Upon binding of a cytokine or growth factor to its respective receptor, the receptor dimerizes and activates JAKs associated with its intracellular domain. These activated JAKs then phosphorylate specific tyrosine residues on the receptor, creating docking sites for STAT proteins. The STATs are subsequently phosphorylated by JAKs, causing them to dimerize and translocate to the nucleus where they initiate transcription of target genes.
