Promoter-specific repression of fimB expression by the Escherichia coli nucleoid-associated protein H-NS.
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.
Donato
G M
GM
Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill 27599, USA.
Lelivelt
M J
MJ
Kawula
T H
TH
D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D004254:DNA Nucleotidyltransferases / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D015964:Gene Expression Regulation, Bacterial; D019426:Integrases; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D012329:RNA, Bacterial; D012333:RNA, Messenger; C081956:fimB protein, E coli; C063055:fimbrillin; D036781:Fimbriae Proteins; D004254:DNA Nucleotidyltransferases; D019426:Integrases