HIGH-LEVEL ACTIVITY OF THE MOUSE CCAAT ENHANCER-BINDING PROTEIN (C EBP-ALPHA) GENE PROMOTER INVOLVES AUTOREGULATION AND SEVERAL UBIQUITOUS TRANSCRIPTION FACTORS/
C. Legraverend et al., HIGH-LEVEL ACTIVITY OF THE MOUSE CCAAT ENHANCER-BINDING PROTEIN (C EBP-ALPHA) GENE PROMOTER INVOLVES AUTOREGULATION AND SEVERAL UBIQUITOUS TRANSCRIPTION FACTORS/, Nucleic acids research, 21(8), 1993, pp. 1735-1742
The promoter region of the mouse CCAAT-Enhancer Binding Protein (C/EBP
alpha) gene is capable of directing high levels of expression of repor
ter constructs in various cell lines, albeit even in cells that do not
express their endogenous C/EBPalpha gene. To understand the molecular
mechanisms underlying this ubiquitous expression, we have characteriz
ed the promoter region of the mouse C/EBPalpha gene by a variety of in
vitro and in vivo methods. We show that three sites related in sequen
ce to USF, BTE and C/EBP binding sites and present in promoter region
- 350/ + 3, are recognized by proteins from rat liver nuclear extracts
. The sequence of the C/EBPalpha promoter that includes the USF bindin
g site is also capable of forming stable complexes with purified Myc Max heterodimers and mutation of this site drastically reduces transc
ription of C/EBPalpha promoter luciferase constructs both in liver and
non liver cell lines. In addition, we identify three novel protein-bi
nding sites two of which display similarity to NF-1 and a NFkappaB bin
ding sites. The region located between nucleotides - 197 and - 178 for
ms several heat-stable complexes with liver nuclear proteins in vitro
which are recognized mainly by antibodies specific for C/EBPalpha. Fur
thermore, transient expression of C/EBPalpha and to a lesser extent C/
EBPbeta expression vectors, results in transactivation of a co-transfe
cted C/EBPalpha promoter-luciferase reporter construct. These experime
nts support the notion that the C/EBPalpha gene is regulated by C/EBPa
lpha but other C/EBP-related proteins may also be involved.