Integration host factor is required for the activation of developmentally regulated genes in Caulobacter.
Several temporally controlled flagellar genes in Caulobacter crescentus require a sigma 54 promoter and upstream sites for transcription activation. We demonstrate here that in some of these genes, an AT-rich region containing an integration host factor (IHF) consensus binding site lies between the activator and the promoter, and that this region binds IHF in vitro. Analysis of mutations in the IHF-binding region of the hook operon demonstrated that an intact IHF-binding site is necessary for transcription in vivo. An adjacent and divergent promoter also has an IHF consensus sequence that binds IHF. The IHF and enhancer sites are 3' to the transcription start site in this promoter. We postulate that IHF mediates the formation of a higher order structure between the divergent promoter regions in a manner analogous to the nucleosome-like structure generated for lambda-Escherichia coli DNA recombination and that this higher order structure modulates transcription.
Gober
J W
JW
Department of Developmental Biology, Stanford University School of Medicine, California 94305-5427.
Shapiro
L
L
D001419:Bacteria / Q000254:growth & development*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D015153:Blotting, Western; D003429:Cross Reactions; D004268:DNA-Binding Proteins / Q000235:genetics*; D005407:Flagella / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D005809:Genes, Regulator / Q000235:genetics*; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D011401:Promoter Regions, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D034982:Integration Host Factors