Promoter-specific repression of fimB expression by the Escherichia coli nucleoid-associated protein H-NS

J Bacteriol. 1997 Nov;179(21):6618-25. doi: 10.1128/jb.179.21.6618-6625.1997.


The H-NS protein is a major component of the Escherichia coli nucleoid. Mutations in hns, the gene encoding H-NS, have pleiotropic effects on the cell altering both the expression of a variety of unlinked genes and the inversion rate of the DNA element containing the fimA promoter. We investigated the interaction between H-NS and fimB, the gene encoding the bidirectional recombinase that catalyzes fimA promoter flipping. In beta-galactosidase assays, we found that fimB expression increased approximately fivefold in an hns2-tetR insertion mutant. In gel mobility shift assays with purified H-NS, we have also shown that H-NS bound directly and cooperatively to the fimB promoter region with greater affinity than for any other known H-NS-regulated gene. Furthermore, this high-affinity interaction resulted in a promoter-specific inhibition of fimB transcription. The addition of purified H-NS to an in vitro transcription system yielded a fivefold or greater reduction in fimB-specific mRNA production. However, the marked increase in cellular FimB levels in the absence of H-NS was not the primary cause of the mutant rapid inversion phenotype. These results are discussed in regard to both H-NS as a transcriptional repressor of fimB expression and its role in regulating type 1 pilus promoter inversion.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / biosynthesis*
  • Bacterial Proteins / genetics
  • DNA Nucleotidyltransferases / biosynthesis*
  • DNA-Binding Proteins / biosynthesis*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Escherichia coli / genetics*
  • Escherichia coli Proteins*
  • Fimbriae Proteins*
  • Gene Expression Regulation, Bacterial*
  • Integrases*
  • Mutation
  • Promoter Regions, Genetic*
  • Protein Binding
  • RNA, Bacterial / analysis
  • RNA, Messenger / analysis
  • Transcription, Genetic


  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • H-NS protein, bacteria
  • RNA, Bacterial
  • RNA, Messenger
  • fimB protein, E coli
  • fimbrillin
  • Fimbriae Proteins
  • DNA Nucleotidyltransferases
  • Integrases