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Mol. Cell. Biol., Jun 1997, 3202-3209, Vol 17, No. 6
A Mettouchi, F Cabon, N Montreau, V Dejong, P Vernier, R Gherzi, G Mercier and B Binetruy
In cooperation with an activated ras oncogene, the site-dependent AP-1
transcription factor c-Jun transforms primary rat embryo fibroblasts (REF).
Although signal transduction pathways leading to activation of c- Jun
proteins have been extensively studied, little is known about c-Jun
cellular targets. We identified c-Jun-upregulated cDNA clones homologous to
the tenascin-C gene by differential screening of a cDNA library from REF.
This tightly regulated gene encodes a rare extracellular matrix protein
involved in cell attachment and migration and in the control of cell
growth. Transient overexpression of c-Jun induced tenascin-C expression in
primary REF and in FR3T3, an established fibroblast cell line.
Surprisingly, tenascin-C synthesis was repressed after stable
transformation by c-Jun compared to that in the nontransformed parental
cells. As assessed by using the tenascin-C (-220 to +79) promoter fragment
cloned in a reporter construct, the c- Jun-induced transient activation is
mediated by two binding sites: one GCN4/AP-1-like site, at position -146,
and one NF-kappaB site, at position -210. Furthermore, as demonstrated by
gel shift experiments and cotransfections of the reporter plasmid and
expression vectors encoding the p65 subunit of NF-kappaB and c-Jun, the two
transcription factors bind and synergistically transactivate the tenascin-C
promoter. We previously described two other extracellular matrix proteins,
SPARC and thrombospondin-1, as c-Jun targets. Thus, our results strongly
suggest that the regulation of the extracellular matrix composition plays a
central role in c-Jun-induced transformation.
Copyright © 1997, American Society for Microbiology
The c-Jun-induced transformation process involves complex regulation of tenascin-C expression
Institut de Recherche sur le Cancer, CNRS UPR9079, Villejuif, France.
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