Ectopic expression of FBXO31 promotes growth arrest, induces senescence, and reduces the half-life of MDM2. (A) Cell proliferation assay in MCF7 cells expressing vector, FBXO31, or FBXO31∆F. (B) DNA replication assay, monitored by BrdU incorporation, in MCF7 cells expressing empty vector, FBXO31, or FBXO31∆F. (C) Senescence-associated β-gal activity assay in MCF7 cells expressing empty vector or FBXO31. (Left) Representative images. (Right) Quantification of the percentage of β-gal+ cells.