Jun NH2-terminal kinase phosphorylation of p53 on Thr-81 is important for p53 stabilization and transcriptional activities in response to stress

The p53 tumor suppressor protein plays a key role in the regulation of stre ss-mediated growth arrest and apoptosis. Stress-induced phosphorylation of p53 tightly regulates its stability and transcriptional activities. Mass sp ectrometry analysis of p53 phosphorylated in 293T cells by active Jun NH2-t erminal kinase (JNK) identified T81 as the JNK phosphorylation site. JNK ph osphorylated p53 at T81 in response to DNA damage and stress-inducing agent s, as determined by phospho-specific antibodies to T81. Unlike wild-type p5 3, in response to JNK stimuli p53 mutated on T81 (T81A) did not exhibit inc reased expression or concomitant activation of transcriptional activity, gr owth inhibition, acid apoptosis, Forced expression of MKP5, a JNK phosphata se, in JNK kinase-expressinig cells decreased T81 phosphorylation while red ucing p53 transcriptional activity and p53-mediated apoptosis. Similarly tr ansfection of antisense JNK 1 and -2 decreased T81 phosphorylation in respo nse to UV irradiation. More than 180 human tumors have been reported to con tain p53 with mutations within the region that encompasses T81 and the JNK binding site (amino acids 81 to 116). Our studies identify an additional me chanism for the regulation of p53 stability and functional activities in re sponse to stress.