Micronuclei generation after pRb acute loss in primary human fibroblasts. A) Bar graphs showing micronuclei percentages scored in RB transcriptionally silenced IMR90 cells (siRB) and in IMR90 cells with knock-down of both RB and AURORA-A or PLK1 compared with untransfected cells (untr.) or cells transfected with siRNA-luciferase (siLuc). B) Immunofluorescence microscopy analysis detecting the presence of centromeres (green spots) in IMR90 wild-type cells (b), in micronuclei generated following RB transcriptional silencing (c), and after knock-down of both RB and PLK1 (d) or after knock-down of both RB and AURORA-A (e). In (a) are shown lagging chromosomes (arrow) observed during metaphases in RB transcriptionally silenced cells. Nuclei were stained with DAPI (blue).