Activation of c-Jun-NH2-Kinase by UV Irradiation Is Dependent on p21ras

We have demonstrated previously that Jun-NH 2 -kinase (JNK) activation in vitro is potentiated by association with the p21 ras protein. To determine if in vivo activation of JNK also depends on p21 ras , we have used M1311 cells that carry the cDNA for the neutralizing antibody to p21 ras , Y13-259, under a dexamethasone-inducible promoter. The ability of UV to activate JNK gradually decreased over a 4-day period of cell growth in dexamethasone. This decrease coincides with weaker transcriptional activation measured via gel shift and chloramphenicol acetyltransferase assays. Peptides corresponding to amino acids 96-110 on p21 ras , which were shown to block Ras-JNK association, inhibited UV-mediated JNK activation in mouse fibroblast 3T3-4A cells as well as in M1311 cells, further supporting the role of p21 ras in UV-mediated JNK activation. Overall, the present studies provide in vivo confirmation of the role p21 ras plays in JNK activation by UV irradiation.