Has E3 ubiquitin ligase activity towards IGBP1, promoting its monoubiquitination, which results in deprotection of the catalytic subunit of protein phosphatase PP2A, and its subsequent degradation by polyubiquitination. 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. Homodimer or heterodimer with MID2. Interacts with IGBP1. Microtubule-associated. Ubiquitously expressed in fetus and adult. At 9 dpc-10.5 dpc, highest expression found in frontonasal processes, branchial arches and CNS. From 12.5 dpc to 16.5 dpc, high levels found in rostral part of CNS. At 14.5 dpc, begins to be highly expressed in kidney and lung. At 16.5 dpc, highly expressed in the mucosa of the hindgut and cutaneous region of the stomach. Expressed throughout embryonic development with highest levels from 7-11 dpc. Also expressed in the adult. Phosphorylated. Belongs to the TRIM/RBCC family. Truncated C-terminus.