THE SPECIES-SPECIFIC DIFFERENCES IN THE CAMP REGULATION OF THE TISSUE-TYPE PLASMINOGEN-ACTIVATOR GENE BETWEEN RAT, MOUSE AND HUMAN IS CAUSED BY A ONE-NUCLEOTIDE SUBSTITUTION IN THE CAMP-RESPONSIVE ELEMENT OF THE PROMOTERS

In rat ovarian cells tissue-type plasminogen activator (tPA) is induce d by gonadotropins, by a cAMP-dependent pathway and the induction corr elates with the time of follicle rupture ia vivo. However, in mice, go nadotropins induce the related but distinct protease urokinase-type pl asminogen activator (uPA). Comparison of rat, mouse and human tPA gene s reveal that there is a species-specific difference in the promoter t hat could explain the difference in regulation of the tPA gene between these species. At the position where the rat promoter contains a cons ensus cAMP-responsive element (CRE), the mouse and human counterparts contains a CRE Variant with a one-nucleotide substitution. Transient t ransfection experiments of rat glial and granulosa cells demonstrated that reporter constructs driven by rat but not mouse or human tPA prom oters were efficiently induced by the cAMP-inducing agents forskolin o r follicle-stimulating hormone. Following the conversion of the mouse and human CRE-like sequences to rat consensus CRE these promoters beca me cAMP responsive. In contrast the rat promoter, following conversion of the consensus CRE to the corresponding mouse and human CRE-Like se quence, lost the ability to efficiently respond to cAMP. Deoxyribonucl ease I footprinting analysis and electrophoretic mobility shift assays were used to examine interactions of nuclear factors with the consens us and variant CRE. Compared to rat CRE, the mouse and human CRE-like sequences had a drastically reduced binding affinity for a nuclear fac tor identified as the cAMP-responsive element binding protein. Thus th e inability of the mouse and human tPA promoters to respond efficientl y to forskolin and follicle-stimulating hormone seem to be due to the inability of these CRE-like sequences to efficiently bind transcriptio n factor CRE binding protein.