Open AccessThe histone-like protein H-NS acts as a transcriptional repressor for expression of the anaerobic and growth phase activator AppY of Escherichia coli
Author(s) -
Tove Atlung,
Susanne Sund,
Kirsten Olesen,
Lone Brøndsted
Publication year - 1996
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.178.12.3418-3425.1996
Subject(s) - biology , repressor , operon , microbiology and biotechnology , lac operon , escherichia coli , mutant , activator (genetics) , gene , promoter , regulation of gene expression , rpos , transcription (linguistics) , dna , gene expression , dna binding protein , nucleoid , transcription factor , biochemistry , linguistics , philosophy
The transcriptional activator AppY is required for anaerobic and stationary-phase induction of the cyx-appA and hya operons of Escherichia coli, and expression of the appY gene itself is induced by these environmental conditions. The sequence of the appY gene and its promoter region is unusually AT rich. The nucleoid-associated protein H-NS has a DNA-binding specificity for intrinsically curved AT-rich DNA. Using a single-copy transcriptional appY-lacZ fusion, we have shown that appY gene expression is derepressed in hns mutants during aerobic exponential growth. In the hns mutant, growth phase and growth rate regulation under aerobic conditions was maintained, while ArcA-dependent anaerobic induction was greatly diminished. Judged by two-dimensional gel electrophoresis, the appY promoter fragment exhibits the features characteristic of curved DNA. Gel retardation assays showed that purified H-NS protein bound with high affinity to two different segments of the appY promoter region. The role of H-NS in the AppY regulatory cascade is discussed and compared with its function in the regulatory cascades of the AppY homologs CfaD and VirF.