A 5'-terminal stem-loop structure can stabilize mRNA in Escherichia coli.
The 5'-untranslated region of the long-lived Escherichia coli ompA transcript functions as an mRNA stabilizer capable of prolonging the lifetime in E. coli of a number of heterologous messages to which it is fused. To elucidate the structural basis of differential mRNA stability in bacteria, the domains of the ompA 5'-untranslated region that allow it to protect mRNA from degradation have been identified by mutational analysis. The presence of a stem-loop no more than 2-4 nucleotides from the extreme 5' terminus of this RNA segment is crucial to its stabilizing influence, whereas the sequence of the stem-loop is relatively unimportant. The potential to form a hairpin very close to the 5' end is a feature common to a number of stable prokaryotic messages. Moreover, the lifetime of a normally labile message (bla mRNA) can be prolonged in E. coli by adding a simple hairpin structure at its 5' terminus. Accelerated degradation of ompA mRNA in the absence of a 5'-terminal stem-loop appears to start downstream of the 5' end. We propose that E. coli messages beginning with a single-stranded RNA segment of significant length are preferentially targeted by a degradative ribonuclease that interacts with the mRNA 5' terminus before cleaving internally at one or more distal sites.
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
S A
SA
Emory
P
P
Bouvet
J G
JG
Belasco
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D007700:Kinetics; D008745:Methylation; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000235:genetics; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D001425:Bacterial Outer Membrane Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger