PLASMINOGEN-ACTIVATOR INHIBITOR TYPE-2 GENE INDUCTION BY TUMOR-NECROSIS-FACTOR AND PHORBOL ESTER INVOLVES TRANSCRIPTIONAL AND POSTTRANSCRIPTIONAL EVENTS - IDENTIFICATION OF A FUNCTIONAL NONAMERIC AU-RICH MOTIFIN THE 3'-UNTRANSLATED REGION

Plasminogen activator inhibitor type 2 (PAI-2) mRNA and antigen levels are synergistically induced in HT-1080 fibrosarcoma cells when treate d with a combination of tumor necrosis factor (TNF) and phorbol 12-myr istate 13-acetate (PMA). Here we demonstrate that this effect is not f ully reflected at the level of gene transcription, suggesting a contri bution of post transcriptional events in this induction. Insertion of the 8'-untranslated region (3'-UTR) of PAI-2 mRNA into the 3'-UTR of a rabbit beta-globin reporter gene reduces beta-globin-PAI-2 chimeric m RNA expression in stably transfected cells. The region within the PAI- 2 3'-UTR responsible for this effect is located within the 368-nucieot ide sequence preceding the poly(A) tail, a segment that includes a non americ UUAUUUAUU motif. Mutagenesis of this element abolishes the PAI- 2 3'-UTR destabilizing effect, revealing a functional role for this mo tif. TNF and PMA co-treatment of transfected cells increases beta-glob in-PAI-2 chimeric mRNA expression 3-4-fold, indicating that the inhere ntly unstable 3'-UTR of PAI-2 mRNA can become stabilized in response t o TNF and PMA. Our results indicate that induction of PAI-2 gene expre ssion by TNF and PMA involves both direct transcription as well as mRN A stabilization, the latter involving an AU-rich nonameric motif in th e 3'-UTR.