Cyclin E enhances P53-mediated transactivation.

Plasmids expressing G1 and G2 cyclins were introduced into the Saos-2 cell system monitoring p53-mediated transactivation [(1993) Oncogene 8, 543]. Cyclin E, but not other cyclins, enhanced the p53-mediated transactivation about 2-fold. Co-transfection of a CDK2 expression plasmid caused a 30% increase in the extent of the p53-mediated transactivation. Moreover, the transfected p53 protein became phosphorylated coordinately with the enhanced transactivation. The close correlation between transactivation and p53 phosphorylation suggests that phosphorylation is involved in positive regulation for the transactivation by p53.