FBXO21 (F-Box Protein 21): FBXO21 is a gene that encodes a protein belonging to the F-box family, which plays a key role in the ubiquitin-proteasome system responsible for protein degradation. It is involved in regulating important cellular processes like the cell cycle and signal transduction. Dysregulation of FBXO21 can affect protein homeostasis and is relevant in diseases characterized by disrupted protein turnover, including neurodegenerative disorders and cancers.