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

Second, we monitored the effect of scAluY NF1 RNA expression on the translation efficiency of endogenous mR-NAs after disassembly of the existing pool of polysomes by treatment with sodium arsenite (31) . As expected, arsenite treatment caused a dramatic 96-97% decrease in cellular protein synthesis ( Figure 6E, top panel) . At 60 min after arsenite removal protein synthesis levels remained below 10% compared to normal cells and polysomes were hardly detectable (Supplementary Figure S8C) . We then determined translation rates at 60, 90 and 120 min after removal of arsenite for cells expressing either the scAluY NF1 or the 4.5S RNA, and the values were normalized to the corresponding values for cells transfected with a control vector (Figure 6E, bottom panel) . A reduction in translation rate was specifically seen in cells expressing scAlu NF1 RNA while cells expressing 4.5S RNA were unaffected. Hence, high scAlu RNA levels delayed translation initiation of endogenous mRNAs following disassembly of polysomes.