Alu RNA regulates the cellular pool of active ribosomes by targeted delivery of SRP9/14 to 40S subunits

Ivanova, Elena; Berger, Audrey; Scherrer, Anne; Alkalaeva, Elena; Strub, Katharina

It was previously reported that Alu RNA levels increase in response to viral infection and that these RNAs accumulate in the cytoplasm as SRP9/14 containing RNPs (32, 33) . We used the vesicular stomatitis virus (VSV), a prototype negative strand RNA virus, as a model to investigate the effects of scAluY NF1 RNA expression on viral protein synthesis. VSV induces a shutdown of host translation by interfering with eIF4F complex formation (34) . Although VSV mRNAs are capped and do not contain IRES sequences, their translation proceeds via an unconventional mechanism, which bypasses the need of eIF4F for initiation (35) . HEK 293T cells were transiently transfected with plasmids expressing either scAluY NF1 or the 4.5S control RNA. After 48 h, cells were infected with VSV (MOI = 10) and harvested 6 h later by which time the host translation machinery was reprogrammed by VSV mRNAs. In cells overexpressing scAluY NF1 RNA we observed a reduction in viral protein synthesis by approximately 25% compared to cells expressing 4.5S RNA ( Figure 6F ). This demonstrates that Alu RNPs are able to suppress translation of the VSV mR-NAs in the cell following infection.