Transcriptional activation by MarA, SoxS and Rob of two tolC promoters using one binding site: a complex promoter configuration for tolC in Escherichia coli.
The Escherichia coli tolC encodes a major outer membrane protein with multiple functions in export (e.g. diverse xenobiotics, haemolysin) and as an attachment site for phage and colicins. tolC is regulated in part by MarA, SoxS and Rob, three paralogous transcriptional activators which bind a sequence called the marbox and which activate multiple antibiotic and superoxide resistance functions. Two previously identified tolC promoters, p1 and p2, are not regulated by MarA, SoxS or Rob but p2 is activated by EvgAS and PhoPQ which also regulate other functions. Using transcriptional fusions and primer extension assays, we show here that tolC has two additional strong overlapping promoters, p3 and p4, which are downstream of p1, p2 and the marbox and are activated by MarA, SoxS and Rob. p3 and p4 are configured so that a single marbox suffices to activate transcription from both promoters. At the p3 promoter, the marbox is separated by 20 bp from the -10 hexamer for RNA polymerase but at the p4 promoter, the same marbox is separated by 30 bp from the -10 hexamer. The multiple tolC promoters may allow the cell to respond to diverse environments by co-ordinating tolC transcription with other appropriate functions.
Zhang
Aixia
A
Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-0560, USA.
Rosner
Judah L
JL
Martin
Robert G
RG
D019677:Artificial Gene Fusion; D001425:Bacterial Outer Membrane Proteins / Q000096:biosynthesis*; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000378:metabolism*; D017930:Genes, Reporter; D026901:Membrane Transport Proteins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000378:metabolism*; D024363:Transcription Initiation Site; D015533:Transcriptional Activation
D001425:Bacterial Outer Membrane Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; D026901:Membrane Transport Proteins; C080267:Rob protein, E coli; D015534:Trans-Activators; C073126:tolC protein, E coli; C070725:SoxS protein, E coli