FtsK-dependent and -independent pathways of Xer site-specific recombination.
Homologous recombination between circular chromosomes generates dimers that cannot be segregated at cell division. Escherichia coli Xer site-specific recombination converts chromosomal and plasmid dimers to monomers. Two recombinases, XerC and XerD, act at the E. coli chromosomal recombination site, dif, and at related sites in plasmids. We demonstrate that Xer recombination at plasmid dif sites occurs efficiently only when FtsK is present and under conditions that allow chromosomal dimer formation, whereas recombination at the plasmid sites cer and psi is independent of these factors. We propose that the chromosome dimer- and FtsK-dependent process that activates Xer recombination at plasmid dif also activates Xer recombination at chromosomal dif. The defects in chromosome segregation that result from mutation of the FtsK C-terminus are attributable to the failure of Xer recombination to resolve chromosome dimers to monomers. Conditions that lead to FtsK-independent Xer recombination support the hypothesis that FtsK acts on Holliday junction Xer recombination intermediates.
Recchia
G D
GD
Division of Molecular Genetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
Aroyo
M
M
Wolf
D
D
Blakely
G
G
Sherratt
D J
DJ
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000235:genetics; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D019426:Integrases; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D045522:Recombinases; D011995:Recombination, Genetic; D013014:SOS Response, Genetics / Q000235:genetics
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C096452:FtsK protein, E coli; D008565:Membrane Proteins; D045522:Recombinases; C473360:XerC protein, E coli; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C473361:XerD protein, E coli; C115006:integron integrase IntI1