Fig. 1.

p190 is required for cytokinesis. (A) Depletion of p190 results in multinucleation because of cytokinesis failure. 48 hours after LacZ (control) or p190 siRNA treatment HeLa cells were processed for immunofluorescence for actin staining with phalloidin (green) and DNA staining with DAPI (blue). Arrows indicate multinucleated cells. Scale bars: 10 µm. (B) Quantification of multinucleation in HeLa cells depleted of p190 by siRNA. Cells were depleted of p190 and, as indicated, simultaneously also treated with 1 µg/ml of doxycycline to induce expression of wild-type p190. 48 hours post-transfection and doxycycline treatment, cells were fixed and stained with phalloidin (actin) or DAPI (DNA) and scored blindly for binucleation or multinucleation (n≥300). Results are mean±s.d. from three independent experiments. *P<0.001 (Student's t-test ) for both p190 siRNA-treated cells compared to control, and p190 siRNA-treated cells compared to cells rescued by wild-type p190. (C) Immunoblot to measure relative p190 levels. (D) DIC live-cell imaging of LacZ- or p190-siRNA-treated HeLa cells. Recording started after 24 hours transfection of either siRNA. The top two panels represent LacZ-siRNA-treated cells, and the bottom two panels represent p190-siRNA-treated cells. Arrows indicate single cell divisions after treatment with either siRNA. 195 cells treated with p190 siRNA and 135 cells treated with control siRNA were scored, and the number of multinucleated cells/total number of cells was quantified. Scale bars: 10 µm.