ИСТИНА

RelE/RelB is a well characterized toxin/antitoxin pair involved in the response to nutritional stress in Eubacteria and Archaea. No homolog of RelE was found in Eukaryotes. We show that despite this fact RelE can hydrolyze mRNA in the A-site of the eukaryotic ribosome, suggesting conservation of RelE action mechanism in all three kingdoms of life. This provides possibility of mRNA degradation pathways via A-site mRNA cleavage in Eukaryotes by analogy to Prokaryotes. The prerequisites for the RelE-mediated mRNA cleavage in mRNA-ribosome complexes are the vacant A-site and the codon-anticodon interaction in the P-site. RelE-mediated cleavage of the mRNA in the ribosomal A-site is a novel method for investigation of the eukaryotic translation. For instance, exploiting the RelE-dependent mRNA cleavage (RelE-printing) we show that (a) the HCV IRES-40S binary complex contrary to the 48S complex is insensitive to RelE treatment - one possible reason is that mRNA is not positioned correctly in mRNA binding cleft in this complex; (b) complexes with near-cognate codon-anticodon interactions rather than aberrant intermediates of scanning are formed during the translation initiation on the beta-globin mRNA in the absence of scanning factor eIF1.