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Importance of a 5' stem-loop for longevity of papA mRNA in Escherichia coli
1Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Abstract:
High-level expression of the major pilus subunit (PapA) of uropathogenic strains of Escherichia coli results in part from the unusually long lifetime of the mRNA that encodes this protein. Here we report that the longevity of papA mRNA derives in large measure from the protection afforded by its 5' untranslated region. This papA RNA segment can prolong the lifetime of an otherwise short-lived mRNA to which it is fused. In vivo alkylation studies indicate that, in its natural milieu, the papA message begins with a stem-loop structure. This stem-loop is important for the stabilizing effect of the papA 5' untranslated region, as evidenced by the significant acceleration in papA mRNA decay that results from its removal.
Insights
The 5' untranslated region of uropathogenic Escherichia coli papA mRNA protects it from degradation, extending its lifespan. This stabilization is crucial for high-level PapA protein expression, essential for bacterial virulence.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Uropathogenic Escherichia coli (UPEC) causes urinary tract infections.
- High expression of the major pilus subunit (PapA) is linked to UPEC virulence.
- PapA expression is regulated at the post-transcriptional level, involving mRNA stability.
Purpose of the Study:
- To investigate the mechanisms underlying the long mRNA lifetime of papA in UPEC.
- To determine the role of the 5' untranslated region (5' UTR) in papA mRNA stability.
- To elucidate the structural features of the papA 5' UTR that contribute to mRNA longevity.
Main Methods:
- mRNA stability assays in vivo.
- Fusion of the papA 5' UTR to a reporter mRNA.
- In vivo alkylation studies to probe RNA structure.
- Analysis of papA mRNA decay rates upon 5' UTR manipulation.
Main Results:
- The papA 5' UTR significantly extends the half-life of otherwise unstable mRNAs.
- In vivo alkylation reveals a stem-loop structure at the 5' end of the papA message.
- Deletion of this stem-loop structure leads to rapid decay of papA mRNA.
- The papA 5' UTR's protective effect is dependent on its intact stem-loop structure.
Conclusions:
- The 5' UTR of papA mRNA is a key determinant of its stability in UPEC.
- A specific stem-loop structure within the papA 5' UTR confers protection against mRNA degradation.
- This mRNA stabilization mechanism contributes to high-level PapA protein production, supporting UPEC pathogenesis.