Protection of halogenated DNA from strand breakage and sister-chromatid exchange induced by the topoisomerase I inhibitor camptothecin

Department of Cell Biology, Faculty of Biology, University of Seville, Seville, Spain.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis (Impact Factor: 3.68). 02/2008; 637(1-2):40-8. DOI: 10.1016/j.mrfmmm.2007.06.012
Source: PubMed


The fundamental nuclear enzyme DNA topoisomerase I (topo I), cleaves the double-stranded DNA molecule at preferred sequences within its recognition/binding sites. We have recently reported that when cells incorporate halogenated nucleosides analogues of thymidine into DNA, it interferes with normal chromosome segregation, as shown by an extraordinarily high yield of endoreduplication, and results in a protection against DNA breakage induced by the topo II poison m-AMSA [F. Cortés, N. Pastor, S. Mateos, I. Domínguez, The nature of DNA plays a role in chromosome segregation: endoreduplication in halogen-substituted chromosomes, DNA Repair 2 (2003) 719-726; G. Cantero, S. Mateos, N. Pastor; F. Cortés, Halogen substitution of DNA protects from poisoning of topoisomerase II that results in DNA double-strand breaks (DSBs), DNA Repair 5 (2006) 667-674]. In the present investigation, we have assessed whether the presence of halogenated nucleosides in DNA diminishes the frequency of interaction of topo I with DNA and thus the frequency with which the stabilisation of cleavage complexes by the topo I poison camptothecin (CPT) takes place, in such a way that it protects from chromosome breakage and sister-chromatid exchange. This protective effect is shown to parallel a loss in halogen-substituted cells of the otherwise CPT-increased catalytic activity bound to DNA.

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Available from: Santiago Mateos, Oct 05, 2015
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    • "Our data suggest that DSBs arising as a consequence of 5-azadC incorporation are generated during the second round of DNA replication. It is well accepted that replication-induced DSBs are potent substrates for HR giving rise to RAD51-mediated SCEs formation (24–26). To test this directly, we treated cells with increasing doses of 5-azadC and scored SCEs or RAD51 foci formation. "
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    Nucleic Acids Research 04/2013; 41(11). DOI:10.1093/nar/gkt270 · 9.11 Impact Factor
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    ABSTRACT: Methylation of cytosine in CpG sequences of the DNA in mammalian cells is an epigenetic feature regulated very exactly that bears importance for events like gene expression, DNA replication, transcription and genetic imprinting. Changes in the DNA methylation pattern, both hypermethylation and hypomethylation, have been observed in the carcinogenic process. These changes, in general, influence the DNA conformation in such a way that certain proteins are disturbed in their interactions with the molecule. In this paper, we investigated in cultured Chinese hamster ovary cells the influence of hypomethylation induced by the substitution of 5-aza-2'-deoxycytidine for cytidine in DNA on topoisomerase type I (topo I) function, measured as the capacity of the enzyme inhibitor camptothecin (CPT) to stabilize the topoisomerase-DNA complexes and to induce DNA strand breakage. Our results demonstrate that the degree of methylation in DNA correlates with the effectiveness of CPT to stabilize the topo I-DNA complexes and to induce DNA cleavage. A protective effect of hypomethylation, as a whole, has been observed.
    Mutagenesis 03/2009; 24(3):237-44. DOI:10.1093/mutage/gep002 · 2.79 Impact Factor
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    ABSTRACT: We used the conventional bone marrow micronucleus test complemented with the fluorescent in situ hybridization with the minor satellite DNA probe to investigate the mechanisms of induction of micronuclei in mice treated with camptothecin and its clinical antineoplastic analogues topotecan and irinotecan. All experiments were performed with male Swiss albino mice. Single doses of 1 mg/kg camptothecin or 0.6 mg/kg topotecan were injected intraperitoneally and bone marrow was sampled at 30 hr (camptothecin) or 24 hr (topotecan) after treatment. A dose of 60 mg/kg irinotecan was injected intravenously, once every fourth day for 13 days and bone marrow was sampled 24 hr after the last treatment. In animals treated with camptothecin, a total of 1.07% micronuclei were found and 70% of them were centromere-negative, indicating their formation by DNA strand breaks and reflecting the predominant clastogenic activity of camptothecin. Exposure to topotecan and irinotecan yielded 1.71 and 0.83% micronuclei, respectively. About 52.7 and 48.8% of the induced micronuclei, respectively, were centromere-positive, indicating their formation by whole chromosomes and reflecting the aneugenic activity of both compounds. Correspondingly, about 47.3 and 51.2% of the induced micronuclei, respectively were centromere-negative, demonstrating that topotecan and irinotecan not only induce chromosome loss but also DNA strand breaks. Both the clastogenic and aneugenic potential of these drugs can lead to the development of secondary tumors and abnormal reproductive outcomes. Therefore, the clinical use of these agents must be weighed against the risks of secondary malignancies in cured patients and persistent genetic damage of their potential offspring.
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