RpoS-independent and growth phase-dependent expression of dcuSR operon of Escherichia coli.
The dcuSR operon of Escherichia coli encodes a two-component sensor/kinase-response/regulator system. This system regulates gene expression in response to external C 4 -dicarboxylates. During entry into stationary phase Gram-negative bacteria express genes that impart cellular resistance to environmental stresses. In E. coli , 50 or more genes are triggered by sigma factor ( sigma s ) during entry into stationary phase. Multi-copy dcuS-lacZ and chromosomally integrated dcuS-lacZ fusions analysis showed that the expression of dcuSR is positively regulated during growth phase. Many genes that are required for stationary-phase adaptation are controlled by RpoS, a conserved alternative sigma factor, whose expression is, in turn, controlled by many factors. To understand whether the dcuSR is dependent upon RpoS, a RpoS- dcuS-lacZ strain was generated. beta -Galactosidase assay and Western blot analysis reported that the generated RpoS- dcuS-lacZ strain and the wild type showed the same expression during stationary phase. Surprisingly, the growth phase-dependence of the expression of dcuSR is still present in RpoS- dcuS-lacZ strain suggesting that other growth-phase-dependent regulatory mechanisms (might be the DcuSR system or cAMP/CRP), in addition to RpoS, may control post-exponential dcuSR expression.
University of Taif Department of Biology, Faculty of Science Taif Saudi Arabia Kingdom. abo-amer@lycos.com
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Abo-Amer
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Altalhi
D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000502:physiology*; D015153:Blotting, Western; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis*; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D009876:Operon; D011494:Protein Kinases / Q000096:biosynthesis*; D012808:Sigma Factor / Q000502:physiology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000096:biosynthesis*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C115005:DcuR protein, E coli; D029968:Escherichia coli Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C069567:sigma factor KatF protein, Bacteria; D011494:Protein Kinases; C469359:DcuS protein, E coli; D001616:beta-Galactosidase