E3 ubiquitin-protein ligase. Component of the ribosome quality control complex (RQC), a ribosome-associated complex that mediates ubiquitination and extraction of incompletely synthesized nascent chains for proteasomal degradation. Ubiquitination leads to VCP/p97 recruitment for extraction and degradation of the incomplete translation product. 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. Component of the ribosome quality control complex (RQC), composed of at least the E3 ubiquitin ligase LTN1 and NEMF associated with the 60S ribosomal subunit. The complex probably also contains TCF25 as well as VCP/p97 and its ubiquitin-binding cofactors. Belongs to the LTN1 family.