title: Extragenic Suppression of a Mutation in Herpes Simplex Virus 1 UL34 That Affects Lamina Disruption and Nuclear Egress.
abstract: Nuclear egress of herpesviruses is accompanied by changes in the architecture of the nuclear membrane and nuclear lamina that are thought to facilitate capsid access to the inner nuclear membrane (INM) and curvature of patches of the INM around the capsid during budding. Here we report the properties of a point mutant of pUL34 (Q163A) that fails to induce gross changes in nuclear architecture or redistribution of lamin A/C. The UL34(Q163A) mutant shows a roughly 100-fold defect in single-step growth, and it forms small plaques. This mutant has a defect in nuclear egress, and furthermore, it fails to disrupt nuclear shape or cause observable displacement of lamin A/C despite retaining the ability to recruit the pUS3 and PKC protein kinases and to mediate phosphorylation of emerin. Extragenic suppressors of the UL34(Q163A) phenotype were isolated, and all of them carry a single mutation of arginine 229 to leucine in UL31. Surprisingly, although this UL31 mutation largely restores virus replication, it does not correct the lamina disruption defect, suggesting that, in Vero cells, changes in nuclear shape and gross displacements of lamin A/C may facilitate but are unnecessary for nuclear egress.
  
  
  OBJECTIVE
  Herpesvirus nuclear egress is an essential and conserved process that requires close association of the viral capsid with the inner nuclear membrane and budding of the capsid into that membrane. Access to the nuclear membrane and tight curvature of that membrane are thought to require disruption of the nuclear lamina that underlies the inner nuclear membrane, and consistent with this idea, herpesvirus infection induces biochemical and architectural changes at the nuclear membrane. The significance of the nuclear membrane architectural changes is poorly characterized. The results presented here address that deficiency in our understanding and show that a combination of mutations in two of the viral nuclear egress factors results in a failure to accomplish at least two components of lamina disruption while still allowing relatively efficient viral replication, suggesting that changes in nuclear shape and displacement of lamins are not necessary for herpes simplex virus 1 (HSV-1) nuclear egress.
authors.affiliation: Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Amber
authors.initials: A
authors.lastname: Vu
authors.affiliation: Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa.
authors.forename: Chelsea
authors.initials: C
authors.lastname: Poyzer
authors.affiliation: Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa richard-roller@uiowa.edu.
authors.forename: Richard
authors.initials: R
authors.lastname: Roller
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D053144:Cell Nucleus Shape; D002522:Chlorocebus aethiops; D057809:HEK293 Cells; D018259:Herpesvirus 1, Human / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D034904:Lamin Type A / Q000378:metabolism; D008958:Models, Molecular; D009685:Nuclear Envelope / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D034881:Nuclear Lamina / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D017354:Point Mutation; D011487:Protein Conformation; D014709:Vero Cells; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D057074:Virus Release / Q000235:genetics* / Q000502:physiology*; D014779:Virus Replication
chemical_list: D034904:Lamin Type A; D009687:Nuclear Proteins; C108721:UL31 protein, Human herpesvirus 1; C403420:UL34 protein, Human herpesvirus 1; D014764:Viral Proteins