Nontransformed cells exhibit varied ability to cluster supernumerary centrosomes. (A, left) Quantification of centrosome clustering in tetraploid cells at cytokinesis (n = 150). (Right) Images depicting examples of cells in cytokinesis with extra centrosomes: bipolar clustered and multipolar. Cells were stained for microtubules (α-Tub, red), centrioles (centrin2, green), and DNA (blue). (B) Images from videos of tetraploid MCF10A cells expressing centrin1-GFP and H2B-RFP. Time scale: hours:minutes. (C) Quantification of cells undergoing bipolar divisions by live-cell imaging. (D) Images from videos of tetraploid MCF10A cells expressing H2B-GFP. (E) Schematic representation of the proteasome inhibitor (MG132) treatment and washout. (F) Quantification of centrosome clustering in cells treated with 10 µM MG132 (4 h) at metaphase (n = 300) and cytokinesis (n = 150). For all graphics, error bars represent mean ± SD from three independent experiments. ns, not significant. Bars, 10 µM.