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Virology2011; 417(2); 430-442; doi: 10.1016/j.virol.2011.06.023

Identification of functional domains of the IR2 protein of equine herpesvirus 1 required for inhibition of viral gene expression and replication.

Abstract: The equine herpesvirus 1 (EHV-1) negative regulatory IR2 protein (IR2P), an early 1,165-amino acid (aa) truncated form of the 1487-aa immediate-early protein (IEP), lacks the trans-activation domain essential for IEP activation functions but retains domains for binding DNA, TFIIB, and TBP and the nuclear localization signal. IR2P mutants of the N-terminal region which lack either DNA-binding activity or TFIIB-binding activity were unable to down-regulate EHV-1 promoters. In EHV-1-infected cells expressing full-length IR2P, transcription and protein expression of viral regulatory IE, early EICP0, IR4, and UL5, and late ETIF genes were dramatically inhibited. Viral DNA levels were reduced to 2.1% of control infected cells, but were vey weakly affected in cells that express the N-terminal 706 residues of IR2P. These results suggest that IR2P function requires the two N-terminal domains for binding DNA and TFIIB as well as the C-terminal residues 707 to 1116 containing the TBP-binding domain.
Copyright © 2011 Elsevier Inc. All rights reserved.
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Publication Date: 2011-07-26 PubMed ID: 21794889PubMed Central: PMC3388945DOI: 10.1016/j.virol.2011.06.023Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study investigates the role and function of the IR2 protein (IR2P) of the Equine Herpesvirus 1 (EHV-1) in the inhibition of viral gene expression and replication. The researchers discovered that the IR2P requires certain domains for its function and that mutants lacking these domains cannot suppress EHV-1.

Understanding the IR2 Protein

  • The study focuses on the IR2P of EHV-1, a truncated form of an immediate-early protein (IEP). This protein lacks the trans-activation domain that is essential for IEP functions, but it retains some domains for DNA binding, TFIIB (transcription factor for RNA polymerase II) binding, and TBP (TATA box-binding protein) as well as a nuclear localization signal.
  • The researchers point out that not all parts of the IR2P serve the same functions, and are therefore not of equal importance in its role of suppressing the EHV-1 virus.

Experiments with IR2P

  • The researchers experimented with mutants of IR2P in which the N-terminal region lacked DNA-binding activity or TFIIB-binding activity. The aim was to understand what would happen when certain functions of the IR2P were removed.
  • Results revealed that these mutants could not down-regulate EHV-1 promoters, showing that the DNA and TFIIB-binding activities were crucial for the IR2P’s ability to suppress the virus.

IR2P’s Inhibition of Various Genes

  • In EHV-1-infected cells expressing the full-length IR2P, the researchers observed a significant reduction in the transcript and protein expression of various viral regulatory genes, including IE, EICP0, IR4, UL5, and ETIF.
  • Furthermore, the IR2P also caused a drastic decrease in viral DNA levels, reducing them to just 2.1% compared to control infected cells. This shows the IR2P’s effectiveness in limiting the virus’s ability to replicate.

Concluding Findings

  • Overall, the researchers found that the IR2P requires two N-terminal domains for DNA and TFIIB binding, as well as C-terminal residues 707 to 1116 that contain the TBP-binding domain in order to function effectively.
  • Through understanding the role and functions of the IR2P, this research could have wider implications for the development of treatments for diseases caused by EHV-1.

Cite This Article

APA
Kim SK, Kim S, Dai G, Zhang Y, Ahn BC, O'Callaghan DJ. (2011). Identification of functional domains of the IR2 protein of equine herpesvirus 1 required for inhibition of viral gene expression and replication. Virology, 417(2), 430-442. https://doi.org/10.1016/j.virol.2011.06.023

Publication

Virology
ISSN: 1096-0341
NlmUniqueID: 0110674
Country: United States
Language: English
Volume: 417
Issue: 2
Pages: 430-442

Researcher Affiliations

Kim, Seong K
  • Department of Microbiology and Immunology, and Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, Louisiana LA 71130-3932, USA. skim1@lsuhsc.edu
Kim, Seongman
    Dai, Gan
      Zhang, Yunfei
        Ahn, Byung C
          O'Callaghan, Dennis J

            MeSH Terms

            • Animals
            • DNA-Binding Proteins / genetics
            • DNA-Binding Proteins / metabolism
            • Gene Expression Regulation, Viral
            • Herpesvirus 1, Equid / genetics
            • Herpesvirus 1, Equid / physiology
            • Mutant Proteins / genetics
            • Mutant Proteins / metabolism
            • Mutation
            • Protein Structure, Tertiary
            • Viral Proteins / genetics
            • Viral Proteins / metabolism
            • Virus Replication

            Grant Funding

            • P20 GM103433 / NIGMS NIH HHS
            • R01 AI022001 / NIAID NIH HHS
            • P20 RR018724 / NCRR NIH HHS
            • AI22001 / NIAID NIH HHS
            • P20-RR018724 / NCRR NIH HHS

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            Citations

            This article has been cited 10 times.
            1. Kim SK, Shakya AK, O'Callaghan DJ. Interferon Gamma Inhibits Equine Herpesvirus 1 Replication in a Cell Line-Dependent Manner. Pathogens 2021 Apr 16;10(4).
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            2. Kim SK, Shakya AK, O'Callaghan DJ. Intranasal treatment with CpG-B oligodeoxynucleotides protects CBA mice from lethal equine herpesvirus 1 challenge by an innate immune response. Antiviral Res 2019 Sep;169:104546.
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            3. Kim SK, Shakya AK, O'Callaghan DJ. Immunization with Attenuated Equine Herpesvirus 1 Strain KyA Induces Innate Immune Responses That Protect Mice from Lethal Challenge. J Virol 2016 Sep 15;90(18):8090-104.
              doi: 10.1128/JVI.00986-16pubmed: 27356904google scholar: lookup
            4. Kim SK, Shakya AK, O'Callaghan DJ. Full trans-activation mediated by the immediate-early protein of equine herpesvirus 1 requires a consensus TATA box, but not its cognate binding sequence. Virus Res 2016 Jan 4;211:222-32.
              doi: 10.1016/j.virusres.2015.10.026pubmed: 26541315google scholar: lookup
            5. Kim SK, Shakya AK, Kim S, O'Callaghan DJ. Functional Characterization of the Serine-Rich Tract of Varicella-Zoster Virus IE62. J Virol 2016 Jan 15;90(2):959-71.
              doi: 10.1128/JVI.02096-15pubmed: 26537679google scholar: lookup
            6. Zhang Y, Charvat RA, Kim SK, O'Callaghan DJ. The EHV-1 UL4 protein that tempers viral gene expression interacts with cellular transcription factors. Virology 2014 Jan 20;449:25-34.
              doi: 10.1016/j.virol.2013.11.005pubmed: 24418534google scholar: lookup
            7. Kim S, Ahn BC, O'Callaghan DJ, Kim SK. The early UL31 gene of equine herpesvirus 1 encodes a single-stranded DNA-binding protein that has a nuclear localization signal sequence at the C-terminus. Virology 2012 Oct 25;432(2):306-15.
              doi: 10.1016/j.virol.2012.05.031pubmed: 22721961google scholar: lookup
            8. Dai G, Kim S, O'Callaghan DJ, Kim SK. Development of a bacterial artificial chromosome (BAC) recombineering procedure using galK-untranslated region (UTR) for the mutation of diploid genes. J Virol Methods 2012 Jun;182(1-2):18-26.
              doi: 10.1016/j.jviromet.2012.02.010pubmed: 22407056google scholar: lookup
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              doi: 10.1016/j.virusres.2012.01.005pubmed: 22265772google scholar: lookup
            10. Liu D, Zhao X, Wang X. The Genomic Characterization of Equid Alphaherpesviruses: Structure, Function, and Genetic Similarity. Vet Sci 2025 Mar 3;12(3).
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