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.
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.
Khemici
Vanessa
V
Laboratoire de Microbiologie et Génétique Moléculaire, CNRS, UMR 5100 and Paul Sabatier Université, 118 Route de Narbonne, 31062 Toulouse, France.
Carpousis
Agamemnon J
AJ
D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005095:Exoribonucleases / Q000378:metabolism; D005796:Genes; D009097:Multienzyme Complexes / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009876:Operon; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D011117:Polyribonucleotide Nucleotidyltransferase / Q000378:metabolism*; D020365:RNA Helicases / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*
D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D012329:RNA, Bacterial; D012333:RNA, Messenger; C111244:degradosome; D011062:Polynucleotide Adenylyltransferase; D011117:Polyribonucleotide Nucleotidyltransferase; D004722:Endoribonucleases; D005095:Exoribonucleases; C022535:exoribonuclease II; D020365:RNA Helicases