Figure 2.

Cell cycle-dependent changes in phosphorylation of Wee1 and Cdc25. Fission yeast cells were synchronized by centrifugal elutriation and released into fresh medium at 30°C. The data in panels A and B were generated from the same time course to allow direct comparison of the timing of cell cycle events. (A) Western blots showing the behavior of Wee1, Cdc25, Cdc13, and Cdk1 inhibitory phosphorylation during the cell cycle. A background band was used as a loading control. A single asterisk is used to mark a partially phosphorylated form of Wee1; 2 asterisks mark more extensively phosphorylated forms referred to in the text as hyperphosphorylated forms. Inhibitory phosphorylation of Cdk1 was detected using a phospho-specific antibody. (B) A fluorescence microscopy assay using DAPI and calcofluor staining was used to determine the percentage of binucleated cells and cells undergoing septation.