351
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Abstract
Oncogenic tyrosine kinases (OTKs) are involved in the induction of many types of tumour, including haematological malignancies and cancers of the breast, prostate, colon and lung. Neoplastic cells that express OTKs are usually resistant to apoptosis that is induced by DNA-damaging agents, such as cytostatic drugs and irradiation, and they display genomic instability. So, what are the mechanisms involved, and what is the potential for overcoming OTK-mediated resistance in the clinic?
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Affiliation(s)
- Tomasz Skorski
- Center for Biotechnology, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA.
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352
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Martelli A, Constant JF, Demeunynck M, Lhomme J, Dumy P. Design of site specific DNA damaging agents for generation of multiply damaged sites. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00345-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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353
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Svensson LA, Henning P, Lagergård T. The cytolethal distending toxin of Haemophilus ducreyi inhibits endothelial cell proliferation. Infect Immun 2002; 70:2665-9. [PMID: 11953409 PMCID: PMC127913 DOI: 10.1128/iai.70.5.2665-2669.2002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2001] [Revised: 11/04/2001] [Accepted: 01/29/2002] [Indexed: 11/20/2022] Open
Abstract
Haemophilus ducreyi, the etiologic agent of the sexually transmitted disease chancroid, produces a cytolethal distending toxin (HdCDT) that inhibits mammalian cell proliferation. We investigated the effects of HdCDT on normal human endothelial cells and on tubule formation in an in vitro model of angiogenesis. Endothelial cells were arrested in the G2 phase of the cell cycle, and tubule formation was inhibited in a dose-dependent manner. The antiproliferative activities of HdCDT on endothelial cells might contribute to the characteristic slow healing and persistence of chancroid ulcers.
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Affiliation(s)
- Liselott A Svensson
- Department of Medical Microbiology and Immunology, Göteborg University, S-4136 Göteborg, Sweden
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354
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Braastad CD, Leguia M, Hendrickson EA. Ku86 autoantigen related protein-1 transcription initiates from a CpG island and is induced by p53 through a nearby p53 response element. Nucleic Acids Res 2002; 30:1713-24. [PMID: 11937624 PMCID: PMC113227 DOI: 10.1093/nar/30.8.1713] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The human Ku86 gene and an isoform, KARP-1 (Ku86 autoantigen related protein-1), encode overlapping, but differentially regulated, transcripts. Ku86 is constitutively transcribed at high levels and, although it plays a seminal role in DNA double-strand break repair, its expression is not induced by DNA damage. KARP-1, in contrast, is expressed constitutively only at low levels and its expression is induced by DNA damage in a p53-dependent fashion. The regulatory elements promoting KARP-1 gene expression and p53 responsiveness, however, were unknown. Here, we report that a strong DNase I hypersensitive site (DHS) resides approximately 25 kb upstream from the Ku86 promoter. This DHS is encompassed by a hypomethylated CpG island. Reporter assays demonstrated that this region corresponded to a promoter(s), which promoted transcription of peroxisomal trans-2-enoyl CoA reductase in the centromeric direction and KARP-1 in the telomeric direction. KARP-1 primer extension products were mapped to this CpG island in the correct transcriptional orientation confirming that KARP-1 transcription initiates from this site. Moreover, a p53 response element within the first intron of the KARP-1 transcriptional unit was identified using chromatin immunoprecipitation and antibodies specific to activated forms of p53. These data expand our understanding of this important DNA repair locus.
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Affiliation(s)
- Corey D Braastad
- Department of Molecular Biology, Cellular Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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355
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Abstract
Cancers arise as a result of genetic changes that impact upon cell proliferation through promoting cell division and/or inhibiting cell death. Tumour suppressor (TS) genes are the targets for many of these genetic changes. In general, both alleles of TS genes must be disrupted to observe a phenotypic effect. Broadly speaking, there are two types of TS gene: 'gatekeepers' and 'caretakers'. In contrast to gatekeepers, caretaker genes do not directly regulate proliferation, but act to prevent genomic instability. Thus, mutation of caretaker genes leads to accelerated conversion of a normal cell to a neoplastic cell. Many caretaker genes are required for the maintenance of genome integrity. This review focuses on those caretaker genes that play a role, directly or indirectly, in the repair of DNA strand breaks by the homologous recombination pathway, and that are associated with cancer-prone clinical syndromes, in particular ataxia telangiectasia, hereditary breast cancer, Bloom's syndrome and Werner's syndrome.
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Affiliation(s)
- Nicola C Levitt
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK OX3 9DS
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356
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Sparfel L, Loewert M, Huc L, Payen L, Guillouzo A, Lagadic-Gossmann D, Fardel O. Acute cytotoxicity of the chemical carcinogen 2-acetylaminofluorene in cultured rat liver epithelial cells. Toxicol Lett 2002; 129:245-54. [PMID: 11888708 DOI: 10.1016/s0378-4274(02)00015-2] [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: 11/17/2022]
Abstract
Acute cytotoxic effects of 2-acetylaminofluorene (AAF), a powerful chemical carcinogen, were studied in cultured rat liver epithelial F258 cells. Acute treatment of these cells by AAF resulted in inhibition of cell proliferation, through an arrest in G0/G1 phase of the cell cycle, and a loss of cell viability. By contrast, AAF failed to trigger apoptosis as demonstrated by flow cytometric analysis of hypoploid sub-G1 cells. Cytochrome P4501A1 (CYP1A1), a drug metabolizing enzyme thought to play a major role in biotransformation of AAF, was induced in AAF-treated F258 cells as assessed by Northern blotting. AAF cytotoxic effects were however not blocked by the CYP1A1 inhibitor alpha-naphtoflavone, thus suggesting that they did not require CYP1A1 activity. They were also not prevented by the antioxidant N-acetylcysteine, making unlikely a major contribution of AAF-related reactive oxygen species. These data therefore indicate that AAF can exert acute cellular toxicity, including inhibition of cell growth and cell death, in rat liver epithelial cells without triggering an apoptotic process. Such an acute toxicity may contribute to the well-known promoting effects of AAF.
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Affiliation(s)
- Lydie Sparfel
- INSERM U456, Faculté de Pharmacie, 2 Avenue du Pr L. Bernard, 35043, Rennes, France
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357
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Oakley TJ, Hickson ID. Defending genome integrity during S-phase: putative roles for RecQ helicases and topoisomerase III. DNA Repair (Amst) 2002; 1:175-207. [PMID: 12509252 DOI: 10.1016/s1568-7864(02)00002-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The maintenance of genome stability is important not only for cell viability, but also for the suppression of neoplastic transformation in higher eukaryotes. It has long been recognised that a common feature of cancer cells is genomic instability. Although the so-called three 'Rs' of genome maintenance, DNA replication, recombination and repair, have historically been studied in isolation, a wealth of recent evidence indicates that these processes are intimately interrelated and interdependent. In this article, we will focus on challenges to the maintenance of genome integrity that arise during the S-phase of the cell cycle, and the possible roles that RecQ helicases and topoisomerase III play in the maintenance of genome integrity during the process of DNA replication.
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Affiliation(s)
- Thomas J Oakley
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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358
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Abstract
Over 60 years ago Barbara McClintock described the telomere and suggested that it protected the chromosome from illegitimate or end-to-end fusion, thus functioning to protect the genome. Since that time we have discovered that the telomere is a complex structure composed of both DNA and a growing list of associated proteins that together serve to regulate the length of the telomere and, as predicted by McClintock, protect genomic integrity. In addition to its protective role, the telomere has also been hypothesized to serve as a molecular clock that tallies the number of cell divisions and limits further divisions at a predetermined point. However, the precise role of telomeres in predicting and limiting cellular lifespan remains a matter of much debate. In this review, we highlight some of the salient points of basic telomere biology and relate them to the current controversies surrounding the role of telomeres and telomerase in cellular senescence.
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Affiliation(s)
- Sheila A Stewart
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, MA 02142, USA
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359
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Polager S, Kalma Y, Berkovich E, Ginsberg D. E2Fs up-regulate expression of genes involved in DNA replication, DNA repair and mitosis. Oncogene 2002; 21:437-46. [PMID: 11821956 DOI: 10.1038/sj.onc.1205102] [Citation(s) in RCA: 205] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2001] [Revised: 10/29/2001] [Accepted: 10/29/2001] [Indexed: 12/16/2022]
Abstract
The E2F family of transcription factors plays a pivotal role in the regulation of cell proliferation in higher eukaryotes. We used DNA microarrays and cell lines containing either inducible E2F-1 or inducible E2F-3 to identify novel E2F target genes. Our data indicate that E2F up-regulates the expression of genes not previously described as E2F target genes. A number of these E2F-regulated genes are involved in DNA replication, DNA repair and mitosis. These results suggest that E2F affects cell cycle progression both at S phase and during mitosis. Furthermore, our findings indicate that E2F-dependent gene activation may contribute to the cellular response to DNA damage.
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Affiliation(s)
- Shirley Polager
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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360
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Schimmer AD, Hedley DW, Penn LZ, Minden MD. Receptor- and mitochondrial-mediated apoptosis in acute leukemia: a translational view. Blood 2001; 98:3541-53. [PMID: 11739155 DOI: 10.1182/blood.v98.13.3541] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Affiliation(s)
- A D Schimmer
- Princess Margaret Hospital, University Health Network, Toronto, ON, Canada.
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361
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Abstract
Abasic sites are the most commonly formed DNA lesions in the cell and are produced by numerous endogenous and environmental insults. In addition, they are generated by the initial step of base excision repair (BER). When located within a topoisomerase II DNA cleavage site, "intact" abasic sites act as topoisomerase II poisons and dramatically stimulate enzyme-mediated DNA scission. However, most abasic sites in cells are not intact. They exist as processed BER intermediates that contain DNA strand breaks proximal to the damaged residue. When strand breaks are located within a topoisomerase II DNA cleavage site, they create suicide substrates that are not religated readily by the enzyme and can generate permanent double-stranded DNA breaks. Consequently, the effects of processed abasic sites on DNA cleavage by human topoisomerase IIalpha were examined. Unlike substrates with intact abasic sites, model BER intermediates containing 5'- or 3'-nicked abasic sites or deoxyribosephosphate flaps were suicide substrates. Furthermore, abasic sites flanked by 5'- or 3'-nicks were potent topoisomerase II poisons, enhancing DNA scission approximately 10-fold compared with corresponding nicked oligonucleotides that lacked abasic sites. These findings suggest that topoisomerase II is able to convert processed BER intermediates to permanent double-stranded DNA breaks.
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Affiliation(s)
- A M Wilstermann
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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362
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Abstract
Chromosomal instability can occur when the DNA damage response and repair process fails, resulting in syndromes characterized by growth abnormalities, hematopoietic defects, mutagen sensitivity, and cancer predisposition. Mutations in ATM, NBS1, MRE11, BLM, WRN, and FANCD2 are responsible for ataxia telangiectasia (AT), Nijmegen breakage syndrome, AT-like disorder, Bloom and Werner syndrome, and Fanconi anemia group D2, respectively. This diverse group of disorders is thought to be linked through protein interactions with the breast cancer tumor susceptibility gene product, BRCA1. BRCA1 forms a multi-subunit protein complex referred to as the BRCA1-associated genome surveillance complex (BASC), which includes DNA damage repair proteins such as MSH2-MSH6 and MLH1, as well as ATM, NBS1, MRE11, and BLM. Although still controversial, this finding suggests similarities in the pathogenesis of the human chromosome breakage syndromes and a complementary role for each protein in DNA structure surveillance or damage repair.
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Affiliation(s)
- M Futaki
- Hematology Branch, NHLBI, National Institutes of Health, Building 10, Room 7C103, Bethesda, MD 20892, USA
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363
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Chen MS, Laszlo A, Roti Roti J. Determination of the impact of DNA damage sites on DNA duplex stability by a competitive mobility-shift assay. Anal Biochem 2001; 298:121-4. [PMID: 11673904 DOI: 10.1006/abio.2001.5353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- M S Chen
- Section of Cancer Biology, Radiation Oncology Center, MIR, Washington University School of Medicine, 4511 Forest Park Boulevard, Suite 411, St. Louis, Missouri 63018, USA.
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364
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Chakraverty RK, Kearsey JM, Oakley TJ, Grenon M, de La Torre Ruiz MA, Lowndes NF, Hickson ID. Topoisomerase III acts upstream of Rad53p in the S-phase DNA damage checkpoint. Mol Cell Biol 2001; 21:7150-62. [PMID: 11585898 PMCID: PMC99890 DOI: 10.1128/mcb.21.21.7150-7162.2001] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Deletion of the Saccharomyces cerevisiae TOP3 gene, encoding Top3p, leads to a slow-growth phenotype characterized by an accumulation of cells with a late S/G2 content of DNA (S. Gangloff, J. P. McDonald, C. Bendixen, L. Arthur, and R. Rothstein, Mol. Cell. Biol. 14:8391-8398, 1994). We have investigated the function of TOP3 during cell cycle progression and the molecular basis for the cell cycle delay seen in top3Delta strains. We show that top3Delta mutants exhibit a RAD24-dependent delay in the G2 phase, suggesting a possible role for Top3p in the resolution of abnormal DNA structures or DNA damage arising during S phase. Consistent with this notion, top3Delta strains are sensitive to killing by a variety of DNA-damaging agents, including UV light and the alkylating agent methyl methanesulfonate, and are partially defective in the intra-S-phase checkpoint that slows the rate of S-phase progression following exposure to DNA-damaging agents. This S-phase checkpoint defect is associated with a defect in phosphorylation of Rad53p, indicating that, in the absence of Top3p, the efficiency of sensing the existence of DNA damage or signaling to the Rad53 kinase is impaired. Consistent with a role for Top3p specifically during S phase, top3Delta mutants are sensitive to the replication inhibitor hydroxyurea, expression of the TOP3 mRNA is activated in late G1 phase, and DNA damage checkpoints operating outside of S phase are unaffected by deletion of TOP3. All of these phenotypic consequences of loss of Top3p function are at least partially suppressed by deletion of SGS1, the yeast homologue of the human Bloom's and Werner's syndrome genes. These data implicate Top3p and, by inference, Sgs1p in an S-phase-specific role in the cellular response to DNA damage. A model proposing a role for these proteins in S phase is presented.
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Affiliation(s)
- R K Chakraverty
- Imperial Cancer Research Fund Laboratories, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, United Kingdom
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365
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García-Díaz M, Bebenek K, Kunkel TA, Blanco L. Identification of an intrinsic 5'-deoxyribose-5-phosphate lyase activity in human DNA polymerase lambda: a possible role in base excision repair. J Biol Chem 2001; 276:34659-63. [PMID: 11457865 DOI: 10.1074/jbc.m106336200] [Citation(s) in RCA: 185] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Base excision repair (BER) is a major repair pathway in eukaryotic cells responsible for repair of lesions that give rise to abasic (AP) sites in DNA. Pivotal to this process is the 5'-deoxyribose-5-phosphate lyase (dRP lyase) activity of DNA polymerase beta (Pol beta). DNA polymerase lambda (Pol lambda) is a recently identified eukaryotic DNA polymerase that is homologous to Pol beta. We show here that human Pol lambda exhibits dRP lyase, but not AP lyase, activity in vitro and that this activity is consistent with a beta-elimination mechanism. Accordingly, a single amino acid substitution (K310A) eliminated more than 90% of the wild-type dRP lyase activity, thus suggesting that Lys(310) of Pol lambda is the main nucleophile involved in the reaction. The dRP lyase activity of Pol lambda, in coordination with its polymerization activity, efficiently repaired uracil-containing DNA in an in vitro reconstituted BER reaction. These results suggest that Pol lambda may participate in "single-nucleotide" base excision repair in mammalian cells.
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Affiliation(s)
- M García-Díaz
- Centro de Biologia Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, 28049 Madrid, Spain
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