Selective stimulation of translational expression by Alu RNA.

Human Alu and adenovirus VA1 RNAs each stimulate the translational expression of reporter genes in co-transient transfection assays without affecting either the rate of global protein synthesis or the abundance of the reporter mRNA. This selective, post-transcriptional stimulation of expression, which is observed in human and mouse cell lines and for three reporters, acts through a PKR- independent mechanism. The activity of Alu and VA1 RNAs in this assay is transient, causing a reduction in the lag time for the translational expression of the newly synthesized reporter mRNAs. The reduction in this lag time accounts for the relative selectivity of the effect upon the expression of the reporter and suggests novel roles for Alu and VA1 RNA in cell stress recovery and viral infection. Deletion analysis demonstrates that a specific region residing within the right monomer of the dimeric Alu consensus sequence is necessary for activity. Highly abundant left Alu monomer transcripts are inactive but the right Alu monomer is fully active, although its transcripts are scarce. Mouse B1 and B2 SINE RNAs stimulate reporter gene expression in mouse cells, suggesting that this activity is a general property of eucaryotic SINEs.