DNA bending and the initiation of transcription at sigma54-dependent bacterial promoters.
We have examined the effects on transcription initiation of promoter and enhancer strength and of the curvature of the DNA separating these entities on wild-type and mutated enhancer-promoter regions at the Escherichia coli sigma54-dependent promoters glnAp2 and glnHp2 on supercoiled and linear DNA. Our results, together with previously reported observations by other investigators, show that the initiation of transcription on linear DNA requires a single intrinsic or induced bend in the DNA, as well as a promoter with high affinity for sigma54-RNA polymerase, but on supercoiled DNA requires either such a bend or a high affinity promoter but not both. The examination of the DNA sequence of all nif gene activator- or nitrogen regulator I-sigma54 promoters reveals that those lacking a binding site for the integration host factor have an intrinsic single bend in the DNA separating enhancer from promoter.
Carmona
M
M
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Claverie-Martin
F
F
Magasanik
B
B
D001426:Bacterial Proteins / Q000235:genetics; D003198:Computer Simulation; D004269:DNA, Bacterial / Q000235:genetics*; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000235:genetics*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D012808:Sigma Factor; C497751:rpoN protein, E coli; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54