CCNB1IP1 is an E3 ubiquitin ligase with dual roles in meiosis and cell cycle regulation. During meiosis, CCNB1IP1 functions as a limiting factor for crossover formation by restricting RNF212 colocalization with recombination sites during zygonema, then accumulates at designated crossover sites to promote recombination progression 1. In somatic cells, CCNB1IP1 regulates cyclin B1 stability and G2/M phase progression; its overexpression delays mitotic entry 23. CCNB1IP1 interacts with cyclin B1 through an E3 ubiquitin ligase mechanism to modulate cell cycle checkpoint control 3. In cancer contexts, CCNB1IP1 demonstrates oncogenic potential. In MYCN-amplified neuroblastoma, CCNB1IP1 is transcriptionally activated by MYCN and reciprocally stabilizes MYCN protein by competing with FBXW7 for binding, preventing ubiquitination-mediated degradation and enhancing tumorigenesis 4. In hepatocellular carcinoma, the AdipoR1/ESR1/CCNB1IP1/cyclin B1 axis regulates radiation resistance through cell cycle arrest modulation 2. Notably, CCNB1IP1 also mediates autophagic degradation of NIT2 upon 5-FU stimulation in gastric cancer, affecting chemotherapy response 5. Common genetic variants in CCNB1IP1 are associated with altered crossover recombination and maternal meiotic aneuploidy risk 1, highlighting its importance for reproductive fidelity.