[Isoform 1]: Regulatory component of cullin-RING-based SCF (SKP1-Cullin-F-box protein) E3 ubiquitin-protein ligase complexes (PubMed:22405651, PubMed:22748924). Inhibits E3 ubiquitin ligase activity by binding to RBX1 (via RING domain) and inhibiting its interaction with the E2 ubiquitin-conjugating enzyme CDC34 (PubMed:22405651, PubMed:22748924). Inhibits RBX1-mediated neddylation of CUL1 (PubMed:22405651). Required for normal stability and normal cellular levels of key components of SCF ubiquitin ligase complexes, including FBXW7, RBX1, CUL1, CUL2, CUL3, CUL4A, and thereby contributes to the regulation of CCNE1 and MYC levels (By similarity). Essential for normal development of the vasculature (PubMed:11845407). Contributes to the regulation of RPS6KB1 phosphorylation (PubMed:11571281).
