title: Epstein-Barr virus independent dysregulation of UBP43 expression alters interferon-stimulated gene expression in Burkitt lymphoma.
abstract: Epstein-Barr virus (EBV) persists as a life-long latent infection within memory B cells, but how EBV may circumvent the innate immune response within this virus reservoir is unclear. Recent studies suggest that the latency-associated non-coding RNAs of EBV may actually induce type I (antiviral) interferon production, raising the question of how EBV counters the negative consequences this is likely to have on viral persistence. We addressed this by examining the type I interferon response in Burkitt lymphoma (BL) cell lines, the only in vitro model of the restricted program of EBV latency-gene expression in persistently infected B cells in vivo. Importantly, we observed no effect of EBV on interferon alpha-induced signaling or evidence of type I interferon production, suggesting that EBV in this latent state is silent to the cell's innate antiviral surveillance. We did uncover, however, a defect in the negative feedback control of interferon signaling in a subpopulation of BL lines as was revealed by prolonged interferon-stimulated gene transcription consistent with sustained tyrosine phosphorylation on STAT1 and STAT2. This was due to inadequate induction of expression of the ubiquitin-specific protease UBP43, which removes the ubiquitin-like ISG15 polypeptide conjugated to proteins (ISGylation) in response to type I interferons. Results here are consistent with previous findings in genetically engineered Ubp43(-/-) murine cells that UBP43 down-regulates interferon signaling, independent of its ISG15 isopeptidase activity, by precluding the protein kinase JAK1 from the interferon receptor. This natural deficiency in UBP43 expression may therefore provide a useful model to further probe the biological roles of UBP43 and ISGylation.
authors: Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA, USA. iruf@uci.edu
authors: Ingrid K
authors: IK
authors: Ruf
authors: Jennifer L
authors: JL
authors: Houmani
authors: Jeffery T
authors: JT
authors: Sample
mesh_terms: D000818:Animals; D002051:Burkitt Lymphoma / Q000378:metabolism*; D045744:Cell Line, Tumor; D010450:Endopeptidases / Q000096:biosynthesis*; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D015967:Gene Expression Regulation, Viral; D007372:Interferons / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D010766:Phosphorylation; D050794:STAT1 Transcription Factor / Q000378:metabolism; D043222:Ubiquitin Thiolesterase
chemical_list: D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse; D007372:Interferons; D010450:Endopeptidases; C118306:Usp18 protein, mouse; C485560:USP18 protein, human; D043222:Ubiquitin Thiolesterase