FIG. 7.

Effect of Cdc25A overproduction on cyclin-dependent kinase activities in asynchronously growing HeLa cells. (A) Wild-type Cdc25A was not induced (lanes 1 and 3) or induced (lanes 2 and 4) by tetracycline addition or removal, respectively, for 24 h. The histone H1 kinase activities associated with cyclin A and cyclin E or pRb kinase activities associated with Cdk4 and Cdk6 immunoprecipitates were analyzed. The experiment was performed with clones 55 (lanes 1 and 2) and 83 (lanes 3 and 4). (B) Mutant Cdc25A was either noninduced (−) or induced (+) as described for panel A, and the histone H1 kinase activities associated with cyclin A and cyclin E were analyzed. (C) Wild-type Cdc25A (clone 83) was either noninduced (−) or induced (+) as described for panel A. Cdk2 was immunoprecipitated and analyzed by immunoblotting with antiphosphotyrosine antibodies. P denotes a control precipitation with preimmune serum.