title: Fis activates the RpoS-dependent stationary-phase expression of proP in Escherichia coli.
abstract: Fis is a general nucleoid-associated protein in Escherichia coli whose expression is highly regulated with respect to growth conditions. A random collection of transposon-induced lac fusions was screened for those which give increased expression in the presence of Fis in order to isolate a ProP-LacZ protein fusion. We find that proP, which encodes a low-affinity transporter of the important osmoprotectants proline and glycine betaine, is transcribed from two promoters. proP1 is transiently induced upon subculture and is upregulated by increases in medium osmolarity. As cells enter stationary phase, a second promoter, proP2, is strongly induced. This promoter can also be induced by high medium osmolarity in exponential phase. The activity of proP2 depends on Fis and the stationary-phase sigma factor sigmas. In the presence of Fis, proP2 expression is increased over 50-fold, as judged by the LacZ activity of cells carrying the proP-lacZ fusion as well as by direct RNA analysis, making this the most strongly activated promoter by Fis that has been described. Two Fis binding sites centered at positions -41 (site I) and -81 (site II) with respect to the transcription initiation site of P2 have been defined by DNase I footprinting. Mutations in site I largely abolish stationary-phase activation, while mutations at site II have a minor effect, suggesting that direct binding of Fis to site I is important for Fis-mediated activation of this promoter. In addition to Fis and sigmas, sequences located over 108 bp upstream of the proP2 transcription initiation site are required for efficient expression.
authors.affiliation: Department of Biological Chemistry, UCLA School of Medicine 90095, USA.
authors.forename: J
authors.initials: J
authors.lastname: Xu
authors.forename: R C
authors.initials: RC
authors.lastname: Johnson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D009154:Mutation; D009994:Osmolar Concentration; D011401:Promoter Regions, Genetic / Q000235:genetics; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012808:Sigma Factor / Q000502:physiology*; D027981:Symporters
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; C079244:ProP protein, E coli; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor; D027981:Symporters; C440502:integration host factor, E coli; C069567:sigma factor KatF protein, Bacteria