Fis, an accessorial factor for transcriptional activation of the mar (multiple antibiotic resistance) promoter of Escherichia coli in the presence of the activator MarA, SoxS, or Rob.
Transcription of the multiple antibiotic resistance marRAB operon increases when one of the sequence-related activators, MarA, SoxS, or Rob, binds to the "marbox" centered at -61.5 relative to the transcriptional start site. Previous deletion analyses showed that an adjacent upstream "accessory region" was needed to augment the marbox-dependent activation. To analyze the roles of the marbox and accessory regions on mar transcription, thirteen promoters, each with a different 5-bp transversion of the -96 to -32 sequence, were synthesized, fused to lacZ, and assayed for beta-galactosidase production in single-copy lysogens with appropriate genotypes. The accessory region is shown here to be a binding site for Fis centered at -81 and to bind Fis, a small DNA-binding and -bending protein, with a Kd of approximately 5 nM. The binding of MarA to the marbox and that of Fis to its site were independent of each other. MarA, SoxS, and Rob each activated the mar promoter 1.5-to 2-fold when it had a wild-type marbox but Fis was absent. In the presence of MarA, SoxS, or Rob, Fis further enhanced the activity of the promoter twofold provided the promoter was also capable of binding Fis. However, in the absence of MarA, SoxS, or Rob or in the absence of a wild-type marbox, Fis nonspecifically lowered the activity of the mar promoter about 25% whether or not a wild-type Fis site was present. Thus, Fis acts as an accessory transcriptional activator at the mar promoter.
Martin
R G
RG
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892-0560, USA. rgmartin@helix.nih.gov
Rosner
J L
JL
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; C080002:MarA protein, E coli; C080004:MarR protein, E coli; D012097:Repressor Proteins; C080267:Rob protein, E coli; D015534:Trans-Activators; D014157:Transcription Factors; C440502:integration host factor, E coli; C080003:multiple antibiotic resistance protein B; C070725:SoxS protein, E coli