Ube2S (E2-24K, E2-EPF) shares 38% identity with S.cerevisiae UBC4 with a conserved UBC domain that is characteristic of ubiquitin E2 conjugating enzymes. This E2 enzyme is over-expressed in common human cancers and targets von Hippel-Lindau (VHL) for proteosomal degradation, thereby stabilizing HIF-1α for Ub-mediated destruction. Overexpression of Ube2S in vitro and in vivo boosts tumor-cell proliferation, invasion and metastasis through effects on the pVHL-HIF pathway, and may thus be a novel molecular target for therapeutic intervention. Ube2S has also been identified as a K11-specific E2 for the anaphase-promoting complex (APC/C), and the E2 depends on the cell cycle-dependent association with the APC/C activators Cdc20 and Cdh1 for its activity. In vitro, UBE2S elongates ubiquitin chains initiated by the E2 enzymes UbcH10 and UbcH5, enhancing the degradation of APC/C substrates by the proteasome. This protein has an N-terminal His₆-tag. Accession # NP_055316.2.