A systematic analysis of host factors reveals a Med23-interferon-λ regulatory axis against herpes simplex virus type 1 replication

PLoS Pathog. 2013;9(8):e1003514. doi: 10.1371/journal.ppat.1003514. Epub 2013 Aug 8.

Abstract

Herpes simplex virus type 1 (HSV-1) is a neurotropic virus causing vesicular oral or genital skin lesions, meningitis and other diseases particularly harmful in immunocompromised individuals. To comprehensively investigate the complex interaction between HSV-1 and its host we combined two genome-scale screens for host factors (HFs) involved in virus replication. A yeast two-hybrid screen for protein interactions and a RNA interference (RNAi) screen with a druggable genome small interfering RNA (siRNA) library confirmed existing and identified novel HFs which functionally influence HSV-1 infection. Bioinformatic analyses found the 358 HFs were enriched for several pathways and multi-protein complexes. Of particular interest was the identification of Med23 as a strongly anti-viral component of the largely pro-viral Mediator complex, which links specific transcription factors to RNA polymerase II. The anti-viral effect of Med23 on HSV-1 replication was confirmed in gain-of-function gene overexpression experiments, and this inhibitory effect was specific to HSV-1, as a range of other viruses including Vaccinia virus and Semliki Forest virus were unaffected by Med23 depletion. We found Med23 significantly upregulated expression of the type III interferon family (IFN-λ) at the mRNA and protein level by directly interacting with the transcription factor IRF7. The synergistic effect of Med23 and IRF7 on IFN-λ induction suggests this is the major transcription factor for IFN-λ expression. Genotypic analysis of patients suffering recurrent orofacial HSV-1 outbreaks, previously shown to be deficient in IFN-λ secretion, found a significant correlation with a single nucleotide polymorphism in the IFN-λ3 (IL28b) promoter strongly linked to Hepatitis C disease and treatment outcome. This paper describes a link between Med23 and IFN-λ, provides evidence for the crucial role of IFN-λ in HSV-1 immune control, and highlights the power of integrative genome-scale approaches to identify HFs critical for disease progression and outcome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Gene Deletion
  • Genome, Human*
  • HeLa Cells
  • Herpes Simplex / genetics
  • Herpes Simplex / immunology
  • Herpes Simplex / metabolism
  • Herpesvirus 1, Human / physiology*
  • Humans
  • Interferon Regulatory Factor-7 / genetics
  • Interferon Regulatory Factor-7 / immunology
  • Interferon Regulatory Factor-7 / metabolism
  • Interferons
  • Interleukins / biosynthesis*
  • Interleukins / genetics
  • Interleukins / immunology
  • Mediator Complex / biosynthesis*
  • Mediator Complex / genetics
  • Mediator Complex / immunology
  • Polymorphism, Single Nucleotide
  • RNA Polymerase II / genetics
  • RNA Polymerase II / immunology
  • RNA Polymerase II / metabolism
  • Up-Regulation*
  • Virus Replication / physiology*

Substances

  • IFNL3 protein, human
  • IRF7 protein, human
  • Interferon Regulatory Factor-7
  • Interleukins
  • MED23 protein, human
  • Mediator Complex
  • Interferons
  • RNA Polymerase II