Catalyzes the covalent attachment of ubiquitin to other proteins. Functions in the selective degradation of misfolded membrane proteins from the endoplasmic reticulum (ERAD) and is essential for cells to recover from ER stress (PubMed:28321712). Plays a role in MAPKAPK2-dependent translational control of TNF-alpha synthesis (PubMed:24020373). Acts also as a platform for perinuclear positioning of the endosomal system by mediating ubiquitination of SQSTM1 through interaction with the E3 ubiquitin-protein ligase RNF26 (PubMed:33472082). (Microbial infection) Promotes Dengue virus RNA replication by negatively regulating IFN-beta signaling and mediating 'Lys-48'-linked ubiquitination on IRF3 (PubMed:30157886). S-ubiquitinyl-[E1 ubiquitin-activating enzyme]-L-cysteine + [E2 ubiquitin-conjugating enzyme]-L-cysteine = [E1 ubiquitin-activating enzyme]-L-cysteine + S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine. Protein modification; protein ubiquitination. Component of the HRD1 complex, which comprises at least SYNV1/HRD1, DERL1/2, FAM8A1, HERPUD1/HERP, OS9, SEL1L and UBE2J1 (PubMed:28827405). Interacts with E3 ligase RNF26 (PubMed:33472082). By Dengue virus infection. Phosphorylated at Ser-184 in a cytosolic stress-dependent manner by MAP kinase p38 MAPKAPK2. Phosphorylated UBE2J1 is rapidly ubiquitinated and subsequently degraded by the proteasome. Belongs to the ubiquitin-conjugating enzyme family.