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Mol. Cell. Biol., Jan 1998, 459-467, Vol 18, No. 1
ER Fernandes, JY Zhang and RJ Rooney
Adenovirus E1A proteins influence cell growth and phenotype through
physical interactions with cellular proteins that regulate basic processes
such as cell cycle progression, DNA synthesis, and differentiation. p120E4F
is a low-abundance cellular transcription factor that represses the
adenovirus E4 promoter and is regulated by E1A, through a
phosphorylation-induced reduction of its DNA binding activity, to permit
activation of the E4 promoter during early infection. To determine the
normal biological role of p120E4F, we assessed its ability to influence
fibroblast cell growth and transformation. p120E4F suppressed NIH 3T3
fibroblast colony formation but had little effect when coexpressed with E1A
and/or activated ras. Cells that overexpressed p120E4F were inhibited in
their ability to enter S phase, had elevated levels of the cdk inhibitor
p21WAF1, and reduced cyclin D-cdk4/6 kinase activity. The increase of
p21WAF1 levels occurred through a p53-independent posttranscriptional
mechanism that included a three- to fourfold increase in the half-life of
p21WAF1 protein. Coexpression of activated ras with p120E4F stimulated
cyclin D1 expression, elevated cyclin D-cdk4/6 kinase activity, and
accelerated cell growth. These data suggest an important role for p120E4F
in normal cell division and demonstrate that p21WAF1 can be regulated by
protein turnover.
Copyright © 1998, American Society for Microbiology
Adenovirus E1A-regulated transcription factor p120E4F inhibits cell growth and induces the stabilization of the cdk inhibitor p21WAF1
Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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