Figure 6. Differential effects of PXD101 on activity of cyclin E/cdk2. Whole cell extracts from cells treated with PXD101 for 0, 8, 24, and 48 h were used to perform immunoprecipitation with cyclin E antibody. (A) Bound fractions were subjected to kinase assay with purified histone H1 as substrate. Roscovitine was added to one sample to ensure that the labeling detected was due to the activity of cyclin-dependent kinases. Following SDS-PAGE, gels were dried and exposed to phosphorimaging screens to visualize radiolabeled protein. Representative results from 3 independent experiments in each cell line. (B) Graphical summary of results from 3–4 independent replicates of IP-kinase assays. (*P < 0.05, **P < 0.01).