Figure 2.

PCAF inhibits cyclin/cdk2 complexes in vivo and in vitro. (A) Purified active cyclin A/cdk2, cyclin E/cdk2, cyclin B/cdk1 and cyclin D3/cdk6 complexes were incubated with increasing concentrations of purified recombinant PCAF and kinase assays were performed. (B) HeLa cells were transfected with YFP-PCAF or empty vector as a control. Cell extracts were subjected to IP with anti-cdk2. Kinase assays of the immunoprecipitated endogenous cdk2 were performed and phosphorylation of histone H1 was detected by PhosphorImager. Kinase activity was normalized to the amount of immunoprecipitated cdk2 and represented in the graph. Results shown are the mean ± SE of 3 independent experiments. *P-value <0.05.