resection, and overall survival were evaluated using logistic regression and Cox proportional regression models. RESULTS Five, six, and 10 genotypes were significantly associated with tumor response to preoperative chemoradiotherapy, tumor resectability, and overall survival, respectively, in univariable analysis. TREX1 EX14-460C>T and TP73 Ex2+4G>A genotypes remained as significant predictors for tumor response, MLH1 IVS12-169C>T and TP73 remained as significant predictors for tumor resectability, and EXO1 R354H, TREX1, and TP73 remained as significant predictors for overall survival in multivariable models that included all clinical factors and genotypes examined. A strong combined genotype effect on each clinical end point was observed. For example, 20 of the 25 patients with zero to one adverse genotypes were alive, those with two, three, four, five, and six to seven adverse genotypes had median survival times of 36.2, 23.9, 16.3, 13.0, and 8.3 months, respectively (P < .001). CONCLUSION SNPs of MMR genes have a potential value as predictors for clinical response to chemoradiotherapy and as prognostic markers for tumor resectability and overall survival of patients with resectable pancreatic cancer.
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Affiliation(s)
- Xiaoqun Dong
- Department of Gastrointestinal Medical Oncology, Surgical Oncology, Pathology, and Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030-4009, USA
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35
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Vilgelm A, El-Rifai W, Zaika A. Therapeutic prospects for p73 and p63: rising from the shadow of p53. Drug Resist Updat 2008; 11:152-63. [PMID: 18801697 DOI: 10.1016/j.drup.2008.08.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 08/06/2008] [Accepted: 08/11/2008] [Indexed: 01/15/2023]
Abstract
The p53 protein family consists of three transcription factors: p53, p63, and p73. These proteins share significant structural and functional similarities and each has unique biological functions as well. Although the role of p53 in cellular stress is extensively studied, many questions remain about p63 and p73. In this review we summarize current data on functional interactions within the p53 family, their regulation and roles in response to genotoxic stress. We also discuss the significance of p73 and p63 for cancer therapy and outline novel approaches in development of therapeutic drugs that specifically target the p53 family.
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Affiliation(s)
- Anna Vilgelm
- Department of Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, United States
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36
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Tozluoğlu M, Karaca E, Haliloglu T, Nussinov R. Cataloging and organizing p73 interactions in cell cycle arrest and apoptosis. Nucleic Acids Res 2008; 36:5033-49. [PMID: 18660513 PMCID: PMC2528188 DOI: 10.1093/nar/gkn481] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We have compiled the p73-mediated cell cycle arrest and apoptosis pathways. p73 is a member of the p53 family, consisting of p53, p63 and p73. p73 exists in several isoforms, presenting different domain structures. p73 functions not only as a tumor suppressor in apoptosis but also as differentiator in embryo development. p53 mutations are responsible for half of the human cancers; p73 can partially substitute mutant p53 as tumor suppressor. The pathways we assembled create a p73-centered network consisting of 53 proteins and 176 interactions. We clustered our network into five functional categories: Upregulation, Activation, Suppression, Transcriptional Activity and Degradation. Our literature searches led to discovering proteins (c-Jun and pRb) with apparent opposing functional effects; these indicate either currently missing proteins and interactions or experimental misidentification or functional annotation. For convenience, here we present the p73 network using the molecular interaction map (MIM) notation. The p73 MIM is unique amongst MIMs, since it further implements detailed domain features. We highlight shared pathways between p53 and p73. We expect that the compiled and organized network would be useful to p53 family-based studies.
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Affiliation(s)
- Melda Tozluoğlu
- Polymer Research Center and Chemical Engineering Department, Bogazici University, Bebek-Istanbul 80815, Turkey
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37
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Kim JW, Song PI, Jeong MH, An JH, Lee SY, Jang SM, Song KH, Armstrong CA, Choi KH. TIP60 Represses Transcriptional Activity of p73β via an MDM2-bridged Ternary Complex. J Biol Chem 2008; 283:20077-86. [DOI: 10.1074/jbc.m800161200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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38
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Kpm/Lats2 is linked to chemosensitivity of leukemic cells through the stabilization of p73. Blood 2008; 112:3856-66. [PMID: 18565851 DOI: 10.1182/blood-2007-09-111773] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Down-regulation of the Kpm/Lats2 tumor suppressor is observed in various malignancies and associated with poor prognosis in acute lymphoblastic leukemia. We documented that Kpm/Lats2 was markedly decreased in several leukemias that were highly resistant to conventional chemotherapy. Silencing of Kpm/Lats2 expression in leukemic cells did not change the rate of cell growth but rendered the cells more resistant to DNA damage-inducing agents. Expression of p21 and PUMA was strongly induced by these agents in control cells, despite defective p53, but was only slightly induced in Kpm/Lats2-knockdown cells. DNA damage-induced nuclear accumulation of p73 was clearly observed in control cells but hardly detected in Kpm/Lats2-knockdown cells. Chromatin immunoprecipitation (ChIP) assay showed that p73 was recruited to the PUMA gene promoter in control cells but not in Kpm/Lats2-knockdown cells after DNA damage. The analyses with transient coexpression of Kpm/Lats2, YAP2, and p73 showed that Kpm/Lats2 contributed the stability of YAP2 and p73, which was dependent on the kinase function of Kpm/Lats2 and YAP2 phosphorylation at serine 127. Our results suggest that Kpm/Lats2 is involved in the fate of p73 through the phosphorylation of YAP2 by Kpm/Lats2 and the induction of p73 target genes that underlie chemosensitivity of leukemic cells.
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39
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Koida N, Ozaki T, Yamamoto H, Ono S, Koda T, Ando K, Okoshi R, Kamijo T, Omura K, Nakagawara A. Inhibitory role of Plk1 in the regulation of p73-dependent apoptosis through physical interaction and phosphorylation. J Biol Chem 2008; 283:8555-63. [PMID: 18174154 PMCID: PMC2417181 DOI: 10.1074/jbc.m710608200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Indexed: 11/06/2022] Open
Abstract
In response to DNA damage, p73 plays a critical role in cell fate determination. In this study, we have found that Plk1 (polo-like kinase 1) associates with p73, phosphorylates p73 at Thr-27, and thereby inhibits its pro-apoptotic activity. During cisplatin-mediated apoptosis in COS7 cells in which the endogenous p53 is inactivated by SV40 large T antigen, p73 was induced to accumulate in association with a significant down-regulation of Plk1. Consistent with these observations, Plk1 reduced the stability of the endogenous p73. Immunoprecipitation and in vitro pulldown assay demonstrated that p73 binds to the kinase domain of Plk1 through its NH(2)-terminal region. Luciferase reporter assay and reverse transcription-PCR analysis revealed that Plk1 is able to block the p73-mediated transcriptional activation. Of note, kinase-deficient Plk1 mutant (Plk1(K82M)) retained an ability to interact with p73; however, it failed to inactivate the p73-mediated transcriptional activation, suggesting that kinase activity of Plk1 is required for the inhibition of p73. Indeed, in vitro kinase assay indicated that p73 is phosphorylated at Thr-27 by Plk1. Furthermore, small interference RNA-mediated knockdown of the endogenous Plk1 in p53-deficient H1299 cells resulted in a significant increase in the number of cells with sub-G(1) DNA content accompanied by the up-regulation of p73 and pro-apoptotic p53(AIP1) as well as the proteolytic cleavage of poly(ADP-ribose) polymerase. Thus, our present results suggest that Plk1-mediated dysfunction of p73 is one of the novel molecular mechanisms to inhibit the p53-independent apoptosis, and the inhibition of Plk1 might provide an attractive therapeutic strategy for cancer treatment.
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Affiliation(s)
- Nami Koida
- Division of Biochemistry, Chiba Cancer Center Research Institute, Chiba, Japan
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40
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Abstract
The JNK (c-Jun N-terminal kinase)/mitogen-activated protein kinase signalling pathway is a major mediator of stress responses in cells, including the response to DNA damage. DNA damage also causes the stabilization and activation of p73, a member of the p53 family of transcription factors. p73, like p53, can mediate apoptosis by up-regulating the expression of pro-apoptotic genes, including Bax (Bcl2-associated X protein) and PUMA (p53 up-regulated modulator of apoptosis). Changes in p73 expression have been linked to tumour progression, particularly in neuroblastomas, whereas in tumours that feature inactivated p53 there is evidence that p73 may mediate the apoptotic response to chemotherapeutic agents. In the present study, we demonstrate a novel link between the JNK signalling pathway and p73. We use pharmacological and genetic approaches to show that JNK is required for p73-mediated apoptosis induced by the DNA damaging agent cisplatin. JNK forms a complex with p73 and phosphorylates it at several serine and threonine residues. The mutation of JNK phosphorylation sites in p73 abrogates cisplatin-induced stabilization of p73 protein, leading to a reduction in p73 transcriptional activity and reduced p73-mediated apoptosis. Our results demonstrate that the JNK pathway is an important regulator of DNA damage-induced apoptosis mediated by p73.
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Affiliation(s)
- Emma V. Jones
- *Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, U.K
| | - Mark J. Dickman
- †Department of Chemical and Process Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, U.K
| | - Alan J. Whitmarsh
- *Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, U.K
- To whom correspondence should be addressed (email )
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41
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Marabese M, Vikhanskaya F, Broggini M. p73: a chiaroscuro gene in cancer. Eur J Cancer 2007; 43:1361-72. [PMID: 17428654 DOI: 10.1016/j.ejca.2007.01.042] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 01/19/2007] [Accepted: 01/25/2007] [Indexed: 11/24/2022]
Abstract
p73 is a member of the p53 family which is gaining increasing importance in the field of cancer. Its structural homology with p53 led to the assumption that it could act as a new tumour suppressor gene. Increasing knowledge of its function, however, has cast doubts on this role. A particularly interesting characteristic of p73 is that the cell contains different isoforms with distinct and sometimes opposite functions. Evidence in the last few years clearly indicates that p73 does share some activities with p53 but also that it has some distinct functions. This review focuses on p73's role in the development and progression of cancer, analysing the gene structure and regulation and discussing similarities with p53 and differences. Recent results obtained with specific detection methods on the levels and functions of the different isoforms in tumours are also discussed.
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Affiliation(s)
- Mirko Marabese
- Laboratory of Molecular Pharmacology, Istituto di Ricerche Farmacologiche Mario Negri, Via Eritrea 62, 20157 Milan, Italy.
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42
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Zhang J, Chen X. DeltaNp73 modulates nerve growth factor-mediated neuronal differentiation through repression of TrkA. Mol Cell Biol 2007; 27:3868-80. [PMID: 17353261 PMCID: PMC1899982 DOI: 10.1128/mcb.02112-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
p73, a member of the p53 family, expresses two classes of proteins: the full-length TAp73 and the N-terminally truncated DeltaNp73. While TAp73 possesses many p53-like features, DeltaNp73 is dominant negative towards TAp73 and p53 and appears to have distinct functions in tumorigenesis and neuronal development. Given its biological importance, we investigated the role of DeltaNp73 in nerve growth factor (NGF)-mediated neuronal differentiation in PC12 cells. We show that overexpression of DeltaNp73alpha or DeltaNp73beta inhibits NGF-mediated neuronal differentiation in both p53-dependent and -independent manners. In line with this, we showed that the level of endogenous DeltaNp73 is progressively diminished in differentiating PC12 cells upon NGF treatment and knockdown of DeltaNp73 promotes NGF-mediated neuronal differentiation. Interestingly, we found that the ability of DeltaNp73 to suppress NGF-mediated neuronal differentiation is correlated with its ability to regulate the expression of TrkA, the high-affinity NGF receptor. Specifically, we found that DeltaNp73 directly binds to the TrkA promoter and transcriptionally represses TrkA expression, which in turn attenuates the NGF-mediated mitogen-activated protein kinase pathway. Conversely, the steady-state level of TrkA is increased upon knockdown of DeltaNp73. Furthermore, we found that histone deacetylase 1 (HDAC1) and HDAC2 are recruited by DeltaNp73 to the TrkA promoter and act as corepressors to suppress TrkA expression, which can be relieved by trichostatin A, an HDAC inhibitor. Taken together, we conclude that DeltaNp73 negatively regulates NGF-mediated neuronal differentiation by transrepressing TrkA.
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Affiliation(s)
- Jin Zhang
- Center for Comparative Oncology, 2128 Tupper Hall, University of California at Davis, Davis, CA 95616, USA
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43
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Bell HS, Dufes C, O’Prey J, Crighton D, Bergamaschi D, Lu X, Schätzlein AG, Vousden KH, Ryan KM. A p53-derived apoptotic peptide derepresses p73 to cause tumor regression in vivo. J Clin Invest 2007; 117:1008-18. [PMID: 17347683 PMCID: PMC1810568 DOI: 10.1172/jci28920] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 01/09/2007] [Indexed: 01/09/2023] Open
Abstract
The tumor suppressor p53 is a potent inducer of tumor cell death, and strategies exist to exploit p53 for therapeutic gain. However, because about half of human cancers contain mutant p53, application of these strategies is restricted. p53 family members, in particular p73, are in many ways functional paralogs of p53, but are rarely mutated in cancer. Methods for specific activation of p73, however, remain to be elucidated. We describe here a minimal p53-derived apoptotic peptide that induced death in multiple cell types regardless of p53 status. While unable to activate gene expression directly, this peptide retained the capacity to bind iASPP - a common negative regulator of p53 family members. Concordantly, in p53-null cells, this peptide derepressed p73, causing p73-mediated gene activation and death. Moreover, systemic nanoparticle delivery of a transgene expressing this peptide caused tumor regression in vivo via p73. This study therefore heralds what we believe to be the first strategy to directly and selectively activate p73 therapeutically and may lead to the development of broadly applicable agents for the treatment of malignant disease.
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Affiliation(s)
- Helen S. Bell
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Christine Dufes
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Jim O’Prey
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Diane Crighton
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Daniele Bergamaschi
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Xin Lu
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Andreas G. Schätzlein
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Karen H. Vousden
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Kevin M. Ryan
- Tumour Cell Death Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Centre for Oncology and Applied Pharmacology, University of Glasgow, Glasgow, United Kingdom.
Ludwig Institute for Cancer Research, University College London, London, United Kingdom.
Tumour Suppression Laboratory, Beatson Institute for Cancer Research, Glasgow, United Kingdom
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44
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Abstract
The p53-related genes p63 and p73 exhibit significant structural homology to p53; however, they do not function as classical tumor suppressors and are rarely mutated in human cancers. Both p63 and p73 exhibit tissue-specific roles in normal development and a complex contribution to tumorigenesis that is due to their expression as multiple protein isoforms. The predominant p63/p73 isoforms expressed both in normal development and in many tumors lack the conserved transactivation (TA) domain; these isoforms instead exhibit a truncated N-terminus (DeltaN) and function at least in part as transcriptional repressors. p63 and p73 isoforms are regulated through both transcriptional and post-translational mechanisms, and they in turn regulate diverse cellular functions including proliferation, survival and differentiation. The net effect of p63/p73 expression in a given context depends on the ratio of TA/DeltaN isoforms expressed, on physical interaction between p63 and p73 isoforms, and on functional interactions with p53 at the promoters of specific downstream target genes. These multifaceted interactions occur in diverse ways in tumor-specific contexts, demonstrating a functional 'p53 family network' in human tumorigenesis. Understanding the regulation and mechanistic contributions of p63 and p73 in human cancers may ultimately provide new therapeutic opportunities for a variety of these diseases.
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Affiliation(s)
- M P Deyoung
- Massachusetts General Hospital Cancer Center, Boston, MA 02114, USA
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45
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Okita N, Kudo Y, Tanuma SI. Checkpoint Kinase 1 Is Cleaved in a Caspase-Dependent Pathway during Genotoxic Stress-Induced Apoptosis. Biol Pharm Bull 2007; 30:359-62. [PMID: 17268080 DOI: 10.1248/bpb.30.359] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Checkpoint kinase 1 (Chk1) plays important roles in genotoxic stress-induced cell cycle checkpoint and in normal cell cycle progression. Here, we show that Chk1 is cleaved in the treatment of apoptotic dose of etoposide (ETP) or cisplatin (CIS) but not of viable dose in HeLa S3 cells. The cleavage of Chk1 was completely inhibited by an irreversible and cell-permeable pan-caspase inhibitor, N-benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethylketone (z-VAD-fmk). These results identify Chk1 as a novel substrate that is cleaved by a caspase-dependent manner during genotoxic stress-induced apoptosis. Our data may also indicate the existence of a novel Chk1-regulated apoptotic pathway.
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Affiliation(s)
- Naoyuki Okita
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan
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46
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Watson IR, Blanch A, Lin DCC, Ohh M, Irwin MS. Mdm2-mediated NEDD8 modification of TAp73 regulates its transactivation function. J Biol Chem 2006; 281:34096-103. [PMID: 16980297 DOI: 10.1074/jbc.m603654200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mutations in p73 are rare in cancer. Emerging evidence suggests that the relative expression of various p73 isoforms may contribute to tumorigenesis. Alternative promoters and N-terminal splicing result in the transcription and processing of either full-length (TA) or N-terminally truncated (deltaN) p73 isoforms. TAp73 possesses pro-apoptotic functions, while deltaNp73 has anti-apoptotic properties via functional inhibition of TAp73 and p53. Here, we report that TAp73, but not deltaNp73, is covalently modified by NEDD8 under physiologic conditions in an Mdm2-dependent manner. Co-expression of NEDP1, a cysteine protease that specifically cleaves NEDD8 conjugates, was shown to deneddylate TAp73. In addition, blockage of the endogenous NEDD8 pathway increased TAp73-mediated transactivation of p53- and p73-responsive promoter-driven reporter activity, and in conjunction, neddylated TAp73 species were found preferentially in the cytoplasm. These results suggest that Mdm2 attenuates TAp73 transactivation function, at least in part, by promoting NEDD8-dependent TAp73 cytoplasmic localization and provide the first evidence of a covalent post-translational modification exclusively targeting the TA isoforms of p73.
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Affiliation(s)
- Ian R Watson
- Cancer Research Program and Division of Haematology-Oncology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada
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47
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Gonzalez S, Klatt P, Delgado S, Conde E, Lopez-Rios F, Sanchez-Cespedes M, Mendez J, Antequera F, Serrano M. Oncogenic activity of Cdc6 through repression of the INK4/ARF locus. Nature 2006; 440:702-6. [PMID: 16572177 DOI: 10.1038/nature04585] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Accepted: 01/18/2006] [Indexed: 01/01/2023]
Abstract
The INK4/ARF locus encodes three tumour suppressors (p15(INK4b), ARF and p16(INK4a)) and is among the most frequently inactivated loci in human cancer. However, little is known about the mechanisms that govern the expression of this locus. Here we have identified a putative DNA replication origin at the INK4/ARF locus that assembles a multiprotein complex containing Cdc6, Orc2 and MCMs, and that coincides with a conserved noncoding DNA element (regulatory domain RD(INK4/ARF)). Targeted and localized RNA-interference-induced heterochromatinization of RD(INK4/ARF) results in transcriptional repression of the locus, revealing that RD(INK4/ARF) is a relevant transcriptional regulatory element. Cdc6 is overexpressed in human cancers, where it might have roles in addition to DNA replication. We have found that high levels of Cdc6 result in RD(INK4/ARF)-dependent transcriptional repression, recruitment of histone deacetylases and heterochromatinization of the INK4/ARF locus, and a concomitant decrease in the expression of the three tumour suppressors encoded by this locus. This mechanism is reminiscent of the silencing of the mating-type HM loci in yeast by replication factors. Consistent with its ability to repress the INK4/ARF locus, Cdc6 has cellular immortalization activity and neoplastic transformation capacity in cooperation with oncogenic Ras. Furthermore, human lung carcinomas with high levels of Cdc6 are associated with low levels of p16(INK4a). We conclude that aberrant expression of Cdc6 is oncogenic by directly repressing the INK4/ARF locus through the RD(INK4/ARF) element.
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Affiliation(s)
- Susana Gonzalez
- Tumor Suppression Group, Spanish National Cancer Research Center (CNIO), E-28029 Madrid, Spain
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48
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Abstract
Loss of DNA mismatch repair (MMR) in mammalian cells, as well as having a causative role in cancer, has been linked to resistance to certain DNA damaging agents including clinically important cytotoxic chemotherapeutics. MMR-deficient cells exhibit defects in G2/M cell cycle arrest and cell killing when treated with these agents. MMR-dependent cell cycle arrest occurs, at least for low doses of alkylating agents, only after the second S-phase following DNA alkylation, suggesting that two rounds of DNA replication are required to generate a checkpoint signal. These results point to an indirect role for MMR proteins in damage signalling where aberrant processing of mismatches leads to the generation of DNA structures (single-strand gaps and/or double-strand breaks) that provoke checkpoint activation and cell killing. Significantly, recent studies have revealed that the role of MMR proteins in mismatch repair can be uncoupled from the MMR-dependent damage responses. Thus, there is a threshold of expression of MSH2 or MLH1 required for proper checkpoint and cell-death signalling, even though sub-threshold levels are sufficient for fully functional MMR repair activity. Segregation is also revealed through the identification of mutations in MLH1 or MSH2 that provide alleles functional in MMR but not in DNA damage responses and mutations in MSH6 that compromise MMR but not in apoptotic responses to DNA damaging agents. These studies suggest a direct role for MMR proteins in recognizing and signalling DNA damage responses that is independent of the MMR catalytic repair process. How MMR-dependent G2 arrest may link to cell death remains elusive and we speculate that it is perhaps the resolution of the MMR-dependent G2 cell cycle arrest following DNA damage that is important in terms of cell survival.
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Affiliation(s)
- Vincent O'Brien
- Centre for Oncology and Applied Pharmacology, Cancer Research UK Beatson Laboratories, Garscube Estate, Glasgow G61 1BD, UK.
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49
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Ozaki T, Hosoda M, Miyazaki K, Hayashi S, Watanabe KI, Nakagawa T, Nakagawara A. Functional implication of p73 protein stability in neuronal cell survival and death. Cancer Lett 2005; 228:29-35. [PMID: 15907364 DOI: 10.1016/j.canlet.2004.12.050] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2004] [Accepted: 12/02/2004] [Indexed: 12/01/2022]
Abstract
p73, a newly identified member of p53 family, locates at human chromosome 1p36.2-3, a region which is frequently deleted in a wide variety of human tumors including neuroblastoma. p73 is induced to be accumulated in response to a subset of DNA damaging agents such as cisplatin, and thereby promoting G1/S cell cycle arrest and/or apoptosis. Since the expression levels of p73 are kept extremely low under normal conditions, stabilization of p73 is critical for its effects on cell growth inhibition and apoptosis. Indeed, p73 is induced at protein level in SH-SY5Y neuroblastoma cells exposed to cisplatin. Several lines of evidence indicate that stress-induced post-translational modifications of p73 such as phosphorylation and acetylation lead to a marked extension of its half-life. p73 stability is regulated at least in part by proteasome-dependent degradation pathway, however, MDM2 which mediates ubiquitination and subsequent degradation of p53 by the 26S proteasome, does not promote the proteolytic degradation of p73, implying that the protein stability of p73 is regulated through a pathway distinct from that of p53. Although little is known about the regulation of p73 turnover, we are now beginning to understand the regulatory mechanisms by which p73 is induced to be stabilized in response to apoptotic stimuli, and exerts its pro-apoptotic activity. In this review, we discuss about the cellular proteins implicated in the stability control of p73.
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Affiliation(s)
- Toshinori Ozaki
- Division of Biochemistry, Chiba Cancer Center Research Institute, 666-2 Nitona, Chuoh-ku, Chiba 260-8717, Japan
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50
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Abstract
p73 belongs to a family of p53-related nuclear transcription factors that includes p53, p73 and p63. The overall structure and sequence homology indicates that a p63/p73-like protogene is the ancestral gene, whereas p53 evolved later in higher organisms. In accordance with their structural similarity, p73 functions in a manner analogous to p53 by inducing tumor cell apoptosis and participating in the cell cycle checkpoint control through transactivating an overlapping set of p53/p73-target genes. In sharp contrast to p53, however, p73 is expressed as two NH(2)-terminally distinct isoforms including transcriptionally active (TA) and transcriptionally inactive (DeltaN) forms. DeltaNp73, which has oncogenic potential, acts in a dominant negative manner against TAp73 as well as p53. p73 is induced to be stabilized in response to a subset of DNA-damaging agents in a way that is distinct from that of p53, and exerts its pro-apoptotic activity. Several lines of evidence suggest that p73 can induce tumor cell apoptosis in a p53-dependent and p53-independent manner. Some tumors exhibit resistance to the p53-dependent apoptotic program, therefore p73, which can induce apoptotic cell death by p53-independent mechanisms, is particularly useful. In this review, we discuss the regulatory mechanisms of p73 activity, and also the functional significance of p73 in the regulation of cellular processes including tumorigenesis, apoptosis and neurogenesis.
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Affiliation(s)
- Toshinori Ozaki
- Division of Biochemistry, Chiba Cancer Center Research Institute, Chuoh-ku, Japan
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