This domain, consisting of the distinct N-terminal PRY subdomain followed by the SPRY subdomain, is found at the C terminus of TRIM21, which is also known as Sjogren Syndrome Antigen A (SSA), SSA1, 52kDa Ribonucleoprotein Autoantigen (Ro52, Ro/SSA, SS-A/Ro) or RING finger protein 81 (RNF81). TRIM proteins are defined by the presence of the tripartite motif RING/B-box/coiled-coil region and also known as RBCC proteins []. As an E3 ligase, TRIM21 mediates target specificity in ubiquitination; it regulates type 1 interferon and proinflammatory cytokines via ubiquitination of interferon regulatory factors (IRFs) [, ]. It is up-regulated at the site of autoimmune inflammation, such as cutaneous lupus lesions, indicating a central role in the tissue destructive inflammatory process []. It interacts with auto-antigens in patients with Sjogren syndrome and systemic lupus erythematosus, a chronic systemic autoimmune disease characterized by the presence of autoantibodies against the protein component of the human intracellular ribonucleoprotein-RNA complexes and more specifically TRIM21, Ro60/TROVE2 and La/SSB proteins []. It binds the Fc part of IgG molecules via its PRY-SPRY domain with unexpectedly high affinity [, ].
