CUL1 / RBX1, Neddylated

Background: Cullin-1 (CUL1) is a central scaffold protein in SCF (SKP1–CUL1–F-box) E3 ubiquitin ligase complexes that control the ubiquitylation and turnover of proteins governing cell-cycle progression, signal transduction, and transcription. Within the SCF complex, CUL1 structurally bridges SKP1–F-box substrate-recognition modules with the RBX1 RING subunit, thereby positioning both the bound substrate and an E2 ubiquitin-conjugating enzyme to promote efficient ubiquitin transfer. Biologically, CUL1 is essential for orderly cell-cycle transitions, maintenance of genomic stability, and proper responses to mitogenic and stress signals, and its dysregulation has been linked to tumorigenesis. In vivo, SCF E3 ligase activity depends on covalent attachment of NEDD8 (neddylation) to the CUL1 subunit, which activates the complex and modulates its interactions.