FIG. 7.

flAlu RNA inhibits virus-induced PKR activation in vivo. Human 293 cells were transiently transfected for 48 h with 5 or 15 μg of cloned genes to express various small RNA genes (lanes 4 through 13) or with plasmid DNA (lanes 1 through 3). The type of small-RNA gene employed in each transfection is noted above the corresponding lane. Twenty hours prior to being harvested, cells were mock infected (293; lane 2) or infected with 1 to 5 PFU of either adenovirus (adv; lane 1) or mutant Ad720 (720; lanes 3 through 13). Seventeen hours prior to being harvested, cells were treated with interferon (1,000 U/ml). (A) PKR activity was assayed by in vitro autophosphorylation. (B) PKR protein levels were determined by Western analysis. No PKR activity or PKR protein was detected in a mock precipitation control (lane not shown). (C) Primer extension analysis was employed to assay the levels of expression of various small RNAs in control cells (293), cells infected with mutant Ad720 (720), and cells transfected with either 5 or 15 μg of cloned genes for various small RNAs. The relative amounts of RNA (2 μg is 1×) used in these primer extension assays are indicated.