101
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Sun J, Zhao J, Schwartz MA, Wang JY, Wiedmer T, Sims PJ. c-Abl tyrosine kinase binds and phosphorylates phospholipid scramblase 1. J Biol Chem 2001; 276:28984-90. [PMID: 11390389 DOI: 10.1074/jbc.m102505200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipid scramblase 1 (PLSCR1) is a plasma membrane protein that has been proposed to play a role in the transbilayer movement of plasma membrane phospholipids. PLSCR1 contains multiple proline-rich motifs resembling Src homology 3 (SH3) domain-binding sites. An initial screen against 13 different SH3 domains revealed a marked specificity of PLSCR1 for binding to the Abl SH3 domain. Binding between intracellular PLSCR1 and c-Abl was demonstrated by co-immunoprecipitation of both proteins from several cell lines. Deletion of the proline-rich segment in PLSCR1 (residues 1--118) abolished its binding to the Abl SH3 domain. PLSCR1 was Tyr-phosphorylated by c-Abl in vitro. Phosphorylation was abolished by mutation of Tyr residues Tyr(69)/Tyr(74) within the tandem repeat sequence (68)VYNQPVYNQP(77) of PLSCR1, implying that these residues are the likely sites of phosphorylation. Cellular PLSCR1 was found to be constitutively Tyr-phosphorylated in several cell lines. The Tyr phosphorylation of PLSCR1 was increased upon overexpression of c-Abl and significantly reduced either upon cell treatment with the Abl kinase inhibitor STI571, or in Abl-/- mouse fibroblasts, suggesting that cellular PLSCR1 is a normal substrate of c-Abl. Cell treatment with the DNA-damaging agent cisplatin activated c-Abl kinase and increased Tyr phosphorylation of PLSCR1. The cisplatin-induced phosphorylation of PLSCR1 was inhibited by STI571 and was not observed in Abl-/- fibroblasts. These findings indicate that c-Abl binds and phosphorylates PLSCR1, and raise the possibility that an interaction between c-Abl and plasma membrane PLSCR1 might contribute to the cellular response to genotoxic stress.
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Affiliation(s)
- J Sun
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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102
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Zhu J, Nozell S, Wang J, Jiang J, Zhou W, Chen X. p73 cooperates with DNA damage agents to induce apoptosis in MCF7 cells in a p53-dependent manner. Oncogene 2001; 20:4050-7. [PMID: 11494133 DOI: 10.1038/sj.onc.1204516] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2000] [Revised: 04/03/2001] [Accepted: 04/09/2001] [Indexed: 11/09/2022]
Abstract
p73, a member of the p53 family, can induce apoptosis in cancer cells. Since p53-mediated apoptosis can be augmented by various cancer chemotherapeutic agents, it has been hypothesized that the status of the endogenous p53 gene in cancer cells is a key determinant in the outcome of cancer therapy. To determine whether p73 can sensitize cancer cells to apoptosis by DNA damage agents, several MCF7 adenocarcinoma cell lines that inducibly express p73 or p53 under a tetracycline-regulated promoter were generated. We found that at relevant physiological levels, p73, but not p53, is capable of sensitizing MCF7 cells to apoptosis induced by chemotherapeutic agents. In addition, we found that p73 can cooperate with the DNA damaging agent camptothecin to activate the initiator caspase 2. Furthermore, we found that p73 can cooperate with DNA damaging agents or p53 to induce some p53 target genes and activate their promoters. In contrast, in MCF7E6 cells that ectopically express the human papillomavirus E6 oncogene and are functionally p53-null, the ability of p73 to sensitize cells to apoptosis is abrogated. Taken together, these results suggest that a functional interaction between p53 and p73 in MCF7 cells leads to enhanced induction of apoptosis.
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Affiliation(s)
- J Zhu
- Institute of Molecular Medicine and Genetics Medical College of Georgia, Augusta, Georgia, GA 30912, USA
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103
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Abstract
A cell is a potentially dangerous thing. In unicellular organisms, cells divide and multiply in a manner that is chiefly determined by the availability of nutritional substrates. In a multicellular organism, each cell has a distinct growth potential that is designed to subsume a role in the function of the whole body. Departure from this path to one of uncontrolled cellular proliferation leads to cancer. For this reason, evolution has endowed cells with an elaborate set of systems that cause errant cells to self-destruct. This process of cell suicide is known as apoptosis or programmed cell death and it plays a crucial role in the growth of both normal and malignant cells. In this review, we describe the mechanisms whereby programmed cell death is induced and executed. In particular, we concentrate on how anti-apoptotic signals generated by cytokines promote cell survival and how these signal transduction pathways may be involved in the pathogenesis of neoplasia. Understanding how these processes contribute to tumorigenesis may suggest new therapeutic options.
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Affiliation(s)
- M K White
- Department of Pathology, Anatomy and Cell Biology, The Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA 19107, USA
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104
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Ueda Y, Hijikata M, Takagi S, Chiba T, Shimotohno K. Transcriptional activities of p73 splicing variants are regulated by inter-variant association. Biochem J 2001; 356:859-66. [PMID: 11389695 PMCID: PMC1221914 DOI: 10.1042/0264-6021:3560859] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
p73 has been identified as a gene that encodes a protein with significant identity with the tumour suppressor p53. The main structural difference between p73 and p53 is the additional C-terminal region of p73. Six isoforms of p73 with differing C-terminal structures, alpha, beta, gamma, delta, epsilon and xi, have been reported. These variants differ in transcriptional activity on p53-responsive promoters. Here we report a possible mechanism of transcriptional activation by p73 splicing variants. C-terminal deletion mutants of p73 alpha showed a significantly higher level of transcriptional activity than wild-type p73 alpha, suggesting that the C-terminal structure of p73 alpha functions to repress the transcriptional activity of p73 alpha. The results of immunoprecipitation assays and two-hybrid assays in mammalian cells showed that the p73 variants interacted with each other, but not with p53. The transcriptional activity of p73 beta was reduced by co-expression with either p73 alpha or p73 epsilon, which bears an identical C-terminal structure to p73 alpha. Co-expression of the C-terminal portion of p73 alpha or p73 epsilon with p73 beta also resulted in reduced transcriptional activity. Moreover, we observed that the level of endogenous p21 protein induced by p73 beta was decreased by co-expression of full-length p73 epsilon or the C-terminal region of p73 alpha or p73 epsilon. These observations suggest that p73-mediated gene expression is regulated by the interactions of p73 splicing variants in the cell.
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Affiliation(s)
- Y Ueda
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
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105
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Krause K, Haugwitz U, Wasner M, Wiedmann M, Mössner J, Engeland K. Expression of the cell cycle phosphatase cdc25C is down-regulated by the tumor suppressor protein p53 but not by p73. Biochem Biophys Res Commun 2001; 284:743-50. [PMID: 11396965 DOI: 10.1006/bbrc.2001.5040] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cdc25C phosphatase dephosphorylates cdc2 kinase which then in complex with cyclin B can catalyse transition from the G(2) phase to mitosis. We demonstrate that transcription of cdc25C is repressed by p53 in a dose-dependent manner. In stably transfected DLD-1 colorectal adenocarcinoma cells, cdc25C expression is down-regulated when p53 is induced from a (tet)-off-regulated system. In contrast to p53, its homologue p73 is not able to down-modulate cdc25C expression. A previously identified site in the cdc25C promoter can bind p53 in vitro and, when placed in a heterologous construct, is able to activate transcription. However, transcriptional repression by p53 is not mediated through this site but is dependent on a segment containing three CCAAT-boxes. In general down-regulation of cdc25C transcription by reducing the levels of active cdc2 kinase contributes to G(2) arrest and G(2)/M checkpoint control. This reveals functional differences between p73 and p53 in regulating cell division.
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Affiliation(s)
- K Krause
- Department of Internal Medicine II, University of Leipzig, Max Bürger Research Centre, Johannisallee 30, D-04103 Leipzig, Germany
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106
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Naka M, Ozaki T, Takada N, Takahashi M, Shishikura T, Sakiyama S, Tada M, Todo S, Nakagawara A. Functional characterization of naturally occurring mutants (P405R and P425L) of p73alpha and p73beta found in neuroblastoma and lung cancer. Oncogene 2001; 20:3568-72. [PMID: 11429704 DOI: 10.1038/sj.onc.1204470] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2000] [Revised: 03/06/2001] [Accepted: 03/15/2001] [Indexed: 12/17/2022]
Abstract
The novel candidate tumor suppressor p73, a structural and functional homolog of p53, activates various p53 responsive promoters and induces tumor cell apoptosis. Although p73 is infrequently mutated in human cancers, we have previously found two types of p73 mutation with amino acid substitution (P405R and P425L) in primary neuroblastoma and lung cancer. Here we report generations of the p73 mutants with either P405R or P425L substitution and functional analysis of these naturally occurring mutants. Indirect immunofluorescence staining revealed that nuclear accumulation of p73alpha or p73beta was not affected by these mutations. The P425L substitution reduced the ability of p73alpha to transactivate various p53 responsive promoters (p21(Waf1), Mdm2, and Bax). Moreover, this down-regulation was correlated with the reduced capability of p73alpha(P425L) to suppress cell growth in p53-deficient SAOS-2 cells. In contrast, p73beta(P425L) was as effective as wild-type p73beta in transactivation and growth inhibition. On the other hand, the P405R substitution had no significant effect on both the transcriptional activity and the growth-suppressive ability of p73alpha or p73beta. These results suggested that, at least, one of the naturally occurring p73 mutants, p73alpha(P425L), was a functionally defective mutant of p73.
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Affiliation(s)
- M Naka
- Division of Biochemistry, Chiba Cancer Center Research Institute, 666-2 Nitona, Chiba 260-8717, Japan
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107
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Ueda Y, Hijikata M, Takagi S, Takada R, Takada S, Chiba T, Shimotohno K. p73beta, a variant of p73, enhances Wnt/beta-catenin signaling in Saos-2 cells. Biochem Biophys Res Commun 2001; 283:327-33. [PMID: 11327702 DOI: 10.1006/bbrc.2001.4788] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The Wnt/beta-catenin pathway and p53 are very common targets for genetic alterations in colorectal cancer, and relationships between them have been reported. Here, we describe the relation between Wnt/beta-catenin signaling and the p53-related gene p73. p73, but not p53, activated a promoter containing the Tcf-binding sequence in Saos-2 cells, and the degree of activation was positively correlated with that on a p53-responsive promoter. Moreover, p73beta enhanced Wnt/beta-catenin signaling synergistically with Wnt-3a or exogenously expressed beta-catenin, unlike p53, and the enhancement was not caused by the accumulation of beta-catenin. These results show that the effects of p73 on Wnt/beta-catenin signaling differ from those of p53.
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Affiliation(s)
- Y Ueda
- Department of Viral Oncology, Kyoto University, Sakyo-ku, Kyoto, 606-8507, Japan
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108
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Abstract
Melanoma is the most common fatal malignancy among young adults, and its incidence and mortality continue to increase at an alarming rate. Epidemiologic studies have clearly demonstrated roles for genetic predisposition and sun exposure in melanoma development. In the past few years, substantial information has been added to the body of evidence suggesting that inherited and somatic genetic events contribute to the pathogenesis of melanoma. This review focuses on recent advances in the understanding of the genetic events, particularly aberration of cell cycle control and transcriptional control mechanisms, implicated in the pathogenesis of melanoma.
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Affiliation(s)
- S Halachmi
- Department of Dermatology, Boston University School of Medicine, Boston, Massachusetts 02218, USA
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109
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Mathieu MC, Lapierre I, Brault K, Raymond M. Aromatic hydrocarbon receptor (AhR).AhR nuclear translocator- and p53-mediated induction of the murine multidrug resistance mdr1 gene by 3-methylcholanthrene and benzo(a)pyrene in hepatoma cells. J Biol Chem 2001; 276:4819-27. [PMID: 11096091 DOI: 10.1074/jbc.m008495200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mouse multidrug resistance gene family consists of three genes (mdr1, mdr2, and mdr3) encoding P-glycoprotein. We show that the expression of mdr1 is increased at the transcriptional level upon treatment of the hepatoma cell line Hepa-1c1c7 with the polycyclic aromatic hydrocarbon 3-methylcholanthrene (3-MC). This increase is not observed in the aromatic hydrocarbon receptor (AhR)-defective TAOc1BP(r)c1 and the AhR nuclear translocator (Arnt)-defective BP(r)c1 variants, demonstrating that the induction of mdr1 by 3-MC requires AhR.Arnt. We show that the mdr1 promoter (-1165 to +84) is able to activate the expression of a reporter gene in response to 3-MC in Hepa-1c1c7 but not in BP(r)c1 cells. Deletion analysis indicated that the region from -245 to -141 contains cis-acting sequences mediating the induction, including a potential p53 binding sequence. 3-MC treatment of the cells increased the levels of p53 and induced p53 binding to the mdr1 promoter in an AhR.Arnt-dependent manner. Mutations in the p53 binding site abrogated induction of mdr1 by 3-MC, indicating that p53 binding to the mdr1 promoter is essential for the induction. Benzo(a)pyrene, a polycyclic aromatic hydrocarbon and AhR ligand, which, like 3-MC, is oxidized by metabolizing enzymes regulated by AhR.Arnt, also activated p53 and induced mdr1 transcription. 2,3,7,8-Tetrachlorodibenzo-p-dioxin, an AhR ligand resistant to metabolic breakdown, had no effect. These results indicate that the transcriptional induction of mdr1 by 3-MC and benzo(a)pyrene is directly mediated by p53 but that the metabolic activation of these compounds into reactive species is necessary to trigger p53 activation. The ability of the anticancer drug and potent genotoxic agent daunorubicin to induce mdr1 independently of AhR.Arnt further supports the proposition that mdr1 is transcriptionally up-regulated by p53 in response to DNA damage.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/biosynthesis
- Animals
- Aryl Hydrocarbon Receptor Nuclear Translocator
- Benzo(a)pyrene/pharmacology
- Carcinoma, Hepatocellular
- DNA-Binding Proteins
- Genes, MDR
- Methylcholanthrene/pharmacology
- Mice
- Models, Biological
- Mutation
- Promoter Regions, Genetic
- RNA, Messenger/biosynthesis
- Receptors, Aryl Hydrocarbon/genetics
- Receptors, Aryl Hydrocarbon/physiology
- Response Elements
- Transcription Factors/biosynthesis
- Transcription Factors/genetics
- Transcription Factors/physiology
- Transcriptional Activation
- Tumor Cells, Cultured
- Tumor Suppressor Protein p53/biosynthesis
- Tumor Suppressor Protein p53/physiology
- Xenobiotics/pharmacology
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Affiliation(s)
- M C Mathieu
- Institut de Recherches Cliniques de Montréal, Montréal, Québec H2W 1R7, Canada
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110
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Abstract
Identification of the genes that cause oncogenesis is a central aim of cancer research. We searched the proteins predicted from the draft human genome sequence for paralogues of known tumour suppressor genes, but no novel genes were identified. We then assessed whether it was possible to search directly for oncogenic sequence changes in cancer cells by comparing cancer genome sequences against the draft genome. Apparently chimaeric transcripts (from oncogenic fusion genes generated by chromosomal translocations, the ends of which mapped to different genomic locations) were detected to the same degree in both normal and neoplastic tissues, indicating a significant level of false positives. Our experiment underscores the limited amount and variable quality of DNA sequence from cancer cells that is currently available.
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Affiliation(s)
- P A Futreal
- Cancer Genome Project, Sanger Centre, Cambridge, UK
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111
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Ratovitski EA, Patturajan M, Hibi K, Trink B, Yamaguchi K, Sidransky D. p53 associates with and targets Delta Np63 into a protein degradation pathway. Proc Natl Acad Sci U S A 2001; 98:1817-22. [PMID: 11172034 PMCID: PMC29340 DOI: 10.1073/pnas.98.4.1817] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2000] [Accepted: 12/06/2000] [Indexed: 11/18/2022] Open
Abstract
A human p53 homologue, p63 (p40/p51/p73L/CUSP) that maps to the chromosomal region 3q27-29 was found to produce a variety of transcripts that encode DNA-binding proteins with and without a trans-activation domain (TA- or Delta N-, respectively). The p63 gene locus was found to be amplified in squamous cell carcinoma, and overexpression of Delta Np63 (p40) led to increased growth of transformed cells in vitro and in vivo. Moreover, p63-null mice displayed abnormal epithelial development and germ-line human mutations were found to cause ectodermal dysplasia. We now demonstrate that certain p63 isotypes form complexes with p53. p53 mutations R175H or R248W abolish the association of p53 with p63, whereas V143A or R273H has no effect. Deletion studies suggest that the DNA-binding domains of both p53 and p63 mediate the association. Overexpression of wild type but not mutant (R175H) p53 results in the caspase-dependent degradation of certain Delta Np63 proteins (p40 and Delta Np63 alpha). The association between p53 and Delta Np63 supports a previously unrecognized role for p53 in regulation of Delta Np63 stability. The ability of p53 to mediate Delta Np63 degradation may balance the capacity of Delta Np63 to accelerate tumorigenesis or to induce epithelial proliferation.
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Affiliation(s)
- E A Ratovitski
- Department of Otolaryngology-Head and Neck Surgery, Division of Head and Neck Cancer Research, The Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA.
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112
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Chen X, Zheng Y, Zhu J, Jiang J, Wang J. p73 is transcriptionally regulated by DNA damage, p53, and p73. Oncogene 2001; 20:769-74. [PMID: 11314010 DOI: 10.1038/sj.onc.1204149] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2000] [Revised: 11/30/2000] [Accepted: 12/05/2000] [Indexed: 11/09/2022]
Abstract
p73 is a member of the p53 family. Recent studies have shown that DNA damage can stabilize p73 protein and enhance p73-mediated apoptosis in a c-Abl dependent manner. To determine what regulates p73 transcriptionally, we analysed the expression of p73 in several cell lines following genotoxic stresses. We found that p73 is induced in certain cell lines when treated with therapeutic DNA damaging agents. We also found that p53 and p73, but not mutant p53(R249S) and p73beta292, directly induce the expression of the p73 gene. In addition, we found one potential p53-binding site in the promoter of the p73 gene. This binding site is responsive to p53, p73, and DNA damage. Taken together, these data suggest that p73 is transcriptionally regulated by DNA damage and p53, and is autoregulated.
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Affiliation(s)
- X Chen
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA
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113
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Kelley ML, Winge P, Heaney JD, Stephens RE, Farell JH, Van Beneden RJ, Reinisch CL, Lesser MP, Walker CW. Expression of homologues for p53 and p73 in the softshell clam (Mya arenaria), a naturally-occurring model for human cancer. Oncogene 2001; 20:748-58. [PMID: 11314008 DOI: 10.1038/sj.onc.1204144] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2000] [Revised: 11/22/2000] [Accepted: 11/29/2000] [Indexed: 01/10/2023]
Abstract
Homologues for human p53 (Hsp53) and p73 (Hsp73) genes were cloned and expression patterns for their corresponding proteins analysed in tissues from normal and leukemic softshell clams (Mya arenaria). These are the first structural and functional data for p53 and p73 cDNAs and gene products in a naturally occurring, non-mammalian disease model. Core sequence of the predicted clam p53 (Map53) and p73 (Map73) proteins is virtually identical and includes the following highly conserved regions: the transcriptional activation domain (TAD), MDM2 binding site, ATM phosphorylation site, proline rich domain, DNA binding domains (DBDs) II-V, nuclear import and export signals and the tetramerization domain. The core sequence is a structural mosaic of the corresponding human proteins, with the TAD and DBDs resembling Hsp53 and Hsp73, respectively. This suggests that Map53 and Map73 proteins may function similarly to human proteins. Clam proteins have either a short (Map53) or long (Map73) C-terminal extension. These features suggest that Map53 and Map73 may be alternate splice variants of a p63/p73-like ancestral gene. Map73 is significantly upregulated in hemocytes and adductor muscle from leukemic clams. In leukemic hemocytes, both proteins are absent from the nucleus and sequestered in the cytoplasm. This observation suggests that a non-mutational p53/p73-dependent mechanism may be involved in the clam disease. Further studies of these gene products in clams may reveal p53/p73-related molecular mechanisms that are held in common with Burkitt's lymphoma or other human cancers.
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Affiliation(s)
- M L Kelley
- Department of Biochemistry, Microbiology and Molecular Biology and School of Marine Science, University of Maine, Orono, ME 04469-5751, USA
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114
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Abstract
In the two decades since its original discovery, p53 has found a singularly prominent place in our understanding of human cancer. Although the biochemistry of p53 has been worked out in some detail, our knowledge of the biologic consequences of p53 dysfunction is still quite rudimentary. Over the next several years, it will be important to determine how best to harness the complex properties of p53's ability to induce cellular growth arrest and cell death to generate novel, effective approaches to cancer therapy. Furthermore, a clearer appreciation of the direct interaction of epigenetic factors with p53 will lead to development of strategies to inhibit tumour initiation and progression. The next decade promises to offer exciting opportunities to apply our vast knowledge of this intriguing tumor suppressor to clinical advantage.
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Affiliation(s)
- D Malkin
- Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Ontario, Canada.
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115
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Tan M, Bian J, Guan K, Sun Y. p53CP is p51/p63, the third member of the p53 gene family: partial purification and characterization. Carcinogenesis 2001; 22:295-300. [PMID: 11181451 DOI: 10.1093/carcin/22.2.295] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The p53 tumor suppressor is a transcription factor that upon activation by DNA-damaging agents induces growth arrest or apoptosis mainly through transactivation and transrepression of its downstream target genes. Two additional p53 family members, p73 and p51/p63, were recently identified and characterized. Although the three family members share some similarities in transcription activation and apoptosis induction, each of them appears to play a distinct role in development and tumor suppression. We have previously identified a nuclear protein, p53CP (p53 competing protein), that is not p53 but binds to the p53 consensus sequence. Here we report the partial purification of p53CP from HeLa cells by ammonium sulfate precipitation, followed by a series of chromatography steps through heparin-agarose, Mono S ion exchange and DNA affinity columns, coupled with a gel shift assay. Although p53CP activity is readily detectable in HeLa cells by gel shift assay, only a trace amount of p53CP protein was partially purified, which was not sufficient for direct protein sequencing. Using a monoclonal antibody (4A4) specific for all p51/p63 isoforms or a polyclonal antibody (N-18) recognizing the N-terminus-containing p51/p63 isoforms we detected a significant enrichment of p51/p63 protein in p53CP-containing fractions following each step of purification. Significantly, p51/p63 was detected only in the DNA affinity column fractions that contain p53CP activity. Thus, p53CP appears to be p51/p63, the third member of the p53 gene family.
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Affiliation(s)
- M Tan
- Department of Molecular Biology, Pfizer Global Research and Development, Ann Arbor Laboratories, Ann Arbor, MI 48105, USA
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116
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Fueyo J, Gomez-Manzano C, Liu TJ, Yung WK. Delivery of cell cycle genes to block astrocytoma growth. J Neurooncol 2001; 51:277-87. [PMID: 11407598 DOI: 10.1023/a:1010661131403] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Current therapies for glioblastoma multiforme are ineffective. Therefore, novel therapies that target specific differences between normal and malignant cells are urgently needed. Abnormalities of cell-cycle related genes are a common feature of cancer in general and astrocytic tumors in particular. The role of these proteins is to help to regulate cell proliferation, differentiation and apoptosis. Restoring wild-type activity of critical regulators of the cell cycle to astrocytic tumors generally results in modification of the growth properties, and often the viability, of the cancer cells. Transfer of p53 induces growth arrest and, more importantly, apoptosis. Restoration of the Rb pathway results in either reversible growth arrest or senescence. Expression of E2F-1 induces transient increase of proliferation followed by massive apoptosis. Overexpression of MMAC/PTEN arrests cell cycle progression in G1 and promotes anoikis. Current knowledge of the functions of these cell-cycle controllers can be used to design small peptides and drugs to induce cell-cycle related anti-cancer effect. Inactivation of the p53 and Rb pathways in cancer cells is also being used to engineer mutant viruses that are able to replicate exclusively in cancer cells.
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Affiliation(s)
- J Fueyo
- Department of Neuro-Oncology, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA
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117
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Abstract
c-Myc and p53 are two proteins that have critical roles in the regulation of apoptosis and the cell cycle. The authors review how these two proteins are thought to control the opposing events of proliferation and apoptosis and examine whether their well-documented biological roles in tumorigenesis can be applied to the vascular system.
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Affiliation(s)
- N McCarthy
- Division of Cardiovascular Medicine, Addenbrookes Hospital, Cambridge, United Kingdom
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118
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Abstract
p73, a member of the p53 family, has been shown to exhibit similar biochemical activities to that of p53. However, in contrast to p53, p73 is rarely mutated in human tumors and p73 mutant mice develop neurological, pheromonal, and inflammatory defects, but not spontaneous tumors. Furthermore, p73 mutant mice are deficient in the physiological control of cerebral spinal fluid. To determine what mediates these p73 activities, cDNA subtraction assay was performed to identify cellular genes that are regulated by p73. We found that aquaporin 3 (AQP3), a glycerol and water transporter, is regulated by p73. In addition, we identified a potential p53 response element in the promoter of the AQP3 gene, which is responsive to p73. This suggests that AQP3 may mediate the activity of p73 in maintaining cerebral spinal fluid dynamics.
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Affiliation(s)
- X Zheng
- CB-2803, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA
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119
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Nemoto T, Kamei S, Seyama Y, Kubota S. p53 independent G(1) arrest induced by DL-alpha-difluoromethylornithine. Biochem Biophys Res Commun 2001; 280:848-54. [PMID: 11162600 DOI: 10.1006/bbrc.2000.4227] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ornithine decarboxylase (ODC), which catalyzes polyamine biosynthesis, plays an essential role in cell growth. DL-alpha-Difluoromethylornithine (DFMO), a synthetic inhibitor of ODC, inhibits cell growth. However, the exact mechanism by which polyamine depletion by DFMO results in growth inhibition remains to be elucidated. We clarified the mechanisms by which DFMO inhibits human gastric cancer cell (MKN45) growth. DFMO induced MKN45 cell G(1) phase arrest after 48 h, and the percentage of G(1) arrest cells continued to increase until 72 h. Expression of p21 and phosphorylation of Stat1 were significantly induced by DFMO at 24 h. Luciferase assay and gel shift assay showed specific binding of Stat1 to the p21 promoter, and promoter activity was activated at 24 h. In dominant negative p53 expressing cells, DFMO significantly induced p21 expression, arrested cells at G(1) phase, and suppressed cell growth effectively. These results suggest that DFMO induced MKN45 cell arrest at G(1) phase in a p53 independent manner, and Stat1 is, at least in part, involved in G(1) arrest.
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Affiliation(s)
- T Nemoto
- Department of Physiological Chemistry and Metabolism, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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120
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Pochampally R, Li C, Lu W, Chen L, Luftig R, Lin J, Chen J. Temperature-sensitive mutants of p53 homologs. Biochem Biophys Res Commun 2000; 279:1001-10. [PMID: 11162465 DOI: 10.1006/bbrc.2000.4056] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two homologs of the p53 tumor suppressor, p63 and p73 have recently been discovered. These proteins have activities similar to p53 in cell culture but have distinct developmental functions in vivo. We found that temperature-sensitive mutants of certain p63 and p73 isoforms can be created by single amino acid substitutions of an alanine residue corresponding to alanine 135 of murine p53. The mutants (p63gamma-Pro167, p73alpha-Leu156 and p73beta-Ile156) can be controlled by temperature shift between 32 degrees C and 39 degrees C. They can be stably expressed in p53-null H1299 cells at 39 degrees C, become transcriptionally activated at 32 degrees C, and induce expression of p53-responsive genes MDM2 and p21WAF1. Activation of p73beta-Ile156 in H1299 cells inhibits cell division but induces significant increase in cell size (hypertrophy), whereas activation of p73alpha-Leu156 and p63gamma-Pro167 induces apoptosis. These mutants may be useful tools for gaining further insight to the functions of p53 homologs.
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Affiliation(s)
- R Pochampally
- Molecular Oncology Program, H. Lee Moffitt Cancer Center, University of South Florida, 12902 Magnolia Drive, Tampa, Florida 33612, USA
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121
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122
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Minty A, Dumont X, Kaghad M, Caput D. Covalent modification of p73alpha by SUMO-1. Two-hybrid screening with p73 identifies novel SUMO-1-interacting proteins and a SUMO-1 interaction motif. J Biol Chem 2000; 275:36316-23. [PMID: 10961991 DOI: 10.1074/jbc.m004293200] [Citation(s) in RCA: 311] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Two-hybrid screening in yeast with p73alpha isolated SUMO-1 (small ubiquitin-like modifier 1), the enzyme responsible for its conjugation, Ubc-9, and a number of novel SUMO-1-interacting proteins, including thymine DNA glycosylase, PM-Scl75, PIASx, PKY, and CHD3/ZFH. A subset of these proteins contain a common motif, hhXSXS/Taaa, where h is a hydrophobic amino acid and a is an acidic amino acid, that is shown to interact with SUMO-1 in the two-hybrid system. We show here that p73alpha, but not p73beta, can be covalently modified by SUMO-1. The major SUMO-1-modified residue in p73alpha is the C-terminal lysine (Lys(627)). The sequence surrounding this lysine conforms to a consensus SUMO-1 modification site b(X)XXhKXE, where b is a basic amino acid. SUMO-1-modified p73 is more rapidly degraded by the proteasome than unmodified p73, although SUMO-1 modification is not required for p73 degradation. SUMO-1 modification does not affect the transcriptional activity of p73alpha on an RGC-luciferase reporter gene in SK-N-AS cells. Instead, SUMO-1 modification may alter the subcellular localization of p73, because SUMO-1-modified p73 is preferentially found in detergent-insoluble fractions. Alternatively, it may modulate the interaction of p73 with other proteins that are substrates for SUMO-1 modification or which interact with SUMO-1, such as those identified here.
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Affiliation(s)
- A Minty
- Molecular and Functional Genomics Department, Sanofi-Synthélabo Recherche, 31676 Labège, France.
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123
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Tschan MP, Grob TJ, Peters UR, Laurenzi VD, Huegli B, Kreuzer KA, Schmidt CA, Melino G, Fey MF, Tobler A, Cajot JF. Enhanced p73 expression during differentiation and complex p73 isoforms in myeloid leukemia. Biochem Biophys Res Commun 2000; 277:62-5. [PMID: 11027640 DOI: 10.1006/bbrc.2000.3627] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The p53 homologue p73 is expressed in at least six different isoforms (alpha, beta, gamma, delta, epsilon, and zeta), but unlike p53 it has rarely been found mutated in human cancers. However, altered expression of this gene has been reported in cancer cells. In order to understand if p73 is involved in normal and malignant development of myeloid cells, we investigated the expression pattern of the different p73 isoforms in progenitor and mature normal myeloid cells as well as in cells derived from acute and chronic myeloid leukemias. The results show that expression of p73 is markedly enhanced during differentiation of myeloid leukemic cells and that leukemic blasts from patients show an increased expression of the shorter p73 isoforms (gamma, delta, epsilon, zeta). In particular the epsilon isoform is only expressed in leukemic cells and completely absent in mature myeloid cells. Altogether our data suggest that p73 is involved in myeloid differentiation and its altered expression is involved in leukemic degeneration.
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MESH Headings
- Acute Disease
- Blotting, Southern
- Blotting, Western
- Cell Differentiation
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Gene Expression Regulation, Neoplastic
- Genes, Tumor Suppressor
- HL-60 Cells
- Humans
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology
- Leukemia, Myeloid/genetics
- Leukemia, Myeloid/metabolism
- Leukemia, Myeloid/pathology
- Myeloid Cells/cytology
- Myeloid Cells/metabolism
- Myeloid Progenitor Cells/cytology
- Myeloid Progenitor Cells/metabolism
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Tumor Cells, Cultured
- Tumor Protein p73
- Tumor Suppressor Proteins
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Affiliation(s)
- M P Tschan
- Department of Clinical Research, Institute of Medical Oncology, Bern, Switzerland
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124
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Lissy NA, Davis PK, Irwin M, Kaelin WG, Dowdy SF. A common E2F-1 and p73 pathway mediates cell death induced by TCR activation. Nature 2000; 407:642-5. [PMID: 11034214 DOI: 10.1038/35036608] [Citation(s) in RCA: 263] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Strong stimulation of the T-cell receptor (TCR) on cycling peripheral T cells causes their apoptosis by a process called TCR-activation-induced cell death (TCR-AICD). TCR-AICD occurs from a late G1 phase cell-cycle check point independently of the 'tumour suppressor' protein p53. Disruption of the gene for the E2F-1 transcription factor, an inducer of apoptosis, causes significant increases in T-cell number and splenomegaly. Here we show that T cells undergoing TCR-AICD induce the p53-related gene p73, another mediator of apoptosis, which is hypermethylated in lymphomas. Introducing a dominant-negative E2F-1 protein or a dominant-negative p73 protein into T cells protects them from TCR-mediated apoptosis, whereas dominant-negative E2F-2, E2F-4 or p53 does not. Furthermore, E2F-1-null or p73-null primary T cells do not undergo TCR-mediated apoptosis either. We conclude that TCR-AICD occurs from a late G1 cell-cycle checkpoint that is dependent on both E2F-1 and p73 activities. These observations indicate that, unlike p53, p73 serves to integrate receptor-mediated apoptotic stimuli.
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Affiliation(s)
- N A Lissy
- Howard Hughes Medical Institute, Department of Pathology, Washington University School of Medicine, St Louis Missouri 63110, USA
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125
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Ganguli G, Abecassis J, Wasylyk B. MDM2 induces hyperplasia and premalignant lesions when expressed in the basal layer of the epidermis. EMBO J 2000; 19:5135-47. [PMID: 11013216 PMCID: PMC302089 DOI: 10.1093/emboj/19.19.5135] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The MDM2 oncogene is overexpressed in 5-10% of human tumours. Its major physiological role is to inhibit the tumour suppressor p53. However, MDM2 has p53-independent effects on differentiation and does not predispose to tumorigenesis when it is expressed in the granular layer of the epidermis. These unexpected properties of MDM2 could be tissue specific or could depend on the differentiation state of the cells. Strikingly, we found that MDM2 has p53-dependent effects on differentiation, proliferation and apoptosis when it is expressed in the less differentiated basal layer cells. MDM2 inhibits UV induction of p53, the cell cycle inhibitor p21(WAF1/CIP1) and apoptosis ('sunburn cells'). Importantly, MDM2 increases papilloma formation induced by chemical carcinogenesis and predisposes to the appearance of premalignant lesions and squamous cell carcinomas. p53 has a natural role in the protection against UV damage in the basal layer of the epidermis. Our results show that MDM2 predisposes to tumorigenesis when expressed at an early stage of differentiation, and provide a mouse model of MDM2 tumorigenesis relevant to p53's tumour suppressor functions.
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Affiliation(s)
- G Ganguli
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, 1 Rue Laurent Fries, BP 163, F-67404 Illkirch cedex France
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126
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Strano S, Munarriz E, Rossi M, Cristofanelli B, Shaul Y, Castagnoli L, Levine AJ, Sacchi A, Cesareni G, Oren M, Blandino G. Physical and functional interaction between p53 mutants and different isoforms of p73. J Biol Chem 2000; 275:29503-12. [PMID: 10884390 DOI: 10.1074/jbc.m003360200] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
p53 is the most frequently inactivated tumor suppressor gene in human cancer, whereas its homologue, p73, is rarely mutated. Similarly to p53, p73 can promote growth arrest or apoptosis when overexpressed in certain p53-null tumor cells. It has previously been shown that some human tumor-derived p53 mutants can exert gain of function activity. The molecular mechanism underlying this activity remains to be elucidated. We show here that human tumor-derived p53 mutants (p53His175 and p53Gly281) associate in vitro and in vivo with p73 alpha, beta, gamma, and delta. This association occurs under physiological conditions, as verified in T47D and SKBR3 breast cancer cell lines. The core domain of mutant p53 is sufficient for the association with p73, whereas both the specific DNA binding and the oligomerization domains of p73 are required for the association with mutant p53. Furthermore, p53His175 and p53Gly281 mutants markedly reduce the transcriptional activity of the various isoforms of p73. Thus, human tumor-derived p53 mutants can associate with p73 not only physically but also functionally. These findings define a network involving mutant p53 and the various spliced isoforms of p73 that may confer upon tumor cells a selective survival advantage.
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Affiliation(s)
- S Strano
- Molecular Oncogenesis Laboratory, Regina Elena Cancer Center, Via delle Messi d'Oro 156, Rome 00158, Italy
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127
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Weber JD, Jeffers JR, Rehg JE, Randle DH, Lozano G, Roussel MF, Sherr CJ, Zambetti GP. p53-independent functions of the p19(ARF) tumor suppressor. Genes Dev 2000; 14:2358-65. [PMID: 10995391 PMCID: PMC316930 DOI: 10.1101/gad.827300] [Citation(s) in RCA: 273] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The p19(ARF) tumor suppressor antagonizes Mdm2 to induce p53-dependent cell cycle arrest. Individual TKO (triple knock out) mice nullizygous for ARF, p53, and Mdm2 develop multiple tumors at a frequency greater than those observed in animals lacking both p53 and Mdm2 or p53 alone, demonstrating that p19(ARF) can act independently of the Mdm2-p53 axis in tumor surveillance. Reintroduction of ARF into TKO mouse embryo fibroblasts (MEFs), but not into those lacking both p53 and ARF, arrested the cell division cycle in the G1 phase. Inhibition of the retinoblastoma protein had no effect on the ability of ARF to arrest TKO MEFs. Thus, in the absence of Mdm2, p19(ARF) interacts with other targets to inhibit cell proliferation.
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Affiliation(s)
- J D Weber
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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128
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Banelli B, Casciano I, Romani M. Methylation-independent silencing of the p73 gene in neuroblastoma. Oncogene 2000; 19:4553-6. [PMID: 11002429 DOI: 10.1038/sj.onc.1203807] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
p73 is a p53 homolog that, in vitro, inhibits cell growth and induce apoptosis. In some tumors p73 is monoallelically expressed and this raised the possibility that this gene is subjected to imprinting. Silencing of p73 in acute leukemia and in Burkitt's lymphoma occurs in association with the aberrant methylation of the first exon of the gene. We have analysed the methylation pattern of the p73 promoter and of upstream and downstream sequences in neuroblastoma. Our results demonstrate that p73 expression in this tumor is not regulated by methylation. We concluded that it is unlikely that p73 is imprinted in neuroblastoma and that the methylation-dependent silencing of this gene, thus far, is a characteristic of hematologic malignancies. Oncogene (2000) 19, 4553 - 4556.
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Affiliation(s)
- B Banelli
- Istituto Nazionale per la Ricerca sul Cancro (IST-Genova), Italy
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129
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Pozniak CD, Radinovic S, Yang A, McKeon F, Kaplan DR, Miller FD. An anti-apoptotic role for the p53 family member, p73, during developmental neuron death. Science 2000; 289:304-6. [PMID: 10894779 DOI: 10.1126/science.289.5477.304] [Citation(s) in RCA: 392] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
p53 plays an essential pro-apoptotic role, a function thought to be shared with its family members p73 and p63. Here, we show that p73 is primarily present in developing neurons as a truncated isoform whose levels are dramatically decreased when sympathetic neurons apoptose after nerve growth factor (NGF) withdrawal. Increased expression of truncated p73 rescues these neurons from apoptosis induced by NGF withdrawal or p53 overexpression. In p73-/- mice, all isoforms of p73 are deleted and the apoptosis of developing sympathetic neurons is greatly enhanced. Thus, truncated p73 is an essential anti-apoptotic protein in neurons, serving to counteract the pro-apoptotic function of p53.
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Affiliation(s)
- C D Pozniak
- Center for Neuronal Survival, Brain Tumor Research Center, Montreal Neurological Institute, McGill University, Montreal, Canada H3A 2B4
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130
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Crook T, Nicholls JM, Brooks L, O'Nions J, Allday MJ. High level expression of deltaN-p63: a mechanism for the inactivation of p53 in undifferentiated nasopharyngeal carcinoma (NPC)? Oncogene 2000; 19:3439-44. [PMID: 10918601 DOI: 10.1038/sj.onc.1203656] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Undifferentiated nasopharyngeal carcinoma (NPC) is an epithelial malignancy that is consistently associated with Epstein-Barr virus (EBV) but which very rarely has p53 gene mutations in primary tumours. Since the tumour suppressor p53 is mutated in most human cancers or the wild type protein is inactivated in a significant number of the remainder, here we have investigated cellular factors that could compromise p53 function in primary NPC. Twenty-five primary tumours were judged to carry only wild type p53 by SSCP analysis of all exons and sequence determination of exons 4-9. Only one tumour was found to express significant levels of hMdm2 and in 24/25 there were no detectable mutations or deletions in exons 1beta and 2 of the p14(ARF) gene. However, immunohistochemistry consistently revealed that all the tumour cells express substantial amounts of the p53-related protein p63. Semi-quantitative RT-PCR analysis of mRNA from tumour biopsies showed that the dominant species expressed was invariably the truncated deltaN-isotype. Since this can block p53-mediated transactivation, it is potentially a dominant-negative isoform. In normal nasopharyngeal epithelium the distribution of p63 was restricted to the proliferating basal and suprabasal layers. We suggest that deltaN-p63 is a good candidate as a suppressor of wild type p53 function in these tumours and also that it may prove to be a valuable diagnostic marker for undifferentiated NPC.
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Affiliation(s)
- T Crook
- Ludwig Institute for Cancer Research and Section of Virology and Cell Biology, Imperial College of Science, Technology and Medicine, London, UK
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131
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Abstract
The recent discovery of a Drosophila orthologue of the p53 tumour suppressor promises new insights into the complex function, regulation and evolution of one of the most intensely studied human disease proteins.
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132
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Marin MC, Kaelin WG. p63 and p73: old members of a new family. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1470:M93-M100. [PMID: 10799748 DOI: 10.1016/s0304-419x(00)00010-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- M C Marin
- Dana Farber Cancer Institute and Harvard Medical School, 44 Binney St., Boston, MA 02115, USA
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133
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Lohrum MA, Vousden KH. Regulation and function of the p53-related proteins: same family, different rules. Trends Cell Biol 2000; 10:197-202. [PMID: 10754563 DOI: 10.1016/s0962-8924(00)01736-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The tumour-suppressor protein p53 has recently been shown to belong to a family that includes two structurally related proteins, p63 and p73. Although all three proteins share similar transcriptional functions and the ability to induce apoptosis, each of them appears to play a distinct role in development and tumour suppression. In order for cell division to occur, the antiproliferative activities of these proteins must be tightly controlled, and exciting advances have been made in our understanding of the pathways involved in regulating p53 activity.
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Affiliation(s)
- M A Lohrum
- Regulation of Cell Growth Laboratory, NCI-FCRDC, Frederick, MD 21702-1201, USA
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134
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Holmdahl R. Rheumatoid arthritis viewed using a headache paradigm. ARTHRITIS RESEARCH 2000; 2:169-71. [PMID: 11094426 PMCID: PMC129997 DOI: 10.1186/ar84] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2000] [Accepted: 03/01/2000] [Indexed: 02/02/2023]
Abstract
Results and new hypotheses in animal models often stimulate development of new paradigms in how we view rheumatoid arthritis (RA). The complexity of RA does, however, eventually lead to the rejection of these hypotheses. Here, it is argued that the large number of so-far described animal models, when taken together, also reveals a complex disease. Fortunately, detailed study of each of the animal models will reveal this complexity, and may also be helpful in elucidating the complexity of the human disease. Benoist and Mathis [1] recently contributed a new animal model in which an autoimmune response to a ubiquitous antigen leads to an antibody-mediated inflammatory attack in the joints. It is argued that this new model, as with other animal models, is unlikely to explain RA, but it will add to the tools available to reveal the complexity of RA.
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Affiliation(s)
- R Holmdahl
- Medical Inflammation Research, Lund University, Lund, Sweden.
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135
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Ollmann M, Young LM, Di Como CJ, Karim F, Belvin M, Robertson S, Whittaker K, Demsky M, Fisher WW, Buchman A, Duyk G, Friedman L, Prives C, Kopczynski C. Drosophila p53 is a structural and functional homolog of the tumor suppressor p53. Cell 2000; 101:91-101. [PMID: 10778859 DOI: 10.1016/s0092-8674(00)80626-1] [Citation(s) in RCA: 322] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The importance of p53 in carcinogenesis stems from its central role in inducing cell cycle arrest or apoptosis in response to cellular stresses. We have identified a Drosophila homolog of p53 ("Dmp53"). Like mammalian p53, Dmp53 binds specifically to human p53 binding sites, and overexpression of Dmp53 induces apoptosis. Importantly, inhibition of Dmp53 function renders cells resistant to X ray-induced apoptosis, suggesting that Dmp53 is required for the apoptotic response to DNA damage. Unlike mammalian p53, Dmp53 appears unable to induce a G1 cell cycle block when overexpressed, and inhibition of Dmp53 activity does not affect X ray-induced cell cycle arrest. These data reveal an ancestral proapoptotic function for p53 and identify Drosophila as an ideal model system for elucidating the p53 apoptotic pathway(s) induced by DNA damage.
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Affiliation(s)
- M Ollmann
- Exelixis, Inc., South San Francisco, California 94080, USA
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136
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Müller-Ladner U, Nishioka K. p53 in rheumatoid arthritis: friend or foe? ARTHRITIS RESEARCH 2000; 2:175-8. [PMID: 11094424 PMCID: PMC129999 DOI: 10.1186/ar82] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 02/17/2000] [Accepted: 03/15/2000] [Indexed: 11/10/2022]
Abstract
The knowledge of transcription factors and proto-oncogenes has influenced the understanding of cell regulation, cell cycle, and apoptotic cell death in rheumatoid arthritis (RA) synovium. In addition, the development of normal synovial fibroblasts into transformed-appearing aggressive synovial fibroblasts may be triggered by the lack of antiproliferative factors, such as p53, p53-associated molecules, other tumor suppressors, as well as by upregulation of anti-apoptotic genes. Therefore, data derived from experiments such as those performed by Tak and colleagues in this issue of Arthritis Research not only enrich the intensive discussion addressing the impact of p53 on RA pathophysiology, they also may facilitate development of novel therapeutic approaches including p53-targeted gene therapy.
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Affiliation(s)
- U Müller-Ladner
- Department of Internal Medicine I, University of Regensburg, Regensburg, Germany.
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