title: SARS coronavirus 3b accessory protein modulates transcriptional activity of RUNX1b.
abstract: BACKGROUND
  The causative agent of severe acute respiratory syndrome, SARS coronavirus (SARS-CoV) genome encodes several unique group specific accessory proteins with unknown functions. Among them, accessory protein 3b (also known as ORF4) was lately identified as one of the viral interferon antagonist. Recently our lab uncovered a new role for 3b in upregulation of AP-1 transcriptional activity and its downstream genes. Thus, we believe that 3b might play an important role in SARS-CoV pathogenesis and therefore is of considerable interest. The current study aims at identifying novel host cellular interactors of the 3b protein.
  
  
  RESULTS
  In this study, using yeast two-hybrid and co-immunoprecipitation techniques, we have identified a host transcription factor RUNX1b (Runt related transcription factor, isoform b) as a novel interacting partner for SARS-CoV 3b protein. Chromatin immunoprecipitaion (ChIP) and reporter gene assays in 3b expressing jurkat cells showed recruitment of 3b on the RUNX1 binding element that led to an increase in RUNX1b transactivation potential on the IL2 promoter. Kinase assay and pharmacological inhibitor treatment implied that 3b also affect RUNX1b transcriptional activity by regulating its ERK dependent phosphorylation levels. Additionally, mRNA levels of MIP-1α, a RUNX1b target gene upregulated in SARS-CoV infected monocyte-derived dendritic cells, were found to be elevated in 3b expressing U937 monocyte cells.
  
  
  CONCLUSIONS
  These results unveil a novel interaction of SARS-CoV 3b with the host factor, RUNX1b, and speculate its physiological relevance in upregulating cytokines and chemokine levels in state of SARS virus infection.
authors.affiliation: Virology Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
authors.forename: Bhavna
authors.initials: B
authors.lastname: Varshney
authors.forename: Sudhakar
authors.initials: S
authors.lastname: Agnihothram
authors.forename: Sudhakar
authors.initials: S
authors.lastname: Agnihotram
authors.forename: Yee-Joo
authors.initials: YJ
authors.lastname: Tan
authors.forename: Ralph
authors.initials: R
authors.lastname: Baric
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Lal
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D054405:Chemokine CCL3 / Q000235:genetics / Q000378:metabolism; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics* / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics; D051379:Mice; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D045473:Severe acute respiratory syndrome-related coronavirus / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism*
chemical_list: D054405:Chemokine CCL3; D050676:Core Binding Factor Alpha 2 Subunit; D007376:Interleukin-2; D012333:RNA, Messenger; C493728:RUNX1 protein, human; D017361:Viral Nonstructural Proteins; D054334:Viral Regulatory and Accessory Proteins; C118611:glycoprotein 3b, coronavirus; D048049:Extracellular Signal-Regulated MAP Kinases