Figure 5.

MKK4 and MKK7 cooperate to activate JNK in vivo. Wild-type (WT), Mkk4^−/−, Mkk7^−/−, and Mkk4^−/− Mkk7^−/− MEF were untreated or treated with UV-C (60 J/m²; UV), anisomycin (1 μg/mL; ANISO), TNFα (10 ng/mL; TNF), or IL1α (15 ng/mL; IL1) and then incubated for the indicated times. JNK (A) and p38 MAP kinase (B) activity was measured by in vitro protein kinase assay with the substrates c-Jun and ATF2, respectively. Phosphorylated c-Jun and ATF2 were detected after SDS-PAGE by autoradiography (upper), quantitated by PhosphorImager analysis (Molecular Dynamics), and presented in arbitrary units (lower).