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 study the effect of Alu RNPs on 48S complex assembly, we combined initiation factors, 40S ribosomal subunits, methionyl-tRNA i Met , ATP, GTP and Alu RNPs prior to addition of the mRNA (Material and methods). In the presence of either AluY A or scAluY A RNPs a dose-dependent decrease in the efficiency of 48S complex formation was observed reminiscent of the dose-dependent decrease of translation observed in RRL. Like in RRL, the RNA or protein components alone had no effect on 48S complex formation ( Figure 1E and F). Interestingly, the inhibition seen for AluY A RNP was stronger than for scAluY A RNP suggesting that both arms contribute individually to the activity ( Figure 1F ). This difference was not observed in the RRL, probably because the less stable right arm of the AluY A RNP was partially degraded during the translation reaction (4).