Cullin 2 is a member of the family of human Cullin genes (CUL1, 2, 3, 4a, 4b and 5) homologous to the S. cerevisiae cdc53 gene. It is a component of E3 ubiquitin ligase complexes, including the inactive transcriptional elongation complex SIII, which mediates the ubiquitination of hypoxia-inducible factor (HIF). SIII is formed by three subunits: Elongin C, Elongin B and VHL. Cullin 2 may serve as a rigid scaffold in the complex and may contribute to catalysis through positioning of the substrate and the ubiquitin-conjugating enzyme.