CHARACTERIZATION OF THE HUMAN PROTEASE NEXIN-1 PROMOTER AND ITS REGULATION BY SP1 THROUGH A G C-RICH ACTIVATION DOMAIN/

Protease nexin-1 (PN-1) is a potent inhibitor of serine proteases in t he extracellular environment. It is abundantly expressed in the nervou s system, where it is thought to participate in local injury and repai r processes. Although some information has been obtained regarding PN- 1 gene structure, relatively little is known about the cis- and trans- acting factors that regulate its expression. Elucidation of these fact ors should provide a better understanding of PN-1 function during deve lopment and wound repair. In this report we describe the characterizat ion of the human PN-1 promoter and identify regulatory domains and a t ransactivator mediating its transcriptional activity. The promoter is highly G/C rich proximal to the transcriptional start site. It exhibit s tissue specificity and is negatively regulated by a silencer element upstream of position -480. A positive regulatory element was mapped b etween -199 and -45, which contains multiple putative Sp1 consensus bi nding sites. Electrophoretic mobility shift analysis confirmed that Sp l specifically binds this region of the PN-1 promoter. DNase I footpri nting revealed six potential Spl binding sites between -103 and -56 th at were protected by recombinant Spl, Cotransfection experiments into the Sp1-deficient Drosophila SL2 cell line also showed that Sp1 activa tes PN-1 promoter activity in a dose-dependent fashion. Thus, our anal ysis demonstrates that activation of PN-1 transcription is regulated b y Spl through G/C-rich cis-acting elements in the 5' proximal promoter region.