The mitotic serine/threonine kinase Aurora2/AIK is regulated by phosphorylation and degradation

Aurora2 is a cell cycle regulated serine/threonine protein kinase which is overexpressed in many tumor cell lines. We demonstrate that Aurora2 is regu lated by phosphorylation in a cell cycle dependent manner. This phosphoryla tion occurs on a conserved residue, Threonine 288, within the activation lo op of the catalytic domain of the kinase and results in a significant incre ase in the enzymatic activity. Threonine 288 resides within consensus motif for the cAMP dependent kinase and can be phosphorylated by PKA in vitro. T he protein phosphatase 1 is shown to dephosphorylate this site in vitro, an d in vivo the phosphorylation of T288 is induced by okadaic acid treatment. Furthermore, we show that the Aurora2 kinase is regulated by proteasome de pendent degradation and that Aurora2 phosphorylated on T288 may be targeted for degradation during mitosis, Our experiments suggest that phosphorylati on of T288 is important for regulation of the Aurora2 kinase both for its a ctivity and its stability.