Ubiquitin-conjugating Enzyme E2L 3 (UBE2L3),also known as Ubiquitin-conjugating Enzyme H7 (UbcH7), is a member of the Ubiquitin-conjugating (E2) enzyme family (1). The human UbcH7 protein shares 100% amino acid (aa) sequence identity with the mouse and rat orthologs. UBE2L3 is catalytically active with HECT and RBR domain-containing families of Ubiquitin ligases (E3s). UBE2L3 localizes to both the nucleus and cytoplasm in human cells. UBE2L3 depletion results in an extended S phase and a reduced rate of proliferation, suggesting that it may play a role in the cell cycle. In humans, single nucleotide polymorphisms in UBE2L3 are associated with systemic lupus erythematosus and Crohn's disease, suggesting that UbcH7 is important for proper immune system function.