Transcriptional activator that binds to the consensus sequence 5'-AGATAG-3' and plays a key role in cardiac development (PubMed:35182466). In cooperation with TBX5, it binds to cardiac super-enhancers and promotes cardiomyocyte gene expression, while it down-regulates endocardial and endothelial gene expression (By similarity). Involved in bone morphogenetic protein (BMP)-mediated induction of cardiac-specific gene expression (By similarity). Binds to BMP response element (BMPRE) DNA sequences within cardiac activating regions (By similarity). Acts as a transcriptional activator of ANF in cooperation with NKX2-5 (PubMed:9584153). Promotes cardiac myocyte enlargement (By similarity). Required during testicular development (By similarity). May play a role in sphingolipid signaling by regulating the expression of sphingosine-1-phosphate degrading enzyme, sphingosine-1-phosphate lyase (By similarity). Interacts with ZNF260 (By similarity). Interacts with the homeobox domain of NKX2-5 through its C-terminal zinc finger. Also interacts with JARID2 which represses its ability to activate transcription of ANF. Interacts (via the second Zn finger) with NFATC4 (PubMed:9568714). Interacts with LMCD1 (PubMed:16199866). Forms a complex made of CDK9, CCNT1/cyclin-T1, EP300 and GATA4 that stimulates hypertrophy in cardiomyocytes. Interacts with NR5A1, ZFPM2 and TBX5. Interacts with TBX18. Interacts with GLYR1; the interaction is required for a synergistic activation of GATA4 target genes transcription (By similarity). Heart, intestine, liver, primative endoderm and gonads. By retinoic acid. Methylation at Lys-299 attenuates transcriptional activity.