A. Either selective chromosome arm removal or active centromere recruitment early in prophase could explain RNA Pol II enrichment at metaphase centromeres. B-C RNAP pS2 and pS5 localization (red) in chromosome spreads from RPE-1 cells cycled from interphase (G2) to anaphase. Anti-CENPA antibodies (green) and DAPI (blue) were used to visualize centromeres and DNA respectively. Scale bars, 10 μm. Right, quantification of absolute and relative centromere signal. **, P < 0.005; ***, P < 0.001; ****, P < 0.0001 (one-way ANOVA, Dunnett’s test). D pS2 occupancy at centromeres of chromosomes 1, 3, 7 and X, represented as the % of input recovered following ChIP in G2 or metaphase (M) RPE-1 cells. Occupancy values at the ACTB gene and at a random intergenic region (IR) were included as positive and negative controls, respectively. **, P < 0.005; (ns) no significant differences (t-test). E-F Analysis of CENPC and pS2 localization (red) in metaphase spreads from dicentric MDA-MB 435 cells. ACA (anti-centromere antibodies; green) stains both active (Ac) and inactive (In) centromeres while CENPC and pS2 (red) are only recruited to the active kinetochore region. Scale bars, 5 μm. Quantification of pS2 and CENPC centromere signal is plotted on F. **, P < 0.005 (t-test). G-H Analysis of pS2 localization (red) on metaphase spreads from doxycycline inducible Rad21 KO cells. Anti-CENPA (green) and DAPI (blue) were used to visualize centromeres and DNA, respectively. Scale bars, 10 μm. Quantification of absolute pS2 centromere levels is represented in H. **, P < 0.005 (t-test). In all cases error bars indicate the standard deviation of the mean.