FBXO42 (F-box only protein 42) is a 717 amino acid protein that contains four Kelch repeats and one N-terminal F-box domain, and belongs to the F-box family of proteins. F-box proteins are critical components of the SCF (Skp1-CUL-1-F-box protein) type E3 ubiquitin ligase complex and are involved in substrate recognition and recruitment for ubiquitination. They are members of a larger family of proteins that are involved in the regulation of a wide variety of cellular processes (including the cell cycle, immune response, signaling cascades and developmental processes) through the targeting of proteins, such as cyclins, cyclin-dependent kinase inhibitors, IkB-a and b-catenin, for degradation by the proteasome after ubiquitination.