Attenuation of plasminogen activator inhibitor type-1 promoter activity in serum-stimulated renal epithelial cells by a distal 5' flanking region.

Urokinase plasminogen activator (u-PA) and its fast acting type-1 inhibitor (PAI-1) localize to cellular focal adhesive structures and the adjoining proximal undersurface region, respectively (Kutz et al., J. Cell. Physiol. 176:8-18, 1997). PAI-1 may function in this locale to modulate pericellular proteolytic activity, cell-to-substrate adhesion, or matrix-dependent motility. While PAI-1 synthesis is regulated in an immediate-early response manner in growth "activated" renal cells coincident with cytoskeletal restructuring, adhesive influences both repress the amplitude and prolong the time course of serum-induced PAI-1 transcription (Ryan et al., Biochem. J. 314:1041-1046, 1996). To identify potential adhesion-responsive elements within the PAI-1 gene that function in this complex mode of expression control, reporter constructs containing defined directionally deleted PAI-1 5' genomic fragments cloned upstream of a CAT gene were employed in transient transfection assays. A 483-bp distal PAI-1 flanking segment (corresponding to nucleotides -2395 to -1912) conferred significant adhesion-dependent attenuation on serum-induced PAI-1 transcription. This 483-bp distal PAI-1 segment functioned as a repressor of reporter (CAT) activity under both adhesive and suspension culture conditions, however, when ligated upstream of either an SV40 promoter/enhancer or a minimal PAI-1 promoter. These data suggest that repressor elements located between -2395 and -1912 bp interact with more proximal adhesion-dependent regulatory elements to affect PAI-1 expression attenuation during serum stimulation of adherent renal epithelial cells.