Asymmetric DNA requirements in Xer recombination activation by FtsK.
In bacteria with circular chromosomes, homologous recombination events can lead to the formation of chromosome dimers. In Escherichia coli, chromosome dimers are resolved by the addition of a crossover by two tyrosine recombinases, XerC and XerD, at a specific site on the chromosome, dif. Recombination depends on a direct contact between XerD and a cell division protein, FtsK, which functions as a hexameric double stranded DNA translocase. Here, we have investigated how the structure and composition of DNA interferes with Xer recombination activation by FtsK. XerC and XerD each cleave a specific strand on dif, the top and bottom strand, respectively. We found that the integrity and nature of eight bottom-strand nucleotides and three top-strand nucleotides immediately adjacent to the XerD-binding site of dif are crucial for recombination. These nucleotides are probably not implicated in FtsK translocation since FtsK could translocate on single stranded DNA in both the 5'-3' and 3'-5' orientation along a few nucleotides. We propose that they are required to stabilize FtsK in the vicinity of dif for recombination to occur because the FtsK-XerD interaction is too transient or too weak in itself to allow for XerD catalysis.
Bonné
Laetitia
L
CNRS, Centre de Génétique Moléculaire, FRE 3144, 91198 Gif-sur-Yvette, France.
Bigot
Sarah
S
Chevalier
Fabien
F
Allemand
Jean-François
JF
Barre
François-Xavier
FX
D001483:Base Sequence; D004265:DNA Helicases / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D019426:Integrases / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D009711:Nucleotides / Q000737:chemistry / Q000378:metabolism; D011995:Recombination, Genetic
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C096452:FtsK protein, E coli; D008565:Membrane Proteins; D009711:Nucleotides; C473360:XerC protein, E coli; D019426:Integrases; C473361:XerD protein, E coli; D004265:DNA Helicases