RESUMO
The correct repair of DNA Double Strand Breaks (DSBs) is fundamental to prevent the loss of genetic information, mutations, and chromosome rearrangements. An emerging determinant of DNA repair is chromatin mobility. However, how chromatin mobility can influence DSBs repair is still poorly understood. While increased mobility is generally associated with the correct repair by Homologous Recombination (HR) of DSBs generated in heterochromatin, it promotes the mis-repair of multiple distal DSBs by Non-Homologous End Joining (NHEJ). Here we describe a method for detecting and quantifying DSBs mobility by live-cell imaging in the context of multiple DSBs prone to mis-repair by NHEJ. In addition, we discuss a set of parameters that can be used for quantitative and qualitative analysis of nuclear deformations and to discard nuclei where the deformation could affect the analysis of DSBs mobility. While this method is based on the visualization of DSBs with the mCherry-53BP1-2 fusion protein, we believe that it can also be used to analyze the mobility of nuclear foci formed by different fluorescent proteins.
Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA , Reparo do DNA/genética , Cromatina/genética , Rearranjo GênicoRESUMO
Introduction: The use of contemporary drug-eluting stents (DES) has significantly improved outcomes of patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI). However, concerns exist regarding the long-term proinflammatory effects of durable polymer coatings used in most DES, potentially leading to long-term adverse events. First-generation polymer-free stent technologies, such as sirolimus- and probucol-eluting stents (PF-SES), have shown an excellent safety and efficacy profile. The aim of this study was to evaluate the safety and efficacy of the new ultrathin Coroflex ISAR NEO PF-SES, in a more-comers PCI population. Methods: The CAESAR (a more-Comers populAtion trEated with an ultrathin struts polimer-free Sirolimus stent: An Italian post-maRketing study) registry is a multicenter, prospective study conducted in Italy, enrolling more-comers CAD patients undergoing PCI with the Coroflex ISAR NEO stent. Patients with left main (LM) disease, cardiogenic shock (CS), or severely reduced left-ventricular ejection fraction (LVEF) were excluded. The primary endpoint was target-lesion revascularization (TLR) at 1 year. Results: A total of 425 patients were enrolled at 13 centers (mean age 66.9 ± 11.6 years, Diabetes mellitus 29%, acute coronary syndrome 67%, chronic total occlusion 9%). Of these, 40.9% had multivessel disease (MVD) and in 3.3% cases, the target lesion was in-stent restenosis (ISR). Clinical device success was reached in 422 (99.6%) cases. At 1 year, only two (0.5%) subjects presented ischemia-driven TLR. The 1-year rates of target vessel revascularization and MACE were 0.5% and 5.1%, respectively. Major bleeding was observed in four (1.0%) patients. Conclusion: In this multicenter, prospective registry, the use of a new ultrathin Coroflex ISAR NEO PF-SES in a more-comers PCI population showed good safety and efficacy at 1 year.
RESUMO
Telomeres are heterochromatic structures at the ends of eukaryotic chromosomes. As other heterochromatin regions, telomeres are transcribed, from the subtelomeric region towards chromosome ends into the long non-coding RNA TERRA. Telomere transcription is a widespread phenomenon as it has been observed in species belonging to several kingdoms of the eukaryotic domain. TERRA is part of telomeric heterochromatin in addition to being present in the nucleoplasm. Here, we review the current knowledge of TERRA structure, biogenesis and turnover. In addition, we discuss presumed roles of this RNA during replication of telomeric DNA, heterochromatin formation and the regulation of telomerase.
Assuntos
RNA/genética , Telomerase/genética , Telômero/metabolismo , Animais , Cromatina/genética , Cromatina/metabolismo , Cromossomos/genética , Dano ao DNA , Replicação do DNA/genética , Heterocromatina/genética , Humanos , Cinética , Mamíferos , Neoplasias/genética , RNA/metabolismo , RNA não Traduzido/genética , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Saccharomyces cerevisiae/genética , Telomerase/metabolismo , Telômero/genética , Transcrição GênicaRESUMO
Vertebrate telomeres are transcribed into telomeric repeat-containing RNA (TERRA) that associates with telomeres and may be important for telomere function. Here, we demonstrate that telomeres are also transcribed in Saccharomyces cerevisiae by RNA polymerase II (RNAPII). Yeast TERRA is polyadenylated and stabilized by Pap1p and regulated by the 5' to 3' exonuclease, Rat1p. rat1-1 mutant cells accumulate TERRA and harbor short telomeres because of defects in telomerase-mediated telomere elongation. Overexpression of RNaseH overcomes telomere elongation defects in rat1-1 cells, indicating that RNA/DNA hybrids inhibit telomerase function at chromosome ends in these mutants. Thus, telomeric transcription combined with Rat1p-dependent TERRA degradation is important for regulating telomerase in yeast. Telomere transcription is conserved in different kingdoms of the eukaryotic domain.
Assuntos
Exonucleases/metabolismo , Exorribonucleases/metabolismo , RNA/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Telômero/metabolismo , Proteína 1 de Ligação a Repetições Teloméricas/metabolismo , Exonucleases/genética , Exorribonucleases/genética , Modelos Biológicos , RNA/metabolismo , RNA Fúngico/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteína 1 de Ligação a Repetições Teloméricas/genéticaRESUMO
The highly conserved 14-3-3 proteins participate in many biological processes in different eukaryotes. The BMH1 and BMH2 genes encode the two functionally redundant Saccharomyces cerevisiae 14-3-3 isoforms. In this work we provide evidence that defective 14-3-3 functions not only impair the ability of yeast cells to sustain DNA replication in the presence of sublethal concentrations of methyl methanesulfonate (MMS) or hydroxyurea (HU) but also cause S-phase checkpoint hyperactivation. Inactivation of the catalytic subunit of the histone acetyltransferase NuA4 or of its interactor Yng2, besides leading to S-phase defects and persistent checkpoint activation in the presence of genotoxic agents, is lethal for bmh mutants. Conversely, the lack of the histone deacetylase subunit Rpd3 or Sin3 partially suppresses the hypersensitivity to HU of bmh mutants and restores their ability to complete DNA replication in the presence of MMS or HU. These data strongly suggest that reduced acetyltransferase functionality might account for the S-phase defects of bmh mutants in the presence of genotoxic agents. Consistent with a role of 14-3-3 proteins in acetyltransferase and deacetylase regulation, we find that acetylation of H3 and H4 histone tails is reduced in temperature-sensitive bmh mutants shifted to the restrictive temperature. Moreover, Bmh proteins physically interact, directly or indirectly, with the Esa1 acetyltransferase throughout the cell cycle and with the Rpd3 deacetylase specifically during unperturbed S phase and after HU treatment. Taken together, our results highlight a novel role for 14-3-3 proteins in the regulation of histone acetyltransferase and deacetylase functions in the response to replicative stress.
Assuntos
Proteínas 14-3-3/metabolismo , Replicação do DNA , DNA Fúngico/genética , Histona Acetiltransferases/metabolismo , Histona Desacetilases/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Ciclo Celular/metabolismo , Quinase do Ponto de Checagem 2 , Ativação Enzimática , Genoma Fúngico/genética , Histona Acetiltransferases/genética , Histona Desacetilases/genética , Peptídeos e Proteínas de Sinalização Intracelular , Metanossulfonato de Metila/metabolismo , Mutação/genética , Ligação Proteica , Proteínas Serina-Treonina Quinases/metabolismo , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Fase S , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
14-3-3 proteins are highly conserved polypeptides that participate in many biological processes by binding phosphorylated target proteins. The Saccharomyces cerevisiae BMH1 and BMH2 genes, whose concomitant deletion is lethal, encode two functionally redundant 14-3-3 isoforms. To gain insights into the essential function(s) shared by these proteins, we searched for high-dosage suppressors of the growth defects of temperature-sensitive bmh mutants. Both the protein kinase C1 (Pkc1) and its upstream regulators Wsc2 and Mid2 were found to act as high dosage suppressors of bmh mutants' temperature sensitivity, indicating a functional interaction between 14-3-3 and Pkc1. Consistent with a role of 14-3-3 proteins in Pkc1-dependent cellular processes, shift to the restrictive temperature of bmh mutants severely impaired initiation of DNA replication, polarization of the actin cytoskeleton, and budding, as well as cell wall integrity. Because Pkc1 acts in concert with the Swi4-Swi6 (SBF) transcriptional activator to control all these processes, the defective G(1)/S transition of bmh mutants might be linked to impaired SBF activity. Indeed, the levels of the G(1) cyclin CLN2 transcripts, which are positively regulated by SBF, were dramatically reduced in bmh mutants. Remarkably, budding and DNA replication defects of bmh mutants were suppressed by CLN2 expression from an SBF-independent promoter, suggesting that 14-3-3 proteins might contribute to regulating the late G(1) transcriptional program.
