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Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity
Author(s) -
Overgaard Martin,
Borch Jonas,
Jørgensen Mikkel G.,
Gerdes Kenn
Publication year - 2008
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 - 10.1111/j.1365-2958.2008.06313.x
Subject(s) - operon , biology , transcription (linguistics) , repressor , relb , antitoxin , cooperativity , transcription factor , general transcription factor , genetics , cooperative binding , operator (biology) , microbiology and biotechnology , binding site , promoter , gene , escherichia coli , toxin , gene expression , nfkb1 , linguistics , philosophy
Summary Prokaryotic toxin–antitoxin (TA) loci consist of two genes in an operon that encodes a metabolically stable toxin and an unstable antitoxin. The antitoxin neutralizes its cognate toxin by forming a tight complex with it. In all cases known, the antitoxin autoregulates TA operon transcription by binding to one or more operators in the promoter region while the toxin functions as a co‐repressor of transcription. Interestingly, the toxin can also stimulate TA operon transcription. Here we analyse mechanistic aspects of how RelE of Escherichia coli can function both as a co‐repressor and as a derepressor of relBE transcription. When RelB was in excess to RelE, two trimeric RelB 2 •RelE complexes bound cooperatively to two adjacent operator sites in the relBE promoter region and repressed transcription. In contrast, RelE in excess stimulated relBE transcription and released the RelB 2 •RelE complex from operator DNA. A mutational analysis of the operator sites showed that RelE in excess counteracted cooperative binding of the RelB 2 •RelE complexes to the operator sites. Thus, RelE controls relBE transcription by conditional cooperativity.