The histone-like protein H-NS acts as a transcriptional repressor for expression of the anaerobic and growth phase activator AppY of Escherichia coli

Tove Atlung, Susanne Sund, Kirsten Olesen, Lone Brøndsted

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

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.
Original languageEnglish
JournalJournal of Bacteriology
Volume178
Issue number12
Pages (from-to)3418-3425
ISSN0021-9193
DOIs
Publication statusPublished - 1996

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