Genotoxic stress exerts biological activity by activating downstream effectors, including the p53 tumor suppressor. p53 regulates cell-cycle checkpoint and induction of apoptosis in response to DNA damage; however, molecular mechanisms responsible for committing to these distinct functions remain to be elucidated. Recent studies demonstrated that phosphorylation of p53 at Ser46 is associated with induction of p53AIP1 expression, resulting in commitment to apoptotic cell death. In this regard, the role for Ser46 kinases in p53-dependent apoptosis has been established; however, the kinases responsible for Ser46 phosphorylation have yet to be identified. Here, we demonstrate that the dual-specificity tyrosine-phosphorylation-regulated kinase 2 (DYRK2) directly phosphorylates p53 at Ser46. Upon exposure to genotoxic stress, DYRK2 translocates into the nucleus for Ser46 phosphorylation. Consistent with these results, DYRK2 induces p53AIP1 expression and apoptosis in a Ser46 phosphorylation-dependent manner. These findings indicate that DYRK2 regulates p53 to induce apoptosis in response to DNA damage.

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The tumor suppressor p53 is a transcription factor that regulates cell cycle, DNA repair, senescence, and apoptosis in response to DNA damage. Phosphorylation of p53 at Ser-46 is indispensable for the commitment to apoptotic cell death. A previous study has shown that upon exposure to genotoxic stress, DYRK2 translocates into the nucleus and phosphorylates p53 at Ser-46, thereby inducing apoptosis. However, less is known about mechanisms responsible for intracellular control of DYRK2. Here we show the functional nuclear localization signal at N-terminal domain of DYRK2. Under normal conditions, nuclear and not cytoplasmic DYRK2 is ubiquitinated by MDM2, resulting in its constitutive degradation. In the presence of proteasome inhibitors, we detected a stable complex of DYRK2 with MDM2 at the nucleus. Upon exposure to genotoxic stress, ATM phosphorylates DYRK2 at Thr-33 and Ser-369, which enables DYRK2 to escape from degradation by dissociation from MDM2 and to induce the kinase activity toward p53 at Ser-46 in the nucleus. These findings indicate that ATM controls stability and pro-apoptotic function of DYRK2 in response to DNA damage.Dual-specificity tyrosine-regulated kinases (DYRKs) 3 are a novel subfamily of protein kinases that catalyze their autophosphorylation on tyrosine residues and the phosphorylation of serine/threonine residues on exogenous substrates (1-3). DYRK2 shares a conserved kinase domain and adjacent N-terminal DH box but does not contain a C-terminal PEST (the proline-, glutamic acid-, serine-and threonine-rich) domain. DYRK2 is presumed to be involved in regulating key developmental and cellular processes such as neurogenesis, cell proliferation, cytokinesis, and cellular differentiation. Recent findings have shown that DYRK1A and DYRK2 phosphorylate NFATc, which regulates calcium signaling, to lead NFATc inactivation by its cytoplasmic sequestration (4, 5).Upon exposure to genotoxic stress, p53 is stabilized and activated by phosphorylation at Ser-15 and Ser-20 to regulate a cell cycle checkpoint and DNA repair. In case of the lesion for irreparable DNA damage, p53 induces apoptotic cell death by a mechanism in which an additional phosphorylation increases the binding affinity of p53 to promoters of pro-apoptotic genes, such as p53AIP1. In this context previous studies have established the mechanism in which p53 transactivates p53AIP1 by its additional phosphorylation at Ser-46; thereby, this phosphorylation is essential for p53-dependent apoptosis (6, 7). We recently demonstrated that DYRK2 is a novel Ser-46 kinase (8 -10). Ataxia telangiectasia mutated (ATM) was involved in DYRK2 activation and Ser-46 phosphorylation. Furthermore, DYRK2 accumulated in the nucleus after DNA damage. Significantly, DYRK2 phosphorylation of Ser-46 was associated with the induction of apoptosis. These findings provide a novel signaling mechanism in which phosphorylation of p53 at Ser-46 by DYRK2 regulates apoptotic cell death in response to DNA damage. Although certain insights are, thus, available regardin...