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Unwinding of duplex DNA during transcription initiation at the Escherichia coli galactose operon overlapping promoters
Author(s) -
Chan Bernard,
Minchin Stephen,
Busby Stephen
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80284-p
Subject(s) - promoter , operon , dna , gal operon , rna polymerase , microbiology and biotechnology , transcription (linguistics) , escherichia coli , chemistry , polymerase , rna , biology , mutant , biochemistry , gene , gene expression , linguistics , philosophy
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.