RESUMO
Cleavage of cohesins and cyclin-dependent kinase (CDK) inhibition are thought to be sufficient for triggering chromosome segregation. Here we identify an essential requirement for anaphase chromosome movement. We show that, at anaphase onset, the phosphatase Cdc14 and the polo-like kinase Cdc5 are redundantly required to drive spindle elongation. This role of Cdc14 is mediated by the FEAR network, a group of proteins that activates Cdc14 at anaphase onset, and we suggest that Cdc5 facilitates both Cdc14 activation and CDK inhibition. We further identify the kinesin-5 motor protein Cin8 as a key target of Cdc14. Indeed, Cin8 mutants lacking critical CDK phosphorylation sites suppress the requirement for Cdc14 and Cdc5 in anaphase spindle elongation. Our results indicate that cohesin dissolution and CDK inhibition per se are not sufficient to drive sister chromatid segregation but that the motor protein Cin8 must be activated to elongate the spindle.
Assuntos
Anáfase , Proteínas de Ciclo Celular/genética , Regulação Fúngica da Expressão Gênica , Cinesinas/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas Tirosina Fosfatases/genética , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Proteínas de Ciclo Celular/metabolismo , Cromátides/metabolismo , Cromátides/ultraestrutura , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Segregação de Cromossomos , Ativação Enzimática , Cinesinas/deficiência , Fosforilação , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Tirosina Fosfatases/metabolismo , Saccharomyces cerevisiae/enzimologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Transdução de Sinais , Fuso Acromático/metabolismo , Fuso Acromático/ultraestrutura , CoesinasRESUMO
The eukaryotic genome is replicated according to a specific spatio-temporal programme. However, little is known about both its molecular control and biological significance. Here, we identify mouse Rif1 as a key player in the regulation of DNA replication timing. We show that Rif1 deficiency in primary cells results in an unprecedented global alteration of the temporal order of replication. This effect takes place already in the first S-phase after Rif1 deletion and is neither accompanied by alterations in the transcriptional landscape nor by major changes in the biochemical identity of constitutive heterochromatin. In addition, Rif1 deficiency leads to both defective G1/S transition and chromatin re-organization after DNA replication. Together, these data offer a novel insight into the global regulation and biological significance of the replication-timing programme in mammalian cells.