Structure of Equine Infectious Anemia Virus Matrix Protein

ABSTRACT The Gag polyprotein is key to the budding of retroviruses from host cells and is cleaved upon virion maturation, the N-terminal membrane-binding domain forming the matrix protein (MA). The 2.8-Å resolution crystal structure of MA of equine infectious anemia virus (EIAV), a lentivirus, reveals that, despite showing no sequence similarity, more than half of the molecule can be superimposed on the MAs of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV). However, unlike the structures formed by HIV-1 and SIV MAs, the oligomerization state observed is not trimeric. We discuss the potential of this molecule for membrane binding in the light of conformational differences between EIAV MA and HIV or SIV MA.

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Functional Replacement and Positional Dependence of Homologous and Heterologous L Domains in Equine Infectious Anemia Virus Replication

Journal of Virology ◽

10.1128/jvi.76.4.1569-1577.2002 ◽

2002 ◽

Vol 76 (4) ◽

pp. 1569-1577 ◽

Cited By ~ 57

Author(s):

Feng Li ◽

Chaoping Chen ◽

Bridget A. Puffer ◽

Ronald C. Montelaro

Keyword(s):

Life Cycle ◽

Virus Particle ◽

Matrix Protein ◽

Particle Production ◽

Equine Infectious Anemia Virus ◽

Virus Infectivity ◽

Gag Protein ◽

Equine Infectious Anemia ◽

Anemia Virus ◽

Hiv 1

ABSTRACT We have previously demonstrated by Gag polyprotein budding assays that the Gag p9 protein of equine infectious anemia virus (EIAV) utilizes a unique YPDL motif as a late assembly domain (L domain) to facilitate release of the budding virus particle from the host cell plasma membrane (B. A. Puffer, L. J. Parent, J. W. Wills, and R. C. Montelaro, J. Virol. 71:6541-6546, 1997). To characterize in more detail the role of the YPDL L domain in the EIAV life cycle, we have examined the replication properties of a series of EIAV proviral mutants in which the parental YPDL L domain was replaced by a human immunodeficiency virus type 1 (HIV-1) PTAP or Rous sarcoma virus (RSV) PPPY L domain in the p9 protein or by proviruses in which the parental YPDL or HIV-1 PTAP L domain was inserted in the viral matrix protein. The replication properties of these L-domain variants were examined with respect to Gag protein expression and processing, virus particle production, and virus infectivity. The data from these experiments indicate that (i) the YPDL L domain of p9 is required for replication competence (assembly and infectivity) in equine cell cultures, including the natural target equine macrophages; (ii) all of the functions of the YPDL L domain in the EIAV life cycle can be replaced by replacement of the parental YPDL sequence in p9 with the PTAP L-domain segment of HIV-1 p6 or the PPPY L domain of RSV p2b; and (iii) the assembly, but not infectivity, functions of the EIAV proviral YPDL substitution mutants can be partially rescued by inclusions of YPDL and PTAP L-domain sequences in the C-terminal region of the EIAV MA protein. Taken together, these data demonstrate that the EIAV YPDL L domain mediates distinct functions in viral budding and infectivity and that the HIV-1 PTAP and RSV PPPY L domains can effectively facilitate these dual replication functions in the context of the p9 protein. In light of the fact that YPDL, PTAP, and PPPY domains evidently have distinct characteristic binding specificities, these observations may indicate different portals into common cellular processes that mediate EIAV budding and infectivity, respectively.

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Equine Infectious Anemia Virus Gag Assembly and Export Are Directed by Matrix Protein throughtrans-Golgi Networks and Cellular Vesicles

Journal of Virology ◽

10.1128/jvi.02814-15 ◽

2015 ◽

Vol 90 (4) ◽

pp. 1824-1838 ◽

Cited By ~ 7

Author(s):

Zeli Zhang ◽

Jian Ma ◽

Xiang Zhang ◽

Chao Su ◽

Qiu-Cheng Yao ◽

...

Keyword(s):

Plasma Membrane ◽

Matrix Protein ◽

Equine Infectious Anemia Virus ◽

Multivesicular Bodies ◽

Microtubule Depolymerization ◽

N Terminus ◽

Equine Infectious Anemia ◽

Anemia Virus ◽

Gag Assembly ◽

Hiv 1

ABSTRACTGag intracellular assembly and export are very important processes for lentiviruses replication. Previous studies have demonstrated that equine infectious anemia virus (EIAV) matrix (MA) possesses distinct phosphoinositide affinity compared with HIV-1 MA and that phosphoinositide-mediated targeting to peripheral and internal membranes is a critical factor in EIAV assembly and release. In this study, we compared the cellular assembly sites of EIAV and HIV-1. We observed that the assembly of EIAV particles occurred on interior cellular membranes, while HIV-1 was targeted to the plasma membrane (PM) for assembly. Then, we determined that W7 and K9 in the EIAV MA N terminus were essential for Gag assembly and release but did not affect the cellular distribution of Gag. The replacement of EIAV MA with HIV-1 MA directed chimeric Gag to the PM but severely impaired Gag release. MA structural analysis indicated that the EIAV and HIV-1 MAs had similar spatial structures but that helix 1 of the EIAV MA was closer to loop 2. Further investigation indicated that EIAV Gag accumulated in thetrans-Golgi network (TGN) but not the early and late endosomes. The 9 N-terminal amino acids of EIAV MA harbored the signal that directed Gag to the TGN membrane system. Additionally, we demonstrated that EIAV particles were transported to the extracellular space by the cellular vesicle system. This type of EIAV export was not associated with multivesicular bodies or microtubule depolymerization but could be inhibited by the actin-depolymerizing drug cytochalasin D, suggesting that dynamic actin depolymerization may be associated with EIAV production.IMPORTANCEIn previous studies, EIAV Gag was reported to localize to both the cell interior and the plasma membrane. Here, we demonstrate that EIAV likely uses the TGN as the assembly site in contrast to HIV-1, which is targeted to the PM for assembly. These distinct assembly features are determined by the MA domain. We also identified two sites in the N terminus of EIAV MA that were important for Gag assembly and release. Furthermore, the observation of EIAV transport by cellular vesicles but not by multivesicular bodies sheds light on the mechanisms underlying EIAV cellular replication.

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Distinct Intracellular Trafficking of Equine Infectious Anemia Virus and Human Immunodeficiency Virus Type 1 Gag during Viral Assembly and Budding Revealed by Bimolecular Fluorescence Complementation Assays

Journal of Virology ◽

10.1128/jvi.00431-07 ◽

2007 ◽

Vol 81 (20) ◽

pp. 11226-11235 ◽

Cited By ~ 33

Author(s):

Jing Jin ◽

Timothy Sturgeon ◽

Chaoping Chen ◽

Simon C. Watkins ◽

Ora A. Weisz ◽

...

Keyword(s):

Nuclear Export ◽

Equine Infectious Anemia Virus ◽

Bimolecular Fluorescence Complementation ◽

Immunodeficiency Virus ◽

Equine Infectious Anemia ◽

Cellular Pathways ◽

Anemia Virus ◽

Gag Assembly ◽

Hiv 1

ABSTRACT Retroviral Gag polyproteins are necessary and sufficient for virus budding. Numerous studies of human immunodeficiency virus type 1 (HIV-1) Gag assembly and budding mechanisms have been reported, but relatively little is known about these fundamental pathways among animal lentiviruses. While there may be a general assumption that lentiviruses share common assembly mechanisms, studies of equine infectious anemia virus (EIAV) have indicated alternative cellular pathways and cofactors employed among lentiviruses for assembly and budding. In the current study, we used bimolecular fluorescence complementation to characterize and compare assembly sites and budding efficiencies of EIAV and HIV-1 Gag in both human and rodent cells. The results of these studies demonstrated that replacing the natural RNA nuclear export element (Rev-response element [RRE]) used by HIV-1 and EIAV with the hepatitis B virus posttranscriptional regulatory element (PRE) altered HIV-1, but not EIAV, Gag assembly sites and budding efficiency in human cells. Consistent with this novel observation, different assembly sites were revealed in human cells for Rev-dependent EIAV and HIV-1 Gag polyproteins. In rodent cells, Rev-dependent HIV-1 Gag assembly and budding were blocked, but changing RRE to PRE rescued HIV-1 Gag assembly and budding. In contrast, EIAV Gag polyproteins synthesized from mRNA exported via either Rev-dependent or PRE-dependent mechanisms were able to assemble and bud efficiently in rodent cells. Taken together, our results suggest that lentivirus assembly and budding are regulated by the RNA nuclear export pathway and that alternative cellular pathways can be adapted for lentiviral Gag assembly and budding.

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Replication of Equine Infectious Anemia Virus in Engineered Mouse NIH 3T3 Cells

Journal of Virology ◽

10.1128/jvi.01883-08 ◽

2008 ◽

Vol 83 (4) ◽

pp. 2034-2037 ◽

Cited By ~ 5

Author(s):

Baoshan Zhang ◽

Ronald C. Montelaro

Keyword(s):

Equine Infectious Anemia Virus ◽

3T3 Cells ◽

Cyclin T1 ◽

Immunodeficiency Virus ◽

Equine Infectious Anemia ◽

Anemia Virus ◽

Nih 3T3 ◽

First Time ◽

Hiv 1 ◽

Nih 3T3 Cells

ABSTRACT We employed the equine lentivirus equine infectious anemia virus (EIAV) to investigate the cellular restrictions for lentivirus replication in murine NIH 3T3 cells. The results of these studies demonstrate that NIH 3T3 cells expressing the EIAV receptor ELR1 and equine cyclin T1 supported productive replication of EIAV and produced infectious virions at levels similar to those found in a reference permissive equine cell line. The studies presented here demonstrate, for the first time, differential levels of restriction for EIAV and human immunodeficiency virus type 1 (HIV-1) replication in murine cells and suggest that these differences can be exploited to reveal critical virus-cell interactions required for HIV-1 assembly and budding of lentivirus particles.

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Gag Protein Epitopes Recognized by CD4+T-Helper Lymphocytes from Equine Infectious Anemia Virus-Infected Carrier Horses

Journal of Virology ◽

10.1128/jvi.73.5.4257-4265.1999 ◽

1999 ◽

Vol 73 (5) ◽

pp. 4257-4265 ◽

Cited By ~ 10

Author(s):

S. M. Lonning ◽

W. Zhang ◽

T. C. McGuire

Keyword(s):

Equine Infectious Anemia Virus ◽

Mononuclear Cells ◽

Sequence Similarity ◽

Peptide Vaccine ◽

T Helper ◽

Gag Protein ◽

Immunodeficiency Virus ◽

Equine Infectious Anemia ◽

Anemia Virus ◽

Th Lymphocytes

ABSTRACT Antigen-specific T-helper (Th) lymphocytes are critical for the development of antiviral humoral responses and the expansion of cytotoxic T lymphocytes (CTL). Identification of relevant Th lymphocyte epitopes remains an important step in the development of an efficacious subunit peptide vaccine against equine infectious anemia virus (EIAV), a naturally occurring lentivirus of horses. This study describes Th lymphocyte reactivity in EIAV carrier horses to two proteins, p26 and p15, encoded by the relatively conserved EIAV gag gene. Using partially overlapping peptides, multideterminant and possibly promiscuous epitopes were identified within p26. One peptide was identified which reacted with peripheral blood mononuclear cells (PBMC) from all five EIAV-infected horses, and three other peptides were identified which reacted with PBMC from four of five EIAV-infected horses. Four additional peptides containing both CTL and Th lymphocyte epitopes were also identified. Multiple epitopes were recognized in a region corresponding to the major homology region of the human immunodeficiency virus, a region with significant sequence similarity to other lentiviruses including simian immunodeficiency virus, puma lentivirus, feline immunodeficiency virus, Jembrana disease virus, visna virus, and caprine arthritis encephalitis virus. PBMC reactivity to p15 peptides from EIAV carrier horses also occurred. Multiple p15 peptides were shown to be reactive, but not all infected horses had Th lymphocytes recognizing p15 epitopes. The identification of peptides reactive with PBMC from outbred horses, some of which encoded both CTL and Th lymphocyte epitopes, should contribute to the design of synthetic peptide or recombinant vector vaccines for EIAV.

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Mapping of Equine Lentivirus Receptor 1 Residues Critical for Equine Infectious Anemia Virus Envelope Binding

Journal of Virology ◽

10.1128/jvi.01393-07 ◽

2007 ◽

Vol 82 (3) ◽

pp. 1204-1213 ◽

Cited By ~ 15

Author(s):

Baoshan Zhang ◽

Chengqun Sun ◽

Sha Jin ◽

Michael Cascio ◽

Ronald C. Montelaro

Keyword(s):

Equine Infectious Anemia Virus ◽

Tumor Necrosis Factor Receptor ◽

Binding Domain ◽

Virus Envelope ◽

Immunodeficiency Virus ◽

Equine Infectious Anemia ◽

Anemia Virus ◽

Functional Receptor ◽

Herpesvirus Entry Mediator ◽

Necrosis Factor

ABSTRACT The equine lentivirus receptor 1 (ELR1), a member of the tumor necrosis factor receptor (TNFR) protein family, has been identified as a functional receptor for equine infectious anemia virus (EIAV). Toward defining the functional interactions between the EIAV SU protein (gp90) and its ELR1 receptor, we mapped the gp90 binding domain of ELR1 by a combination of binding and functional assays using the EIAV SU gp90 protein and various chimeric receptor proteins derived from exchanges between the functional ELR1 and the nonbinding homolog, mouse herpesvirus entry mediator (murine HveA). Complementary exchanges of the respective cysteine-rich domains (CRD) between the ELR1 and murine HveA proteins revealed CRD1 as the predominant determinant of functional gp90 binding to ELR1 and also to a chimeric murine HveA protein expressed on the surface of transfected Cf2Th cells. Mutations of individual amino acids in the CRD1 segment of ELR1 and murine HveA indicated the Leu70 in CRD1 as essential for functional binding of EIAV gp90 and for virus infection of transduced Cf2Th cells. The specificity of the EIAV SU binding domain identified for the ELR1 receptor is fundamentally identical to that reported previously for functional binding of feline immunodeficiency virus SU to its coreceptor CD134, another TNFR protein. These results indicate unexpected common features of the specific mechanisms by which diverse lentiviruses can employ TNFR proteins as functional receptors.

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Matrix and Envelope Coevolution Revealed in a Patient Monitored since Primary Infection with Human Immunodeficiency Virus Type 1

Journal of Virology ◽

10.1128/jvi.01213-09 ◽

2009 ◽

Vol 83 (19) ◽

pp. 9875-9889 ◽

Cited By ~ 10

Author(s):

Elodie Beaumont ◽

Daniela Vendrame ◽

Bernard Verrier ◽

Emmanuelle Roch ◽

François Biron ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Amino Acid ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Matrix Protein ◽

Immunodeficiency Virus ◽

The Matrix ◽

Hiv 1

ABSTRACT Lentiviruses, including human immunodeficiency virus type 1 (HIV-1), typically encode envelope glycoproteins (Env) with long cytoplasmic tails (CTs). The strong conservation of CT length in primary isolates of HIV-1 suggests that this factor plays a key role in viral replication and persistence in infected patients. However, we report here the emergence and dominance of a primary HIV-1 variant carrying a natural 20-amino-acid truncation of the CT in vivo. We demonstrated that this truncation was deleterious for viral replication in cell culture. We then identified a compensatory amino acid substitution in the matrix protein that reversed the negative effects of CT truncation. The loss or rescue of infectivity depended on the level of Env incorporation into virus particles. Interestingly, we found that a virus mutant with defective Env incorporation was able to spread by cell-to-cell transfer. The effects on viral infectivity of compensation between the CT and the matrix protein have been suggested by in vitro studies based on T-cell laboratory-adapted virus mutants, but we provide here the first demonstration of the natural occurrence of similar mechanisms in an infected patient. Our findings provide insight into the potential of HIV-1 to evolve in vivo and its ability to overcome major structural alterations.

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