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The aprE leader is a determinant of extreme mRNA stability in Bacillus subtilis
Gustav Hambraeus1, Martin Persson1, Blanka Rutberg1
1Department of Microbiology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden1.
Abstract:
The Bacillus subtilis aprE gene encodes subtilisin, an extracellular proteolytic enzyme produced in stationary phase. The authors examined the stability of aprE mRNA and aprE leader-lacZ fusion mRNA. Both mRNAs were found to be unusually stable, with half-lives longer than 25 min, demonstrating that the aprE leader contains a determinant for extreme mRNA stability. The half-lives were the same in growing and stationary-phase cells. This contrasts with the findings of O. Resnekov et al. (1990) [Proc Natl Acad Sci USA 87, 8355-8359], which suggested a growth-phase-dependent mechanism for decay of aprE mRNA. The discrepancy is explained by the techniques used. Substitution of two bases or deletion of 25 nucleotides in the aprE leader led to a major difference in its predicted secondary structure and resulted in a fivefold reduction of the half-life of aprE mRNA. The authors also determined the half-life of amyE mRNA, which encodes alpha-amylase, another stationary-phase, excreted enzyme and found it to be around 5 min. This shows that extreme stability is not a general property of stationary-phase mRNAs encoding excreted enzymes.
Insights
The Bacillus subtilis aprE gene
Area of Science:
- Molecular biology
- Microbiology
Background:
- The Bacillus subtilis aprE gene encodes subtilisin, a stationary-phase extracellular enzyme.
- mRNA stability is crucial for gene expression regulation.
Purpose of the Study:
- To investigate the stability of aprE mRNA and identify determinants of its stability.
- To compare aprE mRNA stability with that of other stationary-phase mRNAs.
Main Methods:
- Measurement of mRNA half-lives using techniques like Northern blotting or primer extension.
- Analysis of aprE leader sequence for structural elements influencing stability.
- Comparison of mRNA stability in growing versus stationary-phase cells.
Main Results:
- Both aprE mRNA and aprE leader-lacZ fusion mRNA exhibited unusual stability (half-lives > 25 min).
- The aprE leader sequence contains a determinant for extreme mRNA stability, independent of growth phase.
- Mutations in the aprE leader altered predicted secondary structure and reduced mRNA half-life fivefold.
- amyE mRNA, encoding another excreted enzyme, had a significantly shorter half-life (~5 min).
Conclusions:
- The aprE leader sequence confers extreme mRNA stability to aprE.
- This stability is not a universal characteristic of all stationary-phase mRNAs encoding excreted enzymes.
- The findings provide insights into post-transcriptional regulation mechanisms in Bacillus subtilis.