Project description:Up-regulation of motility genes and biosynthesis genes were found in the pck expressing high ATP cell by transcriptome analysis while catabolism genes were down-regulated. Keywords: response depends on intracellular ATP concentration derived by pck or ppc overexpression 1. pck or ppc overexpressing E. coli at early log phase using glucose-minimal medium 2. pck or ppc overexpressing E. coli at chemostat culture (D=0.1 h-1)using LB-glucose medium
Project description:Up-regulation of motility genes and biosynthesis genes were found in the pck expressing high ATP cell by transcriptome analysis while catabolism genes were down-regulated. Keywords: response depends on intracellular ATP concentration derived by pck or ppc overexpression
Project description:To investigate the extent of the effect of poly(A) polymerase (PAP I)-mediated polyadenylation on RNA stability, we performed the first genome-wide study of RNA stability in the absence of PAP I activity. Inactivation of the pcnB gene coding for PAP I led to a global stabilization of E. coli RNAs, with 1403 stabilized transcripts and only 4 destabilized. Stabilized RNAs were involved in essential cellular functions such as DNA replication and repair, translation, RNA degradation, central carbon metabolism but also in stress responses. Because PAP I is an ATP-consuming enzyme we wondered whether the RNA stabilization observed after inactivation of PAP I could also be related to changes in intracellular ATP levels. We demonstrated for the first time in E. coli, that lowering intracellular ATP levels below 1 µM/OD stabilizes RNAs. Although the ATP level was reduced by 20 % in the pcnB mutant on glucose, the ATP level was still too high to have any role in the observed RNA stabilization. However, in experiments where the ATP level was artificially strongly decreased, inactivation of PAP I by substrate availability was implicated in the stabilization mechanism of certain RNAs. This study clearly demonstrates that PAP I is at the crossroads of the regulation of RNA stability by energy status in E. coli cells.
Project description:We have previously reported that phosphoenolpyruvate carboxykinase(Pck) overexpression under glycolytic conditions enables Escherichia coli to harbor a high intracellular ATP pool resulting in enhanced recombinant protein synthesis and biohydrogen production. To understand possible reasons of the high ATP haboring cell, we carried out transcriptome and metabolic flux analysis.
Project description:The post-transcriptional process of RNA polyadenylation sits at the crossroads of energy metabolism and RNA metabolism. RNA polyadenylation is catalyzed by poly(A) polymerases which use ATP as a substrate to add adenine residues to the 3’ end of RNAs, which can alter their stability. In E. coli, RNA polyadenylation mediated by the major poly(A) polymerase (PAP I) was previously shown to facilitate degradation of individual RNAs. In this study, we performed the first ever genome-wide study of RNA stability in the absence of PAP I. Inactivation of the pcnB gene coding for PAP I led to the stabilization of more than a thousand of E. coli RNAs in the form of full-length functional molecules or non-functional fragments, involved in essential cellular functions such as DNA replication and repair, translation, central carbon metabolism, and stress response. The absence of PAP I also altered the energy metabolism, with an almost 20 % reduction in ATP levels. To better understand how RNA and energy metabolisms are interconnected, we investigated the role of ATP levels in regulating RNA stability. When we lowered intracellular ATP levels below 0.5 mM, certain RNAs were stabilized demonstrating the causal link between ATP levels and RNA stability for the first time in E. coli. Above this concentration, changes in ATP levels had no impact on RNA stability. We also demonstrated that some RNAs were stabilized when PAP I was inactivated by low ATP availability. These results clearly demonstrate that PAP I mediates an energy-dependent RNA stabilization which may contribute to cell energy homeostasis under energy-limited conditions.
Project description:Enzyme IIANtr (encoded by ptsN gene) is a component of the nitrogen phosphotransferase system (PTS). It has previously been shown that the dephosphorylated form of EIIANtr is required for the derepression of ilvBN encoding acetohydroxy acid synthase I (AHAS I) catalyzing the first step common to biosynthesis of branched-chain amino acids. Here we examine the effect of deletion of ptsN gene on global gene expression by microarray analysis. Most of the genes down-regulated in a ptsN mutant are controlled by sigma 70, while all the up-regulated genes are controlled by sigma S. As intracellular levels of sigma factors in the ptsN mutant were similar to those of the wild-type strain, this implied that the balance of sigma activities is modified by ptsN deletion.