mRNA degradation by processive 3'-5' exoribonucleases in vitro and the implications for prokaryotic mRNA decay in vivo.
Two 3'-5' exoribonucleases, polynucleotide phosphorylase and ribonuclease II play a central role in the degradation of bacterial mRNA to ribonucleotides. Sequences with the potential to form stem-loop structures can stabilize upstream mRNA against 3'-5' exoribonucleolytic attack in vivo by blocking the processive activities of these enzymes. For many mRNA species stem-loop structures appear to provide a very efficient block to decay from the 3' end, such that the rate-determining step for mRNA decay occurs elsewhere in the transcript. We have examined the stalling of 3'-5' exoribonucleases at stem-loop structures in vitro. Although stem-loop structures alone can impede the progress of both enzymes, the duration of stalling at these structures in vitro is insufficient to account for the increased half-lives that they confer on mRNA in vivo. These data suggest that an additional factor, such as a stem-loop binding protein, is required for stabilization of mRNA by stem-loop structures in vivo. The implications for the regulation of mRNA stability are discussed.
Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, U.K.
R S
RS
McLaren
S F
SF
Newbury
G S
GS
Dance
H C
HC
Causton
C F
CF
Higgins
D000595:Amino Acid Sequence; D001483:Base Sequence; D004247:DNA; D005095:Exoribonucleases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011117:Polyribonucleotide Nucleotidyltransferase / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D012333:RNA, Messenger; D004247:DNA; D011117:Polyribonucleotide Nucleotidyltransferase; D005095:Exoribonucleases; C022535:exoribonuclease II