The RNA degradosome and poly(A) polymerase of Escherichia coli are required in vivo for the degradation of small mRNA decay intermediates containing REP-stabilizers

Authors

  • Vanessa Khemici,

    1. Laboratoire de Microbiologie et Génétique Moléculaire (CNRS, UMR 5100) and Paul Sabatier Université, 118 Route de Narbonne, 31062 Toulouse, France.
    Search for more papers by this author
  • Agamemnon J. Carpousis

    Corresponding author
    1. Laboratoire de Microbiologie et Génétique Moléculaire (CNRS, UMR 5100) and Paul Sabatier Université, 118 Route de Narbonne, 31062 Toulouse, France.
    Search for more papers by this author

Summary

In Escherichia coli, REP-stabilizers are structural elements in polycistronic messages that protect 5′-proximal cistrons from 3′→5′ exonucleolytic degradation. The stabilization of a protected cistron can be an important determinant in the level of gene expression. Our results suggest that RNase E, an endoribonuclease, initiates the degradation of REP-stabilized mRNA. However, subsequent degradation of mRNA fragments containing a REP-stabilizer poses a special challenge to the mRNA degradation machinery. Two enzymes, the DEAD-box RNA helicase, RhlB and poly(A) polymerase (PAP) are required to facilitate the degradation of REP-stabilizers by polynucleotide phosphorylase (PNPase). This is the first in vivo evidence that these enzymes are required for the degradation of REP-stabilizers. Furthermore, our results show that REP degradation by RhlB and PNPase requires their association with RNase E as components of the RNA degradosome, thus providing the first in vivo evidence that this ribonucleolytic multienzyme complex is involved in the degradation of structured mRNA fragments.

Ancillary