The adenovirus VA RNA-derived miRNAs are not essential for lytic virus growth in tissue culture cells

At late times during a lytic infection human adenovirus type 5 produces ∼10(8) copies per cell of virus-associated RNA I (VA RNAI). This short highly structured RNA polymerase III transcript has previously been shown to be essential for lytic virus growth. A fraction of VA RNAI is processed by Dicer into small RNAs, so-called mivaRNAIs, which are efficiently incorporated into the RNA-induced silencing complex. Here, we constructed recombinant adenoviruses with mutations in the seed sequence of both the 5′- and the 3′-strand of the mivaRNAI duplex. The results showed that late viral protein synthesis, as well as new virus progeny formation, was essentially unaffected by the seed sequence mutations under lytic replicative conditions in HeLa or HEK293 cells. Collectively, our results suggest that either strand of the mivaRNAI duplex does not have target mRNA interactions that are critical for the establishment of virus growth under lytic conditions. Further, by depletion of protein kinase R (PKR) in HEK293 cells, we show that the suppressive effect of VA RNAI on the interferon-induced PKR pathway is most critical for late gene expression.