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Protein TRIM21 PDB 2iwg.png
Available structures
PDBOrtholog search: PDBe RCSB
AliasesTRIM21, RNF81, RO52, Ro/SSA, SSA, SSA1, tripartite motif containing 21, Tripartite motif-containing protein 21
External IDsMGI: 106657 HomoloGene: 2365 GeneCards: TRIM21
Gene location (Human)
Chromosome 11 (human)
Chr.Chromosome 11 (human)[1]
Chromosome 11 (human)
Genomic location for TRIM21
Genomic location for TRIM21
Band11p15.4Start4,384,897 bp[1]
End4,393,696 bp[1]
RNA expression pattern
PBB GE TRIM21 204804 at fs.png
More reference expression data
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 11: 4.38 – 4.39 MbChr 7: 102.56 – 102.57 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

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.[5][6] 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.[7]


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.[6]


TRIM21 is an intracellular antibody effector in the intracellular antibody-mediated proteolysis pathway. It recognizes Fc domain[8] and 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.[7]

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.[6]

Clinical significance[edit]

RoSSA interacts with autoantigens in patients with Sjögren's syndrome and systemic lupus erythematosus.[6]

TRIM21 can be used to knockout specific proteins with their corresponding antibodies, a method known as Trim-Away. In this assay, TRIM21 and antibodies are delivered into cells through electroporation, and the targeted protein is degraded within a few minutes.[9]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000132109 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000030966 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ 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.
  6. ^ a b c d "Entrez Gene: TRIM21 tripartite motif-containing 21".
  7. ^ 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)". Proceedings of the National Academy of Sciences of the United States of America. 107 (46): 19985–90. doi:10.1073/pnas.1014074107. PMC 2993423. PMID 21045130.
  8. ^ James LC, Keeble AH, Khan Z, Rhodes DA, Trowsdale J (2007). "Structural basis for PRYSPRY-mediated tripartite motif (TRIM) protein function". Proceedings of the National Academy of Sciences of the United States of America. 104 (15): 6200–5. doi:10.1073/pnas.0609174104. PMC 1851072. PMID 17400754.
  9. ^ Clift D, McEwan WA, Labzin LI, Konieczny V, Mogessie B, James LC, Schuh M. "A Method for the Acute and Rapid Degradation of Endogenous Proteins". Cell. doi:10.1016/j.cell.2017.10.033.

Further reading[edit]