Transcriptional activator that binds 5'-GATA-3'-containing motifs within gene promoters (By similarity). Regulates cardiac-specific transcription during embryogenesis and thereby cardiogenesis. In embryos, expressed in the presumptive heart mesoderm. In adults, expressed at high levels in heart, small intestine, and stomach and at lower levels in lung, pancreas and colon. Expression is up-regulated during gastrulation. Extended N-terminus.