   6.2.1.45 | physiological function |
ubiquitination is the process of covalent conjugation of ubiquitin (UB) to cellular proteins mediated by E1 (UB activating enzyme)-E2 (UB conjugating enzyme)-E3 (UB ligase) enzyme cascade. Ubiquitination plays critical roles in various diseases including cancer. E1 catalyzes the formation of the thioester bond between the C-terminus of UB and the active site cysteine of E1 in presence of ATP, initiating UB transfer to E2 and subsequently to target proteins that are recruited by E3. The non-canonical ubiquitin activating enzyme UBA6 suppresses epithelial-mesenchymal transition of mammary epithelial cells. Ubiquitination pathways initiated specifically by UBA6 set a suppressive barrier against critical steps of mammary carcinogenesis such as loss of polarity, anoikis resistance and epithelial-mesenchymal transition (EMT). The Rho-GTPase CDC42 is one of the specific targets of UBA6-initiated ubiquitination and plays a key role in the function of UBA6 in controlling epithelial homeostasis, since a CDC42 inhibitor, ML141, rescues UBA6-deficient cells from the EMT phenotype. UBA6 is low or undetectable in a substantial population of invasive breast cancer tissues, suggesting the cancer-associated roles for the non-canonical E1 |
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