Activating Ras Mutations Fail to Ensure Efficient Replication of Adenovirus Mutants Lacking VA-RNA

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Abstract
Adenoviruses lacking their PKR-antagonizing VA RNAs replicate poorly in primary cells. It has been suggested that these virus recombinants still replicate efficiently in tumor cells with Ras mutations and might therefore be useful in tumor therapy. The ability of interferon-sensitive viruses to grow in Ras-mutant tumor cells is generally ascribed to a postulated inhibitory effect of mutant Ras on PKR. We have constructed a set of isogenic adenoviruses that lack either or both VA RNA species, and tested virus replication in a variety of cell species with different Ras status. In tendency, VA-less viruses replicated with higher efficiency in Ras-mutant cells, as compared to cell lines without Ras mutation. However, several exceptions to this rule were observed, arguing against a direct inhibition of PKR by mutant Ras. Phosphorylation of the PKR-substrate eIF2? was observed regardless of the Ras mutational status, upon infection with VA-less adenoviruses in the presence of interferon, but also upon addition ...

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