title: Herpes Simplex Virus Capsid Localization to ESCRT-VPS4 Complexes in the Presence and Absence of the Large Tegument Protein UL36p.
abstract: UL36p (VP1/2) is the largest protein encoded by herpes simplex virus 1 (HSV-1) and resides in the innermost layer of tegument, the complex protein layer between the capsid and envelope. UL36p performs multiple functions in the HSV life cycle, including a critical but unknown role in capsid cytoplasmic envelopment. We tested whether UL36p is essential for envelopment because it is required to engage capsids with the cellular ESCRT/Vps4 apparatus. A green fluorescent protein (GFP)-fused form of the dominant negative ATPase Vps4-EQ was used to irreversibly tag ESCRT envelopment sites during infection by UL36p-expressing and UL36-null HSV strains. Using fluorescence microscopy and scanning electron microscopy, we quantitated capsid/Vps4-EQ colocalization and examined the ultrastructure of the corresponding viral assembly intermediates. We found that loss of UL36p resulted in a two-thirds reduction in the efficiency of capsid/Vps4-EQ association but that the remaining UL36p-null capsids were still able to engage the ESCRT envelopment apparatus. It appears that although UL36p helps to couple HSV capsids to the ESCRT pathway, this is likely not the sole reason for its absolute requirement for envelopment.
  
  
  
  Envelopment of the HSV capsid is essential for the assembly of an infectious virion and requires the complex interplay of a large number of viral and cellular proteins. Critical to envelope assembly is the virally encoded protein UL36p, whose function is unknown. Here we test the hypothesis that UL36p is essential for the recruitment of cellular ESCRT complexes, which are also known to be required for envelopment.
authors.affiliation: Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, USA.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Kharkwal
authors.affiliation: Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, USA.
authors.forename: Caitlin G
authors.initials: CG
authors.lastname: Smith
authors.affiliation: Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, USA duncan.wilson@einstein.yu.edu.
authors.forename: Duncan W
authors.initials: DW
authors.lastname: Wilson
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000818:Animals; D015153:Blotting, Western; D002213:Capsid / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003593:Cytoplasm; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006561:Herpes Simplex / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D018259:Herpesvirus 1, Human / Q000502:physiology*; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000502:physiology; D019065:Virus Assembly / Q000502:physiology*; D014779:Virus Replication
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D012333:RNA, Messenger; C084763:UL37 protein, Human herpesvirus 1; D014764:Viral Proteins; D015678:Viral Structural Proteins; D049452:Green Fluorescent Proteins; D025262:Vacuolar Proton-Translocating ATPases; D000074183:ATPases Associated with Diverse Cellular Activities; C490305:VPS4A protein, human