Spindle bipolarization and error correction of kt-MT attachments following STLC wash out requires ABK. (A) Representative maximum projection images of RepEg5 cells before and 2 hours after STLC wash out in the presence and absence of ABK. The cells were fixed and stained for α-tubulin (green), the kinetochore component Ndc80 (red), and DNA (blue). Two hours after removing STLC from control RNAi cells, a majority of spindles have converted from monopolar to bipolar with correction of most kt-MT attachments from syntelic to bioriented. In the absence of ABK, most spindles remain monopolar with a majority syntelic kt-MT attachments following STLC wash out. (B) Quantification of the percentage of monopolar spindles pre- and post-STLC wash out in RepEg5 cells with or without ABK. (Control RNAi, t = 0, n = 503 spindles; t = 60, n = 403; t = 120, n = 199; Aurora B RNAi, t = 0, n = 100 spindles; t = 60, n = 100; t = 120, n = 102). (C) Quantification of kt-MT attachments in RepEg5 cells in the presence and absence of ABK pre- and post-STLC wash out (Control RNAi, t = 0, n = 200 kinetochore pairs; t = 120, n = 193; Aurora B RNAi, t = 0, n = 210 kinetochore pairs; t = 120, n = 241). Error bars are SEM. Scale bars are 10 μm.