 This kinase contains a SH3 domain and a leucine zipper-basic motif.This kinase preferentially activates MAPK8/JNK kinase, and functions as a positive regulator of JNK signaling pathway.This kinase can directly phosphorylate, and activates JNK and p38, and is found to be involved in the transcription activity of AP1 mediated by Rho family GTPases and CDC42.