part of JNK cascade Phosphorylation of MKK4/7 by MAPKKK in cytosol GO:0007256 IEV:0000227 IMR:0000229 IMR:0000262 The initiation of the activity of the inactive enzyme JUN kinase kinase (JNKK) activity in response to phosphorylation by a member of the JUN kinase kinase kinase (JNKKK) family, or another upstream kinase. JNKKs are involved in a signaling pathway that is primarily activated by cytokines and exposure to environmental stress. activation of JNKK activity event Phosphorylation of MAPKK by MAPKKK in cytosol