CHARACTERIZATION OF THE RAT TISSUE-TYPE PLASMINOGEN-ACTIVATOR GENE PROMOTER - IDENTIFICATION OF A TAAT-CONTAINING PROMOTER ELEMENT

Tissue-type plasminogen activator (tPA) activates plasminogen to the a ctive protease plasmin and is implicated in many biological processes that require extracellular proteolysis. In rat ovarian cells, gonadotr opins induce the tPA gene by a cAMP-dependent pathway and this inducti on correlates with the time of follicular rupture. We have previously identified several promoter elements within the first 621 bp of the ra t tPA promoter that are important for constitutive and cAMP-induced ex pression of the gene, including a cAMP responsive element (CRE), a nuc lear factor 1 (NF1) element, a SP1-binding site and a G+G-rich box. Zn this report we have extended our study by analysing promoter construc ts, ranging in size from 7.7 kb to 135 bp fused to the luciferase repo rter gene. Transient transfection analysis of rat granulosa cells and human 293 cells, reveal that the proximal 268 bp of the promoter is en ough to confer high basal and cAMP-induced expression of the gene. At position -162 to -172, between the previously identified CRE and NF1 s ires, a novel TAAT-containine promoter element was identified. Mutatio nal inactivation of the TAAT motif indicates that this element is impo rtant for both constitutive and cAMP-induced expression ol the gene, a nd for the binding of a presumably novel nuclear factor that we have t ermed tPA promoter factor-1 (tPF-1).