Alternative titles; symbols
HGNC Approved Gene Symbol: ISG20
Cytogenetic location: 15q26.1 Genomic coordinates (GRCh38) : 15:88,635,632-88,656,483 (from NCBI)
Binding of interferons (see IFNA, 147660, and IFNB, 147570) to their cell surface receptors triggers rapid nuclear translocation of complexes formed by various phosphorylated STAT proteins (see 600555). These complexes induce genes that mediate the biologic functions of IFNs and may be localized in the cytoplasm, nucleus, or cell surface. The nuclear proteins may localize within the nucleolus or within the nuclear matrix, specifically to nuclear bodies (NBs) or PML (promyelocytic leukemia; 102578) NBs. Proteins of various oncogenic viruses have been found to associate with and disrupt PML NBs, several PML NB-localized proteins, including PML, SP100 (604585), and NDP52 (604587), are inducible by IFN. ISG20 is closely associated with PML and SP100 in PML NBs and is inducible by both type I and type II IFN (Gongora et al., 1997).
By screening an IFN-treated Daudi cell cDNA library, Gongora et al. (1997) obtained a cDNA encoding a deduced 179-amino acid, 20-kD, basic (pI 9.2) interferon-induced protein, termed ISG20, containing 7 lysine and 19 arginine residues. Sequence analysis of ISG20 also predicted a coiled-coil structure in the region of amino acids 78 to 107, suggesting that the protein may be a component of a multiprotein complex. The coiled-coil domain is bordered on both sides by potential phosphorylation sites. ISG20 shares amino acid cluster homologies with XPMC2H (602930), suggesting an antigrowth function, which is also a property of IFNs. On the basis of the lysine- and arginine-rich domains of ISG20, Gongora et al. (1997) suspected nuclear targeting. Using laser confocal immunofluorescence, they found speckled nuclear staining with colocalization of ISG20, PML, and SP100. Northern blot analysis of IFN-treated Daudi cells showed that expression increased in response to stimulus and occurred at the transcriptional level. In the absence of IFN treatment, Northern blot analysis detected ISG20 expression in peripheral blood leukocytes, thymus, spleen, colon, and lung.
By use of differential display-PCR and mRNA from a human cervical cell line, Pentecost (1998) identified a cDNA encoding a 181-amino acid protein that they termed HEM45. HEM45 aligns with the C-terminal half of XPMC2H. The authors found that HEM45 mRNA expression increased in response to estrogen in estrogen receptor (ESR1; 133430)-expressing cells in the presence of cycloheximide.
By radiolabeled probe in situ hybridization, Mattei et al. (1997) mapped the ISG20 gene to chromosome 15q26.
Gongora, C., David, G., Pintard, L., Tissot, C., Hua, T. D., Dejean, A., Mechti, N. Molecular cloning of a new interferon-induced PML nuclear body-associated protein. J. Biol. Chem. 272: 19457-19463, 1997. [PubMed: 9235947] [Full Text: https://doi.org/10.1074/jbc.272.31.19457]
Mattei, M. G., Tissot, C., Gongora, C., Mechti, N. Assignment of ISG20 encoding a new interferon-induced PML nuclear body-associated protein, to chromosome 15q26 by in situ hybridization. Cytogenet. Cell Genet. 79: 286-287, 1997. [PubMed: 9605874] [Full Text: https://doi.org/10.1159/000134745]
Pentecost, B. T. Expression and estrogen regulation of the HEM45 mRNA in human tumor lines and in the rat uterus. J. Steroid Biochem. Molec. Biol. 64: 25-33, 1998. [PubMed: 9569007] [Full Text: https://doi.org/10.1016/s0960-0760(97)00140-4]