Assembly factor of SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase complexes that promotes the exchange of the substrate-recognition F-box subunit in SCF complexes, thereby playing a key role in the cellular repertoire of SCF complexes. Acts as a F-box protein exchange factor (By similarity). Involved in the aging process. Longevity-assurance protein. Interacts with unneddylated cullin CDC53. Preferentially expressed in young cells. Neddylated at Lys-16. Present with 195 molecules/cell in log phase SD medium. Acts as an inhibitor of cullin neddylation and SCF complex assembly in vitro (PubMed:19942853). However in vivo experiments in other organisms strongly suggest that it acts as an essential regulator of SCF complex assembly.