The nuclear factor of activated T-cells (NFAT) transcription complex is required for the expression of a group of proteins that collectively regulate the immune response. Four NFAT proteins, encoded on separate genes and expressed as several splice variants, have been described: NFAT1 (also known as NFATp or NFATc2), NFAT2 (NFATc or NFATc1), NFAT3, and NFAT4 (NFATx or NFATc3). These proteins show a low level of sequence similarity with the Dorsal/Rel/NFkB family of transcription factors. Another NFAT-related protein termed NFAT5 differs from isoforms 1-4 in that it lacks many of the Fos/Jun contact sites observed in its predecessors and its subcellular localization is not calcineurin-dependent.
