Has a ubiquitin-protein ligase activity acting as an E3 ubiquitin protein ligase or as an ubiquitin-ubiquitin ligase promoting elongation of ubiquitin chains on substrates. By mediating 'Lys-48'-linked polyubiquitination of proteins could target them for proteasomal degradation . May also function as a chaperone, playing a role in transport to the cell membrane of BSG/Basigin for instance . Probable inactive PPIase with no peptidyl-prolyl cis-trans isomerase activity .
Nucleus . May also localize to the cytoplasm and the cell membrane. .
Highest expression in thymus, pancreas and testis. Also detected in heart, placenta, lung, liver, skeletal muscle, kidney, spleen, prostate, ovary, small intestine and colon. Poorly detected in brain and leukocytes. Strong protein expression in lymph node (cortical, paracortical and medullar regions), thyroid (follicular epithelial cells), testis (developing spermatozoa), stomach (cells lining the gastric pit), pancreas, kidney (proximal and distal-tubule cells and collecting duct cells but not in glomeruli), endometrium and colon (goblet cells). Moderate protein expression in spleen, prostate (epithelium and squamous cell carcinomas), placenta and adrenal gland. Weak protein expression in liver, heart, breast, ovary, and lung. No protein expression in brain and bladder. High protein expression in most lymphomas and melanomas.
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