The hepatitis E virus ORF3 protein stabilizes HIF-1alpha and enhances HIF-1-mediated transcriptional activity through p300/CBP.
The hepatitis E virus (HEV) causes hepatitis E and is an important human pathogen. We have previously shown that the HEV open reading frame 3 (ORF3) protein promotes survival of the host cell. Here we report finding increased expression of glycolytic pathway enzymes in ORF3-expressing cells. Promoter analysis of these genes revealed the ubiquitous presence of hypoxia inducible factor (HIF) responsive element (HRE). Dominant-negative and siRNA studies showed increased expression of glycolytic pathway genes by the ORF3 to be mediated by the HIF-1 transcription factor. Our results showed that HIF-1alpha, a highly unstable subunit of the HIF-1, was stabilized in ORF3-expressing cells. This was through phosphatidylinositol-3-kinase (PI3K) mediated activation of Akt/protein kinase B. Enhanced binding to the consensus HRE and increased transactivation activity of HIF-1 were also observed in ORF3-expressing cells. The HIF complex recruits the transcriptional adapter/histone acetyltransferase protein p300/CBP to target gene promoters and p300/CBP phosphorylation is required for this interaction. We show that ORF3-mediated extracellularly regulated kinase (Erk) activation was responsible for the observed increase in phosphorylation and transactivation activity of p300/CBP. Our results reveal a two-pronged strategy through which the ORF3 protein might modulate the energy homeostasis in HEV infected cells and thus contribute to pathogenesis.
Moin
Syed M
SM
Virology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
Chandra
Vivek
V
Arya
Rahul
R
Jameel
Shahid
S
D001665:Binding Sites; D002460:Cell Line; D050881:E1A-Associated p300 Protein / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006019:Glycolysis; D016752:Hepatitis E virus / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C400973:ORF3 protein, Hepatitis E virus; D014764:Viral Proteins; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human