title: Spatial patterns of transcriptional activity in the chromosome of Escherichia coli.
abstract: BACKGROUND
  Although genes on the chromosome are organized in a fixed order, the spatial correlations in transcription have not been systematically evaluated. We used a combination of genomic and signal processing techniques to investigate the properties of transcription in the genome of Escherichia coli K12 as a function of the position of genes on the chromosome.
  
  
  RESULTS
  Spectral analysis of transcriptional series revealed the existence of statistically significant patterns in the spatial series of transcriptional activity. These patterns could be classified into three categories: short-range, of up to 16 kilobases (kb); medium-range, over 100-125 kb; and long-range, over 600-800 kb. We show that the significant similarities in gene activities extend beyond the length of an operon and that local patterns of coexpression are dependent on DNA supercoiling. Unlike short-range patterns, the formation of medium and long-range transcriptional patterns does not strictly depend on the level of DNA supercoiling. The long-range patterns appear to correlate with the patterns of distribution of DNA gyrase on the bacterial chromosome.
  
  
  CONCLUSIONS
  Localization of structural components in the transcriptional signal revealed an asymmetry in the distribution of transcriptional patterns along the bacterial chromosome. The demonstration that spatial patterns of transcription could be modulated pharmacologically and genetically, along with the identification of molecular correlates of transcriptional patterns, offer for the first time strong evidence of physiologically determined higher-order organization of transcription in the bacterial chromosome.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA. jeong009@umn.edu
authors.forename: Kyeong Soo
authors.initials: KS
authors.lastname: Jeong
authors.forename: Jaeyong
authors.initials: J
authors.lastname: Ahn
authors.forename: Arkady B
authors.initials: AB
authors.lastname: Khodursky
mesh_terms: D002874:Chromosome Mapping / Q000379:methods; D002876:Chromosomes, Bacterial / Q000235:genetics*; D027081:DNA Gyrase / Q000235:genetics; D048168:Escherichia coli K12 / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D023061:Gene Order / Q000235:genetics; D009643:Norfloxacin / Q000494:pharmacology; D017354:Point Mutation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D059005:Topoisomerase II Inhibitors; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D059005:Topoisomerase II Inhibitors; D027081:DNA Gyrase; D009643:Norfloxacin