Protein kinase A and mitogen-activated protein kinase pathways antagonistically regulate fission yeast fbp1 transcription by employing different modes of action at two upstream activation sites.

A significant challenge to our understanding of eukaryotic transcriptional regulation is to determine how multiple signal transduction pathways converge on a single promoter to regulate transcription in divergent fashions. To study this, we have investigated the transcriptional regulation of the Schizosaccharomyces pombe fbp1 gene that is repressed by a cyclic AMP (cAMP)-dependent protein kinase A (PKA) pathway and is activated by a stress-activated mitogen-activated protein kinase (MAPK) pathway. In this study, we identified and characterized two cis-acting elements in the fbp1 promoter required for activation of fbp1 transcription. Upstream activation site 1 (UAS1), located approximately 900 bp from the transcriptional start site, resembles a cAMP response element (CRE) that is the binding site for the atf1-pcr1 heterodimeric transcriptional activator. Binding of this activator to UAS1 is positively regulated by the MAPK pathway and negatively regulated by PKA. UAS2, located approximately 250 bp from the transcriptional start site, resembles a Saccharomyces cerevisiae stress response element. UAS2 is bound by transcriptional activators and repressors regulated by both the PKA and MAPK pathways, although atf1 itself is not present in these complexes. Transcriptional regulation of fbp1 promoter constructs containing only UAS1 or UAS2 confirms that the PKA and MAPK regulation is targeted to both sites. We conclude that the PKA and MAPK signal transduction pathways regulate fbp1 transcription at UAS1 and UAS2, but that the antagonistic interactions between these pathways involve different mechanisms at each site.