JUN-NH2-TERMINAL KINASE ACTIVATION MEDIATED BY UV-INDUCED DNA LESIONSIN MELANOMA AND FIBROBLAST CELLS

jun-NH2-terminal kinase (JNK) belongs to a family of protein kinases t hat phosphorylates c-Jun, ATF2, and Elk1 in response to various forms of stress including UV irradiation and heat shock. Although in previou s studies we have demonstrated the importance of membrane components f or JNK activation by UV irradiation, here we have elucidated the role of DNA damage in this response. We show that in vitro-irradiated or so nicated DNA that is added to proteins prepared from UV-treated cells c an further induce JNK activation in a dose-dependent manner. When comp ared with UV-B (300 nm), UV-C (254 nm), which is better absorbed by th e DNA, is significantly more potent in activating JNK. Furthermore, wh en wavelengths lower than 300 nm were filtered out, UV-B was no longer able to activate JNK. With the aid of melanoma and fibroblast cells, which exhibit different resistances to irradiation and require differe nt UV doses to generate the same number of DNA lesions, we demonstrate that above a threshold level of 0.45 lesions and up to 0.75 lesions p er 1875 bp, the degree of JNK activation correlates with the amount of lesions induced by UV-C irradiation. Finally, to explore the role of nuclear and mitochondrial DNA (mtDNA) in mediating JNK activation afte r UV irradiation, we have used cells that lack mtDNA. Although the lac k of mtDNA did not impair the ability of UV to activate JNK, when enuc leated, these cells had lost the ability to activate JNK in response t o UV irradiation. Overall, our results suggest that DNA damage in the nuclear compartment is an essential component that acts in concert wit h membrane-anchored proteins to mediate c-Jun phosphorylation by JNK.