Ribonuclease E is a 5′-end-dependent endonuclease

摘要: The selective degradation of messenger RNAs enables cells to regulate the levels particular mRNAs in response changes environment. Ribonuclease (RNase) E (ref. 1), a single-strand-specific endonuclease2,3,4 that is found multi-enzyme complex known as ‘degradosome’5,6,7, initiates many Escherichia coli3,8,9. Its relative lack sequence specificity and presence potential cleavage sites mRNA substrates2,3 cannot explain why decay frequently proceeds net 5′-to-3′ direction9,10,11. I have prepared covalently closed circular derivatives natural substrates, rpsT encoding ribosomal protein S20 2) 9S precursor 5S RNA1,12, find these are considerably more resistant vitro by RNase than linear molecules. Moreover, antisense oligo-deoxynucleotides complementary 5′ end substrates significantly reduce latter's susceptibility attack E. Finally, with terminal 5′-triphosphate groups poorly cleaved vitro, whereas monophosphorylated strongly preferred (compare ref. 13). These results show has inherent vectorial properties, its activity depending on substrates; this can account for direction coli, phenomenon ‘all or none’ decay, stabilization provided stem–loop structures14,15,16,17.