Skp2 is an F box protein within the SCF (Skp, Cullin, F-box containing) ubiquitin ligase complex that targets various tumor suppressors (including p21) for degradation while conversely promoting the activity of oncoproteins (such as c-Myc), consistent with its overexpression in various human cancers [210]. The gene discussed is CDKN1A; the disease is cancer.