FIG. 3.
Protein levels and activities of Cdc25A and G1 cyclins-Cdks in Hs68 human fibroblasts. (A) Hs68 cells were synchronized by serum starvation and released by addition of DMEM containing 20% FCS. Samples were taken for flow cytometry at the indicated times. (B) Total cell extracts were analyzed by SDS-PAGE and immunoblotted with Cdc25A-specific antibodies or with antibodies against the different G1 Cdks and cyclins. (C) Phosphatase and kinase activities from the same time points were determined as described for Fig. 2C. The activities of cyclin D immunocomplexes were measured as phosphorylation of pRb.