title: Control of bacteriophage mu lysogenic repression.
abstract: The transposable and temperate phage Mu infects Escherichia coli where it can enter the lytic life-cycle or reside as a repressed and integrated prophage. The repressor protein Rep is the key element in the lysis-lysogeny decision. We have analyzed the fate of Rep in different mutants by Western blotting under two conditions that can induce a lysogen: high temperature and stationary phase. We show that, unexpectedly, Rep accumulates under all conditions where the prophage is completely derepressed, and that this accumulation is ClpX-dependent. An analysis of the degradation kinetics shows that Rep is a target of two protease systems: inactivation of either the clpP or lon gene results in a stabilization of Rep. Such a reaction scheme explains the counterintuitive observation that derepression is correlated with high repressor concentration. We conclude that under all conditions of phage induction the repressor is sequestered in a non-active form. A quantitative simulation accounts for our experimental data. It provides a model that captures the essential features of Mu induction and explains some of the mechanisms by which the physiological signals affecting the lysis-lysogeny decision converge onto Rep.
authors.affiliation: Laboratoire du Contrôle de l'Expression Génique, Institut Jean Roget-Faculté de Médecine-Pharmacie, Domaine de la Merci, F-38700 La Tronche, France. cranquet@cea.fr
authors.forename: Caroline
authors.initials: C
authors.lastname: Ranquet
authors.forename: Ariane
authors.initials: A
authors.lastname: Toussaint
authors.forename: Hidde
authors.initials: H
authors.lastname: de Jong
authors.forename: Geneviève
authors.initials: G
authors.lastname: Maenhaut-Michel
authors.forename: Johannes
authors.initials: J
authors.lastname: Geiselmann
mesh_terms: D010583:Bacteriophage mu / Q000235:genetics* / Q000502:physiology*; D047369:Chromatin Immunoprecipitation; D015967:Gene Expression Regulation, Viral; D008242:Lysogeny / Q000235:genetics*; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D012097:Repressor Proteins; D014764:Viral Proteins