SSA1 is an alias for the gene, Tripartite motif containing 21, in humans. Other names include: E3 ubiquitin-protein ligase TRIM21; 52 kDa ribonucleoprotein autoantigen Ro/SS-A; RING finger protein 81; Ro(SS-A); Tripartite motif-containing protein 21; 52 kDa Ro protein; E3 ubiquitin-protein ligase TRIM21 ; RNF81; RO52; Ro/SSA. The encoded protein is an enzyme with an amino acid length of 475 and a mass of 54.2 kDa. Other isoforms may exist. SSA1 is a member of the TRIM/RBCC family. This gene shares homology with other species, including: Yeast.