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Negative supercoiling induces spontaneous unwinding of a bacterial promoter.
Author(s) -
Drew H.R.,
Weeks J.R.,
Travers A.A.
Publication year - 1985
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1985.tb03734.x
Subject(s) - biology , dna supercoil , genetics , escherichia coli proteins , bacterial protein , bacteria , biophysics , gene , dna replication
We have examined the influence of negative supercoiling on the DNA structure of a bacterial promoter (tyrT from Escherichia coli), the transcriptional activity of which is strongly enhanced by torsional stress in vitro. Certain regions of this promoter become sensitive to digestion by single‐strand‐specific S1 nuclease as a consequence of negative superhelicity. These regions occur with high frequency (1 per 30‐50 bp) and are normally centered on a TpA doublet. The major positions of cleavage are located in and around the ‐10 sequence TATGATG, the unwinding of which is a prerequisite for gene expression. An apparently trivial change in the ‐10 sequence from TATGATG to TATGAAG reduces both transcriptional activity and S1 nuclease sensitivity at least 10‐fold. Thus the nuclease sensitivity of the promoter correlates strongly with its biological function; and both of these phenomena correlate with certain sequence‐dependent structural properties of the DNA.