1
|
Kim D, Cianfrocco MA, Verhey KJ, Smith GA. The HSV-1 pUL37 protein promotes cell invasion by regulating the kinesin-1 motor. Proc Natl Acad Sci U S A 2024; 121:e2401341121. [PMID: 38696466 PMCID: PMC11087751 DOI: 10.1073/pnas.2401341121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 03/17/2024] [Indexed: 05/04/2024] Open
Abstract
Neurotropic alphaherpesviruses, including herpes simplex virus type 1 (HSV-1), recruit microtubule motor proteins to invade cells. The incoming viral particle traffics to nuclei in a two-step process. First, the particle uses the dynein-dynactin motor to sustain transport to the centrosome. In neurons, this step is responsible for long-distance retrograde axonal transport and is an important component of the neuroinvasive property shared by these viruses. Second, a kinesin-dependent mechanism redirects the particle from the centrosome to the nucleus. We have reported that the kinesin motor used during the second step of invasion is assimilated into nascent virions during the previous round of infection. Here, we report that the HSV-1 pUL37 tegument protein suppresses the assimilated kinesin-1 motor during retrograde axonal transport. Region 2 (R2) of pUL37 was required for suppression and functioned independently of the autoinhibitory mechanism native to kinesin-1. Furthermore, the motor domain and proximal coiled coil of kinesin-1 were sufficient for HSV-1 assimilation, pUL37 suppression, and nuclear trafficking. pUL37 localized to the centrosome, the site of assimilated kinesin-1 activation during infection, when expressed in cells in the absence of other viral proteins; however, pUL37 did not suppress kinesin-1 in this context. These results indicate that the pUL37 tegument protein spatially and temporally regulates kinesin-1 via the amino-terminal motor region in the context of the incoming viral particle.
Collapse
Affiliation(s)
- DongHo Kim
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Michael A. Cianfrocco
- Life Sciences Institute, Department of Biological Chemistry, University of Michigan, Ann Arbor, MI48109
| | - Kristen J. Verhey
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI48109
| | - Gregory A. Smith
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| |
Collapse
|
2
|
Jih J, Liu YT, Liu W, Zhou ZH. The incredible bulk: Human cytomegalovirus tegument architectures uncovered by AI-empowered cryo-EM. SCIENCE ADVANCES 2024; 10:eadj1640. [PMID: 38394211 PMCID: PMC10889378 DOI: 10.1126/sciadv.adj1640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 01/22/2024] [Indexed: 02/25/2024]
Abstract
The compartmentalization of eukaryotic cells presents considerable challenges to the herpesvirus life cycle. The herpesvirus tegument, a bulky proteinaceous aggregate sandwiched between herpesviruses' capsid and envelope, is uniquely evolved to address these challenges, yet tegument structure and organization remain poorly characterized. We use deep-learning-enhanced cryogenic electron microscopy to investigate the tegument of human cytomegalovirus virions and noninfectious enveloped particles (NIEPs; a genome packaging-aborted state), revealing a portal-biased tegumentation scheme. We resolve atomic structures of portal vertex-associated tegument (PVAT) and identify multiple configurations of PVAT arising from layered reorganization of pUL77, pUL48 (large tegument protein), and pUL47 (inner tegument protein) assemblies. Analyses show that pUL77 seals the last-packaged viral genome end through electrostatic interactions, pUL77 and pUL48 harbor a head-linker-capsid-binding motif conducive to PVAT reconfiguration, and pUL47/48 dimers form 45-nm-long filaments extending from the portal vertex. These results provide a structural framework for understanding how herpesvirus tegument facilitates and evolves during processes spanning viral genome packaging to delivery.
Collapse
Affiliation(s)
- Jonathan Jih
- Molecular Biology Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Yun-Tao Liu
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Wei Liu
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Z. Hong Zhou
- Molecular Biology Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| |
Collapse
|
3
|
Sucharita S, Krishnagopal A, van Drunen Littel-van den Hurk S. Comprehensive Analysis of the Tegument Proteins Involved in Capsid Transport and Virion Morphogenesis of Alpha, Beta and Gamma Herpesviruses. Viruses 2023; 15:2058. [PMID: 37896835 PMCID: PMC10611259 DOI: 10.3390/v15102058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 09/21/2023] [Accepted: 09/21/2023] [Indexed: 10/29/2023] Open
Abstract
Herpesviruses are enveloped and have an amorphous protein layer surrounding the capsid, which is termed the tegument. Tegument proteins perform critical functions throughout the viral life cycle. This review provides a comprehensive and comparative analysis of the roles of specific tegument proteins in capsid transport and virion morphogenesis of selected, well-studied prototypes of each of the three subfamilies of Herpesviridae i.e., human herpesvirus-1/herpes simplex virus-1 (Alphaherpesvirinae), human herpesvirus-5/cytomegalovirus (Betaherpesvirinae) and human herpesvirus -8/Kaposi's sarcomavirus (Gammaherpesvirinae). Most of the current knowledge is based on alpha herpesviruses, in particular HSV-1. While some tegument proteins are released into the cytoplasm after virus entry, several tegument proteins remain associated with the capsid and are responsible for transport to and docking at the nucleus. After replication and capsid formation, the capsid is enveloped at the nuclear membrane, which is referred to as primary envelopment, followed by de-envelopment and release into the cytoplasm. This requires involvement of at least three tegument proteins. Subsequently, multiple interactions between tegument proteins and capsid proteins, other tegument proteins and glycoproteins are required for assembly of the virus particles and envelopment at the Golgi, with certain tegument proteins acting as the central hub for these interactions. Some redundancy in these interactions ensures appropriate morphogenesis.
Collapse
Affiliation(s)
- Soumya Sucharita
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; (S.S.); (A.K.)
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
| | - Akshaya Krishnagopal
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; (S.S.); (A.K.)
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
| | - Sylvia van Drunen Littel-van den Hurk
- Biochemistry, Microbiology and Immunology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; (S.S.); (A.K.)
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK S7N 5E3, Canada
| |
Collapse
|
4
|
Collantes TMA, Clark CM, Musarrat F, Jambunathan N, Jois S, Kousoulas KG. Predicted Structure and Functions of the Prototypic Alphaherpesvirus Herpes Simplex Virus Type-1 UL37 Tegument Protein. Viruses 2022; 14:2189. [PMID: 36298744 PMCID: PMC9608200 DOI: 10.3390/v14102189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/30/2022] [Accepted: 09/30/2022] [Indexed: 11/17/2022] Open
Abstract
The alphaherpesvirus UL37 tegument protein is a highly conserved, multi-functional protein. Mutagenesis analysis delineated the UL37 domains necessary for retrograde transport and viral replication. Specifically, the amino-terminal 480 amino acids are dispensable for virus replication in epithelial cell culture, but it is unknown whether this amino-terminal deletion affects UL37 structure and intracellular transport in epithelial cells and neurons. To investigate the structure and function of UL37, we utilized multiple computational approaches to predict and characterize the secondary and tertiary structure and other functional features. The structure of HSV-1 UL37 and Δ481N were deduced using publicly available predictive algorithms. The predicted model of HSV-1 UL37 is a stable, multi-functional, globular monomer, rich in alpha helices, with unfolded regions within the linker and the C-tail domains. The highly flexible C-tail contains predicted binding sites to the dynein intermediate chain, as well as DNA and RNA. Predicted interactions with the cytoplasmic surface of the lipid membrane suggest UL37 is a peripheral membrane protein. The Δ481N truncation did not alter the predicted structure of the UL37 C-terminus protein and its predicted interaction with dynein. We validated these models by examining the replication kinetics and transport of the Δ481N virus toward the nuclei of infected epithelial and neuronal cells. The Δ481N virus had substantial defects in virus spread; however, it exhibited no apparent defects in virus entry and intracellular transport. Using computational analyses, we identified several key features of UL37, particularly the flexible unstructured tail; we then demonstrated that the UL37 C-terminus alone is sufficient to effectively transport the virus towards the nucleus of infected epithelial and neuronal cells.
Collapse
Affiliation(s)
- Therese Marie A. Collantes
- Division of Biotechnology and Molecular Medicine and Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
- College of Veterinary Medicine, University of the Philippines Los Baños, Los Baños, Laguna 4031, Philippines
| | - Carolyn M. Clark
- Division of Biotechnology and Molecular Medicine and Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Farhana Musarrat
- Division of Biotechnology and Molecular Medicine and Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| | | | - Seetharama Jois
- School of Basic Pharmaceutical and Toxicological Sciences, College of Pharmacy, University of Louisiana Monroe, Monroe, LA 71201, USA
| | - Konstantin G. Kousoulas
- Division of Biotechnology and Molecular Medicine and Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| |
Collapse
|
5
|
Stults AM, Sollars PJ, Heath KD, Sillman SJ, Pickard GE, Smith GA. Bovine Herpesvirus 1 Invasion of Sensory Neurons by Retrograde Axonal Transport Is Dependent on the pUL37 Region 2 Effector. J Virol 2022; 96:e0148621. [PMID: 35420461 PMCID: PMC9093089 DOI: 10.1128/jvi.01486-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 03/15/2022] [Indexed: 11/20/2022] Open
Abstract
Following exposure and replication at mucosal surfaces, most alphaherpesviruses invade the peripheral nervous system by retrograde axonal transport and establish lifelong latent infections in the peripheral ganglia. Reactivation of ganglionic infections is followed by anterograde axonal transport of virions back to body surfaces where viral replication results in disease that can range from moderate to severe in presentation. In the case of bovine herpesvirus 1 (BoHV-1), replication in the epithelial mucosa presents as infectious bovine rhinotracheitis (IBR), a respiratory disease of significant economic impact. In this study, we provide a live-cell analysis of BoHV-1 retrograde axonal transport relative to the model alphaherpesvirus pathogen pseudorabies virus (PRV) and demonstrate that this critical neuroinvasive step is conserved between the two viruses. In addition, we report that the BoHV-1 pUL37 tegument protein supports processive retrograde motion in infected axons and invasion of the calf peripheral nervous system. IMPORTANCE A molecular and cellular understanding of the retrograde axonal transport process that underlies the neuroinvasive properties of the alphaherpesviruses is established from studies of herpes simplex virus and pseudorabies virus. The degree to which this phenotype is conserved in other related viruses has largely not been examined. We provide a time-lapse analysis of the retrograde axonal transport kinetics of bovine herpesvirus 1 and demonstrate that mutation of the pUL37 region 2 effector affords a strategy to produce live-attenuated vaccines for enhanced protection of cattle.
Collapse
Affiliation(s)
- Austin M. Stults
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Patricia J. Sollars
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska, USA
| | - Kelly D. Heath
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska, USA
| | - Sarah J. Sillman
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska, USA
| | - Gary E. Pickard
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska, USA
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Gregory A. Smith
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| |
Collapse
|
6
|
Wilson DW. Motor Skills: Recruitment of Kinesins, Myosins and Dynein during Assembly and Egress of Alphaherpesviruses. Viruses 2021; 13:v13081622. [PMID: 34452486 PMCID: PMC8402756 DOI: 10.3390/v13081622] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/11/2021] [Accepted: 08/13/2021] [Indexed: 12/14/2022] Open
Abstract
The alphaherpesviruses are pathogens of the mammalian nervous system. Initial infection is commonly at mucosal epithelia, followed by spread to, and establishment of latency in, the peripheral nervous system. During productive infection, viral gene expression, replication of the dsDNA genome, capsid assembly and genome packaging take place in the infected cell nucleus, after which mature nucleocapsids emerge into the cytoplasm. Capsids must then travel to their site of envelopment at cytoplasmic organelles, and enveloped virions need to reach the cell surface for release and spread. Transport at each of these steps requires movement of alphaherpesvirus particles through a crowded and viscous cytoplasm, and for distances ranging from several microns in epithelial cells, to millimeters or even meters during egress from neurons. To solve this challenging problem alphaherpesviruses, and their assembly intermediates, exploit microtubule- and actin-dependent cellular motors. This review focuses upon the mechanisms used by alphaherpesviruses to recruit kinesin, myosin and dynein motors during assembly and egress.
Collapse
Affiliation(s)
- Duncan W. Wilson
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA; ; Tel.: +1-718-430-2305
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| |
Collapse
|
7
|
Bernstein DI, Cardin RD, Smith GA, Pickard GE, Sollars PJ, Dixon DA, Pasula R, Bravo FJ. The R2 non-neuroinvasive HSV-1 vaccine affords protection from genital HSV-2 infections in a guinea pig model. NPJ Vaccines 2020; 5:104. [PMID: 33298966 PMCID: PMC7648054 DOI: 10.1038/s41541-020-00254-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 10/06/2020] [Indexed: 02/01/2023] Open
Abstract
Herpes simplex virus (HSV) infections are common and can cause severe illness but no vaccine is currently available. The recent failure of subunit HSV vaccines has highlighted the need for vaccines that present a diverse array of antigens, including the development of next-generation live-attenuated vaccines. However, most attenuated HSV strains propagate poorly, limiting their ability to elicit protective immune responses. A live-attenuated vaccine that replicates in non-neural tissue but is ablated for transmission into the nervous system may elicit protective immune responses without evoking neurologic complications or establishing life-long infections. Initial studies of R2, a live-attenuated vaccine that is engineered to be unable to invade the nervous system, used the guinea pig genital HSV model to evaluate the ability of R2 to replicate at the site of inoculation, cause disease and infect neural tissues. R2 was then evaluated as a vaccine using three routes of inoculation: intramuscular (IM), intradermal (ID) and intravaginal (IVag) and compared to IM administered gD2+MPL/Alum vaccine in the same model. R2 replicated in the genital tract but did not produce acute or recurrent disease and did not infect the neural tissue. The R2 vaccine-induced neutralizing antibody and decreased the severity of acute and recurrent HSV-2 disease as well as recurrent shedding. The ID route was the most effective. ID administered R2 was more effective than gD2+MPL/Alum at inducing neutralizing antibody, suppressing acute disease, and acute vaginal virus replication. R2 was especially more effective at reducing recurrent virus shedding, the most common source of HSV transmission. The live-attenuated prophylactic HSV vaccine, R2, was effective in the guinea pig model of genital HSV-2 especially when administered by the ID route. The use of live-attenuated HSV vaccines that robustly replicate in mucosal tissues but are ablated for neuroinvasion offers a promising approach for HSV vaccines.
Collapse
Affiliation(s)
- David I Bernstein
- Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA.
| | - Rhonda D Cardin
- School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA
| | - Gregory A Smith
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Gary E Pickard
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE, USA
| | - Patricia J Sollars
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska, Lincoln, NE, USA
| | - David A Dixon
- Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA
| | - Rajamouli Pasula
- Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA
| | - Fernando J Bravo
- Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA
| |
Collapse
|
8
|
Ahmad I, Wilson DW. HSV-1 Cytoplasmic Envelopment and Egress. Int J Mol Sci 2020; 21:ijms21175969. [PMID: 32825127 PMCID: PMC7503644 DOI: 10.3390/ijms21175969] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/14/2020] [Accepted: 08/16/2020] [Indexed: 12/25/2022] Open
Abstract
Herpes simplex virus type 1 (HSV-1) is a structurally complex enveloped dsDNA virus that has evolved to replicate in human neurons and epithelia. Viral gene expression, DNA replication, capsid assembly, and genome packaging take place in the infected cell nucleus, which mature nucleocapsids exit by envelopment at the inner nuclear membrane then de-envelopment into the cytoplasm. Once in the cytoplasm, capsids travel along microtubules to reach, dock, and envelope at cytoplasmic organelles. This generates mature infectious HSV-1 particles that must then be sorted to the termini of sensory neurons, or to epithelial cell junctions, for spread to uninfected cells. The focus of this review is upon our current understanding of the viral and cellular molecular machinery that enables HSV-1 to travel within infected cells during egress and to manipulate cellular organelles to construct its envelope.
Collapse
Affiliation(s)
- Imran Ahmad
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA;
| | - Duncan W. Wilson
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA;
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
- Correspondence:
| |
Collapse
|
9
|
The pseudorabies virus R2 non-neuroinvasive vaccine: A proof-of-concept study in pigs. Vaccine 2020; 38:4524-4528. [PMID: 32448623 DOI: 10.1016/j.vaccine.2020.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 04/29/2020] [Accepted: 05/01/2020] [Indexed: 11/24/2022]
Abstract
Neurotropic alpha-herpesviruses that infect mammals establish life-long latent infections in the peripheral nervous system after initial infection of exposed mucosal tissues. The neuroinvasive properties can lead to severe complications both with clinical and veterinary alpha-herpesviruses, and vaccines are often unavailable or provide limited protection. Here we assess the properties and efficacy of an R2 vaccine derived from the alpha-herpesvirus, pseudorabies virus (PRV), in pigs. We demonstrate that the PRV R2 vaccine does not invade the porcine peripheral nervous system within the limits of detection. Furthermore, after a single intranasal vaccination, R2 conferred protection to pigs subsequently challenged with a virulent PRV field strain (NIA-3). These findings support that the R2 vaccine design is non-neuroinvasive and is an effective vaccine in the context of a natural host.
Collapse
|
10
|
Metrick CM, Koenigsberg AL, Heldwein EE. Conserved Outer Tegument Component UL11 from Herpes Simplex Virus 1 Is an Intrinsically Disordered, RNA-Binding Protein. mBio 2020; 11:e00810-20. [PMID: 32371601 PMCID: PMC7403781 DOI: 10.1128/mbio.00810-20] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 04/07/2020] [Indexed: 12/23/2022] Open
Abstract
A distinguishing morphological feature of all herpesviruses is the multiprotein tegument layer located between the nucleocapsid and lipid envelope of the virion. Tegument proteins play multiple roles in viral replication, including viral assembly, but we do not yet understand their individual functions or how the tegument is assembled and organized. UL11, the smallest tegument protein, is important for several distinct processes in replication, including efficient virion morphogenesis and cell-cell spread. However, the mechanistic understanding of its role in these and other processes is limited in part by the scant knowledge of its biochemical and structural properties. Here, we report that UL11 from herpes simplex virus 1 (HSV-1) is an intrinsically disordered, conformationally dynamic protein that undergoes liquid-liquid phase separation (LLPS) in vitro Intrinsic disorder may underlie the ability of UL11 to exert multiple functions and bind multiple partners. Sequence analysis suggests that not only all UL11 homologs but also all HSV-1 tegument proteins contain intrinsically disordered regions of different lengths. The presence of intrinsic disorder, and potentially, the ability to form LLPS, may thus be a common feature of the tegument proteins. We hypothesize that tegument assembly may involve the formation of a biomolecular condensate, driven by the heterogeneous mixture of intrinsically disordered tegument proteins.IMPORTANCE Herpesvirus virions contain a unique tegument layer sandwiched between the capsid and lipid envelope and composed of multiple copies of about two dozen viral proteins. However, little is known about the structure of the tegument or how it is assembled. Here, we show that a conserved tegument protein UL11 from herpes simplex virus 1, a prototypical alphaherpesvirus, is an intrinsically disordered protein that undergoes liquid-liquid phase separation in vitro Through sequence analysis, we find intrinsically disordered regions of different lengths in all HSV-1 tegument proteins. We hypothesize that intrinsic disorder is a common characteristic of tegument proteins and propose a new model of tegument as a biomolecular condensate.
Collapse
Affiliation(s)
- Claire M Metrick
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Biochemistry, Tufts School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Andrea L Koenigsberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Tufts School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| |
Collapse
|
11
|
Koenigsberg A, Pitts J, Heldwein E. Identification of Buffer Conditions for Optimal Thermostability and Solubility of Herpesviral Protein UL37 Using the Thermofluor Assay. Bio Protoc 2020; 10:e3662. [DOI: 10.21769/bioprotoc.3662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 03/26/2020] [Accepted: 03/27/2020] [Indexed: 11/02/2022] Open
|
12
|
Diwaker D, Wilson DW. Microtubule-Dependent Trafficking of Alphaherpesviruses in the Nervous System: The Ins and Outs. Viruses 2019; 11:v11121165. [PMID: 31861082 PMCID: PMC6950448 DOI: 10.3390/v11121165] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 12/13/2019] [Accepted: 12/15/2019] [Indexed: 12/12/2022] Open
Abstract
The Alphaherpesvirinae include the neurotropic pathogens herpes simplex virus and varicella zoster virus of humans and pseudorabies virus of swine. These viruses establish lifelong latency in the nuclei of peripheral ganglia, but utilize the peripheral tissues those neurons innervate for productive replication, spread, and transmission. Delivery of virions from replicative pools to the sites of latency requires microtubule-directed retrograde axonal transport from the nerve terminus to the cell body of the sensory neuron. As a corollary, during reactivation newly assembled virions must travel along axonal microtubules in the anterograde direction to return to the nerve terminus and infect peripheral tissues, completing the cycle. Neurotropic alphaherpesviruses can therefore exploit neuronal microtubules and motors for long distance axonal transport, and alternate between periods of sustained plus end- and minus end-directed motion at different stages of their infectious cycle. This review summarizes our current understanding of the molecular details by which this is achieved.
Collapse
Affiliation(s)
- Drishya Diwaker
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA;
| | - Duncan W. Wilson
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA;
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
- Correspondence: ; Tel.: +1-(718)-430-2305
| |
Collapse
|
13
|
Stults AM, Smith GA. The Herpes Simplex Virus 1 Deamidase Enhances Propagation but Is Dispensable for Retrograde Axonal Transport into the Nervous System. J Virol 2019; 93:e01172-19. [PMID: 31462572 PMCID: PMC6819922 DOI: 10.1128/jvi.01172-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 08/19/2019] [Indexed: 02/06/2023] Open
Abstract
Upon replication in mucosal epithelia and transmission to nerve endings, capsids of herpes simplex virus 1 (HSV-1) travel retrogradely within axons to peripheral ganglia, where life-long latent infections are established. A capsid-bound tegument protein, pUL37, is an essential effector of retrograde axonal transport and also houses a deamidase activity that antagonizes innate immune signaling. In this report, we examined whether the deamidase of HSV-1 pUL37 contributes to the neuroinvasive retrograde axonal transport mechanism. We conclude that neuroinvasion is enhanced by the deamidase, but the critical contribution of pUL37 to retrograde axonal transport functions independently of this activity.IMPORTANCE Herpes simplex virus 1 invades the nervous system by entering nerve endings and sustaining long-distance retrograde axonal transport to reach neuronal nuclei in ganglia of the peripheral nervous system. The incoming viral particle carries a deamidase activity on its surface that antagonizes antiviral responses. We examined the contribution of the deamidase to the hallmark neuroinvasive property of this virus.
Collapse
Affiliation(s)
- Austin M Stults
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Gregory A Smith
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| |
Collapse
|
14
|
Carriere J, Rao Y, Liu Q, Lin X, Zhao J, Feng P. Post-translational Control of Innate Immune Signaling Pathways by Herpesviruses. Front Microbiol 2019; 10:2647. [PMID: 31798565 PMCID: PMC6868034 DOI: 10.3389/fmicb.2019.02647] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 10/30/2019] [Indexed: 12/21/2022] Open
Abstract
Herpesviruses constitute a large family of disease-causing DNA viruses. Each herpesvirus strain is capable of infecting particular organisms with a specific cell tropism. Upon infection, pattern recognition receptors (PRRs) recognize conserved viral features to trigger signaling cascades that culminate in the production of interferons and pro-inflammatory cytokines. To invoke a proper immune response while avoiding collateral tissue damage, signaling proteins involved in these cascades are tightly regulated by post-translational modifications (PTMs). Herpesviruses have developed strategies to subvert innate immune signaling pathways in order to ensure efficient viral replication and achieve persistent infection. The ability of these viruses to control the proteins involved in these signaling cascades post-translationally, either directly via virus-encoded enzymes or indirectly through the deregulation of cellular enzymes, has been widely reported. This ability provides herpesviruses with a powerful tool to shut off or restrict host antiviral and inflammatory responses. In this review, we highlight recent findings on the herpesvirus-mediated post-translational control along PRR-mediated signaling pathways.
Collapse
Affiliation(s)
| | | | | | | | | | - Pinghui Feng
- Section of Infection and Immunity, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, United States
| |
Collapse
|
15
|
Grzesik P, Pryce EN, Bhalala A, Vij M, Ahmed R, Etienne L, Perez P, McCaffery JM, Desai APJ. Functional Domains of the Herpes Simplex Virus Type 1 Tegument Protein pUL37: The Amino Terminus is Dispensable for Virus Replication in Tissue Culture. Viruses 2019; 11:E853. [PMID: 31540043 PMCID: PMC6783895 DOI: 10.3390/v11090853] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 09/09/2019] [Accepted: 09/11/2019] [Indexed: 01/01/2023] Open
Abstract
The herpes simplex virus type 1 (HSV-1) UL37 gene encodes for a multifunctional component of the virion tegument, which is necessary for secondary envelopment in the cytoplasm of infected cells, for motility of the viral particle, and for the first steps in the initiation of virus infection. This 120 kDa protein has several known viral interacting partners, including pUL36, gK/pUL20, pUS10, and VP26, and cellular interacting proteins which include TRAF6, RIG-I, and dystonin. These interactions are likely important for the functions of pUL37 at both early and late stages of infection. We employed a genetic approach to determine essential domains and amino acid residues of pUL37 and their associated functions in cellular localization and virion morphogenesis. Using marker-rescue/marker-transfer methods, we generated a library of GFP-tagged pUL37 mutations in the HSV-1 strain KOS genome. Through viral growth and ultra-structural analysis, we discovered that the C-terminus is essential for replication. The N-terminal 480 amino acids are dispensable for replication in cell culture, although serve some non-essential function as viral titers are reduced in the presence of this truncation. Furthermore, the C-terminal 133 amino acids are important in so much that their absence leads to a lethal phenotype. We further probed the carboxy terminal half of pUL37 by alanine scanning mutagenesis of conserved residues among alphaherpesviruses. Mutant viruses were screened for the inability to form plaques-or greatly reduced plaque size-on Vero cells, of which 22 mutations were chosen for additional analysis. Viruses discovered to have the greatest reduction in viral titers on Vero cells were examined by electron microscopy (EM) and by confocal light microscopy for pUL37-EGFP cellular localization. This genetic approach identified both essential and non-essential domains and residues of the HSV-1 UL37 gene product. The mutations identified in this study are recognized as significant candidates for further analysis of the pUL37 function and may unveil previously undiscovered roles and interactions of this essential tegument gene.
Collapse
Affiliation(s)
- Peter Grzesik
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD 21231, USA.
| | - Erin N Pryce
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
| | - Akshay Bhalala
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD 21231, USA.
| | - Mannika Vij
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD 21231, USA.
| | - Ray Ahmed
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD 21231, USA.
| | - Lyns Etienne
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD 21231, USA.
| | - Patric Perez
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA.
| | - And Prashant J Desai
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD 21231, USA.
| |
Collapse
|
16
|
Abstract
The Herpesviridae are structurally complex DNA viruses whose capsids undergo primary envelopment at the inner nuclear membrane and secondary envelopment at organelles in the cytoplasm. In both locations, there is evidence that envelope formation and scission involve the participation of multiple viral proteins and also the cellular ESCRT apparatus. It nevertheless appears that the best-understood viral strategies for ESCRT recruitment, those adopted by the retroviruses and many other families of enveloped RNA viruses, are not utilized by the Herpesviridae, at least during envelopment in the cytoplasm. Thus, although a large number of herpesvirus proteins have been assigned roles in envelopment, there is a dearth of candidates for the acquisition of the ESCRT complex and the control of envelope scission. This review summarizes our current understanding of ESCRT association by enveloped viruses, examines what is known of herpesvirus ESCRT utilization in the nucleus and cytoplasm, and identifies candidate cellular and viral proteins that could link enveloping herpesviruses to cellular ESCRT components.
Collapse
|
17
|
Rana grylio virus 43R encodes an envelope protein involved in virus entry. Virus Genes 2018; 54:779-791. [PMID: 30411182 DOI: 10.1007/s11262-018-1606-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Accepted: 10/06/2018] [Indexed: 12/31/2022]
Abstract
Rana grylio virus (RGV), a member of genus Ranavirus in the family Iridoviridae, is a viral pathogen infecting aquatic animal. RGV 43R has homologues only in Ranavirus and contains a transmembrane (TM) domain, but its role in RGV infection is unknown. In this study, 43R was determined to be associated with virion membrane. The transcripts encoding 43R and the protein itself appeared late in RGV-infected EPC cells and its expression was blocked by viral DNA replication inhibitor, indicating that 43R is a late expressed protein. Subcellular localization showed that 43R-EGFP fusion protein distributed in cytoplasm of EPC cells and that TM domain is essential for its distribution in cytoplasm. 43R-EGFP fusion protein colocalized with viral factories in RGV-infected cells. A recombinant RGV deleting 43R (Δ43R-RGV) was constructed by homologous recombination to investigate its role in virus infection. Compared with wild type RGV, the ability of Δ43R-RGV to induce the cytopathic effect and its virus titers were significantly reduced. Furthermore, it is revealed that 43R deletion significantly inhibited viral entry but did not influence viral DNA replication by measuring and comparing the DNA levels of RGV and Δ43R-RGV in the infected cells at the early stage of infection. RGV neutralization with anti-43R serum reduced the virus titer. Therefore, these data showed that RGV 43R is a late gene that encodes an envelope protein involved in RGV entry.
Collapse
|
18
|
Koenigsberg AL, Heldwein EE. The dynamic nature of the conserved tegument protein UL37 of herpesviruses. J Biol Chem 2018; 293:15827-15839. [PMID: 30166339 PMCID: PMC6187633 DOI: 10.1074/jbc.ra118.004481] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/26/2018] [Indexed: 12/26/2022] Open
Abstract
In all herpesviruses, the space between the capsid shell and the lipid envelope is occupied by the unique tegument layer composed of proteins that, in addition to structural roles, play many other roles in the viral replication. UL37 is a highly conserved tegument protein that has activities ranging from virion morphogenesis to directional capsid trafficking to manipulation of the host innate immune response and binds multiple partners. The N-terminal half of UL37 (UL37N) has a compact bean-shaped α-helical structure that contains a surface region essential for neuroinvasion. However, no biochemical or structural information is currently available for the C-terminal half of UL37 (UL37C) that mediates most of its interactions with multiple binding partners. Here, we show that the C-terminal half of UL37 from pseudorabies virus UL37C is a conformationally flexible monomer composed of an elongated folded core and an unstructured C-terminal tail. This elongated structure, along with that of its binding partner UL36, explains the nature of filamentous tegument structures bridging the capsid and the envelope. We propose that the dynamic nature of UL37 underlies its ability to perform diverse roles during viral replication.
Collapse
Affiliation(s)
- Andrea L Koenigsberg
- From the Department of Molecular Biology and Microbiology and Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Ekaterina E Heldwein
- From the Department of Molecular Biology and Microbiology and Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111
| |
Collapse
|
19
|
Richards AL, Sollars PJ, Pitts JD, Stults AM, Heldwein EE, Pickard GE, Smith GA. The pUL37 tegument protein guides alpha-herpesvirus retrograde axonal transport to promote neuroinvasion. PLoS Pathog 2017; 13:e1006741. [PMID: 29216315 PMCID: PMC5749899 DOI: 10.1371/journal.ppat.1006741] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Revised: 01/02/2018] [Accepted: 11/10/2017] [Indexed: 01/07/2023] Open
Abstract
A hallmark property of the neurotropic alpha-herpesvirinae is the dissemination of infection to sensory and autonomic ganglia of the peripheral nervous system following an initial exposure at mucosal surfaces. The peripheral ganglia serve as the latent virus reservoir and the source of recurrent infections such as cold sores (herpes simplex virus type I) and shingles (varicella zoster virus). However, the means by which these viruses routinely invade the nervous system is not fully understood. We report that an internal virion component, the pUL37 tegument protein, has a surface region that is an essential neuroinvasion effector. Mutation of this region rendered herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV) incapable of spreading by retrograde axonal transport to peripheral ganglia both in culture and animals. By monitoring the axonal transport of individual viral particles by time-lapse fluorescence microscopy, the mutant viruses were determined to lack the characteristic sustained intracellular capsid motion along microtubules that normally traffics capsids to the neural soma. Consistent with the axonal transport deficit, the mutant viruses did not reach sites of latency in peripheral ganglia, and were avirulent. Despite this, viral propagation in peripheral tissues and in cultured epithelial cell lines remained robust. Selective elimination of retrograde delivery to the nervous system has long been sought after as a means to develop vaccines against these ubiquitous, and sometimes devastating viruses. In support of this potential, we find that HSV-1 and PRV mutated in the effector region of pUL37 evoked effective vaccination against subsequent nervous system challenges and encephalitic disease. These findings demonstrate that retrograde axonal transport of the herpesviruses occurs by a virus-directed mechanism that operates by coordinating opposing microtubule motors to favor sustained retrograde delivery of the virus to the peripheral ganglia. The ability to selectively eliminate the retrograde axonal transport mechanism from these viruses will be useful in trans-synaptic mapping studies of the mammalian nervous system, and affords a new vaccination paradigm for human and veterinary neurotropic herpesviruses.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Axonal Transport/genetics
- Axonal Transport/physiology
- Axons/virology
- Ganglia/virology
- Genes, Viral
- Herpesvirus 1, Human/genetics
- Herpesvirus 1, Human/pathogenicity
- Herpesvirus 1, Human/physiology
- Herpesvirus 1, Suid/genetics
- Herpesvirus 1, Suid/pathogenicity
- Herpesvirus 1, Suid/physiology
- Host-Pathogen Interactions/genetics
- Host-Pathogen Interactions/physiology
- Humans
- Male
- Mice
- Mice, Inbred DBA
- Models, Molecular
- Mutation
- Neurons/virology
- Rats
- Rats, Long-Evans
- Viral Structural Proteins/chemistry
- Viral Structural Proteins/genetics
- Viral Structural Proteins/physiology
- Viral Vaccines/genetics
- Virulence/genetics
- Virulence/physiology
- Virus Release/genetics
- Virus Release/physiology
Collapse
Affiliation(s)
- Alexsia L. Richards
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - Patricia J. Sollars
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Jared D. Pitts
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Austin M. Stults
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Gary E. Pickard
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
- Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska
| | - Gregory A. Smith
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
- * E-mail:
| |
Collapse
|
20
|
Molecular Evolution of Herpes Simplex Virus 2 Complete Genomes: Comparison between Primary and Recurrent Infections. J Virol 2017; 91:JVI.00942-17. [PMID: 28931680 DOI: 10.1128/jvi.00942-17] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 09/12/2017] [Indexed: 11/20/2022] Open
Abstract
Herpes simplex virus 1 (HSV-1) and HSV-2 are large, double-stranded DNA viruses that cause lifelong persistent infections characterized by periods of quiescence and recurrent disease. How HSV evolves within an infected individual experiencing multiple episodes of recurrent disease over time is not known. We determined the genome sequences of viruses isolated from two subjects in the Herpevac Trial for Women who experienced primary HSV-2 genital disease and compared them with sequences of viruses isolated from the subsequent fifth or sixth episode of recurrent disease in the same individuals. Each of the HSV-2 genome sequences was initially obtained using next-generation sequencing and completed with Sanger sequencing. Polymorphisms over the entire genomes were mapped, and amino acid variants resulting from nonsynonymous changes were analyzed based on the secondary and tertiary structures of a previously crystallized protein. A phylogenetic reconstruction was used to assess relationships among the four HSV-2 samples, other North American sequences, and reference sequences. Little genetic drift was detected in viruses shed by the same subjects following repeated reactivation events, suggesting strong selective pressure on the viral genome to maintain sequence fidelity during reactivations from its latent state within an individual host. Our results also demonstrate that some primary HSV-2 isolates from North America more closely resemble the HG52 laboratory strain from Scotland than the low-passage-number clinical isolate SD90e from South Africa or laboratory strain 333. Thus, one of the sequences reported here would be a logical choice as a reference strain for inclusion in future studies of North American HSV-2 isolates.IMPORTANCE The extent to which the HSV-2 genome evolves during multiple episodes of reactivation from its latent state within an infected individual is not known. We used next-generation sequencing techniques to determine whole-genome sequences of four viral samples from two subjects in the Herpevac Trial. The sequence of each subject's well-documented primary isolate was compared with the sequence of the isolate from their fifth or sixth episode of recurrent disease. Only 19 genetic polymorphisms unique to the primary or recurrent isolate were identified, 10 in subject A and 9 in subject B. These observations indicate remarkable genetic conservation between primary and recurrent episodes of HSV-2 infection and imply that strong selection pressures exist to maintain the fidelity of the viral genome during repeated reactivations from its latent state. The genome conservation observed also has implications for the potential success of a therapeutic vaccine.
Collapse
|
21
|
Crystal Structure of the N-Terminal Half of the Traffic Controller UL37 from Herpes Simplex Virus 1. J Virol 2017; 91:JVI.01244-17. [PMID: 28768862 DOI: 10.1128/jvi.01244-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 01/23/2023] Open
Abstract
Inner tegument protein UL37 is conserved among all three subfamilies of herpesviruses. Studies of UL37 homologs from two alphaherpesviruses, herpes simplex virus 1 (HSV-1) and pseudorabies virus (PRV), have suggested that UL37 plays an essential albeit poorly defined role in intracellular capsid trafficking. At the same time, HSV and PRV homologs cannot be swapped, which suggests that in addition to a conserved function, UL37 homologs also have divergent virus-specific functions. Accurate dissection of UL37 functions requires detailed maps in the form of atomic-resolution structures. Previously, we reported the crystal structure of the N-terminal half of UL37 (UL37N) from PRV. Here, we report the crystal structure of HSV-1 UL37N. Comparison of the two structures reveals that UL37 homologs differ in their overall shapes, distributions of surface charges, and locations of projecting loops. In contrast, the previously identified R2 surface region is structurally conserved. We propose that within the N-terminal half of UL37, functional conservation is centered within the R2 surface region, whereas divergent structural elements pinpoint regions mediating virus-specific functions and may engage different binding partners. Together, the two structures can now serve as templates for a structure-guided exploration of both conserved and virus-specific functions of UL37.IMPORTANCE The ability to move efficiently within host cell cytoplasm is essential for replication in all viruses. It is especially important in the neuroinvasive alphaherpesviruses, such as human herpes simplex virus 1 (HSV-1), HSV-2, and veterinarian pseudorabies virus (PRV), that infect the peripheral nervous system and have to travel long distances along axons. Capsid movement in these viruses is controlled by capsid-associated tegument proteins, yet their specific roles have not yet been defined. Systematic exploration of the roles of tegument proteins in capsid trafficking requires detailed navigational charts in the form of their three-dimensional structures. Here, we determined the crystal structure of the N-terminal half of a conserved tegument protein, UL37, from HSV-1. This structure, along with our previously reported structure of the UL37 homolog from PRV, provides a much needed 3-dimensional template for the dissection of both conserved and virus-specific functions of UL37 in intracellular capsid trafficking.
Collapse
|
22
|
ORF7 of Varicella-Zoster Virus Is Required for Viral Cytoplasmic Envelopment in Differentiated Neuronal Cells. J Virol 2017; 91:JVI.00127-17. [PMID: 28356523 DOI: 10.1128/jvi.00127-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/24/2017] [Indexed: 12/20/2022] Open
Abstract
Although a varicella-zoster virus (VZV) vaccine has been used for many years, the neuropathy caused by VZV infection is still a major health concern. Open reading frame 7 (ORF7) of VZV has been recognized as a neurotropic gene in vivo, but its neurovirulent role remains unclear. In the present study, we investigated the effect of ORF7 deletion on VZV replication cycle at virus entry, genome replication, gene expression, capsid assembly and cytoplasmic envelopment, and transcellular transmission in differentiated neural progenitor cells (dNPCs) and neuroblastoma SH-SY5Y (dSY5Y) cells. Our results demonstrate that the ORF7 protein is a component of the tegument layer of VZV virions. Deleting ORF7 did not affect viral entry, viral genome replication, or the expression of typical viral genes but clearly impacted cytoplasmic envelopment of VZV capsids, resulting in a dramatic increase of envelope-defective particles and a decrease in intact virions. The defect was more severe in differentiated neuronal cells of dNPCs and dSY5Y. ORF7 deletion also impaired transmission of ORF7-deficient virus among the neuronal cells. These results indicate that ORF7 is required for cytoplasmic envelopment of VZV capsids, virus transmission among neuronal cells, and probably the neuropathy induced by VZV infection.IMPORTANCE The neurological damage caused by varicella-zoster virus (VZV) reactivation is commonly manifested as clinical problems. Thus, identifying viral neurovirulent genes and characterizing their functions are important for relieving VZV related neurological complications. ORF7 has been previously identified as a potential neurotropic gene, but its involvement in VZV replication is unclear. In this study, we found that ORF7 is required for VZV cytoplasmic envelopment in differentiated neuronal cells, and the envelopment deficiency caused by ORF7 deletion results in poor dissemination of VZV among neuronal cells. These findings imply that ORF7 plays a role in neuropathy, highlighting a potential strategy to develop a neurovirulence-attenuated vaccine against chickenpox and herpes zoster and providing a new target for intervention of neuropathy induced by VZV.
Collapse
|
23
|
Zhao J, Zeng Y, Xu S, Chen J, Shen G, Yu C, Knipe D, Yuan W, Peng J, Xu W, Zhang C, Xia Z, Feng P. A Viral Deamidase Targets the Helicase Domain of RIG-I to Block RNA-Induced Activation. Cell Host Microbe 2016; 20:770-784. [PMID: 27866900 DOI: 10.1016/j.chom.2016.10.011] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/08/2016] [Accepted: 10/07/2016] [Indexed: 12/31/2022]
Abstract
RIG-I detects double-stranded RNA (dsRNA) to trigger antiviral cytokine production. Protein deamidation is emerging as a post-translational modification that chiefly regulates protein function. We report here that UL37 of herpes simplex virus 1 (HSV-1) is a protein deamidase that targets RIG-I to block RNA-induced activation. Mass spectrometry analysis identified two asparagine residues in the helicase 2i domain of RIG-I that were deamidated upon UL37 expression or HSV-1 infection. Deamidation rendered RIG-I unable to sense viral dsRNA, thus blocking its ability to trigger antiviral immune responses and restrict viral replication. Purified full-length UL37 and its carboxyl-terminal fragment were sufficient to deamidate RIG-I in vitro. Uncoupling RIG-I deamidation from HSV-1 infection, by engineering deamidation-resistant RIG-I or introducing deamidase-deficient UL37 into the HSV-1 genome, restored RIG-I activation and antiviral immune signaling. Our work identifies a viral deamidase and extends the paradigm of deamidation-mediated suppression of innate immunity by microbial pathogens.
Collapse
Affiliation(s)
- Jun Zhao
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Yi Zeng
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Simin Xu
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Jie Chen
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA; Division of General Surgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Guobo Shen
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Caiqun Yu
- Department of Chemistry, Dornsife College of Arts, Letters, and Sciences, University of Southern California, LJS 369, 840 Downey Way, Los Angeles, CA 90089, USA
| | - David Knipe
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Weiming Yuan
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA
| | - Jian Peng
- Division of General Surgery, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Wenqing Xu
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Chao Zhang
- Department of Chemistry, Dornsife College of Arts, Letters, and Sciences, University of Southern California, LJS 369, 840 Downey Way, Los Angeles, CA 90089, USA
| | - Zanxian Xia
- State Key Laboratory of Medical Genetics and School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Pinghui Feng
- Department of Molecular Microbiology and Immunology, Norris Comprehensive Cancer Center, University of Southern California, 1441 Eastlake Street, Los Angeles, CA 90033, USA.
| |
Collapse
|
24
|
Herpes Simplex Virus 1 UL37 Protein Tyrosine Residues Conserved among All Alphaherpesviruses Are Required for Interactions with Glycoprotein K, Cytoplasmic Virion Envelopment, and Infectious Virus Production. J Virol 2016; 90:10351-10361. [PMID: 27630233 PMCID: PMC5105669 DOI: 10.1128/jvi.01202-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 08/31/2016] [Indexed: 12/18/2022] Open
Abstract
The herpes simplex virus 1 (HSV-1) UL37 protein functions in virion envelopment at trans-Golgi membranes, as well as in retrograde and anterograde transport of virion capsids. Recently, we reported that UL37 interacts with glycoprotein K (gK) and its interacting partner protein UL20 (N. Jambunathan, D. Chouljenko, P. Desai, A. S. Charles, R. Subramanian, V. N. Chouljenko, and K. G. Kousoulas, J Virol 88:5927–5935, 2014, http://dx.doi.org/10.1128/JVI.00278-14), facilitating cytoplasmic virion envelopment. Alignment of UL37 homologs encoded by alphaherpesviruses revealed the presence of highly conserved residues in the central portion of the UL37 protein. A cadre of nine UL37 site-specific mutations were produced and tested for their ability to inhibit virion envelopment and infectious virus production. Complementation analysis revealed that replacement of tyrosines 474 and 480 with alanine failed to complement the UL37-null virus, while all other mutated UL37 genes complemented the virus efficiently. The recombinant virus DC474-480 constructed with tyrosines 474, 476, 477, and 480 mutated to alanine residues produced a gK-null-like phenotype characterized by the production of very small plaques and accumulation of capsids in the cytoplasm of infected cells. Recombinant viruses having either tyrosine 476 or 477 replaced with alanine produced a wild-type phenotype. Immunoprecipitation assays revealed that replacement of all four tyrosines with alanines substantially reduced the ability of gK to interact with UL37. Alignment of HSV UL37 with the human cytomegalovirus and Epstein-Barr virus UL37 homologs revealed that Y480 was conserved only for alphaherpesviruses. Collectively, these results suggest that the UL37 conserved tyrosine 480 residue plays a crucial role in interactions with gK to facilitate cytoplasmic virion envelopment and infectious virus production. IMPORTANCE The HSV-1 UL37 protein is conserved among all herpesviruses, functions in both retrograde and anterograde transport of virion capsids, and plays critical roles in cytoplasmic virion envelopment by interacting with gK. We show here that UL37 tyrosine residues conserved among all alphaherpesviruses serve critical roles in cytoplasmic virion envelopment and interactions with gK.
Collapse
|
25
|
Herpes Simplex Virus Capsid Localization to ESCRT-VPS4 Complexes in the Presence and Absence of the Large Tegument Protein UL36p. J Virol 2016; 90:7257-7267. [PMID: 27252536 PMCID: PMC4984650 DOI: 10.1128/jvi.00857-16] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 05/24/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED UL36p (VP1/2) is the largest protein encoded by herpes simplex virus 1 (HSV-1) and resides in the innermost layer of tegument, the complex protein layer between the capsid and envelope. UL36p performs multiple functions in the HSV life cycle, including a critical but unknown role in capsid cytoplasmic envelopment. We tested whether UL36p is essential for envelopment because it is required to engage capsids with the cellular ESCRT/Vps4 apparatus. A green fluorescent protein (GFP)-fused form of the dominant negative ATPase Vps4-EQ was used to irreversibly tag ESCRT envelopment sites during infection by UL36p-expressing and UL36-null HSV strains. Using fluorescence microscopy and scanning electron microscopy, we quantitated capsid/Vps4-EQ colocalization and examined the ultrastructure of the corresponding viral assembly intermediates. We found that loss of UL36p resulted in a two-thirds reduction in the efficiency of capsid/Vps4-EQ association but that the remaining UL36p-null capsids were still able to engage the ESCRT envelopment apparatus. It appears that although UL36p helps to couple HSV capsids to the ESCRT pathway, this is likely not the sole reason for its absolute requirement for envelopment. IMPORTANCE Envelopment of the HSV capsid is essential for the assembly of an infectious virion and requires the complex interplay of a large number of viral and cellular proteins. Critical to envelope assembly is the virally encoded protein UL36p, whose function is unknown. Here we test the hypothesis that UL36p is essential for the recruitment of cellular ESCRT complexes, which are also known to be required for envelopment.
Collapse
|
26
|
Bigalke JM, Heldwein EE. Expression, Purification and Crystallization of the Herpesvirus Nuclear Egress Complex (NEC). Bio Protoc 2016; 6:e1872. [PMID: 28042595 DOI: 10.21769/bioprotoc.1872] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
The protocol describes the production and crystallization of the soluble form of the nuclear egress complex (NEC) from Herpes simplex virus 1 and Pseudorabies virus. The NEC is a heterodimer that consists of conserved proteins UL31 and UL34. NEC oligomerization deforms the inner nuclear membrane around the capsid in infected cells, thereby mediating capsid budding into the perinuclear space during nuclear egress. We have successfully developed a protocol for large-scale preparation of highly pure NEC from two different viruses in a prokaryotic expression system, which enabled us to crystallize these viral protein complexes and determine their structures. This procedure may be adapted to purify and crystallize other soluble protein complexes.
Collapse
Affiliation(s)
- Janna M Bigalke
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, USA
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, USA
| |
Collapse
|
27
|
Metrick CM, Heldwein EE. Novel Structure and Unexpected RNA-Binding Ability of the C-Terminal Domain of Herpes Simplex Virus 1 Tegument Protein UL21. J Virol 2016; 90:5759-69. [PMID: 27053559 PMCID: PMC4886797 DOI: 10.1128/jvi.00475-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 04/01/2016] [Indexed: 02/08/2023] Open
Abstract
UNLABELLED Proteins forming the tegument layers of herpesviral virions mediate many essential processes in the viral replication cycle, yet few have been characterized in detail. UL21 is one such multifunctional tegument protein and is conserved among alphaherpesviruses. While UL21 has been implicated in many processes in viral replication, ranging from nuclear egress to virion morphogenesis to cell-cell spread, its precise roles remain unclear. Here we report the 2.7-Å crystal structure of the C-terminal domain of herpes simplex virus 1 (HSV-1) UL21 (UL21C), which has a unique α-helical fold resembling a dragonfly. Analysis of evolutionary conservation patterns and surface electrostatics pinpointed four regions of potential functional importance on the surface of UL21C to be pursued by mutagenesis. In combination with the previously determined structure of the N-terminal domain of UL21, the structure of UL21C provides a 3-dimensional framework for targeted exploration of the multiple roles of UL21 in the replication and pathogenesis of alphaherpesviruses. Additionally, we describe an unanticipated ability of UL21 to bind RNA, which may hint at a yet unexplored function. IMPORTANCE Due to the limited genomic coding capacity of viruses, viral proteins are often multifunctional, which makes them attractive antiviral targets. Such multifunctionality, however, complicates their study, which often involves constructing and characterizing null mutant viruses. Systematic exploration of these multifunctional proteins requires detailed road maps in the form of 3-dimensional structures. In this work, we determined the crystal structure of the C-terminal domain of UL21, a multifunctional tegument protein that is conserved among alphaherpesviruses. Structural analysis pinpointed surface areas of potential functional importance that provide a starting point for mutagenesis. In addition, the unexpected RNA-binding ability of UL21 may expand its functional repertoire. The structure of UL21C and the observation of its RNA-binding ability are the latest additions to the navigational chart that can guide the exploration of the multiple functions of UL21.
Collapse
Affiliation(s)
- Claire M Metrick
- Department of Molecular Biology and Microbiology and Graduate Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USAUniversity of California, Irvine
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology and Graduate Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USAUniversity of California, Irvine
| |
Collapse
|
28
|
Deletion of Murid Herpesvirus 4 ORF63 Affects the Trafficking of Incoming Capsids toward the Nucleus. J Virol 2015; 90:2455-72. [PMID: 26676769 DOI: 10.1128/jvi.02942-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 12/08/2015] [Indexed: 12/19/2022] Open
Abstract
UNLABELLED Gammaherpesviruses are important human and animal pathogens. Despite the fact that they display the classical architecture of herpesviruses, the function of most of their structural proteins is still poorly defined. This is especially true for tegument proteins. Interestingly, a potential role in immune evasion has recently been proposed for the tegument protein encoded by Kaposi's sarcoma-associated herpesvirus open reading frame 63 (ORF63). To gain insight about the roles of ORF63 in the life cycle of a gammaherpesvirus, we generated null mutations in the ORF63 gene of murid herpesvirus 4 (MuHV-4). We showed that disruption of ORF63 was associated with a severe MuHV-4 growth deficit both in vitro and in vivo. The latter deficit was mainly associated with a defect of replication in the lung but did not affect the establishment of latency in the spleen. From a functional point of view, inhibition of caspase-1 or the inflammasome did not restore the growth of the ORF63-deficient mutant, suggesting that the observed deficit was not associated with the immune evasion mechanism identified previously. Moreover, this growth deficit was also not associated with a defect in virion egress from the infected cells. In contrast, it appeared that MuHV-4 ORF63-deficient mutants failed to address most of their capsids to the nucleus during entry into the host cell, suggesting that ORF63 plays a role in capsid movement. In the future, ORF63 could therefore be considered a target to block gammaherpesvirus infection at a very early stage of the infection. IMPORTANCE The important diseases caused by gammaherpesviruses in human and animal populations justify a better understanding of their life cycle. In particular, the role of most of their tegument proteins is still largely unknown. In this study, we used murid herpesvirus 4, a gammaherpesvirus infecting mice, to decipher the role of the protein encoded by the viral ORF63 gene. We showed that the absence of this protein is associated with a severe growth deficit both in vitro and in vivo that was mainly due to impaired migration of viral capsids toward the nucleus during entry. Together, our results provide new insights about the life cycle of gammaherpesviruses and could allow the development of new antiviral strategies aimed at blocking gammaherpesvirus infection at the very early stages.
Collapse
|
29
|
Owen DJ, Crump CM, Graham SC. Tegument Assembly and Secondary Envelopment of Alphaherpesviruses. Viruses 2015; 7:5084-114. [PMID: 26393641 PMCID: PMC4584305 DOI: 10.3390/v7092861] [Citation(s) in RCA: 134] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 08/22/2015] [Accepted: 08/26/2015] [Indexed: 02/07/2023] Open
Abstract
Alphaherpesviruses like herpes simplex virus are large DNA viruses characterized by their ability to establish lifelong latent infection in neurons. As for all herpesviruses, alphaherpesvirus virions contain a protein-rich layer called "tegument" that links the DNA-containing capsid to the glycoprotein-studded membrane envelope. Tegument proteins mediate a diverse range of functions during the virus lifecycle, including modulation of the host-cell environment immediately after entry, transport of virus capsids to the nucleus during infection, and wrapping of cytoplasmic capsids with membranes (secondary envelopment) during virion assembly. Eleven tegument proteins that are conserved across alphaherpesviruses have been implicated in the formation of the tegument layer or in secondary envelopment. Tegument is assembled via a dense network of interactions between tegument proteins, with the redundancy of these interactions making it challenging to determine the precise function of any specific tegument protein. However, recent studies have made great headway in defining the interactions between tegument proteins, conserved across alphaherpesviruses, which facilitate tegument assembly and secondary envelopment. We summarize these recent advances and review what remains to be learned about the molecular interactions required to assemble mature alphaherpesvirus virions following the release of capsids from infected cell nuclei.
Collapse
Affiliation(s)
- Danielle J Owen
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Colin M Crump
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
| | - Stephen C Graham
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
| |
Collapse
|
30
|
Diefenbach RJ. Conserved tegument protein complexes: Essential components in the assembly of herpesviruses. Virus Res 2015; 210:308-17. [PMID: 26365681 DOI: 10.1016/j.virusres.2015.09.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 09/07/2015] [Accepted: 09/08/2015] [Indexed: 11/18/2022]
Abstract
One of the structural components of herpesviruses is a protein layer called the tegument. Several of the tegument proteins are highly conserved across the herpesvirus family and serve as a logical focus for defining critical interactions required for viral assembly. A number of studies have helped to elucidate a role for conserved tegument proteins in the process of secondary envelopment during the course of herpesviral assembly. This review highlights how these tegument proteins directly contribute to bridging the nucleocapsid and envelope of virions during secondary envelopment.
Collapse
Affiliation(s)
- Russell J Diefenbach
- Centre for Virus Research, Westmead Millennium Institute for Medical Research, The University of Sydney, Westmead, NSW 2145, Australia.
| |
Collapse
|
31
|
Herpes Simplex Virus Capsid-Organelle Association in the Absence of the Large Tegument Protein UL36p. J Virol 2015; 89:11372-82. [PMID: 26339048 DOI: 10.1128/jvi.01893-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 08/25/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED UL36p (VP1/2) is the largest protein encoded by herpes simplex virus 1 (HSV-1) and resides in the innermost layer of the viral tegument, lying between the capsid and the envelope. UL36p performs multiple functions in the HSV life cycle, including an essential role in cytoplasmic envelopment. We earlier described the isolation of a virion-associated cytoplasmic membrane fraction from HSV-infected cells. Biochemical and ultrastructural analyses showed that the organelles in this buoyant fraction contain enveloped infectious HSV particles in their lumens and naked capsids docked to their cytoplasmic surfaces. These organelles can also recruit molecular motors and transport their cargo virions along microtubules in vitro. Here we examine the properties of these HSV-associated organelles in the absence of UL36p. We find that while capsid envelopment is clearly defective, a subpopulation of capsids nevertheless still associate with the cytoplasmic faces of these organelles. The existence of these capsid-membrane structures was confirmed by subcellular fractionation, immunocytochemistry, lipophilic dye fluorescence microscopy, thin-section electron microscopy, and correlative light and electron microscopy. We conclude that capsid-membrane binding can occur in the absence of UL36p and propose that this association may precede the events of UL36p-driven envelopment. IMPORTANCE Membrane association and envelopment of the HSV capsid are essential for the assembly of an infectious virion. Envelopment involves the complex interplay of a large number of viral and cellular proteins; however, the function of most of them is unknown. One example of this is the viral protein UL36p, which is clearly essential for envelopment but plays a poorly understood role. Here we demonstrate that organelles utilized for HSV capsid envelopment still accumulate surface-bound capsids in the absence of UL36p. We propose that UL36p-independent binding of capsids to organelles occurs prior to the function of UL36p in capsid envelopment.
Collapse
|
32
|
Human Cytomegalovirus pUL47 Modulates Tegumentation and Capsid Accumulation at the Viral Assembly Complex. J Virol 2015; 89:7314-28. [PMID: 25948747 DOI: 10.1128/jvi.00603-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 04/30/2015] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED Human cytomegalovirus (HCMV) tegument protein pUL47 is an interaction partner of pUL48 and highly conserved among herpesviruses. It is closely associated with the capsid and has an important function early in infection. Here, we report a specific role of pUL47 in the tegumentation of capsids in the cytoplasm. A newly generated mutant virus (TB-47stop), in which expression of pUL47 is blocked, exhibited a severe impairment in cell-to-cell spread and release of infectivity from infected cells. Ultrastructural analysis of TB-47stop-infected cells clearly showed cytoplasmic accumulations of nonenveloped capsids that were only partially tegumented, indicating that these capsids failed to complete tegumentation. Nevertheless, these accumulations were positive for HCMV inner tegument proteins pp150 and pUL48, suggesting that their attachment to capsids occurs independently of pUL47. Despite these morphological alterations, fully enveloped virus particles were found in the extracellular space and at the viral assembly complex (vAC) of TB-47stop-infected cells, indicating that pUL47 is not essential for the generation of virions. We confirmed findings that incorporation of pUL48 into virions is impaired in the absence of pUL47. Interestingly, pUL47 exhibited a strong nuclear localization in transfected cells, whereas it was found exclusively at the vAC in the context of virus infection. Colocalization of pUL47 and pUL48 at the vAC is consistent with their interaction. We also found a shift to a more nuclear localization of pUL47 when the expression of pUL48 was reduced. Summarizing our results, we hypothesize that pUL48 directs pUL47 to the vAC to promote tegumentation and secondary envelopment of capsids. IMPORTANCE Generation of infectious HCMV particles requires an organized and multistep process involving the action of several viral and cellular proteins as well as protein-protein interactions. A better understanding of these processes is important for understanding the biology of HCMV and may help to identify targets for antiviral intervention. Here, we identified tegument protein pUL47 to function in tegumentation and proper trafficking of capsids during late phases of infection. Although pUL47 is not essential for the generation and release of infectious virions, its absence led to massive accumulations of partially tegumented capsids at the cell periphery. Detection of pUL48 at these accumulations indicated a pUL47-independent attachment of pUL48 to the capsid. On the other hand, localization of pUL47 to the vAC during infection appeared to be dependent on tegument protein pUL48, which suggests an intricate interplay of these proteins for normal generation of infectious virus progeny.
Collapse
|
33
|
The unusual fold of herpes simplex virus 1 UL21, a multifunctional tegument protein. J Virol 2014; 89:2979-84. [PMID: 25540382 DOI: 10.1128/jvi.03516-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UL21 is a conserved protein in the tegument of alphaherpesviruses and has multiple important albeit poorly understood functions in viral replication and pathogenesis. To provide a roadmap for exploration of the multiple roles of UL21, we determined the crystal structure of its conserved N-terminal domain from herpes simplex virus 1 to 2.0-Å resolution, which revealed a novel sail-like protein fold. Evolutionarily conserved surface patches highlight residues of potential importance for future targeting by mutagenesis.
Collapse
|
34
|
Diefenbach RJ, Fraefel C, Cunningham AL. The interaction of HSV-1 tegument proteins pUL36 and pUL37: a novel target for antivirals that inhibit viral assembly. Future Virol 2014. [DOI: 10.2217/fvl.14.56] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Russell J Diefenbach
- Centre for Virus Research, Westmead Millennium Institute, The University of Sydney & Westmead Hospital, Westmead, NSW 2145, Australia
| | - Cornel Fraefel
- Institute of Virology, University of Zurich, 8057 Zurich, Switzerland
| | - Anthony L Cunningham
- Centre for Virus Research, Westmead Millennium Institute, The University of Sydney & Westmead Hospital, Westmead, NSW 2145, Australia
| |
Collapse
|
35
|
Recovery of an HMWP/hmwBP (pUL48/pUL47) complex from virions of human cytomegalovirus: subunit interactions, oligomer composition, and deubiquitylase activity. J Virol 2014; 88:8256-67. [PMID: 24829352 DOI: 10.1128/jvi.00971-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED We report that the human cytomegalovirus (HCMV) high-molecular-weight tegument protein (HMWP, pUL48; 253 kDa) and the HMWP-binding protein (hmwBP, pUL47; 110 kDa) can be recovered as a complex from virions disrupted by treatment with 50 mM Tris (pH 7.5), 0.5 M NaCl, 0.5% NP-40, and 10 mM dithiothreitol [DTT]. The subunit ratio of the complex approximates 1:1, with a shape and structure consistent with an elongated heterodimer. The HMWP/hmwBP complex was corroborated by reciprocal coimmunoprecipitation experiments using antipeptide antibodies and lysates from both infected cells and disrupted virus particles. An interaction of the amino end of pUL48 (amino acids [aa] 322 to 754) with the carboxyl end of pUL47 (aa 693 to 982) was identified by fragment coimmunoprecipitation experiments, and a head-to-tail self-interaction of hmwBP was also observed. The deubiquitylating activity of pUL48 is retained in the isolated complex, which cleaves K11, K48, and K63 ubiquitin isopeptide linkages. IMPORTANCE Human cytomegalovirus (HCMV, or human herpesvirus 5 [HHV-5]) is a large DNA-containing virus that belongs to the betaherpesvirus subfamily and is a clinically important pathogen. Defining the constituent elements of its mature form, their organization within the particle, and the assembly process by which it is produced are fundamental to understanding the mechanisms of herpesvirus infection and developing drugs and vaccines against them. In this study, we report isolating a complex of two large proteins encoded by HCMV open reading frames (ORFs) UL47 and UL48 and identifying the binding domains responsible for their interaction with each other and of pUL47 with itself. Our calculations indicate that the complex is a rod-shaped heterodimer. Additionally, we determined that the ubiquitin-specific protease activity of the ORF UL48 protein was functional in the complex, cleaving K11-, K48-, and K63-linked ubiquitin dimers. This information builds on and extends our understanding of the HCMV tegument protein network that is required to interface the HCMV envelope and capsid.
Collapse
|