Figure 3.

Cyclin-dependent kinase activity. HeLa cell extracts were prepared at the indicated hours after E2 infection or mock-infection. After immunoprecipitation with control antibodies or antibodies specific for cyclin E (dotted line), cdk2 (dashed line), or cyclin A (solid line), kinase activity toward histone H1 was measured. The signal obtained was quantitated and expressed as the percentage of the corrected signal obtained with mock-infected samples. (Inset) Western analysis of cdk components. HeLa cell proteins were harvested at the indicated times from mock-infected or E2-infected cells. After electrophoresis and transfer, samples were probed with antibodies specific for cyclin A, cyclin E, and cdk2, as indicated.