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 (PubMed:18815128). Along with NFATC4, involved in embryonic heart development (By similarity). 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 (By similarity). 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. Isoform 1 is predominantly expressed in thymus and is also found in peripheral blood leukocytes and kidney. Isoform 2 is predominantly expressed in skeletal muscle and is also found in thymus, kidney, testis, spleen, prostate, ovary, small intestine, heart, placenta and pancreas. Isoform 3 is expressed in thymus and kidney. Isoform 4 is expressed in thymus and skeletal muscle. Rel Similarity Domain (RSD) allows DNA-binding and cooperative interactions with AP1 factors. Phosphorylated by NFATC-kinase; dephosphorylated by calcineurin.