SummaryThe ptsG mRNA encoding the major glucose transporter is rapidly degraded in an RNase E-dependent manner in response to the accumulation of glucose 6-P or fructose 6-P when the glycolytic pathway is blocked at its early steps in Escherichia coli . RNase E, a major endonuclease, is associated with polynucleotide phosphorylase (PNPase), RhlB helicase and a glycolytic enzyme, enolase, which bind to its Cterminal scaffold region to form a multienzyme complex called the RNA degradosome. The role of enolase within the RNase E-based degradosome in RNA decay has been totally mysterious. In this article, we demonstrate that the removal of the scaffold region of RNase E suppresses the rapid degradation of ptsG mRNA in response to the metabolic stress without affecting the expression of ptsG mRNA under normal conditions. We also demonstrate that the depletion of enolase but not the disruption of pnp or rhlB eliminates the rapid degradation of ptsG mRNA. Taken together, we conclude that enolase within the degradosome plays a crucial role in the regulation of ptsG mRNA stability in response to a metabolic stress. This is the first instance in which a physiological role for enolase in the RNA degradosome has been demonstrated. In addition, we show that PNPase and RhlB within the degradosome cooperate to eliminate short degradation intermediates of ptsG mRNA.

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cell-derived small intestinal epithelial cell; hPEC, human primary enterocyte; MeIQx,quinoxaline; MES, 2-(N-morpholino)ethanesulfonic acid; NEAA, nonessential amino acids solution; P app , apparent permeability coefficient; RT-PCR, reverse transcription polymerase chain reaction; UGT, UDP-glucuronosyltransferase; UPLC-MS/MS, ultraperformance liquid chromatography-tandem mass spectrometry

Epoxidized fatty acids are generated during food processing and detected in various lipid-and oil-containing foods. Although compounds with an epoxide structure have high reactivity and there is increasing concern about their potential toxic effects such as genotoxicity and cellular damage, information regarding the toxicity of epoxy fatty acids is largely unknown. Therefore, we conducted three in vitro genotoxicity studies (bacterial reverse mutation assay, in vitro micronucleus test, and p53R2-dependent luciferase reporter gene assay) and HepG2 cytotoxicity assays for epoxyoleic acid (EOA) and diepoxylinoleic acid (DELA). The in vitro genotoxicity results of EOA and DELA were uniformly negative. In the cytotoxicity assay, EOA and DELA induced weak cytotoxicity at high concentrations, but the effect was similar to those of oleic and linoleic acids at low concentrations. Considering the existing toxicity information on epoxidized soybean oil, which is a similar compound, there might be little concern concerning the health effects of epoxy fatty acids at low concentrations.