Effect of INCENP mutations on the spindle checkpoint. (A) INCENP^OFF cells exhibit a robust spindle checkpoint response to nocodazole treatment that is slightly reduced if aurora B is inhibited with ZM447438 (P = 0.01). (B) INCENP^OFF cells exhibit an impaired spindle checkpoint response to 10 nM taxol treatment that is significantly worsened by the addition of ZM447439 (P = 0.005). (C) INCENP^OFF cells expressing TrAP-INCENP^WT, TrAP-INCENP^W766G, and TrAP-INCENP^F802A all exhibit a robust spindle checkpoint response to nocodazole treatment that is reduced for TrAP-INCENP^WT if ZM447438 (ZM) is added (P = 0.003). (D) INCENP^OFF cells expressing TrAP-INCENP^WT or TrAP-INCENP^F802A exhibit a robust spindle checkpoint response to 10 nM taxol treatment. INCENP^OFF cells expressing TrAP-INCENP^W766G exhibit an impaired response to 10 nM taxol (P = 0.0014). All three cell lines exhibit a normal checkpoint response if treated with 100 nM taxol. Three independent experiments were performed. WT, wild type. Error bars indicate SD.