Escherichia coli σ 70 senses sequence and conformation of the promoter spacer region

SS Singh, A Typas, R Hengge… - Nucleic acids …, 2011 - academic.oup.com
Nucleic acids research, 2011academic.oup.com
In bacteria, promoter identification by RNA polymerase is mediated by a dissociable σ factor.
The housekeeping σ 70 factor of Escherichia coli recognizes two well characterized DNA
sequence elements, known as the '− 10'and '− 35'hexamers. These elements are separated
by 'spacer'DNA, the sequence of which is generally considered unimportant. Here, we use a
combination of bioinformatics, genetics and biochemistry to show that σ 70 can sense the
sequence and conformation of the promoter spacer region. Our data illustrate how …
Abstract
In bacteria, promoter identification by RNA polymerase is mediated by a dissociable σ factor. The housekeeping σ 70 factor of Escherichia coli recognizes two well characterized DNA sequence elements, known as the ‘−10’ and ‘−35’ hexamers. These elements are separated by ‘spacer’ DNA, the sequence of which is generally considered unimportant. Here, we use a combination of bioinformatics, genetics and biochemistry to show that σ 70 can sense the sequence and conformation of the promoter spacer region. Our data illustrate how alterations in spacer region sequence can increase promoter activity. This stimulatory effect requires σ 70 side chain R451, which is located in close proximity to the non-template strand at promoter position −18. Conversely, R451 is not required to mediate transcriptional stimulation by improvement of the −10 element. Mutation of σ 70 residue R451, which is highly conserved, results in reduced growth rate, consistent with a central role in promoter recognition.
Oxford University Press