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Mol. Cell. Biol., 07 1995, 3748-3758, Vol 15, No. 7
G Bergers, P Graninger, S Braselmann, C Wrighton and M Busslinger
Constitutive expression of c-Fos, FosB, Fra-1, or c-Jun in rat fibroblasts
leads to up-regulation of the immediate-early gene fra-1. Using the
posttranslational FosER induction system, we demonstrate that this
AP-1-dependent stimulation of fra-1 expression is rapid, depends on a
functional DNA-binding domain of FosER, and is a general phenomenon
observed in different cell types. In vitro mutagenesis and functional
analysis of the rat fra-1 gene in stably transfected Rat-1A- FosER
fibroblasts indicated that basal and AP-1-regulated expression of the fra-1
gene depends on regulatory sequences in the first intron which comprise a
consensus AP-1 site and two AP-1-like elements. We have also investigated
the transactivating and transforming properties of the Fra-1 protein to
address the significance of fra-1 up- regulation. The entire Fra-1 protein
fused to the DNA-binding domain of Ga14 is shown to lack any
transactivation function, and yet it possesses oncogenic potential, as
overexpression of Fra-1 in established rat fibroblasts results in
anchorage-independent growth in vitro and tumor development in athymic
mice, fra-1 is therefore not only induced by members of the Fos family, but
its gene product may also contribute to cellular transformation by these
proteins. Together, these data identify fra-1 as a unique member of the fos
gene family which is under positive control by AP-1 activity.
Copyright © 1995, American Society for Microbiology
Transcriptional activation of the fra-1 gene by AP-1 is mediated by regulatory sequences in the first intron
Research Institute of Molecular Pathology, Vienna, Austria.
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