A novel role for the mitotic spindle during DNA segregation in yeast:: Promoting 2μm plasmid-cohesin association
A novel role for the mitotic spindle during DNA segregation in yeast:: Promoting 2μm plasmid-cohesin association
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DOI：
10.1128/mcb.25.10.4283-4298.2005
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发表时间：
2005-05-01
影响因子：
5.3
通讯作者：
Velmurugan, S
中科院分区：
文献类型：
--
作者：
Mehta, S;Yang, XM;Velmurugan, S
酿酒酵母中的2μm环状质粒是稳定、高拷贝数、染色体外“自私”DNA元件的模型。通过结合分配系统和扩增系统，质粒确保其稳定繁殖和拷贝数维持，即使它不为其宿主提供任何选择优势。最近的证据表明，分配系统将质粒分离与染色体分离结合起来。我们现在证明有丝分裂纺锤体在质粒分配途径中具有意想不到的非常规作用。纺锤体指定 2 μm 圆的核地址，并促进粘连蛋白复合物募集到质粒分配基因座 STB。在 STB 上加载粘连蛋白时只需要核微管，而不需要细胞质微管。在从诺考达唑诱导的纺锤体解聚和 G(2)/M 停滞中恢复的细胞中，可以在纺锤体恢复的同时建立粘连蛋白-STB 关联。这种复制后粘连蛋白的募集在均分中不起作用。然而，正常获得的粘连蛋白可以在复制后失活，而不会导致质粒错误分离。在mtw1-1突变酵母菌株中，质粒与纺锤体和纺锤体相关染色体共分离；相比之下，大量染色体与纺锤体无关。这些结果与纺锤体以染色体连锁方式促进质粒分离的模型一致。
The 2 mu m circle plasmid in Saccharomyces cerevisiae is a model for a stable, high-copy-number, extrachromosomal "selfish" DNA element. By combining a partitioning system and an amplification system, the plasmid ensures its stable propagation and copy number maintenance, even though it does not provide any selective advantage to its host. Recent evidence suggests that the partitioning system couples plasmid segregation to chromosome segregation. We now demonstrate an unexpected and unconventional role for the mitotic spindle in the plasmid-partitioning pathway. The spindle specifies the nuclear address of the 2 mu m circle and promotes recruitment of the cohesin complex to the plasmid-partitioning locus STB. Only the nuclear microtubules, and not the cytoplasmic ones, are required for loading cohesin at STB. In cells recovering from nocodazole-induced spindle depolymerization and G(2)/M arrest, cohesin-STB association can be established coincident with spindle restoration. This postreplication recruitment of cohesin is not functional in equipartitioning. However, normally acquired cohesin can be inactivated after replication without causing plasmid missegregation. In the mtw1-1 mutant yeast strain, the plasmid cosegregates with the spindle and the spindle-associated chromosomes; by contrast, a substantial number of the chromosomes are not associated with the spindle. These results are consistent with a model in which the spindle promotes plasmid segregation in a chromosome-linked fashion.