FIG. 2.

Loss of p21 results in deregulated cyclin E/Cdk2 kinase activity during MTI-induced endoreduplication. (A) Western analysis of pRb and cyclin E. Asynchronous cells were treated with nocodazole (83 nM) for the indicated times, and protein was harvested. (B) Cyclin E and Cdk2 kinase activity in HCT116 p21^+/+ and p21^−/− cells. Anti-cyclin E or anti-Cdk2 antibody was used to immunoprecipitate kinase complexes; GST-pRb was used as a substrate. Quantification of the autoradiogram signals is presented in the histograms. Results are representative of three independent experiments. (C) Whole-cell lysates from HCT116 p21^+/+ cells were immunoprecipitated with anti-Cdk2, separated by SDS-PAGE, and analyzed for coimmunoprecipitation of p21 by Western blot analysis.