HIPK2-and IKKβ-dependent phosphorylation stabilizes TAp63α during the oocyte DNA damage response

Abstract TAp63α, a member of the p53 family, serves as a central quality control factor in oocytes, safeguarding genomic integrity during the prolonged dictyate arrest of meiosis. In healthy oocytes, TAp63α is maintained in an inactive dimeric state; upon DNA damage, it undergoes phosphorylation-dependent tetramerization, enabling transcriptional activation of pathways that determine oocyte fate. While the upstream activation cascade of TAp63α has been well characterized, the mechanisms that regulate its stability during the DNA damage response remain incompletely understood. Here, we identify the kinases HIPK2 and IKKβ as key regulators of TAp63α stability. We show that TAp63α interacts with both kinases and is phosphorylated at distinct residues, T452 by HIPK2 and S4/S12 by IKKβ in vitro and in vivo, in addition to previously described CHK2 and CK1-mediated phosphorylation. Functionally, these phosphorylation events do not primarily contribute to activation, but instead stabilize TAp63α by limiting MDM4-dependent ubiquitination and subsequent proteasomal degradation. Mechanistically, our data support a model in which CHK2 and CK1 initiate TAp63α phosphorylation, while HIPK2 and IKKβ act in a complementary manner to maintain protein stability during genotoxic stress. Disruption of HIPK2 or IKKβ activity reduces TAp63α stability, whereas their inhibition in vivo attenuates oocyte loss following DNA damage, resulting in increased preservation of the follicle pool. Importantly, these effects are observed across multiple systems, including mouse models and ex vivo goat ovary cultures, supporting an evolutionarily conserved role for this regulatory axis. Together, our findings uncover a previously unidentified layer of TAp63α regulation, in which phosphorylation not only contributes to its activation but also enhances protein stability, thereby fine-tuning oocyte responses to DNA damage. Our results further indicate that HIPK2 and IKKβ-mediated phosphorylation modulates oocyte survival under genotoxic stress, highlighting this pathway as a potential target for strategies aimed at limiting oocyte loss. Competing Interest Statement The authors have declared no competing interest.