Sp1-mediated transactivation of the rabbit alpha 1 acid glycoprotein-encoding gene involves a cis-acting element in...

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 transcription factor Sp1. DNase I footprinting and competition with Sp1-specific wild-type oligodeoxyribonucleotides showed that Sp1 interacts with a tandem array of GGGCGG motifs within the alpha 1-AGP promoter. Transfection assays using both liver and nonliver cells have demonstrated that these Sp1-binding elements are transcriptionally active and overproduction of Sp1 can significantly induce the expression of this gene. Previously, 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-AGP promoter and transactivate the expression of this gene in an independent manner.