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

To confirm that the inhibitory effect was dependent on h9/14, we expressed a mutated scAluY NF1 RNA where C25 replaced G25. This mutation causes a 60-fold decrease in affinity for h9/14 (30) . Notably, the mutation does not completely abolish complex formation, since the dissociation constant of the complex with the mutated RNA remains rather high (nanomolar range). The mutated RNA was expressed at comparable levels as the wild type scAluY NF1 RNA ( Figure 6B ). For five out of six reporter mRNAs tested, luciferase expression levels were significantly higher in cells expressing the mutated scAluY NF1 RNA than in cells expressing the wild type RNA ( Figure 6C ). Thus, the G25C mutation diminished the inhibitory activity as expected if, as observed in the in vitro experiments, Alu RNA binding to h9/14 was required for translation inhibition in vivo.