Transactivation of the urokinase-type plasminogen activator receptor gene through a novel promoter motif bound with an activator protein-2 alpha-related factor

The urokinase receptor overexpressed in invasive cancers promotes laminin d egradation. The current study was undertaken to identify cis elements and t rans-acting factors activating urokinase receptor expression through a foot printed (-148/-124) region of the promoter containing putative activator pr otein-2- and Sp1-binding motifs, Mobility shifting experiments using nuclea r extract from a high urokinase receptor-expressing cell line (RKO) indicat ed that Sp1, Sp3, and a factor similar to, but distinct from, activator pro tein-2 alpha bound to this region, Mutations preventing the binding of the activator protein 2 alpha-related factor diminished urokinase receptor prom oter activity. In RKO cells, the expression of a negative regulator of acti vator protein-2 function diminished urokinase receptor promoter activity, p rotein, and laminin degradation. Conversely, urokinase receptor promoter ac tivity in low urokinase receptor-expressing GEO cells was increased by acti vator protein-2 alpha A expression. Although using GEO nuclear extract, lit tle activator protein-2 alpha-related factor bound to the footprinted regio n, phorbol 12-myristate 13-acetate treatment, which induces urokinase recep tor expression, increased complex formation. Mutations preventing the activ ator protein-2 alpha-related factor and Sp1/Sp8 binding reduced urokinase r eceptor promoter stimulation by this agent. Thus, the constitutive and phor bol 12-myristate 13-acetate-inducible expression of the urokinase receptor is mediated partly through trans-activation of the promoter via a sequence (-152/-135) bound with an activator protein-2 alpha-related factor.