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. Plays a role in MAPKAPK2-dependent translational control of TNF-alpha synthesis. 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. 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. Interacts with E3 ligase RNF26. 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. Deletion mice have reduced viability and fail to thrive early after birth. Specific components of the ER dislocation machinery are up-regulated. In addition, males are sterile due to a defect in late spermatogenesis. Belongs to the ubiquitin-conjugating enzyme family.