Amino-terminal-derived JNK fragment alters expression and activity of c-Jun, ATF2, and p53 and increases H2O2-induced cell death

The stress-activated protein kinase JNK plays an important role in the stab ility and activities of key regulatory proteins, including c-Jun, ATF2, and p53. To better understand mechanisms underlying the regulation of JNK acti vities, we studied the effect of expression of the amino-terminal JNK fragm ent (N-JNK; amino acids 1-206) on the stability and activities of JNK subst rates under nonstressed growth conditions, as well as after exposure to hyd rogen peroxide. Mouse fibroblasts that express N-JNK under tetracycline-off (tet-off) inducible promoter exhibited elevated expression of c-Jun, ATF2, and p53 upon tetracycline removal. This increased coincided with elevated transcriptional activities of p53, but not of c-Jun or ATF2, as reflected i n luciferase activities of p21(Waf1/Cip1)-Luc, AP1-Luc, and Jun2-Luc, respe ctively. Expression of N-JNK; in cells that were treated with H2O2 impaired transcriptional output as reflected in a delayed and lower level of c-Jun- , limited ATF2-, and reduced p53-transcriptional activities. N-JNK elicited an increase in H2O2-induced cell death, which is p53-dependent, because it was not seen in p53 null cells yet could be observed upon coexpression of p53 and N-JNK. The ability to alter the activity of ATF2, c-Jun, and p53 an d the degree of stress-induced cell death by a JNK-derived fragment identif ies new means to elucidate the nature of JNK regulation and to alter the ce llular response to stress.