RESUMO
Eukaryotic genomes are folded into DNA loops mediated by structural maintenance of chromosomes (SMC) complexes such as cohesin, condensin, and Smc5/6. This organization regulates different DNA-related processes along the cell cycle, such as transcription, recombination, segregation, and DNA repair. During the G2 stage, SMC-mediated DNA loops coexist with cohesin complexes involved in sister chromatid cohesion (SCC). However, the articulation between the establishment of SCC and the formation of SMC-mediated DNA loops along the chromatin remains unknown. Here, we show that SCC is indeed a barrier to cohesin-mediated DNA loop expansion along G2/M Saccharomyces cerevisiae chromosomes.
Assuntos
Proteínas Cromossômicas não Histona , Proteínas de Saccharomyces cerevisiae , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ciclo Celular/metabolismo , Cromátides/genética , Cromátides/metabolismo , Coesinas , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , DNA/genética , DNA/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Cohesin, a member of the SMC complex family, holds sister chromatids together but also shapes chromosomes by promoting the formation of long-range intra-chromatid loops, a process proposed to be mediated by DNA loop extrusion. Here we describe the roles of three cohesin partners, Pds5, Wpl1, and Eco1, in loop formation along either unreplicated or mitotic Saccharomyces cerevisiae chromosomes. Pds5 limits the size of DNA loops via two different pathways: the canonical Wpl1-mediated releasing activity and an Eco1-dependent mechanism. In the absence of Pds5, the main barrier to DNA loop expansion appears to be the centromere. Our data also show that Eco1 acetyl-transferase inhibits the translocase activity that powers loop formation and contributes to the positioning of loops through a mechanism that is distinguishable from its role in cohesion establishment. This study reveals that the mechanisms regulating cohesin-dependent chromatin loops are conserved among eukaryotes while promoting different functions.
Assuntos
Acetiltransferases/metabolismo , Proteínas de Ciclo Celular/metabolismo , Cromátides/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Cromossomos Fúngicos/química , Proteínas Nucleares/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Acetiltransferases/genética , Proteínas de Ciclo Celular/genética , Cromátides/genética , Proteínas Cromossômicas não Histona/genética , Segregação de Cromossomos , Cromossomos Fúngicos/genética , Cromossomos Fúngicos/metabolismo , Mitose , Proteínas Nucleares/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , CoesinasRESUMO
Cohesin is a DNA translocase that is instrumental in the folding of the genome into chromatin loops, with functional consequences on DNA-related processes. Chromatin loop length and organization likely depend on cohesin processivity, translocation rate and stability on DNA. Here, we investigate and provide a comprehensive overview of the roles of various cohesin regulators in tuning chromatin loop expansion in budding yeast Saccharomyces cerevisiae. We demonstrate that Scc2, which stimulates cohesin ATPase activity, is also essential for cohesin translocation, driving loop expansion in vivo. Smc3 acetylation during the S phase counteracts this activity through the stabilization of Pds5, which finely tunes the size and stability of loops in G2.