FIG. 10.

The JNK pathway is activated and dominant-negative (DN) MEKK-1 and JNKK-1 constructs inhibit promoter activation upon treatment with chemotherapeutic drugs. (A) C-Jun and JNK are phosphorylated in HepG2 cells upon treatment with 100 μg of 5-FU/ml. At the indicated time points after treatment with 5-FU, cells were harvested and either activity of JNK was measured by an in vitro kinase immunocomplex assay with GST-c-Jun as a substrate (GST-c-Jun-P) or phosphorylation of JNK was determined by Western blotting with antibodies specific for phosphorylated JNK1/2 (anti-P-JNK). (B) Cotransfection experiments with a control vector (pUCSV) or with dominant-negative mutants for the stress-activated protein kinases JNKK-1, MEKK-1, MKK3, and MKK6. Values of fold induction were calculated as described above. One representative experiment out of three independent experiments is shown.