Ig. Ruiz et al., Sp family of transcription factors is involved in iron-induced collagen alpha 1(I) gene expression, DNA CELL B, 19(3), 2000, pp. 167-178
The purpose of this study was to identify the cis-acting elements and the t
rans-acting factors involved in the iron-induced expression of the collagen
alpha 1(I) (COL1 alpha I) gene. Rat hepatic stellate cells were cultured i
n the presence of 50 mu M ferric chloride, 50 mu M ascorbic acid, and 250 m
u M citric acid (Fe/AA/CA), and the effects on collagen gene expression and
the binding of nuclear proteins to the COL1aI promoter were measured, The
Fe/AA/CA treatment induced a time- and dose-dependent increase in the cellu
lar levels of COL1aI mRNA that was abrogate by pretreating cells with cyclo
heximide, antioxidants, and inhibitors of aldehyde-protein adduct formation
. Transient transfection experiments showed that Fe/AA/CA exerted its effec
t through regulatory elements located between -220 and -110 bp of the COL1a
I promoter. Gel retardation assays showed that Fe/AA/CA increased the bindi
ng of nuclear proteins to two elements located between -161 and -110 bp of
the COL1aI promoter. These bindings were blocked by unlabeled consensus Spl
oligonucleotide and supershifted with Sp1 and Sp3 antibodies. Finally, Fe/
AA/CA increased cellular levels of the Spl and Sp3 proteins and Spl mRNA, T
reatment with Fe/AA/CA stimulates COL1aI gene expression by inducing the sy
nthesis of Spl and Sp3 and their binding to two regulatory elements located
between -161 and -110 bp of the COL1aI promoter.