Actin dynamics in the actin cluster. (A) Time-lapse confocal images of HeLa cells expressing GFP-actin during prometaphase. Images were taken every 7.3 s. At time 0, photobleaching was performed in the area shown by the red circle. Bar, 5 µm. (B) Quantification of FRAP analysis (n = 30). Error bars indicate SD. (C) A model of the amorphous actin cluster movement during mitosis. A region (pink) in the bottom part of the cell indicates a zone in which actin polymerization and depolymerization occur actively. Red, actin filaments; yellow, the direction of the revolving movement.