Fig. 2. Overexpression of kinase-active but not kinase-inactive Wee1 causes a G2 cell cycle delay. A, mitotic index measurements were made to assess whether cells expressing Wee1 were delaying in the G2 or M phases of the cell cycle. Cells were synchronized and infected with adenoviruses as described in Fig. 1 . Nocodazole was added to trap cells in mitosis. At various times after release from the block, mitotic chromosome spreads were prepared and scored. At least 500 nuclei were counted in each experiment. B, cellular lysates described in Fig. 1 were resolved by SDS-PAGE, and Cdc2 phosphorylation status was monitored by Western blotting. Species a, b, and c represent different electrophoretic forms of Cdc2 (see text for details). m.o.i., multiplicity of infection.