title: Identification of conserved motifs in the West Nile virus envelope essential for particle secretion.
abstract: BACKGROUND
  Enveloped viruses utilize cellular membranes to bud from infected cells. The process of virion assembly and budding is often facilitated by the presence of certain conserved motifs within viral proteins in conjunction with cellular factors. We hence examined the West Nile Virus (WNV) Envelope protein for the presence of any such motifs and their functional characterization.
  
  
  RESULTS
  We identified conserved 461PXAP464 and 349YCYL352 motifs in the WNV envelope glycoprotein bearing resemblance to retroviral late domains. Disruptive mutations of PXAP to LAAL and of the highly conserved Cys350 in the YCYL motif, led to a severe reduction in WNV particle production. Similar motifs in case of retroviruses are known to interact with components of host sorting machinery like PXAP with Tsg101 and YXXL with Alix. However, in the case of WNV, siRNA mediated depletion of Alix or Tsg101 did not have an effect on WNV release. Molecular modeling suggested that while the 461PXAP464 motif is surface accessible and could potentially interact with cellular proteins required for WNV assembly, the 349YCYL352 motif was found to be internal with Cys350 important for protein folding via disulphide bonding.
  
  
  CONCLUSIONS
  The conserved 461PXAP464 and 349YCYL352 motifs in the WNV envelope are indispensable for WNV particle production. Although these motifs bear sequence similarity to retroviral late domains and are essential for WNV assembly, they are functionally distinct suggesting that they are not the typical late domain like motifs of retroviruses and may play a role other than Alix/Tsg101 utilization/dependence.
authors.affiliation: Department of Biomedical Sciences, Texas Tech University Health Sciences Center, 5001 El Paso Dr, MSB-1 Annex, El Paso, TX 79905, USA. anjali.joshi@ttuhsc.edu.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Garg
authors.forename: Raphael T C
authors.initials: RT
authors.lastname: Lee
authors.forename: Ng Oon
authors.initials: NO
authors.lastname: Tek
authors.forename: Sebastian
authors.initials: S
authors.lastname: Maurer-Stroh
authors.forename: Anjali
authors.initials: A
authors.lastname: Joshi
mesh_terms: D020816:Amino Acid Motifs; D002460:Cell Line; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D014759:Viral Envelope Proteins / Q000235:genetics* / Q000378:metabolism*; D057074:Virus Release; D014902:West Nile virus / Q000502:physiology*
chemical_list: D014759:Viral Envelope Proteins