A conserved mechanism of APOBEC3 relocalization by herpesviral ribonucleotide reductase large subunits

Adam Z. Cheng, Sofia N. Moraes, Claire Attarian, Jaime Yockteng-Melgar, Matthew C. Jarvis, Matteo Biolatti, Ganna Galitska, Valentina Dell'Oste, Lori Frappier, Craig J. Bierle, Stephen A. Rice, Reuben S. Harris

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

An integral part of the antiviral innate immune response is the APOBEC3 family of single-stranded DNA cytosine deaminases, which inhibits virus replication through deamination-dependent and -independent activities. Viruses have evolved mechanisms to counteract these enzymes, such as HIV-1 Vif-mediated formation of a ubiquitin ligase to degrade virus-restrictive APOBEC3 enzymes. A new example is Epstein-Barr virus (EBV) ribonucleotide reductase (RNR)-mediated inhibition of cellular APOBEC3B (A3B). The large subunit of the viral RNR, BORF2, causes A3B relocalization from the nucleus to cytoplasmic bodies and thereby protects viral DNA during lytic replication. Here, we use coimmunoprecipitation and immunofluorescence microscopy approaches to ask whether this mechanism is shared with the closely related gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV) and the more distantly related alphaherpesvirus herpes simplex virus 1 (HSV-1). The large RNR subunit of KSHV, open reading frame 61 (ORF61), coprecipitated multiple APOBEC3s, including A3B and APOBEC3A (A3A). KSHV ORF61 also caused relocalization of these two enzymes to perinuclear bodies (A3B) and to oblong cytoplasmic structures (A3A). The large RNR subunit of HSV-1, ICP6, also coprecipitated A3B and A3A and was sufficient to promote the relocalization of these enzymes from nuclear to cytoplasmic compartments. HSV-1 infection caused similar relocalization phenotypes that required ICP6. However, unlike the infectivity defects previously reported for BORF2-null EBV, ICP6 mutant HSV-1 showed normal growth rates and plaque phenotypes. Combined, these results indicate that both gamma- and alphaherpesviruses use a conserved RNR-dependent mechanism to relocalize A3B and A3A and furthermore suggest that HSV-1 possesses at least one additional mechanism to neutralize these antiviral enzymes. IMPORTANCE The APOBEC3 family of DNA cytosine deaminases constitutes a vital innate immune defense against a range of different viruses. A novel counterrestriction mechanism has recently been uncovered for the gammaherpesvirus EBV, in which a subunit of the viral protein known to produce DNA building blocks (ribonucleotide reductase) causes A3B to relocalize from the nucleus to the cytosol. Here, we extend these observations with A3B to include a closely related gammaherpesvirus, KSHV, and a more distantly related alphaherpesvirus, HSV-1. These different viral ribonucleotide reductases also caused relocalization of A3A, which is 92% identical to A3B. These studies are important because they suggest a conserved mechanism of APOBEC3 evasion by large double-stranded DNA herpesviruses. Strategies to block this host-pathogen interaction may be effective for treating infections caused by these herpesviruses.

Original languageEnglish (US)
Article numbere01539-19
JournalJournal of virology
Volume9
Issue number23
DOIs
StatePublished - Dec 1 2019

Bibliographical note

Funding Information:
These studies were supported in part by NCI grant P01 CA234228 and funds from the University of Minnesota College of Biological Sciences and Academic Health Center (to R.S.H.) as well as Canadian Institutes of Health Research (CIHR) project grant 153014 (to L.F.). NIH training grants provided salary support for A.Z.C. (F30 CA200432 and T32 GM008244) and M.C.J. (T32 CA009138). J.Y.-M. was supported by the Secretaría Nacio-nal de Educación Superior, Ciencia, Tecnología e Innovación (SENESCYT). G.G. is a scholar under the Horizon2020 program (H2020 MSCA-ITN-2015). V.D.O. is supported by research grants from the University of Turin (RILO18) and from the Italian Ministry of Education, University and Research (MIUR) (PRIN 2015 and 2015RMNSTA). R.S.H. is the Margaret Harvey Schering Land Grant Chair for Cancer Research, a Distinguished McKnight University Professor, and an Investigator of the Howard Hughes Medical Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Funding Information:
We thank Sandy Weller, Neal Deluca, and Prashant Desai for HSV-1 strains; M. Sanders and staff at the University of Minnesota Imaging Center for assistance with fluorescence microscopy; J. Becker for assistance with confocal microscopy; D. Ebrahimi for bioinformatics analyses of A3 expression in different cell types; and P. Southern for thoughtful comments and feedback on the manuscript. These studies were supported in part by NCI grant P01 CA234228 and funds from the University of Minnesota College of Biological Sciences and Academic Health Center (to R.S.H.) as well as Canadian Institutes of Health Research (CIHR) project grant 153014 (to L.F.). NIH training grants provided salary support for A.Z.C. (F30 CA200432 and T32 GM008244) and M.C.J. (T32 CA009138). J.Y.-M. was supported by the Secretar?a Nacional de Educaci?n Superior, Ciencia, Tecnolog?a e Innovaci?n (SENESCYT). G.G. is a scholar under the Horizon2020 program (H2020 MSCA-ITN-2015). V.D.O. is supported by research grants from the University of Turin (RILO18) and from the Italian Ministry of Education, University and Research (MIUR) (PRIN 2015 and 2015RMNSTA). R.S.H. is the Margaret Harvey Schering Land Grant Chair for Cancer Research, a Distinguished McKnight University Professor, and an Investigator of the Howard Hughes Medical Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. R.S.H. is a cofounder, shareholder, and consultant of ApoGen Biotechnologies Inc. The other authors have declared that no competing interests exist.

Publisher Copyright:
Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords

  • APOBEC3A
  • APOBEC3B
  • Herpesviruses
  • Innate antiviral immunity
  • Ribonucleotide reductase

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