Overexpression of cyclin E and cyclin-dependent kinase inhibitor (p27Kip1): effect on cell cycle regulation in HeLa cells.

Transfection of the epithelioid cell line HeLa with p27(Kip1) resulted in an accumulation of cells in the G1 phase of the cell cycle. Although the cellular level of cdk2 was not decreased as a result of this transfection, there was a significant decline in the cdk2 associated kinase activity. Restoration of the cdk2 kinase activity was proportional to the amount of cotransfected cyclin E plasmid DNA. Overexpression of cyclin E also reversed the p27(Kip1) mediated G1 growth arrest. These findings suggest that the overexpression of cyclin E reverses the p27(Kip1) mediated G1 growth arrest by binding the inhibitor restoring the cdk2 associated kinase activity necessary for the G1/S transition.