Chromosome detachment from the nuclear envelope is required for genomic stability in closed mitosis

Mitosis in metazoans involves detachment of chromosomes from the nuclear envelope (NE) and NE breakdown, whereas yeasts maintain the nuclear structure throughout mitosis. It remains unknown how chromosome attachment to the NE might affect chromosome movement in yeast. By using a rapamycin-induced dimerization system to tether a specific locus of the chromosome to the NE, I found that the tethering delays the separation and causes missegregation of the region distal to the tethered site. The phenotypes are exacerbated by mutations in kinetochore components and Aurora B kinase Ipl1. The chromosome region proximal to the centromere is less affected by the tether, but it exhibits excessive oscillation before segregation. Furthermore, the tether impacts full extension of the mitotic spindle, causing abrupt shrinkage or bending of the spindle in shortened anaphase. The study supports detachment of chromosomes from the NE being required for faithful chromosome segregation in yeast and segregation of tethered chromosomes being dependent on a fully functional mitotic apparatus.