TRIM21 and systemic lupus erythematosus: Ro52 (also denoted TRIM21 and SSA1) is a member of the tripartite motif (TRIM) family of single-protein E3 ligases and is known to be a target for autoantibody production in systemic lupus erythematosus and Sjögren's syndrome [20], [21], [22], [23], [24], [25].