title: Hepatitis E virus ORF2 protein activates the pro-apoptotic gene CHOP and anti-apoptotic heat shock proteins.
abstract: BACKGROUND
  Hepatitis E virus (HEV) is a non-enveloped plus-strand RNA virus that causes acute hepatitis. The capsid protein open reading frame 2 (ORF2) is known to induce endoplasmic reticulum stress in ORF2 expressing cells.
  
  
  RESULTS
  In this study we found that HEV ORF2 activates the expression of the pro-apoptotic gene C/EBP homologous protein (CHOP). ORF2 stimulates the CHOP promoter mainly through AARE (amino acid response elements) and to a minor extent the ERSE (endoplasmic reticulum stress response elements). Activating transcription factor 4 (ATF4) protein binds and activates the AARE regulatory sites of the CHOP promoter. ORF2 expression also leads to increased phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α) that in turn initiates the translation of ATF4 mRNA. The pro-apoptotic gene CHOP is an important trigger to initiate endoplasmic reticulum stress induced apoptosis. However, the activation of CHOP by ORF2 in this study did not induce apoptosis, nor did BCL2-associated X protein (Bax) translocate to mitochondria. Microarray analysis revealed an ORF2 specific increased expression of chaperones Hsp72, Hsp70B', and co-chaperone Hsp40. Co-immunoprecipitation (Co-IP) and in silico molecular docking analysis suggests that HEV ORF2 interacts with Hsp72. In addition, Hsp72 shows nuclear accumulation in ORF2 expressing cells.
  
  
  CONCLUSIONS
  These data provide new insight into simultaneously occurring counter-acting effects of HEV ORF2 that may be part of a strategy to prevent host suicide before completion of the viral replication cycle.
authors.affiliation: Department of Vectorology and Experimental Gene Therapy, Biomedical Research Center, University of Rostock Medical School, Rostock, Germany.
authors.forename: Lijo
authors.initials: L
authors.lastname: John
authors.forename: Saijo
authors.initials: S
authors.lastname: Thomas
authors.forename: Ottmar
authors.initials: O
authors.lastname: Herchenröder
authors.forename: Brigitte M
authors.initials: BM
authors.lastname: Pützer
authors.forename: Stephan
authors.initials: S
authors.lastname: Schaefer
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D016752:Hepatitis E virus / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D011485:Protein Binding; D060888:Real-Time Polymerase Chain Reaction; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C497249:DDIT3 protein, human; D015852:Eukaryotic Initiation Factor-2; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins; C544598:HSPA6 protein, human; C400971:ORF2 protein, Hepatitis E virus; D014764:Viral Proteins; D051701:Activating Transcription Factor 4; D051742:Transcription Factor CHOP