FBXO42 (F-box protein 42) functions as a substrate-recognition component of SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complexes, directing multiple protein targets for ubiquitination and degradation 1. FBXO42 recognizes diverse substrates including ACAA2 in hepatic lipid metabolism 1, SUMO1 in cancer cells 2, mutant p53 variants 3, Ataxin-2 during endoplasmic reticulum stress 4, p57Kip2 in hepatocellular carcinoma 5, and RBPJ in Notch signaling 6. The protein also regulates chr1-microtubule dynamics critical for mitotic checkpoint control in cancer cells 7. Mechanistically, FBXO42-mediated ubiquitination can proceed via lysine-63 linkage for non-degradative signaling functions or proteasomal degradation pathways 6. Disease relevance spans hepatocellular carcinoma, where FBXO42 overexpression drives progression through p57Kip2 degradation 5, glioblastoma stemness 7, Notch-driven leukemia 6, and potentially Parkinson's disease susceptibility 8. FBXO42 represents a therapeutic target, with small-molecule degraders activating FBXO42 showing anticancer efficacy against multiple tumor types 2, while FBXO42 inhibition may benefit NAFLD and certain leukemias 16.