InterPro domain: IPR033044

Cullins are a family of hydrophobic proteins that act as scaffolds for ubiquitin ligases (E3). Cullins are found throughout eukaryotes. Humans express seven cullins (Cul1, 2, 3, 4A, 4B, 5 and 7), each forming part of a multi-subunit ubiquitin complex.

Cullin-4B (CUL4B) is a core component of multiple cullin-RING-based E3 ubiquitin-protein ligase complexes which mediate the ubiquitination and subsequent proteasomal degradation of target proteins. CUL4B may act within the complex as a scaffold protein, contributing to catalysis through positioning of the substrate and the ubiquitin-conjugating enzyme [ 1 , 2 ]. Mutations in the CUL4B gene cause X-linked mental retardation [ 3 ].

1. The molecular basis of CRL4DDB2/CSA ubiquitin ligase architecture, targeting, and activation. Cell 147, 1024-39
2. CRL4B interacts with and coordinates the SIN3A-HDAC complex to repress CDKN1A and drive cell cycle progression. J. Cell. Sci. 127, 4679-91
3. Mutation in CUL4B, which encodes a member of cullin-RING ubiquitin ligase complex, causes X-linked mental retardation. Am. J. Hum. Genet. 80, 561-6