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Open complex formation by Escherichia coli RNA polymerase: the mechanism of polymerase‐induced strand separation of double helical DNA
Author(s) -
DeHaseth Pieter L.,
Helmann John D.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.tb02309.x
Subject(s) - biology , dna clamp , rna polymerase , polymerase , escherichia coli , dna , microbiology and biotechnology , dna polymerase , biophysics , genetics , rna , gene , reverse transcriptase
Summary Escherichia coli RNA polymerase is able to site‐specifically melt 12 bp of promoter DNA at temperatures far below those normally associated with DNA melting. Here we consider several models to explain how RNA polymerase destabilizes duplex DNA. One popular model proposes that upon binding to the promoter, RNA polymerase untwists the spacer DNA between the –10 and –35 regions, which results in a destabilization of the –10 region at a TA base step where melting initiates. Promoter untwisting may result, in part, from extensive wrapping of the DNA around RNA polymerase. Formation of the strand‐separated open complex appears to be facilitated by specific protein‐DNA interactions which occur predominantly on the non‐template strand. Recent evidence suggests that these include important contacts with Sigma factor region 2.3, which we propose binds the displaced single strand of DNA.