Glycogen synthase kinase 3 β activity is required for hBora/Aurora A-mediated mitotic entry

The synthesis and degradation of hBora is important for the regulation of mitotic entry and exist. In G 2 phase, hBora can complex with Aurora A to activate Plk1 and control mitotic entry. However, whether the post-translational modification of hBora is relevant to the mitotic entry still unclear. Here, we used the LC-MS/MS phosphopeptide mapping assay to identify 13 in vivo hBora phosphorylation sites and characterized that GSK3 beta can interact with hBora and phosphorylate hBora at Ser274 and Ser278. Pharmacological inhibitors of GSK3 beta reduced the retarded migrating band of hBora in cells and diminished the phosphorylation of hBora by in vitro kinase assay. Moreover, as well as in GSK3 beta activity-inhibited cells, specific knockdown of GSK3 beta by shRNA and S274A/S278 hBora mutant-expressing cells also exhibited the reduced Plk1 activation and a delay in mitotic entry. It suggests that GSK3 beta activity is required for hBora-mediated mitotic entry through Ser274 and Ser278 phosphorylation.