Tripartite motif-containing protein 21, also known as E3 ubiquitin-protein ligase TRIM21, is a protein that in humans is encoded by the TRIM21gene.[5][6] Alternatively spliced transcript variants for this gene have been described but the full-length nature of only one has been determined. It is expressed in most human tissues.[7]
TRIM21 is part of the RoSSA ribonucleoprotein, which includes a single polypeptide and one of four small RNA molecules. The RoSSA particle localizes to both the cytoplasm and the nucleus.[6]
Clinical significance
RoSSA interacts with autoantigens in patients with Sjögren's syndrome and systemic lupus erythematosus.[6] In addition, the inability for lupus-prone macrophages to degrade immune complexes in the lysosome results in the leakage of autoantibodies into the cytosol that can bind to TRIM21 and enhance NF-κB signaling.[10]
TRIM21 can be used to knockout specific proteins with their corresponding antibodies, a method known as Trim-Away. In this assay, TRIM21 and antibodies are delivered into cells through electroporation, and the targeted protein is degraded within a few minutes.[11]
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