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: 4.44). 02/2008; 637(1-2):40-8. DOI: 10.1016/j.mrfmmm.2007.06.012
Source: PubMed

ABSTRACT 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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    ABSTRACT: esponja marina del Caribe colombiano Topsentia ophiraphidites (Fracción T4). Materiales y métodos. La fracción T4 de la esponja marina Topsentia ophiraphidites fue obtenida en el laboratorio de Productos Naturales Marinos de la Universidad de Antioquia. La actividad antiproliferativa se evaluó mediante ensayos de eficiencia de clonación, función de acumulación y cinética proliferativa por intercambio de cromátidas hermanas (ICH); la actividad genotóxica se evaluó mediante electroforesis en gel de células individuales (Ensayo cometa) e intercambio de cromátidas hermanas (ICH). Todas las pruebas fueron realizadas sobre las líneas celulares Jurkat y CHO. Resultados. La fracción T4 afectó el ciclo celular de las células CHO y mostró daño genotóxica crónico en las células Jurkat. Conclusiones. Se recomienda la evaluación de la fracción T4 en otras líneas celulares derivadas de tumor con el fin de determinar un posible efecto diferencial, además de evaluar otras actividades de tipo antimicrobiano, antimalárico, entre otros. ABSTRACT Objective. To evaluate the antiproliferative and genotoxic activity of a fraction (T4 fraction) of the Colombian Caribbean marine sponge Topsentia ophiraphidites, with cytotoxic activity. Materials and methods. T4 fraction from the marine sponge Topsentia ophiraphidites was provided by the group of marine natural products from Universidad de Antioquia. The antiproliferative activity was evaluated by cloning efficiency tests, accumulation function, and proliferative kinetics by sister chromatid exchange (SCE), genotoxic activity was evaluated by SCE and gel electrophoresis of individual cells (Comet assay). All tests were performed on Jurkat and CHO cell lines. Results. The T4 fraction affected the cell cycle of CHO cells and presented chronic genotoxic damage in Jurkat cells. Conclusions. It is recommended to evaluate the T4 fraction in other derived tumor cell lines, in order to observe a possible differential effect, and to evaluate antimicrobial and antimalarial activities among others.
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    ABSTRACT: A series of title compounds 2 and 3 were efficiently synthesized via the condensation of 10–hydroxycamptothecin with various symmetric (O,O′-monoaryl)-thiophosphoryl chlorides and asymmetric (O-ethyl-O′-aryl)-thiophosphoryl chlorides in sodium hydroxide powder and acetonitrile system. The structures of title compounds 2 and 3 were confirmed by elemental analysis, IR, H NMR, C NMR, P[H] NMR,and mass spectral data. These symmetric [(O,O′-monoaryl)-thiophosphoryl)]-(20S)-camptothecin (2a–f) and asymmetric [(O-ethyl-O′-aryl)-thiophosphoryl)]-(20S)-camptothecin (3a–f) compounds were also tested for their in vitro antimicrobial activities against some bacterial strains, namely, S. aureus, B. Simplex, E. acetylicum, E. coli, P. aeruginosa, S. flexenari, S. aureus, S. typhi, and some fungal strains Aspergillus niger, Aspergillus flavus (molds), S. cerevisiae, C. albicans, T. longifucus, A. flavus, M. canis, F. solani, and C. glaberata (yeasts).Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the related elements to view the free supplemental file.
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    ABSTRACT: 5-Aza-2'-deoxycytidine (5-azadC) is a DNA methyltransferase (DNMT) inhibitor increasingly used in treatments of hematological diseases and works by being incorporated into DNA and trapping DNMT. It is unclear what DNA lesions are caused by 5-azadC and if such are substrates for DNA repair. Here, we identify that 5-azadC induces DNA damage as measured by γ-H2AX and 53BP1 foci. Furthermore, 5-azadC induces radial chromosomes and chromatid breaks that depend on active replication, which altogether suggest that trapped DNMT collapses oncoming replication forks into double-strand breaks. We demonstrate that RAD51-mediated homologous recombination (HR) is activated to repair 5-azadC collapsed replication forks. Fanconi anemia (FA) is a rare autosomal recessive disorder, and deaths are often associated with leukemia. Here, we show that FANCG-deficient cells fail to trigger HR-mediated repair of 5-azadC-induced lesions, leading to accumulation of chromatid breaks and inter-chromosomal radial fusions as well as hypersensitivity to the cytotoxic effects of 5-azadC. These data demonstrate that the FA pathway is important to protect from 5-azadC-induced toxicity. Altogether, our data demonstrate that cytotoxicity of the epigenetic drug 5-azadC can, at least in part, be explained by collapsed replication forks requiring FA-mediated HR for repair.
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