Regulated degradation of misfolded, damaged or short-lived proteins in eukaryotes occurs via the ubiquitin (Ub)-proteasome system (UPS). An integral part of the UPS system is the ubiquitination of target proteins and covalent linkage of Ub-containing proteins to form polymeric chains, marking them as targets for 26S proteasome-mediated degradation. Ubiquitination of proteins is mediated by a cascade of enzymes which includes E1 (ubiquitin activating), E2 (ubiquitin conjugating), and E3 (ubiquitin ligases) enzymes. This gene encodes a member of the E2 enzyme family. Substrates of this enzyme include the tumor suppressor protein p53 and peroxisomal biogenesis factor 5 (PEX5). Alternative splicing results in multiple transcript variants of this gene. [provided by RefSeq, May 2013],catalytic activity:ATP + ubiquitin + protein lysine = AMP + diphosphate + protein N-ubiquityllysine.,function:Catalyzes the covalent attachment of ubiquitin to other proteins. Mediates the selective degradation of short-lived and abnormal proteins. Functions in the E6/E6-AP-induced ubiquitination of p53/TP53.,pathway:Protein modification; protein ubiquitination.,similarity:Belongs to the ubiquitin-conjugating enzyme family.,subunit:Interacts with SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase complex and with E3 ubiquitin-protein ligase PJA2.,