title: Isomerization of a binary sigma-promoter DNA complex by transcription activators.
abstract: Multisubunit RNA polymerases are targets of sophisticated signal transduction pathways that link environmental or temporal cues to changes in gene expression. Here we show that the sigma 54 protein (sigma54), responsible for promoter specific binding by bacterial RNA polymerase, undergoes a nucleotide hydrolysis dependent isomerization on DNA. Changes in protein structure are evident. The isomerization has all the known requirements of sigma 54-dependent transcription, including a dependence on enhancer binding activator proteins and occurs independently of the core RNA polymerase. We suggest that activator driven changes in sigma54 conformation trigger the conversion of a transcriptionally silent RNA polymerase conformation to one able to interact productively with template DNA. Our results illustrate the types of changes that must occur for multisubunit complexes to manipulate DNA, and show that transcription activators can remodel key nucleoprotein structures to achieve direct activation of transcription.
authors.affiliation: Department of Biology, Sir Alexander Fleming Building, Imperial College of Science Technology and Medicine, London SW7 2AZ, UK.
authors.forename: W V
authors.initials: WV
authors.lastname: Cannon
authors.forename: M T
authors.initials: MT
authors.lastname: Gallegos
authors.forename: M
authors.initials: M
authors.lastname: Buck
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D007536:Isomerism; D007711:Klebsiella pneumoniae / Q000235:genetics; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009711:Nucleotides / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011487:Protein Conformation; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000737:chemistry* / Q000378:metabolism*; D016962:Sinorhizobium meliloti / Q000235:genetics; D013698:Templates, Genetic; D013816:Thermodynamics; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D020035:Holoenzymes; D009692:Nucleic Acid Heteroduplexes; D009711:Nucleotides; D012808:Sigma Factor; D015534:Trans-Activators; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54