DDB1 and neoplasm: The mechanistic basis for the anti-tumor properties of this drug class has been tracked to their ability to bind to cereblon, which in turn is enabled to form a complex with three other proteins: CUL4 (cullin4), Roc1 (regulator of cullins 1), and DDB1 (DNA damage-binding protein 1), which collectively constitute cullin-4 RING E3 ligase (CRL4), an enzyme with E3 ubiquitin ligase activity.