Evidence In Vivo That The Dead-Box Rna Helicase Rhib Facilitates The Degradation Of Ribosome-Free Mrna By Rnase E

The RNA degradosome of Escherichia coli is a ribonucleolytic multienzyme complex containing RNase E, polynucleotide phosphorylase, RhIB, and enolase. Previous in vitro and in vivo work has shown that RhIB facilitates the exonucleolytic degradation of structured mRNA decay intermediates by polynucleotide phosphorylase in an ATPase-dependent reaction. Here, we show that deleting the gene encoding RhIB stabilizes a lacZ mRNA transcribed by bacteriophage T7 RNA polymerase. Deleting the gene encoding enolase has little if any effect. Other messages transcribed by T7 polymerase are also stabilized by Delta rhIB. The effect of point mutations inactivating RhIB is comparable with the effect of deleting the gene. Primer extension analysis of the lacZ message indicates that RhIB facilitates endoribonucleolytic cleavage by RNase E, demonstrating a functional interaction between the RNA helicase and the endoribonuclease. The possible physiological role of an RhIB-RNase E pathway and the mechanisms by which RhIB could facilitate RNase E cleavage are discussed.