RppH-dependent pyrophosphohydrolysis of mRNAs is regulated by direct interaction with DapF in Escherichia coli

Area of Science:

• Molecular Biology
• Biochemistry
• Microbiology

Background:

• The enzyme RppH (RNA pyrophosphohydrolase) is crucial for mRNA degradation in Escherichia coli, acting as a rate-limiting step.
• The regulatory mechanisms governing RppH activity remain largely unknown, despite its importance.
• Previous observations suggest an uncharacterized regulatory system for RppH, as its overexpression alone does not significantly alter mRNA decay.

Purpose of the Study:

• To identify and characterize novel regulators of RppH activity in Escherichia coli.
• To elucidate the mechanism by which RppH activity is controlled.
• To understand the implications of RppH regulation on mRNA degradation pathways.

Main Methods:

• Protein-protein interaction studies to identify RppH-binding partners.
• Enzymatic assays to measure RppH pyrophosphohydrolase activity in vitro.
• Gene overexpression experiments in E. coli to assess the impact on mRNA decay rates.
• Biochemical characterization of DapF and its interaction with RppH.

Main Results:

• Diaminopimelate (DAP) epimerase DapF was identified as a novel regulator of RppH.
• DapF exhibits a high-affinity interaction with RppH.
• DapF significantly enhances the RNA pyrophosphohydrolase activity of RppH.
• Co-overexpression of DapF and RppH resulted in a two-fold increase in the decay rates of RppH target RNAs.

Conclusions:

• Cellular levels of DapF are critical for regulating RppH-catalyzed pyrophosphate removal.
• DapF acts as a positive regulator of RppH, influencing the degradation of specific mRNAs.
• This discovery reveals a new layer of control in bacterial mRNA turnover, linking amino acid metabolism to RNA decay.