FBOX21 (F-Box Protein 21): FBOX21 is a member of the F-box protein family, which plays a crucial role in the ubiquitin-proteasome system responsible for protein degradation. This system is vital for regulating protein levels within cells, affecting processes such as cell cycle progression, signal transduction, and apoptosis. FBOX21 specifically facilitates the targeting of proteins for degradation, thereby maintaining cellular homeostasis. Dysregulation of FBOX21 can lead to diseases, including cancers, where abnormal protein accumulation or degradation drives the progression of the disease.