Acts as a regulator of transcriptional activation. Plays a role in the inducible expression of cytokine genes in T-cells, especially in the induction of the IL-2 (By similarity). Along with NFATC4, involved in embryonic heart development (PubMed:12750314). Member of the multicomponent NFATC transcription complex that consists of at least two components, a pre-existing cytoplasmic component NFATC2 and an inducible nuclear component NFATC1. Other members such as NFATC4, or members of the activating protein-1 family, MAF, GATA4 and Cbp/p300 can also bind the complex. NFATC proteins bind to DNA as monomers. Interacts with TRIM17; this interaction prevents NFATC3 nuclear localization (PubMed:25215946). Cytoplasmic for the phosphorylated form and nuclear after activation that is controlled by calcineurin-mediated dephosphorylation. Rapid nuclear exit of NFATC is thought to be one mechanism by which cells distinguish between sustained and transient calcium signals. The subcellular localization of NFATC plays a key role in the regulation of gene transcription. Expressed in thymus. Weakly expressed in muscle, spleen and kidney. Also expressed in lymph node. Expressed in the heart (PubMed:12370307). Expressed in the developing heart at 13.5 and 16.5 dpc, during the transition from spongy to compact myocardium. Rel Similarity Domain (RSD) allows DNA-binding and cooperative interactions with AP1 factors. Phosphorylated by NFATC-kinase; dephosphorylated by calcineurin. At 10.5 dpc, knockout embryo exhibit normal heart development (PubMed:12750314). Adults show attenuated phenotype during calcineurin-induced cardiac hypertrophy compared to wild-type littermates (PubMed:12370307). Simultaneous knockout of NFATC3 and NFATC4 results in embryonic death soon after 10.5 dpc. Embryos appear normal at 9.5 dpc. At 10.5 dpc, they exhibit defects in cardiac development, including dilated thin translucent hearts, pericardial effusion and anemia. Despite a mild generalized developmental delay, the heads, tails, and limb buds are well developed. By 11.5 dpc, mutant embryos are either necrotic or resorbed (PubMed:12750314).