Nuclear factor of activated T-cells (NFAT) is a transcription factor required for T-cell expression of the interleukin 2 gene. NFAT binds to a sequence in the interleukin 2 gene enhancer known as the antigen receptor response element 2. In addition, NFAT can bind RNA and is an essential component for encapsidation and protein priming of hepatitis B viral polymerase. NFAT is a heterodimer of 45 kDa and 90 kDa proteins, the smaller of which is the product of this gene. The encoded protein binds strongly to the 90 kDa protein and stimulates its ability to enhance gene expression.