(A) U2OS before (CT) and after si-RNA-mediated MYPT1-knockdown (MYPT1 KD) stained for DNA, centromere-specific human antisera (ACA), tubulin, and Plk1 as indicated. Scale bar, 5 µm. (B) Quantification of the intensity of kinetochore Plk1 staining in U2OS before (Control) and after si-RNA-mediated MYPT1-knockdown (MYPT1 KD) in prometaphase (Prometa) and metaphase (Meta) cells (n ≥ 100 kinetochores per condition. p<0.0001, unpaired, two-tailed t-test). (C) U2OS before (CT) and after si-RNA-mediated MYPT1-knockdown (MYPT1 KD) in either prometaphase (Prometa) or metaphase (Meta) stained for DNA, centromere-specific human antisera (ACA), tubulin, and pPlk1-Thr210 as indicated. Scale bar, 5 µm. (D) Quantification of the intensity of kinetochore pPlk1-Thr210 staining in U2OS cells before (Control) and after si-RNA-mediated MYPT1-knockdown (MYPT1 KD) in prometaphase (Prometa) and metaphase (Meta) cells (n ≥ 100 kinetochores per condition. p<0.0001, MYPT1KD prometaphase vs metaphase, p<0.0001, CT vs MYPT1 KD prometaphase; p=0.01 CT vs MYPT1 KD metaphase; unpaired, two-tailed t-test).