title: DNA microloops and microdomains: a general mechanism for transcription activation by torsional transmission.
abstract: Prokaryotic transcriptional activation often involves the formation of DNA microloops upstream of the polymerase binding site. There is substantial evidence that these microloops function to bring activator and polymerase into close spatial proximity. However additional functions are suggested by the ability of certain activators, of which FIS is the best characterised example, to facilitate polymerase binding, promoter opening and polymerase escape. We review here the evidence for the concept that the topology of the microloop formed by such activators is tightly coupled to the structural transitions in DNA mediated by RNA polymerase. In this process, which we term torsional transmission, a major function of the activator is to act as a local topological homeostat. We argue that the same mechanism may also be employed in site-specific DNA inversion.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, England.
authors.forename: A
authors.initials: A
authors.lastname: Travers
authors.forename: G
authors.initials: G
authors.lastname: Muskhelishvili
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D015964:Gene Expression Regulation, Bacterial; D034982:Integration Host Factors; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics; D012808:Sigma Factor / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D002352:Carrier Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; D012808:Sigma Factor; D014157:Transcription Factors; C440502:integration host factor, E coli; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases