(A) Chromosome spreads from nocodazole-treated U2OS before (CT) and after si-RNA-mediated Cyclin A-knockdown (CycA KD) stained for DNA, centromere-specific human antisera (ACA), antibody specific to MYPT1 pSer473 (pMYPT1 Ser473). Scale bar, 5 µm. Insets highlight centromeres at 3X magnification. (B) Quantification of the intensity of centromere MYPT1 pSer473 staining on chromosome spreads (n ≥ 100 centromeres/condition. p<0.0001, unpaired, two-tailed t-test). (C) Western blots using whole cell lysates from U2OS before (CT) and after si-RNA-mediated Cyclin A-knockdown (CycA KD) for the indicated protein targets. Numbers indicate protein levels relative to actin loading control in each column. (D) U2OS before (CT) and after si-RNA-mediated Cyclin A-knockdown (CycA KD) stained for DNA, MYPT1, and centromere-specific human antisera (ACA). Scale bar, 5 µm. Insets highlight centromeres at 5X magnification.