This gene encodes a dual specificity protein kinase that belongs to the Ser/Thr protein kinase family. This kinase is a direct activator of MAP kinases in response to various environmental stresses or mitogenic stimuli. It has been shown to activate MAPK8 / JNK1, MAPK9 / JNK2, and MAPK14 / p38, but not MAPK1 / ERK2 or MAPK3 / ERK3. This kinase is phosphorylated, and thus activated by MAP3K1 / MEKK. The knockout studies in mice suggested the roles of this kinase in mediating survival signal in T cell development, as well as in the organogenesis of liver