(A)Chk1 colocalizes with BubR1 at kinetochores during prometaphase. Example of a
Chk1−/−cell expressing Chk1:GFP and analyzed by
confocal microscopy. Red, BubR1; green, Chk1:GFP; blue, DNA. A single image
plane is shown. The scale bar is 5 μm.
(B and C) Mitotic index analysis of G2/M-elutriated DT40,
Chk1−/−, and revertant (Rev) cells during treatment
with (B) taxol or (C) nocodazole. pH3, phosphorylated Ser10 of histone H3. Error
bars show the standard deviation from the mean from three experiments.
(D)Upper panels: CDK1-associated histone H1 kinase activity and western blot
analysis of CDK1 (Tyr15-phosphorylated and total) and actin during treatment of
G2/M-elutriated cells with taxol. Lower panels: western blot analysis of cyclin
B2 and actin. Phosphorylated cyclin B2 is marked by an asterisk.
(E)Phosphorylated cyclin B2 as a percentage of the total cyclin B2 protein during
treatment of G2/M-elutriated cells with taxol. Error bars show the standard
deviation from the mean from three experiments.
(F)Endoreduplication in Chk1−/− cells during treatment
with taxol. Cells were treated as in (B), and the percentage of cells with
greater than 4N DNA content was determined. Error bars show the standard
deviation from the mean from three experiments.