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Type: Journal article
Title: Action at a distance in Cl repressor regulation of the bacteriophage 186 genetic switch
Author: Dodd, I.
Egan, J.
Citation: Molecular Microbiology, 2002; 45(3):697-710
Publisher: Blackwell Science Ltd
Issue Date: 2002
ISSN: 0950-382X
Statement of
Ian B. Dodd and J. Barry Egan
Abstract: The non-lambdoid coliphage 186 provides an alternative model to the lytic-lysogenic switch of phage λ. Like λ, the key switch regulator, the CI repressor, associates to octamers. Unlike λ, the lytic promoter (pR) and the lysogenic promoter (pL) are face-to-face, 62 bp apart and are flanked by distal CI binding sites (FL and FR) located ≈ 300 bp away. Using reporter and footprinting studies, we show that the outcome, but not the mechanism, of regulation by 186 CI is very similar to λ. 186 CI stimulates pL transcription indirectly by repressing convergent interfering transcription from pR. However, in the absence of the flanking FL and FR sites, CI bound at pR interacts co-operatively with a weak CI binding site at pL and represses both promoters. FL and FR play a critical role; they assist repression of pR and simultaneously alleviate repression of pL, thus allowing high pL activity. We propose that the 186 switch is regulated by a novel mechanism in which a CI octamer bound at pR forms alternative DNA loops to pL or to a flanking site, depending on CI concentration.
Keywords: Bacteriophage lambda; DNA-Binding Proteins; Repressor Proteins; Viral Proteins; DNA, Viral; DNA Footprinting; Lysogeny; Gene Expression Regulation, Viral; Kinetics; Models, Genetic; Viral Regulatory and Accessory Proteins
RMID: 0020020065
DOI: 10.1046/j.1365-2958.2002.03038.x
Appears in Collections:Molecular and Biomedical Science publications

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