Human as well murine STAT4 genes lie next to  STAT1 gene locus suggesting that the genes arose by gene duplication. STAT proteins have six functional domains: 1. N-terminal interaction domain – crucial for dimerization of inactive STATs and nuclear translocation; 2.helical coiled coil domain –  association with regulatory factors; 3. central DNA-binding domain – binding to the enhancer region of IFN-γ activated sequence (GAS) family genes; 4. linker domain –  assisting during the DNA binding process; 5. Src homology 2  (SH2) domain – critical for specific binding to the cytokine receptor after tyrosine phosphorylation; 6. C-terminal transactivation domain – triggering the transcriptional process. The length of the protein is 748 amino acids, and the molecular weight is 85 941 Dalton.