ИСТИНА

Human mobile genetic elements present in genome predominantly as Alu repeats. There was found near 1.3 million ones that form 10% of human genome. Most of Alu repeats are transcribed by RNApol III generating Alu RNA. Alu RNA tends to degrade to scAlu RNA (small cellular Alu RNA). These ncRNAs specifically bind protein heterodimer SRP 9/14. Alu RNP complexes inhibit translation initiation at uncapped mRNA without 5’UTR in cell-free translation systems. We carried out action of Alu/scAlu RNP to understand mechanism of the inhibition. For this purpose we used cell-free system and reconstituted eukaryotic translation system (RETS). We estimated effect of Alu/scAlu RNP on mRNA with different 5’UTRs in rabbit reticulocyte lysate. The influence of Alu/scAlu RNP and RNA on initiation complex assembly was detected by toe-print analysis in RETS. We have found that scAlu RNP inhibits mRNA containing IRES’s translation in RRL. However Alu/scAlu RNP had no effect on capdependent initiation (on mRNA with β-actin and BRCA1 leaders). But uncapped β-actin leader was inhibited by scAlu RNP. Also we have found inhibition of 80S assembling on CrPV leader by Alu RNP in REST but scAlu RNP had no effect. Ribosome assembling on mRNA containing uncapped β-globin UTR was affected by both Alu and scAlu RNP. We propose that scAlu RNP inhibits any cap-independent loading of mRNA in 40S ribosomal subunit.