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J. Virol., Apr 1995, 2491-2500, Vol 69, No. 4
TF Kowalik, J DeGregori, JK Schwarz and JR Nevins
Various experiments have demonstrated a role for the E2F transcription
factor in the regulation of cell growth during the G0/G1/S phase
transition. Indeed, overexpression of the E2F1 product, a component of the
cellular E2F activity, induces DNA synthesis in quiescent fibroblasts. To
provide an approach to a more detailed biochemical analysis of these
events, we have made use of a recombinant adenovirus containing the E2F1
cDNA in order to efficiently express the E2F1 product in an entire
population of cells. We demonstrate an induction of DNA synthesis when
quiescent cells are infected with the E2F1 recombinant virus. However, we
also find that the induction does not lead to a complete replication of the
cellular genome, as revealed by flow cytometry. The incomplete nature of
cellular DNA replication is due, at least in part, to the fact that E2F1
overexpression leads to massive cell death that is characteristic of
apoptosis. This E2F1- mediated induction of apoptosis is largely dependent
on endogenous wild- type p53 activity and can be subverted by introducing
mutant forms of p53 into these cells or by overexpressing E2F1 in
fibroblasts derived from p53-null mouse embryos. We conclude that E2F1 can
induce events leading to S phase but that the process is not normal and
appears to result from the activation of a cell death pathway.
Copyright © 1995, American Society for Microbiology
E2F1 overexpression in quiescent fibroblasts leads to induction of cellular DNA synthesis and apoptosis
Department of Genetics, Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
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