The endoribonucleolytic N-terminal half of Escherichia coli RNase E is evolutionarily conserved in Synechocystis sp. and other bacteria but not the C-terminal half, which is sufficient for degradosome assembly

摘要

Escherichia coli RNase E, an essentialsingle-stranded specific endoribonuclease, is required for bothribosomal RNA processing and the rapid degradation of mRNA. Theavailability of the complete sequences of a number of bacterial genomesprompted us to assess the evolutionarily conservation of bacterialRNase E. We show here that the sequence of the N-terminalendoribonucleolytic domain of RNase E is evolutionarily conserved inSynechocystis sp. and other bacteria. Furthermore, wedemonstrate that the Synechocystis sp. homologue bindsRNase E substrates and cleaves them at the same position as theE. coli enzyme. Taken together these results suggestthat RNase E-mediated mechanisms of RNA decay are not confined toE. coli and its close relatives. We also show that theC-terminal half of E. coli RNase E is both sufficientand necessary for its physical interaction with the 3′–5′exoribonuclease polynucleotide phosphorylase, the RhlB helicase, andthe glycolytic enzyme enolase, which are components of a“degradosome” complex. Interestingly, however, the sequence ofthe C-terminal half of E. coli RNase E is not highlyconserved evolutionarily, suggesting diversity of RNase E interactionswith other RNA decay components in different organisms. This notion issupported by our finding that the Synechocystis sp.RNase E homologue does not function as a platform for assembly ofE. coli degradosome components.