title: The Product of the Herpes Simplex Virus 2 UL16 Gene Is Critical for the Egress of Capsids from the Nuclei of Infected Cells.
abstract: The herpes simplex virus (HSV)UL16gene is conserved throughout theHerpesviridaeand encodes a poorly understood tegument protein. The HSV-1 UL16 protein forms complexes with several viral proteins, including UL11, gE, VP22, and UL21. We previously demonstrated that HSV-2UL21was essential for virus propagation due to the failure of DNA-containing capsids (C capsids) to exit the nucleus. We hypothesized that if a UL16/UL21 complex was required for nuclear egress, HSV-2 lacking UL16 would have a phenotype similar to that of HSV-2 lacking UL21. Deletion of HSV-2UL16(Δ16) resulted in a 950-fold reduction in virus propagation in mouse L cell fibroblasts and a 200-fold reduction in virus propagation in Vero cells that was fully reversed upon the repair of Δ16 (Δ16R) and partially reversed by infecting UL16-expressing cells with Δ16. The kinetics of viral gene expression in cells infected with Δ16 were indistinguishable from those of cells infected with Δ16R or the parental virus. Additionally, similar numbers of capsids were isolated from the nuclei of cells infected with Δ16 and the parental virus. However, transmission electron microscopy, fluorescencein situhybridization experiments, and fluorescent capsid localization assays all indicated a reduction in the ability of Δ16 C capsids to exit the nucleus of infected cells. Taken together, these data indicate that, likeUL21,UL16is critical for HSV-2 propagation and suggest that the UL16 and UL21 proteins may function together to facilitate the nuclear egress of capsids.IMPORTANCEHSV-2 is a highly prevalent sexually transmitted human pathogen that is the main cause of genital herpes infections and is fueling the epidemic transmission of HIV in sub-Saharan Africa. Despite important differences in the pathological features of HSV-1 and HSV-2 infections, HSV-2 is understudied compared to HSV-1. Here we demonstrate that a deletion of the HSV-2UL16gene results in a substantial inhibition of virus replication due to a reduction in the ability of DNA-containing capsids to exit the nucleus of infected cells. The phenotype of thisUL16mutant resembles that of an HSV-2UL21mutant described previously by our laboratory. Because UL16 and UL21 interact, these findings suggest that a complex containing both proteins may function together in nuclear egress.
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.
authors.forename: Jie
authors.initials: J
authors.lastname: Gao
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.
authors.forename: Thomas J M
authors.initials: TJM
authors.lastname: Hay
authors.affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada bruce.banfield@queensu.ca.
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Banfield
mesh_terms: D000818:Animals; D002213:Capsid / Q000502:physiology*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000821:virology*; D002522:Chlorocebus aethiops; D005347:Fibroblasts / Q000821:virology; D018258:Herpesvirus 2, Human / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D014709:Vero Cells; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*; D019065:Virus Assembly; D057074:Virus Release; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins; D014764:Viral Proteins
keywords: UL16; UL21; herpes simplex virus; nuclear egress; tegument