1: Oncogene. 1991 Apr;6(4):567-76. 

fosB is a transforming gene encoding a transcriptional activator.

Schuermann M, Jooss K, Muller R.

Institut fur Molekularbiologie und Tumorforschung (IMT) Philipps-Universitat
Marburg, Federal Republic of Germany.

The fosB gene encodes a nuclear protein that shows a high degree of homology
with c-Fos in several of the known functionally crucial domains, e.g., the
leucine zipper and the DNA-binding site, but shows considerable divergence in
other regions. Here, we report that FosB, when placed under the control of a
constitutive promoter, exhibits clear transforming properties in focus assays
using mouse NIH3T3 or rat 208F fibroblasts. The transforming potential of FosB
is considerably stronger than that of a corresponding c-fos construct and
resembles that of viral fos genes. Using chimeric fos/fosB constructs we show
that the C-terminal half of FosB is responsible for these stronger transforming
properties, apparently by giving rise to significantly higher levels of protein
as compared with the corresponding c-fos sequence. Surprisingly, substitution of
the N-terminus of Fos with that of FosB decreases its transforming potential.
These differences in the transforming potential are not related to DNA or
protein expression, but rather seem to reflect differences in the molecular
function(s) encoded in the N-terminal halves of Fos and FosB protein. Both,
fosB- and v-fos transformed cells show increased expression of a number of
endogenous genes, including c-jun, transin, alpha 1(III) collagen and tissue
plasminogen activator. Transactivation by FosB and v-fos of the c-jun and alpha
1(III) collagen gene promoters and of a 3 x TRE-tk chimeric promoter could be
shown in transient CAT assays. v-Fos, but not FosB-transformed cells, also show
elevated levels of urokinase and plasminogen activator inhibitor mRNAs, pointing
to potential differences in the gene regulatory properties of the two Fos family
members.

PMID: 1903195 [PubMed - indexed for MEDLINE]


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