Promoter recognition by bacterial alternative sigma factors: the price of high selectivity?
A key step in bacterial transcription initiation is melting of the double-stranded promoter DNA by the RNA polymerase holoenzyme. Primary sigma factors mediate the melting of thousands of promoters through a conserved set of aromatic amino acids. Alternative sigmas, which direct transcription of restricted regulons, lack the full set of melting residues. In this issue of Genes & Development, Koo and colleagues (pp. 2426-2436) show that introducing the primary sigma melting residues into alternative sigmas relaxes their promoter specificity, pointing to a trade-off of reduced promoter melting capacity for increased promoter stringency.
Feklistov
Andrey
A
The Rockefeller University, New York, New York 10065, USA.
Darst
Seth A
SA
D001419:Bacteria / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D009691:Nucleic Acid Denaturation; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000378:metabolism*
D001426:Bacterial Proteins; D012808:Sigma Factor