May play a role in microtubule stabilization. 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. Homodimer or heterodimer with MID1. Interacts with IGBP1. Microtubule-associated. Low abundance in brain and lung, with even lower levels in heart, liver, and kidney. At 10.5 dpc, a very low level is mostly confined to the central nervous system and the developing heart and kidney, while at later stages it is present in other organ systems. The tripartite motif (RBCC; RING- and B box-type zinc fingers and coiled coil domains) mediates dimerization. Associates with microtubules in a manner that is dependent on the C-terminal B30.2 domain. Phosphorylated on serine and threonine residues. Belongs to the TRIM/RBCC family. It is uncertain whether Met-1 or Met-21 is the initiator. Truncated N-terminus. Truncated N-terminus.