Herpes Simplex Virus Tegument Protein VP22 Contains an Internal VP16 Interaction Domain and a C-Terminal Domain That Are Both Required for VP22 Assembly into the Virus Particle

Abstract

Many steps along the herpesvirus assembly and maturation pathway remain unclear. In particular, the acquisition of the virus tegument is a poorly understood process, and the molecular interactions involved in tegument assembly have not yet been defined. Previously we have shown that the two major herpes simplex virus tegument proteins VP22 and VP16 are able to interact, although the relevance of this to virus assembly is not clear. Here we have constructed a number of recombinant viruses expressing N-and C-terminal truncations of VP22 and have used them to identify regions of the protein involved in its assembly into the virus structure. Analysis of the packaging of these VP22 variants into extracellular virions revealed that the C terminus of VP22 is absolutely required for this process, with removal of the C-terminal 89 residues abrogating its incorporation. However, while these 89 residues alone were sufficient for specific incorporation of small amounts of VP22 into the tegument, efficient packaging of VP22 to the levels of full-length protein required an additional 52 residues of the protein. Coimmunoprecipitation assays indicated that these 52 residues also contained the interaction domain for VP16. Furthermore, analysis of the subcellular localization of the mutant forms of VP22 revealed that only those truncations that were efficiently assembled formed characteristic cytoplasmic trafficking complexes, suggesting that these complexes may represent the cellular location for VP22 assembly into the virus. Taken together, these results suggest that there are two determinants involved in the packaging of VP22-a C-terminal domain and an internal VP16 interaction domain, both of which are required for the efficient recruitment of VP22 to sites of virus assembly.

The Amino Terminus of the Herpes Simplex Virus 1 Protein Vhs Mediates Membrane Association and Tegument Incorporation

“…These 42 residues lie in conserved domain 1 of many alphaherpesvirus Vhs molecules, including those of HSV-2, cercopithecine herpesviruses 1 and 2, bovine herpesvirus 2, suid herpesvirus 1, pseudorabies virus, and equine herpesvirus 4. In contrast, the C-terminal conserved region of VP22 has been identified as important for membrane association, virion incorporation, and interaction with VP16 (3,15). We observed that D1(42)GFP had similar properties to full-length Vhs.…”

Virion Incorporation of the Herpes Simplex Virus Type 1 Tegument Protein VP22 Occurs via Glycoprotein E-Specific Recruitment to the Late Secretory Pathway

“…9A, WT). We have previously provided evidence to suggest that localization of VP22 to these complexes correlates with efficient assembly of VP22 into the virus structure (23). Hence, to determine the effect of abolishing gE binding on VP22 localization to these complexes, we next determined the localization of GFP-VP22 ⌬gEbind in Vero cells infected in the same manner and imaged 8 h after infection.…”

“…In addition, we and others have previously shown that HSV-1 VP22 interacts directly with a second tegument protein, namely, VP16 (13,33), an interaction that could provide an alternative route for VP22 to enter the virion. In a previous study, we concluded that the region of VP22 containing its VP16 interaction domain was required but not sufficient for optimal VP22 packaging into the assembling virion, with an additional C-terminal determinant also involved (23). We also demonstrated that the same region of VP22 that was required for virion packaging was essential to target the protein to its characteristic cytoplasmic trafficking complexes, suggesting that these specific sites may be the location in the cell for VP22 assembly into the virion (23).…”

“…In a previous study, we concluded that the region of VP22 containing its VP16 interaction domain was required but not sufficient for optimal VP22 packaging into the assembling virion, with an additional C-terminal determinant also involved (23). We also demonstrated that the same region of VP22 that was required for virion packaging was essential to target the protein to its characteristic cytoplasmic trafficking complexes, suggesting that these specific sites may be the location in the cell for VP22 assembly into the virion (23). Since that study, O'Regan and coworkers have reported that the C-terminal half of HSV-1 VP22 also contains the binding site for gE (32), providing a possible candidate for an additional VP22 binding partner.…”

DNA-tumor virus entry—From plasma membrane to the nucleus

“…While the UL48 (VP16) transcription factor associated with UL49 (VP22) and supported virus assembly (152), the knock out of UL49 (VP22) had no effects on the expression levels of the immediate early viral protein ICP0 (153), indicating that UL49 (VP22) has no important role for nuclear import of HSV1 DNA.…”