title: Anatomy of Escherichia coli sigma70 promoters.
abstract: Information theory was used to build a promoter model that accounts for the -10, the -35 and the uncertainty of the gap between them on a common scale. Helical face assignment indicated that base -7, rather than -11, of the -10 may be flipping to initiate transcription. We found that the sequence conservation of sigma70 binding sites is 6.5 +/- 0.1 bits. Some promoters lack a -35 region, but have a 6.7 +/- 0.2 bit extended -10, almost the same information as the bipartite promoter. These results and similarities between the contacts in the extended -10 binding and the -35 suggest that the flexible bipartite sigma factor evolved from a simpler polymerase. Binding predicted by the bipartite model is enriched around 35 bases upstream of the translational start. This distance is the smallest 5' mRNA leader necessary for ribosome binding, suggesting that selective pressure minimizes transcript length. The promoter model was combined with models of the transcription factors Fur and Lrp to locate new promoters, to quantify promoter strengths, and to predict activation and repression. Finally, the DNA-bending proteins Fis, H-NS and IHF frequently have sites within one DNA persistence length from the -35, so bending allows distal activators to reach the polymerase.
authors.affiliation: Center for Cancer Research Nanobiology Program, National Cancer Institute at Frederick, PO Box B, Building 469, Room 144, Frederick, MD 21702-1201, USA.
authors.forename: Ryan K
authors.initials: RK
authors.lastname: Shultzaberger
authors.forename: Zehua
authors.initials: Z
authors.lastname: Chen
authors.forename: Karen A
authors.initials: KA
authors.lastname: Lewis
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Schneider
mesh_terms: D000465:Algorithms; D001483:Base Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007257:Information Theory; D008957:Models, Genetic; D011401:Promoter Regions, Genetic; D012270:Ribosomes / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases