Role of Jak kinases and STATS in cytokine signal transduction

The Janus family tyrosine kinase-signal transducer and activator of transcr iption (Jak-STAT) signaling pathway is broadly used by interferons and type I cytokines. These cytokines and interferons activate Janus family tyrosin e kinases (Jak kinases), which in turn phosphorylate and thereby activate S TAT proteins. Before activation, STAT proteins are cytosolic proteins. afte r activation, however. they are translocated to the nucleus where they func tion as transcription factors. This review summarizes salient features of t he Jak-STAT pathway and focuses on the functional role of the different Jak kinases and STATs in vivo. (C) 2001 The Japanese Society of Hematology.