ก were originally described as latent cytoplasmic transcription factors that require phosphorylation for nuclear retention. The unphosphorylated STAT proteins shuttle between cytosol and the nucleus waiting for its activation signal. Once the activated transcription factor reaches the nucleus, it binds to consensus DNA-recognition motif called gamma-activated sites (GAS) in the promoter region of cytokine-inducible genes and activates transcription of these genes.