Fbxo30, a member of the F-box protein family, is an E3 ubiquitin ligase. F-box proteins are crucial components of Skp1-Cullin-F-box complexes, which recognize substrates for ubiquitination. Ubiquitination is a key process in protein-level regulation, especially important in processes where de novo mRNA transcription is absent, like oocyte meiosis [1].

In mouse oocytes, Fbxo30 is enriched, and its expression declines after the metaphase of the first meiosis (MI). Depletion of Fbxo30 causes chromosome compaction, chromosome segregation failure, and arrest at the MI stage, not due to over-activation of the spindle assembly checkpoint. It was found that stem-loop-binding protein (SLBP) is a substrate of Fbxo30, and SLBP overexpression from Fbxo30 depletion leads to excessive histone H3 on chromosomes, inhibiting segregation [1].

In clear cell renal cell carcinoma (ccRCC), FBXO30 has lower expression in tumor tissues. It acts as a tumor suppressor, mediating the ubiquitination and degradation of hypoxia-inducible factor-1α (HIF-1α) under normoxia. Also, hZIP1 is an upstream regulator of FBXO30, regulating its and HIF-1α's expression by recruiting Zn2+ [2].

Fbxo30-/-female mice have defective mammopoiesis. Fbxo30 interacts with the bipolar spindle kinesin EG5, targeting it for ubiquitinylation and controlling its oscillation during the cell cycle. Rescue of Eg5 activity in Fbxo30-/-mice can normalize defects in centrosome homeostasis, mitotic spindle formation, and proliferation [3].

In conclusion, Fbxo30 is essential in multiple biological processes. In oocytes, it regulates chromosome segregation during meiosis. In ccRCC, it functions as a tumor suppressor. In mammopoiesis, it plays a critical role through its interaction with Eg5. The study of Fbxo30 using gene knockout mouse models has provided insights into these biological functions and disease-related mechanisms, contributing to our understanding of oocyte development, cancer biology, and mammary gland development.