Expression of non-degradable cyclin B1 leads to a modest increase in mitotic arrest and activation of Cdk1, and rapid apoptosis.

<p>HeLa cells were transfected with 2 µg plasmid DNA encoding GFP vector or encoding non-degradable cyclin B1-R42A-GFP for the times indicated and subjected to: <b>A.</b> Immunoblotting for GFP and cyclin B1. GAPDH was used as a loading control. Apparent molecular weights of the proteins are indicated on the left. <b>B.</b> Cell cycle analysis by propidium iodide staining and flow cytometry. Mitotic arrest is indicated by an increase in the percentage of cells with 4N DNA content. <b>C.</b> Cdk1 assay performed as described in Materials and Methods. ³²P incorporation was determined by scintillation counting. Values shown have been corrected for background kinase activity (no substrate) and represent the mean ± standard deviation (n = 3). <b>D.</b> Cell death ELISA, as described in Materials and Methods. Untransfected HeLa cells were used as a negative control. Results given are mean ± standard deviation (n = 3).