Enhancement of RNA polymerase binding to promoters by a transcriptional activator, OmpR, in Escherichia coli: its positive and negative effects on transcription.
The OmpR binding sequence (OBS) in the upstream region of the ompF promoter of Escherichia coli was fused to 27 synthetic promoters. Transcription from a number of weak promoters, regardless of their sequences, was dramatically activated in the presence of OmpR, a transcriptional activator. In vivo DNA footprinting revealed that OmpR enhanced the binding of RNA polymerase to the promoters. This enhancement was essential for transcription of weak promoters, while OmpR binding to the OBS fused to a strong promoter was inhibitory for transcription. These results indicate that OmpR stabilizes the formation of an RNA polymerase-promoter complex, possibly a closed promoter complex, and that a transcription activator can serve not only as a positive but also as a negative regulator for gene expression.
Tsung
K
K
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey at Rutgers, Piscataway 08854.
Brissette
R E
RE
Inouye
M
M
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009710:Nucleotide Mapping; D015345:Oligonucleotide Probes / Q000138:chemical synthesis; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015183:Restriction Mapping; D014158:Transcription, Genetic
D001425:Bacterial Outer Membrane Proteins; D015345:Oligonucleotide Probes; D012321:DNA-Directed RNA Polymerases