title: Repression of the Klebsiella aerogenes nac promoter.
abstract: Transcription of the nitrogen-regulated nac promoter of Klebsiella aerogenes requires sigma54 RNA polymerase, is activated by the phosphorylated form of the transcription factor nitrogen regulator I (NRI) (NtrC), and is repressed by the product of the nac gene, Nac. Nac protects a large portion of the nac control region, extending from positions -130 to -70, from digestion by DNase I. This site(s) lies immediately upstream from the site at which sigma 54 RNA polymerase binds, is downstream of a high-affinity binding site for the transcriptional activator NRI approximately P, and partially overlaps a low-affinity NRI approximately P-binding site. Binding of Nac to the DNA resulted in bending of the DNA but did not interfere with the binding of sigma 54 RNA polymerase to the promoter or with the binding of NRI approximately P to either the high-affinity site or low-affinity site. Furthermore, transcription assays with various wild-type and mutant templates suggested that Nac did not exclude NRI approximately P from either the low- or high-affinity sites, nor did Nac interfere with the ability of the polymerase to form the open complex when the binding sites for NRI approximately P were moved to different locations upstream from the promoter. Rather, Nac seemed to repress by an antiactivation mechanism in which the interaction of the NRI approximately P, bound at its normal sites, with sigma 54 RNA polymerase, bound to the promoter, was prevented.
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48109, USA.
authors.forename: J
authors.initials: J
authors.lastname: Feng
authors.forename: T J
authors.initials: TJ
authors.lastname: Goss
authors.forename: R A
authors.initials: RA
authors.lastname: Bender
authors.forename: A J
authors.initials: AJ
authors.lastname: Ninfa
mesh_terms: D001426:Bacterial Proteins; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005974:Glutamate-Ammonia Ligase / Q000235:genetics; D007711:Klebsiella pneumoniae / Q000235:genetics*; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic / Q000235:genetics; D051922:PII Nitrogen Regulatory Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics*; D051877:RNA Polymerase Sigma 54; D012097:Repressor Proteins / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C072712:NAC protein, bacteria; D051922:PII Nitrogen Regulatory Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D015534:Trans-Activators; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54; C081173:glutamine synthetase I; D005974:Glutamate-Ammonia Ligase