Messenger RNA interferase RelE controls relBE transcription by conditional cooperativity.
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.
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Martin
M
Overgaard
Jonas
J
Borch
Mikkel G
MG
Jørgensen
Kenn
K
Gerdes
D001427:Bacterial Toxins / Q000235:genetics* / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006706:Homeostasis; D009875:Operator Regions, Genetic; D009876:Operon; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D051841:Transcription Factor RelB
D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C465567:RelB protein, E coli; D051841:Transcription Factor RelB; C465566:RelE protein, E coli