The function of ENSG00000168894 (RNF181, ring finger protein 181) is as follows. E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates (PubMed:18331836). Catalyzes monoubiquitination of 26S proteasome subunit PSMC2/RPT1 (PubMed:24811749). {ECO:0000269|PubMed:18331836, ECO:0000269|PubMed:24811749}.