Essential component of a SCF-type E3 ligase complex, SCF(NIPA), a complex that controls mitotic entry by mediating ubiquitination and subsequent degradation of cyclin B1 (CCNB1). Its cell-cycle-dependent phosphorylation regulates the assembly of the SCF(NIPA) complex, restricting CCNB1 ubiquitination activity to interphase. Its inactivation results in nuclear accumulation of CCNB1 in interphase and premature mitotic entry (By similarity). Overexpression may be able to protect from apoptosis induced by IL-3 withdrawal. Protein modification; protein ubiquitination. Interacts with SKP1. Component of a SCF(NIPA) E3 complex with SKP1, RBX1 and CUL1 when not phosphorylated on Ser-353. Interacts with CCNB1 (By similarity). The F-box-like region is required for the interaction with SKP1. Phosphorylated. Phosphorylated on Ser residues at G2/M phase, but not during S and G0 phases. May also be weakly phosphorylated on Tyr residues. Ser-353 phosphorylation, a major site during the course of cell-cycle-dependent phosphorylation, results in its dissociation from the SCF(NIPA) complex, thereby preventing CCNB1 degradation leading to mitotic entry (By similarity).