REGULATION OF UROKINASE-TYPE PLASMINOGEN-ACTIVATOR GENE-TRANSCRIPTIONBY MACROPHAGE-COLONY-STIMULATING FACTOR

The mouse urokinase-type plasminogen activator (uPA) gene was used as a model macrophage colony-stimulating factor 1 (CSF-1)-inducible gene to investigate CSF-1 signalling pathways, Nuclear run-on analysis show ed that induction of uPA mRNA by CSF-1 and phorbol myristate acetate ( PMA) was at the transcriptional level in bone marrow-derived macrophag es, CSF-1 and PMA synergized strongly in the induction of uPA mRNA, sh owing that at least some components of CSF-1 action are mediated indep endently of protein kinase C. Promoter targets of CSF-1 signalling wer e investigated with NIH 3T3 cells expressing the human CSF-1 receptor (c-fms), uPA mRNA was induced in these cells by treatment with CSF-1, and a PEA3/AP-1 element at -2.4 kb in the uPA promoter was involved in this response. Ets transcription factors can act through PEA3 sequenc es, and the involvement of Ets factors in the induction of uPA was con firmed by use of a dominant negative Ets-2 factor, Expression of the D NA binding domain of Ets-2 fused to the lacZ gene product prevented CS F-1-mediated induction of uPA mRNA in NTH 3T3 cells expressing the CSF -1 receptor, Examination of ets-2 mRNA expression in macrophages showe d that it was also induced synergistically by CSF-1 and PMA. In the ma crophage cell line RAW264, the uPA PEA3/AP-1 element mediated a respon se to both PMA and cotransfected Ets-2, uPA promoter constructs were i nduced 60- to 130-fold by Ets-2 expression, and the recombinant Ets-2 DNA binding domain was able to bind to the uPA PEA3/AP-1 element, This work is consistent with a proposed pathway for CSF-1 signalling invol ving sequential activation of fms, ras, and Ets factors.