Substrate-recognition component of some SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex. Specifically recognizes p53/TP53, promoting its ubiquitination and degradation. Component of some SCF complex, composed of CUL1, SKP1, RBX1 and FBXO42. Interacts (via the kelch domain) with p53/TP53; interaction is direct.