Figure 3.

Decrease in kinetochore-associated BubR1 in Scc1-deficient cells following topo II inhibitor treatment. (A, B) All Scc1^OFF cells in early mitosis have levels of BubR1 accumulation at kinetochores characteristic of prometaphase for both aligned and nonaligned chromosomes. (C, D) Treatment of Scc1^OFF cells with the topoisomerase inhibitors ICRF-159 (C) and ICRF-187 (D) promotes the alignment of chromosomes at a metaphase plate and results in a downregulation of BubR1 levels at the kinetochores. Synchronized, Scc1-deficient cells were treated as for Fig 2. Staining is shown with antibodies to α-tubulin (red) and BubR1 (green), along with DAPI (grey in the right panels). (E) Treatment of Scc1^OFF cells with ICRF-159 promotes the bipolar attachment of sister kinetochores to opposite spindle poles. Synchronized, Scc1-deficient cells were treated as for Fig 2. Staining is shown with antibodies to α-tubulin (green) and CENP-C (red), along with DAPI (blue). Scale bars, 5 μm.