The protein encoded by this gene is a transcription factor that contains two GATA type zinc fingers. The encoded protein is known to bind to hepatocyte nuclear factor-1alpha (HNF 1 alpha), and this interaction is essential for cooperative activation of the intestinal lactase phlorizin hydrolase promoter. In other organisms, similar proteins may be involved in the establishment of cardiac smooth muscle cell diversity. GATA5 is induced at an early stage of endothelial-endocardial differentiation prior to expression of such early endocardial markers as Tie2 and ErbB3. It is required for differentiation of cardiogenic precursors into endothelial endocardial cells.