CK2 phosphorylates AP-2α and increases its transcriptional activity

Transcription factor AP-2α involves in the process of mammalian embryonic development and tumorigenesis. Many studies have shown that AP-2α functions in association with other interacting proteins. In a two-hybrid screening, the regulatory subunit β of protein casein kinase 2 (CK2β) was identified as an interacting protein of AP-2α; we confirmed this interaction using in-vitro GST pull-down and in-vivo co-immunoprecipitation assays; in an endogenous co-immunoprecipitation experiment, we further found the catalytic subunit α of protein casein kinase 2 (CK2α) also exists in the complex. Phosphorylation analysis revealed that AP-2α was phosphorylated by CK2 kinase majorly at the site of Ser429, and such phosphorylation could be blocked by CK2 specific inhibitor 4,5,6,7-tetrabromobenzotriazole (TBB) in a dose-dependent manner. Luciferase assays demonstrated that both CK2α and CK2β enhanced the transcription activity of AP-2α; moreover, CK2β increased the stability of AP-2α. Our data suggest a novel cellular function of CK-2 as a transcriptional co-activator of AP-2α.