Oocyte death is triggered by the stabilization of TAp63α dimers in response to cisplatin.

The TAp63α protein is highly expressed in primordial follicle oocytes, where it typically exists in an inactive dimeric form. Upon DNA damage, TAp63α undergoes hyperphosphorylation, transitioning from a dimeric to a tetrameric structure, which initiates oocyte apoptosis by upregulating pro-apoptotic gene. Our results demonstrate that cisplatin, an alkylating anti-cancer agent, predominantly produced the TAp63α dimer rather than the tetramer. We further observed that TAp63α protein accumulation occurred in primordial follicle oocytes following cisplatin treatment, and this accumulation was significantly reduced by cycloheximide, a protein synthesis inhibitor. These findings suggest that TAp63α accumulation is driven primarily by de novo protein synthesis in response to DNA damage. Notably, cycloheximide protected oocytes from cisplatin-induced apoptosis, as evidenced by reduced levels of both PUMA, a known pro-apoptotic target gene of TAp63α, and TAp63α itself. Additionally, TAp63α turnover appears to be regulated by ubiquitination and proteasome degradation, as evidenced by TAp63α accumulation without oocyte death when treated with PYR-41, a pharmacological inhibitor. However, when TAp63α was stabilized by PYR-41 and subsequently activated by cisplatin, oocyte death occurred, marked by increased γH2AX and Cleaved PARP. Moreover, the Casein kinase 1 inhibitor PF-670462 effectively blocked cisplatin-induced oocyte death, indicating that CK1-mediated phosphorylation is essential for TAp63α activation, even in the absence of tetramer formation. The ATR inhibitor BEZ235 prevented cisplatin-induced TAp63α accumulation, suggesting that TAp63α accumulation precedes its phosphorylation-driven activation. Collectively, our study reveals a novel mechanism of cisplatin-induced apoptosis in primordial follicle oocyte through TAp63α stabilization and accumulation, independent of tetramerization.