title: Novel Role for Protein Inhibitor of Activated STAT 4 (PIAS4) in the Restriction of Herpes Simplex Virus 1 by the Cellular Intrinsic Antiviral Immune Response.
abstract: Small ubiquitin-like modifier (SUMO) is used by the intrinsic antiviral immune response to restrict viral pathogens, such as herpes simplex virus 1 (HSV-1). Despite characterization of the host factors that rely on SUMOylation to exert their antiviral effects, the enzymes that mediate these SUMOylation events remain to be defined. We show that unconjugated SUMO levels are largely maintained throughout infection regardless of the presence of ICP0, the HSV-1 SUMO-targeted ubiquitin ligase. Moreover, in the absence of ICP0, high-molecular-weight SUMO-conjugated proteins do not accumulate if HSV-1 DNA does not replicate. These data highlight the continued importance for SUMO signaling throughout infection. We show that the SUMO ligase protein inhibitor of activated STAT 4 (PIAS4) is upregulated during HSV-1 infection and localizes to nuclear domains that contain viral DNA. PIAS4 is recruited to sites associated with HSV-1 genome entry through SUMO interaction motif (SIM)-dependent mechanisms that are destabilized by ICP0. In contrast, PIAS4 accumulates in replication compartments through SIM-independent mechanisms irrespective of ICP0 expression. Depletion of PIAS4 enhances the replication of ICP0-null mutant HSV-1, which is susceptible to restriction by the intrinsic antiviral immune response. The mechanisms of PIAS4-mediated restriction are synergistic with the restriction mechanisms of a characterized intrinsic antiviral factor, promyelocytic leukemia protein, and are antagonized by ICP0. We provide the first evidence that PIAS4 is an intrinsic antiviral factor. This novel role for PIAS4 in intrinsic antiviral immunity contrasts with the known roles of PIAS proteins as suppressors of innate immunity.
  
  
  OBJECTIVE
  Posttranslational modifications with small ubiquitin-like modifier (SUMO) proteins regulate multiple aspects of host immunity and viral replication. The protein inhibitor of activated STAT (PIAS) family of SUMO ligases is predominantly associated with the suppression of innate immune signaling. We now identify a unique and contrasting role for PIAS proteins as positive regulators of the intrinsic antiviral immune response to herpes simplex virus 1 (HSV-1) infection. We show that PIAS4 relocalizes to nuclear domains that contain viral DNA throughout infection. Depletion of PIAS4, either alone or in combination with the intrinsic antiviral factor promyelocytic leukemia protein, significantly impairs the intrinsic antiviral immune response to HSV-1 infection. Our data reveal a novel and dynamic role for PIAS4 in the cellular-mediated restriction of herpesviruses and establish a new functional role for the PIAS family of SUMO ligases in the intrinsic antiviral immune response to DNA virus infection.
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Conn
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Wasson
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: Steven
authors.initials: S
authors.lastname: McFarlane
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: Lily
authors.initials: L
authors.lastname: Tong
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: James R
authors.initials: JR
authors.lastname: Brown
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: Kyle G
authors.initials: KG
authors.lastname: Grant
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.
authors.forename: Patricia
authors.initials: P
authors.lastname: Domingues
authors.affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom chris.boutell@glasgow.ac.uk.
authors.forename: Chris
authors.initials: C
authors.lastname: Boutell
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002460:Cell Line; D004261:DNA Replication; D004279:DNA, Viral; D018450:Disease Progression; D015870:Gene Expression; D016679:Genome, Viral; D006561:Herpes Simplex / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D018259:Herpesvirus 1, Human / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D000071156:Promyelocytic Leukemia Protein; D011485:Protein Binding; D050828:Protein Inhibitors of Activated STAT / Q000737:chemistry / Q000235:genetics*; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D025842:SUMO-1 Protein / Q000378:metabolism; D058207:Sumoylation; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D050828:Protein Inhibitors of Activated STAT; D011993:Recombinant Fusion Proteins; D025842:SUMO-1 Protein; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D044767:Ubiquitin-Protein Ligases; C051804:Vmw110 protein, Human herpesvirus 1