Has E3 ubiquitin ligase activity, promoting ubiquitination and degradation of target proteins. Involved in activation of the JAK/STAT pathway. Catalyzes ubiquitination of methylated RBM15. Plays a role in quality control of translation of mitochondrial outer membrane-localized mRNA. As part of the PINK1-regulated signaling, upon mitochondria damage, ubiquitinates ABCE1 and thereby recruits autophagy receptors to the mitochondrial outer membrane to initiate mitophagy. 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 CNOT1 via its C-terminus but does not stably associate with the CCR4-NOT complex. Interacts (via RING domain) with UBE2D2. Interacts with ABCE1, PINK1 and PELO. Autoubiquitinated.