RESUMEN

Chromosome segregation depends on sister chromatid cohesion mediated by cohesin. The cohesin subunits Smc1, Smc3, and Scc1 form tripartite rings that are thought to open at distinct sites to allow entry and exit of DNA. However, direct evidence for the existence of open forms of cohesin is lacking. We found that cohesin's proposed DNA exit gate is formed by interactions between Scc1 and the coiled-coil region of Smc3. Mutation of this interface abolished cohesin's ability to stably associate with chromatin and to mediate cohesion. Electron microscopy revealed that weakening of the Smc3-Scc1 interface resulted in opening of cohesin rings, as did proteolytic cleavage of Scc1. These open forms may resemble intermediate states of cohesin normally generated by the release factor Wapl and the protease separase, respectively.

Asunto(s)

Proteínas de Ciclo Celular/metabolismo , Proteoglicanos Tipo Condroitín Sulfato/metabolismo , Proteínas Cromosómicas no Histona/metabolismo , Segregación Cromosómica , ADN/metabolismo , Proteínas Nucleares/metabolismo , Fosfoproteínas/metabolismo , Secuencia de Aminoácidos , Animales , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Proteoglicanos Tipo Condroitín Sulfato/química , Proteoglicanos Tipo Condroitín Sulfato/genética , Cromatina/metabolismo , Proteínas Cromosómicas no Histona/química , Proteínas Cromosómicas no Histona/genética , Replicación del ADN , Proteínas de Unión al ADN , Humanos , Espectrometría de Masas , Microscopía Electrónica , Datos de Secuencia Molecular , Proteínas Nucleares/química , Proteínas Nucleares/genética , Fosfoproteínas/química , Fosfoproteínas/genética , Multimerización de Proteína , Estructura Terciaria de Proteína , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas/metabolismo , Separasa/metabolismo , Cohesinas