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Interferon-stimulated gene 20 kDa protein

Known also as: Estrogen-regulated transcript 45 protein, Promyelocytic leukemia nuclear body-associated protein ISG20

Known abbreviations: ISG20, HEM45


Exonuclease with specificity for single-stranded RNA and, to a lesser extent for DNA. Degrades RNA at a rate that is approximately 35-fold higher than its rate for single-stranded DNA. Involved in the antiviral function of IFN against RNA viruses.
Besides its function in antiviral defense, ISG20 may play additional roles in the maturation of snRNAs and rRNAs, and in ribosome biogenesis.


Exonucleolytic cleavage in the 3'- to 5'-direction to yield nucleoside 5'-phosphates.


Binds 2 manganese ions per subunit.


Associates with PML and SP100 in the PML NB complex.




Highly expressed in peripheral blood leukocytes, spleen, thymus, colon and lung.


Induced by interferons alpha and beta. Weaker induction was seen with interferon gamma. Increased expression was seen at the transcriptional level. Ref.1 Ref.6

NCBI GI number(s): 6857800
Species: Homo sapiens

Links to other databases:

Database ID Link
Uniprot Q96AZ6 Q96AZ6
KEGG hsa:3669 hsa:3669
PFAM: - Q96AZ6 (Link - using uniprot id)
InterPro: - Q96AZ6 (Link - using uniprot id)
CATH: - -
SCOP: - -
Solved crystal structures: 1WLJ
[PDB] [details]

Protein sequence:

Interferon-stimulated gene 20 kDa protein (Homo sapiens) is product of expression of ISG20 interferon stimulated exonuclease gene 20kDa gene.

Interferon-stimulated gene 20 kDa protein (Homo sapiens) belongs to following protein families:

Title Authors Journal Publication date (Issue) PubMed ID
ISG20, a new interferon-induced RNase specific for single-stranded RNA, defines an alternative antiviral pathway against RNA genomic viruses. Espert L, Degols G, Gongora C, Blondel D, Williams BR, Silverman RH, Mechti N J Biol Chem 2003-05-02 (278) 12594219
Interferon-induced exonuclease ISG20 exhibits an antiviral activity against human immunodeficiency virus type 1. Espert L, Degols G, Lin YL, Vincent T, Benkirane M, Mechti N J Gen Virol 2005-08-01 (86) 16033969
The exonuclease ISG20 mainly localizes in the nucleolus and the Cajal (Coiled) bodies and is associated with nuclear SMN protein-containing complexes. Espert L, Eldin P, Gongora C, Bayard B, Harper F, Chelbi-Alix MK, Bertrand E, Degols G, Mechti N J Cell Biochem 2006-08-01 (98) 16514659
The human interferon- and estrogen-regulated ISG20/HEM45 gene product degrades single-stranded RNA and DNA in vitro. Nguyen LH, Espert L, Mechti N, Wilson DM 3rd Biochemistry 2001-06-19 (40) 11401564
ISG20, an actor of the innate immune response. Degols G, Eldin P, Mechti N. Biochemie 2007-06-30 (None) 17445960
The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Gerhard DS, Wagner L, Feingold EA, Shenmen CM, Grouse LH, Schuler G, Klein SL, Old S, Rasooly R, Good P, Guyer M, Peck AM, Derge JG, Lipman D, Collins FS, Jang W, Sherry S, Feolo M, Misquitta L, Lee E, Rotmistrovsky K, Greenhut SF, Schaefer CF, Buetow K, Bonner TI, Haussler D, Kent J, Kiekhaus M, Furey T, Brent M, Prange C, Schreiber K, Shapiro N, Bhat NK, Hopkins RF, Hsie F, Driscoll T, Soares MB, Casavant TL, Scheetz TE, Brown-stein MJ, Usdin TB, Toshiyuki S, Carninci P, Piao Y, Dudekula DB, K Genome Res 2004-10-01 (14) 15489334
Expression and estrogen regulation of the HEM45 MRNA in human tumor lines and in the rat uterus. Pentecost BT J Steroid Biochem Mol Biol 1998-02-01 (64) 9569007
Initial characterization of the human central proteome. Burkard TR, Planyavsky M, Kaupe I, Breitwieser FP, Burckstummer T, Bennett KL, Superti-Furga G, Colinge J BMC Syst Biol 2011-01-01 (5) 21269460
Molecular cloning of a new interferon-induced PML nuclear body-associated protein. Gongora C, David G, Pintard L, Tissot C, Hua TD, Dejean A, Mechti N J Biol Chem 1997-08-01 (272) 9235947
Crystal structure of human ISG20, an interferon-induced antiviral ribonuclease. Horio T, Murai M, Inoue T, Hamasaki T, Tanaka T, Ohgi T FEBS Lett 2004-11-05 (577) 15527770

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Last modification of this entry: Sept. 25, 2012.

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