Fig. 1

The activating phosphorylation site in the kinase domain of Polo controls its nuclear localization. a Syncytial embryos expressing Polo^WT-GFP, Polo^T182A-GFP, or Polo^T182D-GFP were observed by time-lapse microscopy. N: a nucleus; arrow: a centrosome; yellow arrowhead: centromere/kinetochore; green arrowhead: midbody ring. Bar: 10 μm. b Time-lapse imaging of stable cell lines expressing Polo^WT-GFP, Polo^T182A-GFP, or Polo^T182D-GFP with RFP-Lamin. The time between the initial detection of Polo-GFP at centromeres (green arrows in green box and enlarged images, right) and NEB (T ₀) is shown. NEB was determined when RFP-Lamin starts to dissolve into the cytoplasm. Bar: 5 μm. c Quantification of the GFP fluorescence ratio (nucleus/total cell) in the period preceding NEB, from experiments in b. (n = 10, error bars: SD). d Quantification following treatment with Binucleine 2, as in c. See Supplementary Fig. 2a–d for images. **P < 0.01; ***P < 0.001; Student’s t test, between Polo^WT-GFP + DMSO vs. Binucleine 2