Interferons are antiviral cytokines that exert their action by inducing transcription of interferon-regulated genes. Two important interferon-regulated genes are the double-stranded RNA dependent protein kinase PKR and RNA-specific adenosine deaminase ADAR1. The roles of PKR and ADAR1 during measles virus infection were studied using human HeLa cells with stable RNAi-mediated knockdown of PKR or ADAR1, together with Moraten vaccine-derived measles virus and isogenic mutant viruses deficient in the innate immune-control proteins V or C. In PKR-sufficient parental HeLa cells, the C-deficient virus grew poorly and was a potent inducer of apoptosis. In PKR-deficient cells, however, the C-deficient virus multiplied to higher yields and did not induce apoptosis. Moreover, in PKR-sufficient cells, the C-deficient virus was a potent inducer of interferon-β, but interferon-β induction by this virus was substantially decreased in PKR-deficient cells. The enhanced induction of interferon-β in PKR-sufficient cells correlated with enhanced PKR-mediated activation of NF-κB and MAP kinase pathways. In contrast, in ADAR1-deficient compared to ADAR1-sufficient parental HeLa cells, all three measles viruses studied (WT, V-deficient, and C-deficient) grew to lower yields, and the WT and V-deficient virus induced greater amounts of apoptosis. Enhanced apoptosis in the ADAR1-deficient cells correlated with enhanced activation of PKR and IRF-3. Taken together, these results indicate that PKR is an antiviral and pro-apoptotic host factor in the context of measles virus infection, whereas ADAR1 enhances virus multiplication and suppresses virus-induced apoptosis, presumably by opposing PKR and perhaps other double-stranded RNA-dependent antiviral pathways. Finally, additional observations regarding ADAR1 translational and post-translation modifications, including apparent caspase cleavage following virus infection, are described.
|Advisor:||Samuel, Charles E.|
|Commitee:||Cattaneo, Roberto, Feinstein, Stuart C., Foltz, Kathleen R., Ma, Dzwokai|
|School:||University of California, Santa Barbara|
|Department:||Molecular, Cellular & Developmental Biology|
|School Location:||United States -- California|
|Source:||DAI-B 70/03, Dissertation Abstracts International|
|Subjects:||Molecular biology, Virology|
|Keywords:||ADAR1, Adenosine deaminase, Deaminase, Interferon, Measles virus, PKR, Protein kinase|
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