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Tripartite motif containing 21
Protein TRIM21 PDB 2iwg.png
Crystallographic structure of two molecules of the C-terminal PRYSPRY domain of TRIM21 (top right and top left) complexed with homodimeric Ig gamma-1 chain C region (center). Each chain is individually rainbow colored (N-terminus = blue, C-terminus = red).[1]
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols TRIM21 ; RNF81; RO52; Ro/SSA; SSA; SSA1
External IDs OMIM109092 MGI106657 HomoloGene2365 GeneCards: TRIM21 Gene
EC number 6.3.2.-
RNA expression pattern
PBB GE TRIM21 204804 at tn.png
More reference expression data
Species Human Mouse
Entrez 6737 20821
Ensembl ENSG00000132109 ENSMUSG00000030966
UniProt P19474 Q62191
RefSeq (mRNA) NM_003141 NM_001082552
RefSeq (protein) NP_003132 NP_001076021
Location (UCSC) Chr 11:
4.38 – 4.39 Mb
Chr 7:
102.56 – 102.57 Mb
PubMed search [1] [2]

Tripartite motif-containing protein 21 also known as E3 ubiquitin-protein ligase TRIM21 is a protein that in humans is encoded by the TRIM21 gene.[2][3] 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.[4]


TRIM21 is a member of the tripartite motif (TRIM) family. The TRIM motif includes three zinc-binding domains, a RING finger domain, a B-box type 1 and a B-box type 2 zinc finger, and a coiled coil region.[3]


TRIM21 is an intracellular antibody effector in the intracellular antibody-mediated proteolysis pathway. It binds to immunoglobulin G as well as 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.[4]

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.[3]

Clinical significance[edit]

RoSSA interacts with autoantigens in patients with Sjögren's syndrome and systemic lupus erythematosus.[3]


  1. ^ PDB: 2IWG​; James LC, Keeble AH, Khan Z, Rhodes DA, Trowsdale J (April 2007). "Structural basis for PRYSPRY-mediated tripartite motif (TRIM) protein function". Proc. Natl. Acad. Sci. U.S.A. 104 (15): 6200–5. doi:10.1073/pnas.0609174104. PMC 1851072. PMID 17400754. 
  2. ^ Frank MB, Itoh K, Fujisaku A, Pontarotti P, Mattei MG, Neas BR (Mar 1993). "The mapping of the human 52-kD Ro/SSA autoantigen gene to human chromosome 11, and its polymorphisms". Am J Hum Genet 52 (1): 183–91. PMC 1682114. PMID 8094596. 
  3. ^ a b c d "Entrez Gene: TRIM21 tripartite motif-containing 21". 
  4. ^ a b Mallery DL, McEwan WA, Bidgood SR, Towers GJ, Johnson CM, James LC (2010). "Antibodies mediate intracellular immunity through tripartite motif-containing 21 (TRIM21)". Proc. Natl. Acad. Sci. U.S.A. 107 (46): 19985–19990. doi:10.1073/pnas.1014074107. PMC 2993423. PMID 21045130. 

Further reading[edit]