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Mol. Cell. Biol., 07 1995, 3926-3933, Vol 15, No. 7
A Deffie, M Hao, R Montes de Oca Luna, DL Hulboy and G Lozano
The wild-type p53 protein is a potent growth suppressor when overexpressed
in vitro. It functions as a transcriptional activator and causes growth
arrest at the G1/S stage of the cell cycle. We monitored p53
transactivation as an indicator of p53 function throughout the cell cycle.
We first demonstrate that cells which exhibited contact inhibition of
growth lacked p53 transactivation function at high cell density. Since
these cells were noncycling, we examined whether the ectopic expression of
any cyclin could override contact inhibition of growth and restore p53
transactivation function. The transfection of cyclin E at high cell density
stimulated the progression of cells through the cell cycle and restored p53
transactivation function. The transcriptional activity of p53 induced by
cyclin E was regulated at the level of DNA binding. Cells that did not show
contact inhibition of growth had a functional p53 regardless of cell
density. Thus, contact inhibition of cell growth corresponded to a lack of
p53 transactivation function and the overexpression of cyclin E in these
contact-inhibited cells stimulated cell cycle progression and resulted in
p53 transcriptional activity.
Copyright © 1995, American Society for Microbiology
Cyclin E restores p53 activity in contact-inhibited cells
Department of Molecular Genetics, M. D. Anderson Cancer Center, University of Texas, Houston 77030, USA.
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