Abstract 690: Transcription Factor Gata-4 Is Activated By cGMP Dependant Protein Kinase I
cGMP/cGMP-dependent protein kinase signal transduction pathways play an important role in maintaining cardiovascular function. However, the downstream transcriptional regulatory targets of cGMP-dependent protein kinase I( PKG I) are not well understood. GATA proteins are potent tissue-specific transcriptional factors and GATA-4 plays a pivotal role in directing cardiomyocyte gene transcription. In this study GATA-4 strongly activated the atrial natriuretic factor (ANF) promoter activity in conjuction with PKG I in response to cGMP. Therefore, GATA-4 might be a downstream target of PKG. Bioinformatics revealed the presence of a conserved PKG phosphorylation site located in the link region between two zinc finger domains of GATA4. In vitro phosphorylation assays revealed a PKG I target region localized to a GATA-4 fragment from 208 to 328 aa which contains the consensus PKG motif. Mutagenesis identified serine 261 as the PKG I phosphorylation site. Moreover, a block to phosphorelation by conversion of the serine to an alanine in the S261A mutant decreased GATA4 transcription activity. Electrophoretic mobility shift assays showed that decreased DNA binding between the GATA4-S261A mutant and the ANF promoter. Elucidation of the transcriptional control mechanism of cGMP/PKG/GATA-4 pathway will provide a candidate model system for understanding a role for cGMP dependent signalling in cardiomyocyte gene transcription and cardiovascular development.