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  • rXXXX American Chemical Society A dx.doi.org/10.1021/pr200628s | J. Proteome Res. XXXX, XXX, 000000

    ARTICLE

    pubs.acs.org/jpr

    Varicella Zoster Virus ORF25 Gene Product: An Essential Hub ProteinLinking Encapsidation Proteins and the Nuclear Egress ComplexMaria G. Vizoso Pinto,*, Venkata R. Pothineni, Rudolf Haase, Mathias Woidy, Amelie S. Lotz-Havla,

    Sren W. Gersting, Ania C. Muntau, Jurgen Haas,,Marvin Sommer,|| AnnM. Arvin,|| and Armin Baiker,^

    Max von Pettenkofer-Institute, Ludwig-Maximilians-University, Munich, GermanyDepartment of Molecular Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University, Munich, GermanyDivision of Pathway Medicine, University of Edinburgh, United Kingdom

    )Department of Pediatrics, Stanford University, Stanford, California, United States^Bavarian Health and Food Safety Authority, Oberschleissheim, Germany

    bS Supporting Information

    INTRODUCTION

    Varicella zoster virus (VZV) causes chickenpox upon pri-mary infection and establishes latency in the dorsal rootganglia, from where it may reactivate causing herpes zoster.As a member of the -Herpesviruses, VZV belongs to themost complex viruses known. The virion particles consist of adouble-stranded (ds) DNA genome packaged into a nucleo-capsid, a proteinaceous matrix called the tegument, and a cell-derived lipid envelope.1 The dsDNA replication of -herpes-viruses is believed to follow a rolling-circle mechanism, whereconcatemers of genomes arranged in a head-to-tail fashion areformed. The cleavage of single genomes is tightly coupled totheir energy-dependent packaging into precapsids, a processmediated by multiprotein complexes, which resembles thepackaging of genomes in the tailed dsDNA bacteriophages.1,2

    In HSV-1, at least seven proteins are known to be responsiblefor these processes: UL6, UL15, UL17, UL25, UL28, UL32and UL33.3,4 Three of them, HSV-1 UL15, UL28 and UL33,have been shown to interact with each other and are con-sidered to form the terminase complex.5,6 Deletion of these

    genes is lethal as the viruses are not able to package thedsDNA into the capsid.4,7,8

    VZV ORF25, the orthologue of HSV-1 UL33, is a 156 aaprotein that belongs to a set of approximately 40 core proteinsthat are conserved throughout the Herpesviridae. In HSV-1,UL33 has been shown to be essential and involved in DNApackaging.3,4,9 Within a comprehensive Y2H analysis of the VZVprotein interaction network, we previously showed that VZVORF25 constitutes a central hub interacting with many otherVZV proteins.10 Interestingly, VZV ORF25 interacts with onlyfour cellular proteins (unpublished results). Recently, Visalli et al.have shown that ORF25 interacts with two components, that is,ORF30 andORF45/42 (HSV-1UL28 andUL15), of the putativeterminase complex by pull-down assays in an in vitro translationsystem.11 Not yet well understood, however, is the linkagebetween cleavage/encapsidation of viral DNA and the nuclearegress ofmature capsids.Herewe investigate the interactions of all

    Received: July 5, 2011

    ABSTRACT:Varicella zoster virus (VZV)ORF25 is a 156 amino acid proteinbelonging to the approximately 40 core proteins that are conserved through-out theHerpesviridae. By analogy to its functional orthologue UL33 in Herpessimplex virus 1 (HSV-1), ORF25 is thought to be a component of theterminase complex. To investigate how cleavage and encapsidation of viralDNA links to the nuclear egress of mature capsids in VZV, we tested 10 VZVproteins that are predicted to be involved in either of the two processes forprotein interactions against each other using three independent proteinprotein interaction (PPI) detection systems: the yeast-two-hybrid (Y2H)system, a luminescence based MBP pull-down interaction screening assay(LuMPIS), and a bioluminescence resonance energy transfer (BRET) assay. Aset of 20 interactions was consistently detected by at least 2 methods andresulted in a dense interaction network between proteins associated inencapsidation and nuclear egress. The results indicate that the terminase complex in VZV consists of ORF25, ORF30, andORF45/42 and support a model in which both processes are closely linked to each other. Consistent with its role as a central hub forprotein interactions, ORF25 is shown to be essential for VZV replication.

    KEYWORDS: Varicella zoster virus, ORF25, encapsidation, nuclear egress complex, LuMPIS, BRET, Y2H, terminase

  • B dx.doi.org/10.1021/pr200628s |J. Proteome Res. XXXX, XXX, 000000

    Journal of Proteome Research ARTICLE

    the VZV proteins that are predicted to be related to the encapsida-tion process and the nuclear egress complex (NEC) by means ofthree independent proteinprotein interaction (PPI) detectionsystems: Y2H, luminescence based MBP pull-down interactionscreening (LuMPIS) and bioluminescence resonance energy trans-fer (BRET).10,12 Furthermore, we demonstrate that ORF25 isessential for virus replication by generating ORF25 mutant virusesusing a cosmid based system.

    MATERIALS AND METHODS

    Recombinatorial Cloning of VZV ORFsThe nucleotide sequences of all VZV ORFs used in this study

    were obtained from the NCBI (http://www.ncbi.nlm.nih.gov/).BP recombination reactions of VZV ORFs into pDONR207(Invitrogen, Germany) were performed as described earlier.10,13

    LR recombination reactions using LR-clonase II enzyme mix(Invitrogen, Germany) were performed according to themanufacturers instructions. Briefly, pENTR207-VZV-ORF vectorscontaining VZV-ORFs flanked by attL-sites were recombinato-rially cloned into the attR-sites of the customized vectors pCR3-MBP-N-[rfB], pCR3-eGFPLuc-N-[rfB],12 pCR3-Venus-N-[rfB]and respective BRET destination vectors with anN- or C-terminalcoding sequence of Renilla luciferase (Rluc) or yellow fluores-cence protein (YFP). The vector pCR3-Venus-N-[rfB] has beenconstructed by insertion of a customized cassette consisting of 50-HindIII-ATG-[Venus]-EcoRV-[ccdB/CmR(rfB)]-EcoRV-30 intothe backbone of the pCR3 (Invitrogen, Germany). LR clonasereactions were incubated at 37 C for 2 h and subsequentlytransformed into chemically competent E. coli DH5. PlasmidDNA of individual colonies grown on LB-plates supplementedwith 100 g/mL ampicillin (Sigma-Aldrich, Germany) wasisolated and the integrity of the resulting pCR3-based vectorswas verified by restriction analysis.

    Construction of VZV Cosmids and Generation of ORF25Mutant Viruses

    The complete genome of the parental OKA (pOKA) VZVstrain has been subcloned as four overlapping fragments within thecosmids: pvSpe14, pvFsp73, pvSpe23AvrII, andpvPme2.14,15 Foreasier handling, the pvSpe14 cosmid was split into two smallercosmids designated pNhe and pPvu within this work (Figure 1,lane 3). For the construction of pNhe, the original vector pvSpe14was digested with NheI, treated with Klenow enzyme and sub-sequently digested with AscI. The 26964bp AscI/(NheI-)bluntend fragment comprising the VZV-specific nucleotides 1 (AscI)26964 (NheI) of pvSpe14 was isolated and inserted into SuperCosvector (Stratagene, La Jolla, CA). For this purpose, SuperCosvector was digested with AvrII, blunt ended with Klenow enzymeand digested with AscI. The religation of blunt ended NheI andAvrII sites reconstituted a functional NheI site. Prior to cosmidtransfections, the SuperCos vector part of pNhewas separated fromthe 26964bp genomic VZV-sequence by AscI and NheI doubledigest. For the construction of pPvu, the original vector pvSpe14was digestedwithPvuI. The 21602bpPvuI fragment comprising theVZV-specific nucleotides 2468740080 of pvSpe14 and approxi-mately 5000bp of its 6800bp SuperCos vector backbone wasisolated and ligated to an 1800bp, PvuI-digested PCR-fragmentdesigned to reconstitute the functional (full length) Super-Cos vector backbone within pPvu. The latter PCR-fragmentwas amplified from pvSpe14, by using the primers 45215upper(50-TTCCGACCCTGCCGCTTACC-30) and end+PvuI lower

    (50-TCACCGATCGGGCGCGCCGGATCCTTTAGT-30).Prior to cosmid transfections, the SuperCos vector part of pPvuwas separated from the 15393bp genomic VZV-sequence by AscIdigest.

    The strategy for the deletion of endogenous ORF25 wascritical, since its reading frame overlapped with the reading frameof ORF26 (Figure 1, lane 4). Therefore, deletion of ORF25 wasachieved by introducing the stop codon TAA at amino acidposition 2, leading to a silent mutation within ORF26. For theintroduction of the respective mutation, the 4.2kb ApaI/NheIfragment of pNhe was subcloned into the multiple cloning site ofpGFP-C1 (Clontech, Mountain View, CA), resulting in theshuttle vector pGFP[4.2kb]. PCR mutagenesis was performedby two rounds of PCR within the 800bp ApaI/NotI fragment ofpGFP[4.2kb]. The resulting ApaI/NotI PCR fragment compris-ing the ORF25 deletion and its endogenous promoter was TA-cloned into pGEM-T easy, verified by sequencing, placed backinto pGFP[4.2kb] and finally into the pNhe cosmid backboneresulting in the cosmid pNheORF25 (Figure 1, lane 4).

    For the generation of pOKA-ORF25 (rescue) mutant viruseswithin the pOKAORF25 backbone, wild type ORF25 mutant andits endogenous promoter cassette was isolated as an AvrII fragmentfrom its respective pGEM-T easy construct and integrated into thesingle AvrII site of pvSpe23AvrII15 (Figure 1, lane 5). The cosmidpvSpe23-@ORF25-WT, containing the wildtype ORF25 sequencewas constructed analogously as control. The integrity of the generatedpvSpe23AvrII-based (rescue) cosmids was verified by restrictionanalysis and deep sequencing (LGC Genomics, Germany).

    Figure 1. Construction of p-OKA cosmid vectors with VZV ORF25deletion and substitution mutants. Line 1 shows a schematic diagram ofthe pOKA genome and the localization of orf25 in the unique longregion. Line 2 depicts the overlapping segments of the pOKA genomesubcloned into the respective pOKA cosmids: pvFspe73, pvSpe14,pvSpe23, and pvPme 2. L

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