Fbw7 is a member of the F box protein family which are characterized by an approximately 40 amino acid motif, the F box. The F box proteins constitute one of the four subunits of ubiquitin protein ligase complex called SCFs (SKP1-cullin-F box), which function in phosphorylation-dependent ubiquitination. The F box proteins are divided into 3 classes: Fbws containing WD40 domains, Fbls containing leucine rich repeats, and Fbxs containing either different protein-protein interaction modules or no recognizable motifs. Fbw7 belongs to the Fbws class; in addition to an F box, this protein contains 7 tandem WD40 repeats. It binds directly to cyclin E and probably targets cyclin E for ubiquitin mediated degradation. Mutations of this gene are detected in ovarian and breast cancer cell lines. Alternative splicing of this gene generates 2 transcript variants diverging at the 5' termini.