Activation of c-Jun-NH2-Kinase by UV Irradiation Is Dependent on p21

The extracellular-signal-regulated protein kinases (Erks) are required for UV-induced AP-1 activation in JB6 cells

“…It is known that mammalian cells contain at least three signaling pathways which are structurally related to the MAPKs pathway. It is believed that stress-related signals, including UV, induce the MEK kinase (MEKK)/SAPK/Erk kinase (SEK)?JNKs/SAPKs and the MAP kinase kinase3 (MKK3) or MKK6/ P38 kinase pathway (Adler et al, 1995(Adler et al, , 1996De rijard et al, 1994;Sa nchez et al, 1994), while growth factors acting through Ras primarily stimulate the Raf/MEK/ Erks cascade of protein kinases (Cowley et al, 1994;Dalton and Treisman, 1992;PageÁ s et al, 1993;Wan et al, 1996;Xia et al, 1995). However, activation of these three pathways cannot be completely separated from each other.…”

“…Previous studies demonstrate that induced AP-1 activity is required for tumor promotion (Dong et al, 1995a,b;Huang et al, 1996cHuang et al, , 1998. Signal transduction pathways leading to transcription factor AP-1 activation in UV response have been extensively studied (Adler et al, 1995(Adler et al, , 1996Denhardt, 1996;Huang et al, 1996a;Radler-Pohl et al, 1993). However, some issues in UV-induced signal transduction pathways remain unresolved.…”

“…The Ras?Raf?MEK?Erks cascade is the signaling cascade that leads to Erks activation. Previous studies have found that cell exposure to UV irradiation caused activation of both Erks (Denhardt, 1996;PageÁ s et al, 1993) and JNKs (Adler et al, 1995(Adler et al, , 1996De rijard et al, 1994;Van Blesen et al, 1995;Verheij et al, 1996;Wan et al, 1996) pathways, but the extent of activation between these two pathways was di erent (Canman and Kasten, 1996;Denhardt, 1996;Ludwig et al, 1996;Radler-Pohl et al, 1993). JNKs were e ciently activated in cells exposed to UV, while UV irradiation only induced weak activation of Erks.…”

“…It is believed that Erks are strongly activated and play a critical role in transmitting signals initiated by 12-0-tetradecanoylphorbol-13-acetate (TPA) and growth factors such as epidermal growth factor (EGF), platelet-derived growth factor (PDGF) (Cowley et al, 1994;Dalton and Treisman, 1992;L'Allemain et al, 1992;PageÁ s et al, 1993;Robbins et al, 1993;Wan et al, 1996;Xia et al, 1995). Whereas the JNKs/SAPKs and P38 kinases are potently activated by various forms of stress, such as ultraviolet light (UV), heat shock and in¯ammation (Adler et al, 1995(Adler et al, , 1996BuÈ scher et al, 1988; Denhardt, 1996;Ludwig et al, 1996;Minden et al, 1994; Sa nchez et al, 1994), the activation of these pathways is not mutually exclusive. For example, heat shock and UV irradiation partially activate the Erk1/Erk2 cascade and EGF partially activates the JNKs/SAPKs pathway (Denhardt, 1996, Minden et al, 1994.…”

p38 protects human melanoma cells from UV-induced apoptosis through down-regulation of NF-κB activity and Fas expression

“…Protein kinase assays were carried out using fusion proteins, GST-IkBa, as a substrate as previously described (Adler et al, 1996). Brie¯y, the GST-IkBa fusion protein (0.5 mg/assay) was bound to glutathione-sepharose beads after addition of melanoma proteins as the source of IKK (10 mg/assay) in the presence of kinase bu er (20 mM HEPES, pH 7.6, 1 mM EGTA, 1 mM dithiothreitol, 2 mM MgCl 2 , 2 mM MnCl 2 , 5 mM NaF, 1 mM NaVO 3 , 50 mM NaCl) at room temperature for 15 min.…”