title: Multiple pathways to bypass the enhancer requirement of sigma 54 RNA polymerase: roles for DNA and protein determinants.
abstract: Sigma 54 is a required factor for bacterial RNA polymerase to respond to enhancers and directs a mechanism that is a hybrid between bacterial and eukaryotic transcription. Three pathways were found that bypass the enhancer requirement in vitro. These rely on either deletion of the sigma 54 N terminus or destruction of the DNA consensus -12 promoter recognition element or altering solution conditions to favor transient DNA melting. Each of these allows unstable heparin-sensitive pre-initiation complexes to form that can be driven to transcribe in the absence of both enhancer protein and ATP beta-gamma hydrolysis. These disparate pathways are proposed to have a common basis in that multiple N-terminal contacts may mediate the interactions between the polymerase and the DNA region where melting originates. The results raise possibilities for common features of open complex formation by different RNA polymerases.
authors.affiliation: Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Syed
authors.forename: J D
authors.initials: JD
authors.lastname: Gralla
mesh_terms: D000595:Amino Acid Sequence; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D008969:Molecular Sequence Data; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D012808:Sigma Factor; D004247:DNA; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54