Jean Michel Louarn

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In Escherichia coli, chromosome dimers are generated by recombination between circular sister chromosomes. Dimers are lethal unless resolved by a system that involves the XerC, XerD and FtsK proteins acting at a site (dif) in the terminus region. Resolution fails if dif is moved from its normal position. To analyse this positional requirement, dif was(More)
Chromosome dimers form in bacteria by recombination between circular chromosomes. Resolution of dimers is a highly integrated process involving recombination between dif sites catalysed by the XerCD recombinase, cell division and the integrity of the division septum-associated FtsK protein and the presence of dif inside a restricted region of the chromosome(More)
The recombination site dif is the target on the Escherichia coli chromosome of the site-specific recombinases XerC and XerD. The dif/XerC-D system plays a role during the cell cycle, probably by favoring sister chromosome monomerization or separation. A phenomenon of regional control over dif activity, also analyzed in this issue, is demonstrated here by(More)
Plasmid pSC101 harbors a 28-bp sequence which is homologous to dif, the target site of the XerC/XerD-dependent recombination system in Escherichia coli. Using a technique which allows very sensitive detection of plasmid loss, we show that recombination at this site, termed psi for pSC101 stabilized inheritance, causes a moderate increase in pSC101(More)
Inversion of many predetermined segments of the Escherichia coli chromosome was attempted by using a system for in vivo selection of genomic rearrangements. Two types of constraints on these inversions were observed: (i) a sensitivity to rich medium when the distance between oriC and the 86- to 91-min region (which carries loci essential for transcription(More)
We have studies the phenotypic suppression of a dnaA46 mutation by plasmid integration at preselected chromosomal sites after introducing homologous sequences (Mu prophages) onto both the chromosomes and the suppressive plasmid. The plasmids used were all derived from plasmid R100.1. We found that the conditions required to get viable suppressive(More)
FtsK is a multifunctional protein that acts in Escherichia coli cell division and chromosome segregation. Its C-terminal domain is required for XerCD-mediated recombination between dif sites that resolve chromosome dimers formed by recombination between sister chromosomes. We report the construction and analysis of a set of strains carrying different Xer(More)
Suppression of a dnaA46 mutation by integration of plasmid R100.1 derivatives in the termination region of chromosome replication in E. coli results in medium dependence, the suppressed bacteria being sensitive to rich medium at 42° C. Derivatives of such bacteria have been selected for growth at 42° C in rich medium and we have analyzed representatives of(More)
The frequency of excisive homologous recombination has been measured at various positions along the Escherichia coli chromosome. The reporter system makes use of a lambda cI857 prophage integrated by homologous recombination within Tn5 or Tn10 transposons already installed at known positions in the E. coli chromosome. The excision frequency per cell and per(More)