E3 ubiquitin-protein ligase which promotes ubiquitination of YBX1, leading to its degradation by the proteasome (By similarity). May play a role as a scaffold protein to promote the assembly of the p53/TP53-MDM2 complex, resulting in increase of MDM2-mediated ubiquitination and degradation of p53/TP53; may function as negative regulator of p53/TP53, leading to both apoptosis and cell growth retardation (PubMed:17470788). Regulates DNA-replication and common fragile sites (CFS) stability in a ZBTB38- and MCM10-dependent manner. Controls ZBTB38 protein stability and abundance via ubiquitination and proteasomal degradation, and ZBTB38 in turn negatively regulates the expression of MCM10 which plays an important role in DNA-replication (PubMed:24726359). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts with MDM2 and YBX1 (By similarity). Interacts also with p53/TP53 and RB1. Interacts with NEK6 (By similarity). Interacts with ZBTB38 (By similarity). Colocalizes with mitotic chromosomes. Co-localizes with NEK6 in the centrosome (By similarity). Highly expressed in testis. Expressed at lower levels in brain, heart, kidney, liver, lung, skeletal muscle, spleen, thymus and tongue. Expression is reduced during terminal differentiation. Expression is induced in the G2/M phase of the cell cycle (at protein level). Contains a N-terminus DWNN domain, a zinc-finger domain and a C4C4 zinc-binding RING finger domain (By similarity). The ring finger may indeed be a U-box domain (By similarity). Phosphorylated by NEK6. Early embryonic lethality before 7.5 dpc, accompanied by accumulation of p53 and widespread apoptosis.