Crystal structure of human ISG20, an interferon‐induced antiviral ribonuclease

Horio, Takekazu; Murai, Masatoshi; Inoue, Toshihiko; Hamasaki, Toshikazu; Takano, Teruo; Ohgi, Tadaaki

doi:10.1016/j.febslet.2004.09.074

Cited by 51 publications

(65 citation statements)

References 28 publications

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“…ISG20 is a 3Ј-to-5Ј exonuclease with a strong preference for single-stranded RNA and minor activity toward single-stranded DNA (51). According to the bioinformatic analysis and recently published crystal structural data, ISG20 belongs to the DEDD superfamily of 3Ј-to-5Ј exonucleases that is defined by four conserved acidic residues, three aspartates (D) and one glutamate (E), distributed among three separate sequence motifs (Exo I to III) (19,21,34,74). Previous studies demonstrated that replacement of Asp96 in Exo II with a glycine inactivates the enzymatic activity of ISG20 (19).…”

Section: Pkrmentioning

confidence: 99%

Identification of Three Interferon-Inducible Cellular Enzymes That Inhibit the Replication of Hepatitis C Virus

Jiang

Guo

et al. 2008

J Virol

257

299

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Hepatitis C virus (HCV) infection is a common cause of chronic hepatitis and is currently treated with alpha interferon (IFN-␣)-based therapies.However, the underlying mechanism of IFN-␣ therapy remains to be elucidated. To identify the cellular proteins that mediate the antiviral effects of IFN-␣, we created a HEK293-based cell culture system to inducibly express individual interferon-stimulated genes (ISGs) and determined their antiviral effects against HCV. By screening 29 ISGs that are induced in Huh7 cells by IFN-␣ and/or up-regulated in HCV-infected livers, we discovered that viperin, ISG20, and double-stranded RNA-dependent protein kinase (PKR) noncytolytically inhibited the replication of HCV replicons. Mechanistically, inhibition of HCV replication by ISG20 and PKR depends on their 3-5 exonuclease and protein kinase activities, respectively. Moreover, our work, for the first time, provides strong evidence suggesting that viperin is a putative radical S-adenosyl-L-methionine (SAM) enzyme. In addition to demonstrating that the antiviral activity of viperin depends on its radical SAM domain, which contains conserved motifs to coordinate [4Fe-4S] cluster and cofactor SAM and is essential for its enzymatic activity, mutagenesis studies also revealed that viperin requires an aromatic amino acid residue at its C terminus for proper antiviral function. Furthermore, although the N-terminal 70 amino acid residues of viperin are not absolutely required, deletion of this region significantly compromises its antiviral activity against HCV. Our findings suggest that viperin represents a novel antiviral pathway that works together with other antiviral proteins, such as ISG20 and PKR, to mediate the IFN response against HCV infection. Hepatitis C virus (HCV) is the sole member of the genusHepacivirus in the family Flaviviridae (43). It establishes persistent infections in the vast majority of infected individuals and is the only known positive-stranded RNA virus that causes persistent life-long infections in humans. Currently, HCV chronically infects more than 170 million people worldwide. Although the initial infection is largely asymptomatic, prolonged infection carries a high risk of chronic hepatitis, cirrhosis, and primary hepatocellular carcinoma (2).Although it has been elegantly demonstrated that HCV can evade the host cellular innate defense response through proteolytic cleavage of RIG-I/MDA5 adaptor protein MAVS and Tolllike receptor 3 adaptor protein TRIF (7,22,25,42,44,48,69), microarray studies performed with liver samples obtained from HCV transiently infected chimpanzees and chronically infected humans revealed that the induction of interferon (IFN)-stimulated genes (ISGs) in HCV-infected livers is a hallmark of the virus infection (5,6,33,39,58,61). These discoveries suggest that the HCV-infected liver is a constant battlefield between the virus and host innate immunity defense systems, and thus IFN-mediated innate responses induced by HCV may play an important role in shaping the pathogenesis and clini...

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Section: Pkrmentioning

confidence: 99%

Identification of Three Interferon-Inducible Cellular Enzymes That Inhibit the Replication of Hepatitis C Virus

Jiang

Guo

et al. 2008

J Virol

257

299

View full text Add to dashboard Cite

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“…Like other exonucleases, ISG20 may play a role in cleaving both DNA and RNA. However, ISG20 has distinctive residues, Met14 and Arg53, to accommodate hydrogen bonds with the 2'-OH group of the UMP ribose, which promotes a preference for RNA substrates (1). Further, a stem-loop structure at the 3' end of RNA substrates leads to a strong reduction in the activity of ISG20 RNase, and ISG20 operates poorly on doublestranded regions (5).…”

Section: Function and Mechanismmentioning

confidence: 99%

“…The 20-kDa protein of interferonstimulated exonuclease gene 20 (ISG20) is a protein induced by interferons or double-stranded RNA (2,3). Its involvement in antiviral mechanisms was elucidated in a recent study (4), where overexpression of recombinant ISG20 in cultured cells was found to increase cellular resistance to infection by some RNA genomic viruses (1). ISG20 is an exonuclease that can cleave single-stranded RNA and DNA (5,6).…”

Section: Introductionmentioning

confidence: 99%

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Interferon-stimulated gene 20-kDa protein (ISG20) in infection and disease: Review and outlook

Zheng

Wang

Pan

2017

IRDR

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“…Atom N d from His195 presented interactions with dTMP O1P and O2P, while N e remained exposed to the solvent. Therefore, in TREX1, Asp18/Glu20/Asp130/Asp200/His195 comprised the characteristic DEDDh exonuclease motif, which presented interactions with the nucleotide similar to those determined for other members of this family (Hamdan et al 2002b;Cheng and Patel 2004;Horio et al 2004).…”

Section: Active Sitementioning

confidence: 99%

Structural and biochemical studies of TREX1 inhibition by metals. Identification of a new active histidine conserved in DEDDh exonucleases

et al. 2008

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TREX1 is the major exonuclease in mammalian cells, exhibiting the highest level of activity with a 39!59 activity. This exonuclease is responsible in humans for Aicardi-Goutières syndrome and for an autosomal dominant retinal vasculopathy with cerebral leukodystrophy. In addition, this enzyme is associated with systemic lupus erythematosus. TREX1 belongs to the exonuclease DEDDh family, whose members display low levels of sequence identity, while possessing a common fold and active site organization. For these exonucleases, a catalytic mechanism has been proposed that involves two divalent metal ions bound to the DEDD motif. Here we studied the interaction of TREX1 with the monovalent cations lithium and sodium. We demonstrate that these metals inhibit the exonucleolytic activity of TREX1, as measured by the classical gel method, as well as by a new technique developed for monitoring the real-time exonuclease reaction. The X-ray structures of the enzyme in complex with these two cations and with a nucleotide, a product of the exonuclease reaction, were determined at 2.1 Å and 2.3 Å , respectively. A comparison with the structures of the active complexes (in the presence of magnesium or manganese) explains that the inhibition mechanism is caused by the noncatalytic metals competing with distinct affinities for the two metal-binding sites and inducing subtle rearrangements in active centers. Our analysis also reveals that a histidine residue (His124), highly conserved in the DEDDh family, is involved in the activity of TREX1, as confirmed by mutational studies. Our results shed further light on the mechanism of activity of the DEDEh family of exonucleases.Keywords: exonucleases; TREX1; DEDDh family; structure; enzymatic activityThe 39!59 exonucleases play a crucial role in many biological processes by removing nucleotides at the 39 termini from DNA ends, which must then be remodeled in order to prevent the formation of aberrant structures. The 39!59 exonucleases were initially found as proofreading enzymes associated with DNA polymerases. However, in recent years several eukaryotic 39!59 exonucleases, such as p53, the Werner syndrome protein (WRN), and MRE11, 3 These two authors contributed equally to this work.

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Crystal structure of human ISG20, an interferon‐induced antiviral ribonuclease

Cited by 51 publications

References 28 publications

Identification of Three Interferon-Inducible Cellular Enzymes That Inhibit the Replication of Hepatitis C Virus

Identification of Three Interferon-Inducible Cellular Enzymes That Inhibit the Replication of Hepatitis C Virus

Interferon-stimulated gene 20-kDa protein (ISG20) in infection and disease: Review and outlook

Structural and biochemical studies of TREX1 inhibition by metals. Identification of a new active histidine conserved in DEDDh exonucleases

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