MITOGEN-ACTIVATED PROTEIN-KINASE KINASE-7 IS AN ACTIVATOR OF THE C-JUN NH2-TERMINAL KINASE

The c-Jun NH2-terminal kinase (JNK) group of mitogen-activated protein (MAP) kinases is activated by phosphorylation on Thr and Tyr. Here we report the molecular cloning of a new member of the mammalian MAP kin ase kinase group (MKK7) that functions as an activator of JNK. In vitr o protein kinase assays demonstrate that MKK7 phosphorylates and activ ates JNK, but not the p38 or extracellular signal-regulated kinase gro ups of MAP kinase. Expression of MKK7 in cultured cells causes activat ion of the JNK signal transduction pathway. MKK7 is therefore establis hed to be a novel component of the JNK signal transduction pathway.