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Two roles for integration host factor at an enhancer‐dependent nifA promoter
Author(s) -
Wassem Roseli,
De Souza Emanuel Maltempi,
Yates Marshall Geoffrey,
Pedrosa Fábio de Oliveira,
Buck Martin
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01746.x
Subject(s) - biology , enhancer , sigma factor , rna polymerase , transcription (linguistics) , transcription factor , dna footprinting , microbiology and biotechnology , dna , promoter , polymerase , footprinting , dna binding protein , genetics , rna , gene , gene expression , linguistics , philosophy
Control of transcription in prokaryotes often involves direct contact of regulatory proteins with RNA polymerase. For the σ 54 RNA polymerase, regulatory proteins bound to distally located enhancers engage the polymerase via DNA looping. The σ 54 ‐dependent nifA promoter of Herbaspirillum seropedicae ( Hs ) is activated under nitrogen‐limiting growth conditions. Potential enhancers for the nitrogen control activators NTRC and NIFA and binding sites for integration host factor (IHF) and σ 54 ‐holoenzyme were identified. DNA footprinting experiments showed that these sites functioned for protein binding. Their involvement in the promoter regulation was explored. In vitro , activation of the Hs nifA promoter by NTRC is stimulated by the DNA bending protein IHF. In marked contrast, activation by NIFA is greatly reduced by IHF, thus diminishing potentially destabilizing autoactivation of the nifA promoter by NIFA. Additionally, high levels of NIFA appear to limit NTRC‐dependent activation. This inhibition is IHF dependent. Therefore, IHF acts positively and negatively at the nifA promoter to restrict transcription activation to NTRC and one signal transduction pathway.