Abstract
Similar to decapping of eukaryotic mRNAs, the RppH-catalyzed conversion of 5′-terminal triphosphate to monophosphate has recently been identified as the rate-limiting step for the degradation of a subset of mRNAs in Escherichia coli. However, the regulation of RppH pyrophosphohydrolase activity is not well understood. Because the overexpression of RppH alone does not affect the decay rate of most target mRNAs, the existence of a mechanism regulating its activity has been suggested. In this study, we identified DapF, a diaminopimelate (DAP) epimerase catalyzing the stereoinversion of L,L-DAP to meso-DAP, as a regulator of RppH. DapF showed a high affinity interaction with RppH and increased its RNA pyrophosphohydrolase activity. The simultaneous overexpression of both DapF and RppH increased the decay rates of RppH target RNAs by about a factor of two. Together, our data suggest that the cellular level of DapF is a critical factor regulating the RppH-catalyzed pyrophosphate removal and the subsequent degradation of target mRNAs.
Highlights
IntroductionNudix (nucleoside diphosphate X) hydrolases are widespread among eukaryotes, bacteria, archaea and viruses and hydrolyze a wide range of organic pyrophosphates
Nudix hydrolases are widespread among eukaryotes, bacteria, archaea and viruses and hydrolyze a wide range of organic pyrophosphates
We show that DapF, the diaminopimelate (DAP) epimerase catalyzing the biosynthesis of lysine and peptidoglycan [21], forms a tight complex with RppH to stimulate its RNA pyrophosphohydrolase activity both in vitro and in vivo
Summary
Nudix (nucleoside diphosphate X) hydrolases are widespread among eukaryotes, bacteria, archaea and viruses and hydrolyze a wide range of organic pyrophosphates. In. Escherichia coli, 13 Nudix hydrolase genes have been found, and the physiological functions of some of these proteins were studied genetically and enzymatically [1,2,3,4,5,6]. Escherichia coli, 13 Nudix hydrolase genes have been found, and the physiological functions of some of these proteins were studied genetically and enzymatically [1,2,3,4,5,6] Among these genes, the nudH gene forms an operon with the downstream gene ptsP encoding the first component (enzyme INtr) of the nitrogen-regulatory phosphoenolpyruvatedependent phosphotransferase system (PTSNtr) [7,8,9]. The physiological importance of this activity is not clear
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