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 functional activity of the Alu RNP depends on specific amino acid residues in SRP9/14, which are also required for elongation arrest activity of SRP Mutational analysis of SRP9/14 revealed that it contains two positively charged patches of amino acid residues, a basic pentapeptide in the C-terminal region of SRP14 and three lysines in SRP9 ( Figure 2D , residues labeled in black) that are essential for the elongation arrest activity of the SRP (14, 21) . The two patches are located in proximity in SRP9/14 and were therefore proposed to form together a functional minidomain (21) . We decided to investigate the possibility that the same amino acid residues may also be required for Alu RNP-mediated inhibition of translation. We assembled scAluY A RNPs with the mutated proteins h9/14A5 and h9-3A/14 ( Figure 2D ). The scAluY A RNA formed stable complexes with both mutated protein dimers (Supplementary Figure S4A) .