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

Next, we examined whether an excess of Alu RNA over Alu RNP affected the activity of the Alu RNP. An equal amount or a 2-fold excess of the scAluY A RNA over the scAluY A RNP attenuated the inhibition ( Figure 5F , middle panel). These results are consistent with the mutually exclusive and reversible binding of SRP9/14 to either the Alu RNA or to a functionally important site in the 40S subunit. The competition between 40S and Alu RNA may also explain why the inhibitory effect of Alu RNPs saturated at around 50% ( Figure 1B and F) . The targeted transfer of SRP9/14 from the Alu RNP to 40S leads to the release of free RNA and to the concomitant decrease in the amount of 40S subunits available for SRP9/14 binding. Saturation is reached when 40S subunits are no longer able to compete with the Alu RNA for SRP9/14 binding.