Belonging to the F-box family of proteins, FBXO35 (F-box only protein 35), also designated F-box and WD-40 domain-containing protein 12 (FBXW12 or FBXO12), is a 464 amino acid protein that contains one C-terminal F-box domain. 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 mechanisms, including the cell cycle, the immune response, signaling cascades and developmental processes. They function by targeting proteins, such as cyclins, cyclin-dependent kinase inhibitors, I?B-? and ???-catenin, for degradation by the proteasome after ubiquitination. Via its F-box domain, FBXO35 can directly interact with Skp1 p19 and CUL-1. FBXO35 is ubiquitously expressed at low levels in most human tissues.