SP1-MEDIATED TRANSACTIVATION OF THE RABBIT ALPHA(1) ACID GLYCOPROTEIN-ENCODING GENE INVOLVES A CIS-ACTING ELEMENT IN THE 5'-PROXIMAL PROMOTER REGION

Analysis of the regulatory promoter region of the rabbit alpha(1)-acid glycoprotein (alpha(1)-AGP)-encoding gene revealed the presence of a G + C-rich region that is a potential binding site for the transcripti on factor Sp1. DNase I footprinting and competition with Sp1-specific wild-type oligodeoxyribonucleotides showed that Sp1 interacts with a t andem array of GGGCGG motifs within the alpha(1)-AGP promoter. Transfe ction assays using both liver and nonliver cells have demonstrated tha t these Sp1-binding elements are transcriptionally active and overprod uction of Sp1 can significantly induce the expression of this gene. Pr eviously, we have identified two adjacent C/EBP-binding elements just upstream from these Sp1-binding regions. We now demonstrate by both in vivo and in vitro analyses that C/EBP and Sp1 bind to the alpha(1)-AG P promoter and transactivate the expression of this gene in an indepen dent manner.