Trim21

TRIM21 is a human gene encoding tripartite motif-containing protein 21, which also known as E3 ubiquitin-protein ligase TRIM21. its activity is dependent on E2 enzymes, UBE2D1, UBE2D2, UBE2E1 and UBE2E2. This protein Forms a ubiquitin ligase complex in cooperation with the E2 UBE2D2 that is used not only for the ubiquitination of USP4 and IKBKB but also for its self-ubiquitination. TRIM21 is an intracellular antibody effector in the intracellular antibody-mediated proteolysis pathway. It recognizes Fc domain and binds to immunoglobulin G, immunoglobuin A and immunoglobulin M on antibody marked non-enveloped virions which have infected the cell. Either by autoubiquitination or by ubiquitination of a cofactor, it is then responsible for directing the virions to the proteasome. TRIM21 itself is not degraded in the proteasome unlike both the viral capsid and the bound antibody. Moreover, 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.