Transcriptional activator which probably serves as a general switch factor for cell-specific development. It binds to DNA sites with the consensus sequence 5'-[AT]GATA[AG]-3' within regulatory regions of genes. Expressed only in definitive (adult) erythrocytes within the red cell lineage, and is also abundantly expressed in T-lymphocytes and brain. Binds DNA via the 2 GATA-type zinc fingers.