Pin1 and JNK1 cooperatively modulate TAp63γ

Abstract

The p63 gene encodes at least 10 isoforms, which can be classified into TA and ∆N isotypes (TAp63 and ∆Np63 proteins) according to their differences at the N termini. TAp63γ is an important transcription factor. We previously reported that peptidyl‐prolyl isomerase (PPI) Pin1 directly binds to TAp63γ protein and identified that serine 12 (S12) in the transactivation domain (TAD) of TAp63γ is required for regulation of its transcriptional activity. In the present study, we report that Pin1 stimulates transcriptional and pro‐apoptotic activities of TAp63γ; this Pin1‐mediated stimulation may depend on phosphorylation of S12 mediated by JNK1 and results in striking activation of TAp63γ. JNK1 represses transactivity of TAp63γ in cells without abundant Pin1 proteins and enhances it in the presence of sufficient levels of Pin1. Collectively, our data suggest a novel mechanism for regulation of TAp63γ transactivity: TAp63γ with unphosphorylated S12 is moderately active, phosphorylation at this residue (pS12) makes it hypoactive, and Pin1 binds to the pS12‐P13 motif and makes TAp63γ hyperactive. Our findings will aid in the elucidation of the mechanism underlying modulation of TAp63γ.

CDK1 Promotes Epithelial–Mesenchymal Transition and Migration of Head and Neck Squamous Carcinoma Cells by Repressing ∆Np63α-Mediated Transcriptional Regulation

“…Mechanistically, it can inhibit epithelial-mesenchymal transition (EMT) and cell migration by regulating the expression of various genes related to cell adhesion and motility [35,37]. Previous data from our lab and other groups reveal that p63 proteins can be phosphorylated and modulated by several kinases [53,[63][64][65][66][67][68].…”

“…With the resultant mass spectrometry (MS) analysis, we identified several ∆Np63α-interacting kinases including CDK1 (listed in Supplementary Table S1), as well as multiple phosphorylated residues in ∆Np63α (depicted in Supplementary Figure S1). Among these phospho-sites, 15 are located in the DNA binding domain (DBD) or trans-inhibitory domain (TID), both of which are crucial to ∆Np63α-mediated transcriptional regulation [53]. To investigate the effects of these phospho-sites within DBD and TID on ∆Np63α-mediated transcriptional regulation, we generated a series of mutant ∆Np63α constructs, with serine (S) or threonine (T) substituted with alanine (A) to prevent the potential phosphorylation.…”

“…Luciferase assays were performed as described previously [53,84]. HEK293T cells were transfected with a mixture of K14-or BPAG1-Luc and pRL-TK-Renilla plus indicated plasmids or siRNAs.…”