Unwinding of duplex DNA during transcription initiation at the Escherichia coli galactose operon overlapping promoters.
We have used potassium permanganate as a probe to detect DNA duplex unwinding in vitro, in open complexes between E. coli RNA polymerase and DNa fragments carrying the E. coli galactose operon regulatory region. This zone contains 3 overlapping promoters which specify transcription initiation at 3 distinct startpoints. We have used mutant gal derivatives carrying different single point mutations, each of which allows initiation from only one of the 3 start sites. This has allowed us to compare duplex unwinding in open complexes at the 3 different promoters, and to show that the extent of the unwinding is similar in each case. Further, the pattern of DNA modification by potassium permanganate suggests a model for discrimination between the upper and lower strands. Finally, we show that DNA modification by potassium permanganate at the gal promoters is the same in vivo as in vitro.
School of Biochemistry, University of Birmingham, UK.
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Chan
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Minchin
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Busby
D001483:Base Sequence; D004261:DNA Replication; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000235:genetics*; D005690:Galactose / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon; D011196:Potassium Permanganate; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
D004269:DNA, Bacterial; D011196:Potassium Permanganate; D005690:Galactose