title: Dynamic Nucleolar Targeting of Dengue Virus Polymerase NS5 in Response to Extracellular pH.
abstract: The nucleolar subcompartment of the nucleus is increasingly recognized as an important target of RNA viruses. Here we document for the first time the ability of dengue virus (DENV) polymerase, nonstructural protein 5 (NS5), to accumulate within the nucleolus of infected cells and to target green fluorescent protein (GFP) to the nucleolus of live transfected cells. Intriguingly, NS5 exchange between the nucleus and nucleolus is dynamically modulated by extracellular pH, responding rapidly and reversibly to pH change, in contrast to GFP alone or other nucleolar and non-nucleolar targeted protein controls. The minimal pH-sensitive nucleolar targeting region (pHNTR), sufficient to target GFP to the nucleolus in a pH-sensitive fashion, was mapped to NS5 residues 1 to 244, with mutation of key hydrophobic residues, Leu-165, Leu-167, and Val-168, abolishing pHNTR function in NS5-transfected cells, and severely attenuating DENV growth in infected cells. This is the first report of a viral protein whose nucleolar targeting ability is rapidly modulated by extracellular stimuli, suggesting that DENV has the ability to detect and respond dynamically to the extracellular environment.
  
  
  
  Infections by dengue virus (DENV) threaten 40% of the world's population yet there is no approved vaccine or antiviral therapeutic to treat infections. Understanding the molecular details that govern effective viral replication is key for the development of novel antiviral strategies. Here, we describe for the first time dynamic trafficking of DENV nonstructural protein 5 (NS5) to the subnuclear compartment, the nucleolus. We demonstrate that NS5's targeting to the nucleolus occurs in response to acidic pH, identify the key amino acid residues within NS5 that are responsible, and demonstrate that their mutation severely impairs production of infectious DENV. Overall, this study identifies a unique subcellular trafficking event and suggests that DENV is able to detect and respond dynamically to environmental changes.
authors.affiliation: Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
authors.forename: Johanna E
authors.initials: JE
authors.lastname: Fraser
authors.affiliation: Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Rawlinson
authors.affiliation: Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Heaton
authors.affiliation: Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia david.jans@monash.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Jans
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D003716:Dengue Virus / Q000737:chemistry / Q000201:enzymology* / Q000254:growth & development* / Q000378:metabolism; D005110:Extracellular Space / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009154:Mutation; D021381:Protein Transport; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
chemical_list: C582223:NS5 protein, dengue virus; D017361:Viral Nonstructural Proteins; D049452:Green Fluorescent Proteins