RESUMO
Previously, we reported that IκB kinase-ß(IKKß) phosphorylates and stabilizes TAp63γ. However, the effect of this phosphorylation on TAp63γ transcriptional activity remains unclear. In this study, we showed that overexpression of IKKß, but not its kinase dead mutant and IKKα, can surprisingly inhibit TAp63γ transcriptional activity as measured by luciferase assays and real-time PCR analyses of p63 target genes. This inhibition was impaired by ACHP, an IKKß inhibitor, and enhanced by TNFα that activates IKKß. Consistently, IKKß inhibited the binding between TAp63γ and p300, a co-activator of TAp63γ, and consequently counteracted the positive effect of p300 on TAp63γ transcriptional activity. Through phosphorylation site prediction and mass spectrometry, we identified that Ser-4 and Ser-12 of p63 are IKKß-targeting residues. As expected, IKKß fails to suppress the transcriptional activity of the S4A/S12A double mutant p63. These results indicate that IKKß can suppress TAp63γ activity by interfering with the interaction between TAp63γ and p300.
