FIG. 8.
Expression of nonphosphorylatable CK2α abrogates the SAC. (A) Cell cycle profiles of cells expressing CK2α-HA, CK2α-4D-HA, CK2α-4E-HA, or CK2α-4A-HA that were arrested in mitosis by nocodazole treatment in the presence or absence of tetracycline (Tet), followed by fixation and PI staining. Samples were analyzed by flow cytometry. (B) Cdk1 was immunoprecipitated from lysates prepared from nocodazole-arrested cells expressing CK2α-HA, CK2α-4D-HA, CK2α-4E-HA, or CK2α-4A-HA. Immunoprecipitates (IP) were immunoblotted for Cdk1 and cyclin B1 or used in kinase assays with histone H1 and [γ-32P]ATP. Phosphorylation is shown by a representative autoradiograph. Total histone H1 is shown by Coomassie blue staining. (C) Graphical representation of Cdk1 kinase activity. Results are the average of three independent experiments. Error bars indicate 1 standard deviation from the mean.