RESUMO
The Saccharomyces cerevisiae TOP3 gene encodes the type IA topoisomerase (Top3p) that is highly conserved in evolution. Deletion of TOP3 leads to a reduction in cell viability, hyper-recombination between repetitive DNA sequences, and abnormalities in both cell cycle progression and responses to DNA damaging agents. Deletion of SGS1, encoding the sole RecQ family helicase in S. cerevisiae, strongly suppresses the phenotypic effects of loss of TOP3 function. Here, we show that many of the adverse phenotypic effects of TOP3 deletion can also be partially alleviated by disruption of homologous recombination (HR) functions. This genetic interaction is seen both in strains deleted for TOP3 and in wild-type strains over-expressing a dominant-negative Top3p mutant form that confers a top3-like phenotype. Moreover, we show that this genetic interaction is conserved in the distantly-related fission yeast, Schizosaccharomyces pombe. Our results implicate topoisomerase III enzymes in recombination repair events required for cellular protection against DNA damaging agents and DNA replication inhibitors.
Assuntos
Proteínas de Ciclo Celular , DNA Helicases/metabolismo , DNA Topoisomerases Tipo I/metabolismo , Recombinação Genética/genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/enzimologia , Schizosaccharomyces/enzimologia , Western Blotting , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/genética , Ciclo Celular/efeitos da radiação , Sobrevivência Celular , Quinase do Ponto de Checagem 2 , Dano ao DNA , DNA Helicases/antagonistas & inibidores , DNA Helicases/genética , Reparo do DNA , DNA Topoisomerases Tipo I/deficiência , DNA Topoisomerases Tipo I/genética , Epistasia Genética , Regulação Fúngica da Expressão Gênica , Genes Dominantes/genética , Humanos , Metanossulfonato de Metila/farmacologia , Mutagênese , Mutagênicos/farmacologia , Fenótipo , Fosforilação , Proteínas Serina-Treonina Quinases/metabolismo , RecQ Helicases , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/genética , Schizosaccharomyces/efeitos dos fármacos , Schizosaccharomyces/genética , Deleção de Sequência , Raios UltravioletaRESUMO
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.
