RESUMO
DNA damage tolerance (DDT) mechanisms facilitate replication resumption and completion when DNA replication is blocked by bulky DNA lesions. In budding yeast, template switching (TS) via the Rad18/Rad5 pathway is a favored DDT pathway that involves usage of the sister chromatid as a template to bypass DNA lesions in an error-free recombination-like process. Here, we establish that the Snf2 family translocase Irc5 is a novel factor that promotes TS and averts single-stranded DNA persistence during replication. We demonstrate that, during replication stress, Irc5 enables replication progression by assisting enrichment of cohesin complexes, recruited in an Scc2/Scc4-dependent fashion, near blocked replication forks. This allows efficient formation of sister chromatid junctions that are crucial for error-free DNA lesion bypass. Our results support the notion of a key role of cohesin in the completion of DNA synthesis under replication stress and reveal that the Rad18/Rad5-mediated DDT pathway is linked to cohesin enrichment at sites of perturbed replication via the Snf2 family translocase Irc5.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Dano ao DNA , Replicação do DNA , DNA Fúngico/biossíntese , Saccharomyces cerevisiae/metabolismo , Proteínas de Ciclo Celular/genética , Sistema Livre de Células/metabolismo , Cromátides/genética , Cromátides/metabolismo , Proteínas Cromossômicas não Histona/genética , DNA Helicases , DNA Fúngico/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , CoesinasRESUMO
Antimony is a toxic metalloid with poorly understood mechanisms of toxicity and uncertain carcinogenic properties. By using a combination of genetic, biochemical and DNA damage assays, we investigated the genotoxic potential of trivalent antimony in the model organism Saccharomyces cerevisiae. We found that low doses of Sb(III) generate various forms of DNA damage including replication and topoisomerase I-dependent DNA lesions as well as oxidative stress and replication-independent DNA breaks accompanied by activation of DNA damage checkpoints and formation of recombination repair centers. At higher concentrations of Sb(III), moderately increased oxidative DNA damage is also observed. Consistently, base excision, DNA damage tolerance and homologous recombination repair pathways contribute to Sb(III) tolerance. In addition, we provided evidence suggesting that Sb(III) causes telomere dysfunction. Finally, we showed that Sb(III) negatively effects repair of double-strand DNA breaks and distorts actin and microtubule cytoskeleton. In sum, our results indicate that Sb(III) exhibits a significant genotoxic activity in budding yeast.
Assuntos
Antimônio/toxicidade , Dano ao DNA/efeitos dos fármacos , Replicação do DNA/efeitos dos fármacos , DNA/metabolismo , Quebras de DNA de Cadeia Dupla/efeitos dos fármacos , Dano ao DNA/genética , Reparo do DNA/efeitos dos fármacos , DNA Topoisomerases Tipo I/metabolismo , Estresse Oxidativo/genética , Recombinação Genética/efeitos dos fármacos , Recombinação Genética/genética , Reparo de DNA por Recombinação/efeitos dos fármacos , Reparo de DNA por Recombinação/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomycetales/genética , Saccharomycetales/metabolismo , Telômero/metabolismoRESUMO
Faithful transmission of genetic material is crucial for all organisms since changes in genetic information may result in genomic instability that causes developmental disorders and cancers. Thus, understanding the mechanisms that preserve genome integrity is of fundamental importance. Cohesin is a multiprotein complex whose canonical function is to hold sister chromatids together from S-phase until the onset of anaphase to ensure the equal division of chromosomes. However, recent research points to a crucial function of cohesin in the DNA damage response (DDR). In this review, we summarize recent advances in the understanding of cohesin function in DNA damage signaling and repair. First, we focus on cohesin architecture and molecular mechanisms that govern sister chromatid cohesion. Next, we briefly characterize the main DDR pathways. Finally, we describe mechanisms that determine cohesin accumulation at DNA damage sites and discuss possible roles of cohesin in DDR.