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

The previous results suggested that the functional association of SRP9/14 with the 40S subunit mediated by the Alu RNA is sufficient to render 40S incompetent for initiation. If indeed the continuous association of the Alu RNA were not required to inactivate the 40S subunit, the released RNA might serve in another round of targeted delivery of free SRP9/14 to 40S. To assess this hypothesis, we supplemented the RRL translation reaction containing scAluY A RNP with an equal amount or a 2-fold excess of h9/14. The presence of excess h9/14 significantly enhanced the inhibitory activity of the scAluY A RNP, while the protein alone at the same concentrations had no effect on translation ( Figure 5F, left panel) . Hence, the Alu RNA is not part of the inactive 40S complex.