FIGURE 4.

D-type cyclin-CDK activity is not required for st and cyclin E cooperation to induce CDK2 activation, pocket protein hyperphosphorylation, E2F-dependent gene expression, and mitogen-independent cell cycle entry. Levels of D-type cyclins were determined using the protein samples described in the legend to Fig. 3 via Western blot analysis (A). BJ fibroblasts were synchronized as described in the legend to Fig. 1 and transduced at an MOI of 150 with the indicated adenoviruses or restimulated with FBS. Cells were harvested at the indicated time points and processed for PI/FACS (B) or for Western blot (C) analyses. The Thr-160-phosphorylated form of CDK2 is marked with an asterisk.