The nuclear factor of activated T cells (NFAT) group of transcription factors is 
retained in the cytoplasm of quiescent cells. NFAT activation is mediated in 
part by induced nuclear import. This process requires calcium-dependent 
dephosphorylation of NFAT caused by the phosphatase calcineurin. The c-Jun 
amino-terminal kinase (JNK) phosphorylates NFAT4 on two sites. Mutational 
removal of the JNK phosphorylation sites caused constitutive nuclear 
localization of NFAT4. In contrast, JNK activation in calcineurin-stimulated 
cells caused nuclear exclusion of NFAT4. These findings show that the nuclear 
accumulation of NFAT4 promoted by calcineurin is opposed by the JNK signal 
transduction pathway.