JAK-STAT signal transduction pathway.

Ligand-induced receptor oligomerization activates JAKs that subsequently phosphorylate tyrosine residues on the cytoplasmic portion of the receptor. The quiescent STAT monomers are then recruited to the activated receptor complex via the interaction of the SH2 domains with phosphotyrosine docking sites. STATs are phosphorylated by the JAKs on a conserved tyrosine residue in the c-terminal domain to form STAT homodimers or heterodimers. STATs dissociate from the receptor after the dimerization and translocate into the nucleus. In the nucleus, STATs bind to specific response elements and induce gene transcription.