scholarly journals Cytoplasmic Residues of Herpes Simplex Virus Glycoprotein gE Required for Secondary Envelopment and Binding of Tegument Proteins VP22 and UL11 to gE and gD

2006 ◽  
Vol 81 (1) ◽  
pp. 319-331 ◽  
Author(s):  
Aaron Farnsworth ◽  
Todd W. Wisner ◽  
David C. Johnson
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Affinity Purification ◽  
Viral Proteins ◽  
Viral Glycoprotein ◽  
Tegument Proteins ◽  
Final Assembly ◽  
Herpes Simplex Virus Glycoprotein ◽  
Simplex Virus

ABSTRACT The final assembly of herpes simplex virus (HSV) involves binding of tegument-coated capsids to viral glycoprotein-enriched regions of the trans-Golgi network (TGN) as enveloped virions bud into TGN membranes. We previously demonstrated that HSV glycoproteins gE/gI and gD, acting in a redundant fashion, are essential for this secondary envelopment. To define regions of the cytoplasmic (CT) domain of gE required for secondary envelopment, HSVs lacking gD and expressing truncated gE molecules were constructed. A central region (amino acids 470 to 495) of the gE CT domain was important for secondary envelopment, although more C-terminal residues also contributed. Tandem affinity purification (TAP) proteins including fragments of the gE CT domain were used to identify tegument proteins VP22 and UL11 as binding partners, and gE CT residues 470 to 495 were important in this binding. VP22 and UL11 were precipitated from HSV-infected cells in conjunction with full-length gE and gE molecules with more-C-terminal residues of the CT domain. gD also bound VP22 and UL11. Expression of VP22 and gD or gE/gI in cells by use of adenovirus (Ad) vectors provided evidence that other viral proteins were not necessary for tegument/glycoprotein interactions. Substantial quantities of VP22 and UL11 bound nonspecifically onto or were precipitated with gE and gD molecules lacking all CT sequences, something that is very unlikely in vivo. VP16 was precipitated equally whether gE/gI or gD was present in extracts or not. These observations illustrated important properties of tegument proteins. VP22, UL11, and VP16 are highly prone to binding nonspecifically to other proteins, and this did not represent insolubility during our assays. Rather, it likely reflects an inherent “stickiness” related to the formation of tegument. Nevertheless, assays involving TAP proteins and viral proteins expressed by HSV and Ad vectors supported the conclusion that VP22 and UL11 interact specifically with the CT domains of gD and gE.

scholarly journals Evidence that the Herpes Simplex Virus Type 1 ICP0 Protein Does Not Initiate Reactivation from Latency In Vivo

2006 ◽  
Vol 80 (22) ◽  
pp. 10919-10930 ◽  
Author(s):  
R. L. Thompson ◽  
N. M. Sawtell
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Host Cell ◽  
Infectious Virus ◽  
Viral Proteins ◽  
Lytic Cycle ◽  
Latently Infected ◽  
Host Cell Factors ◽  
Simplex Virus

ABSTRACT The stress-induced host cell factors initiating the expression of the herpes simplex virus lytic cycle from the latent viral genome are not known. Previous studies have focused on the effect of specific viral proteins on reactivation, i.e., the production of detectable infectious virus. However, identification of the viral protein(s) through which host cell factors transduce entry into the lytic cycle and analysis of the promoter(s) of this (these) first protein(s) will provide clues to the identity of the stress-induced host cell factors important for reactivation. In this report, we present the first strategy developed for this type of analysis and use this strategy to test the established hypothesis that the herpes simplex virus ICP0 protein initiates reactivation from the latent state. To this end, ICP0 null and promoter mutants were analyzed for the abilities (i) to exit latency and produce lytic-phase viral proteins (initiate reactivation) and (ii) to produce infectious viral progeny (reactivate) in explant and in vivo. Infection conditions were manipulated so that approximately equal numbers of latent infections were established by the parental strains, the mutants, and their genomically restored counterparts, eliminating disparate latent pool sizes as a complicating factor. Following hyperthermic stress (HS), which induces reactivation in vivo, equivalent numbers of neurons exited latency (as evidenced by the expression of lytic-phase viral proteins) in ganglia latently infected with either the ICP0 null mutant dl1403 or the parental strain. In contrast, infectious virus was detected in the ganglia of mice latently infected with the parental strain but not with ICP0 null mutant dl1403 or FXE. These data demonstrate that the role of ICP0 in the process of reactivation is not as a component of the switch from latency to lytic-phase gene expression; rather, ICP0 is required after entry into the lytic cycle has occurred. Similar analyses were carried out with the ΔTfi mutant, which contains a 350-bp deletion in the ICP0 promoter, and the genomically restored isolate, ΔTfiR. The numbers of latently infected neurons exiting latency were not different for ΔTfi and ΔTfiR. However, ΔTfi did not reactivate in vivo, whereas ΔTfiR reactivated in ∼38% of the mice. In addition, ICP0 was detected in ΔTfiR-infected neurons exiting latency but was not detected in those neurons exiting latency infected with ΔTfi. We conclude that while ICP0 is important and perhaps essential for infectious virus production during reactivation in vivo, this protein is not required and appears to play no major role in the initiation of reactivation in vivo.

scholarly journals Analysis of the Interaction between the UL11 and UL16 Tegument Proteins of Herpes Simplex Virus

2008 ◽  
Vol 82 (21) ◽  
pp. 10693-10700 ◽  
Author(s):  
Pei-Chun Yeh ◽  
David G. Meckes ◽  
John W. Wills
Keyword(s):  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Disulfide Bonds ◽  
Viral Proteins ◽  
Deletion Mutants ◽  
Tegument Proteins ◽  
Multidomain Structure ◽  
Cytoplasmic Face ◽  
Simplex Virus ◽  
Golgi Network

ABSTRACT The UL11 and UL16 tegument proteins of herpes simplex virus are conserved throughout the herpesvirus family. Previous studies have shown that these proteins interact, perhaps to link UL16-bound nucleocapsids to UL11, which resides on the cytoplasmic face of the trans-Golgi network, where maturation budding occurs. Little is known about the interaction except that it requires the leucine-isoleucine (LI) and acidic cluster motifs in UL11 and that no other viral proteins are involved. In particular, the important question of whether these two proteins bind to each other directly has not been addressed. Accordingly, UL11 and UL16 were expressed in bacteria, and the purified proteins were found to retain the ability to interact in a manner that was dependent upon the LI and acidic cluster. In an attempt to map the UL11-binding site contained in UL16, a large number of deletion mutants were constructed. The first 40 (nonconserved) amino acids were found to be dispensable, but all the other constructs failed to bind UL11 or had poor expression in transfected cells, suggesting that UL16 is very sensitive to alterations and probably lacks a multidomain structure. As an alternative strategy for identifying residues that are important for the interaction, the cysteines of UL16 were investigated, because many of these are highly conserved. Approximately half of the 20 cysteines in UL16 have been shown to be covalently modified by N-ethylmaleimide, and this treatment was found to block the interaction with UL11. Moreover, individual serine replacements of six of the most conserved cysteine residues were made, and four of these disrupted the interaction with UL11 without affecting protein stability. However, the UL11-UL16 interaction does not involve the formation of interspecies disulfide bonds, because binding occurred even when all the cysteines in UL11 were eliminated. Thus, UL16 directly interacts with UL11 and does so in a manner that requires free cysteines.

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