Novel BRCA1-PLK1-CIP2A axis orchestrates homologous recombination-mediated DNA repair to maintain chromosome integrity during oocyte meiosis.

Double-strand breaks (DSBs) are a formidable threat to genome integrity, potentially leading to cancer and various genetic diseases. The prolonged lifespan of mammalian oocytes increases their susceptibility to DNA damage over time. While somatic cells suppress DSB repair during mitosis, oocytes exhibit a remarkable capacity to repair DSBs during meiotic maturation. However, the precise mechanisms underlying DSB repair in oocytes remain poorly understood. Here, we describe the pivotal role of the BRCA1-PLK1-CIP2A axis in safeguarding genomic integrity during meiotic maturation in oocytes. We found that inhibition of homologous recombination (HR) severely impaired chromosome integrity by generating chromosome fragments during meiotic maturation. Notably, HR inhibition impaired the recruitment of CIP2A to damaged chromosomes, and the depletion of CIP2A led to chromosome fragmentation following DSB induction. Moreover, BRCA1 depletion impaired chromosomal recruitment of CIP2A, but not vice versa. Importantly, the impaired chromosomal recruitment of CIP2A could be rescued by PLK1 inhibition. Consequently, our findings not only underscore the importance of the chromosomal recruitment of CIP2A in preventing chromosome fragmentation, but also demonstrate the regulatory role of the BRCA1-PLK1-CIP2A axis in this process during oocyte meiotic maturation.