NF-AT components define a family of transcription factors targeted in T-cell activation

THE NF-AT transcription complex 1 is required for the expression of a group of proteins that collectively coordinate the immune response 2–4 . Here we purify two proteins encoded by separate genes that represent the pre-existing (p) and cytosolic (c) components of NF-AT. Expression of the full-length complementary DNA enco-ding NF-AT c activates the interleukin (IL-2) promoter in non-T lymphocytes, whereas a dominant negative of NF-AT c specifically blocks activation of the IL-2 promoter in T lymphocytes, indicating that NF-AT c is required for IL-2 gene expression. NF-AT c RNA expression is largely restricted to lymphoid tissues and is induced upon T-cell activation. The other protein, NF-AT p , is highly homo-logous to NF-AT c over a limited domain which shows similarity to the Dorsal/Rel family 5 , but has a wider tissue distribution. Agents that increase intracellular Ca 2+ or activate protein kinase C independently modify NF-AT c , indicating that distinct signalling pathways converge on NF-AT c to regulate its function.