ACTIVATION OF C-JUN-NH2-KINASE BY UV IRRADIATION IS DEPENDENT ON P21(RAS)

We have demonstrated previously that Jun-NH2-kinase (JNK) activation i n vitro is potentiated by association with the p21(ras) protein. To de termine 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 abil ity of UV to activate JNK gradually decreased over a 4-day period of c ell growth in dexamethasone. This decrease coincides with weaker trans criptional activation measured via gel shift and chloramphenicol acety ltransferase assays. Peptides corresponding to amino acids 96-110 on p 21(ras), which were shown to block Ras-JNK association, inhibited UV-m ediated JNK activation in mouse fibroblast 3T3-4A cells as well as in M1311 cells, further supporting the role of p21(ras) in UV-mediated JN K activation. Overall, the present studies provide in vivo confirmatio n of the role p21(ras) plays in JNK activation by UV irradiation.