10 nM siRNA

The p53 family member p63 has been shown to be critical for growth, proliferation and chemosensitivity. Here we demonstrate that the c-Abl tyrosine kinase phosphorylates the widely expressed DeltaNp63alpha isoform and identify multiple sites by mass spectrometry in vitro and in vivo. Phopshorylation by c-Abl results in greater protein stability of both ectopically expressed and endogenous DeltaNp63alpha. c-Abl phosphorylation of DeltaNp63alpha induces its binding to Yes-associated protein (YAP) and silencing of YAP by siRNA reduces the c-Abl-induced increase of DeltaNp63alpha levels. We further show that cisplatin induces c-Abl phosphorylation of DeltaNp63alpha and its binding to YAP. Overexpression of DeltaNp63alpha, but not the c-Abl phosphosites mutant, protects cells from cisplatin treatment. Finally, we demonstrate the rescue of p63 siRNA-mediated loss of viability with p63siRNA insensitive construct of DeltaNp63alpha but not the phosphosites mutant. These results demonstrate that c-Abl phosphorylation of DeltaNp63alpha regulates its protein stability, by inducing binding of YAP, and is critical for cell viability.