Cleavage of poly(A) tails on the 3'-end of RNA by ribonuclease E of Escherichia coli.
RNase E initiates the decay of Escherichia coli RNAs by cutting them internally near their 5'-end and is a component of the RNA degradosome complex, which also contains the 3'-exonuclease PNPASE: Recently, RNase E has been shown to be able to remove poly(A) tails by what has been described as an exonucleolytic process that can be blocked by the presence of a phosphate group on the 3'-end of the RNA. We show here, however, that poly(A) tail removal by RNase E is in fact an endonucleolytic process that is regulated by the phosphorylation status at the 5'- but not the 3'-end of RNA. The rate of poly(A) tail removal by RNase E was found to be 30-fold greater when the 5'-terminus of RNA substrates was converted from a triphosphate to monophosphate group. This finding prompted us to re-analyse the contributions of the ribonucleolytic activities within the degradosome to 3' attack since previous studies had only used substrates that had a triphosphate group on their 5'-end. Our results indicate that RNase E associated with the degradosome may contribute to the removal of poly(A) tails from 5'-monophosphorylated RNAs, but this is only likely to be significant should their attack by PNPase be blocked.
Walsh
A P
AP
Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
Tock
M R
MR
Mallen
M H
MH
Kaberdin
V R
VR
von Gabain
A
A
McDowall
K J
KJ
D020413:3' Untranslated Regions; D001483:Base Sequence; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011061:Poly A / Q000378:metabolism*; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*
D020413:3' Untranslated Regions; D009841:Oligonucleotides; D012333:RNA, Messenger; D011061:Poly A; D004722:Endoribonucleases; C022537:ribonuclease E