Dissection of a functional interaction between the DNA translocase, FtsK, and the XerD recombinase

Abstract

SummarySuccessful bacterial circular chromosome segregation requires that any dimeric chromosomes, which arise by crossing over during homologous recombination, are converted to monomers. Resolution of dimers to monomers requires the action of the XerCD site-specific recombinase at dif in the chromosome replication terminus region. This reaction requires the DNA translocase, FtsK C , which activates dimer resolution by catalysing an ATP hydrolysis-dependent switch in the catalytic state of the nucleoprotein recombination complex. We show that a 62-aminoacid fragment of FtsK C interacts directly with the XerD C-terminus in order to stimulate the cleavage by XerD of BSN, a dif-DNA suicide substrate containing a nick in the 'bottom' strand. The resulting recombinase-DNA covalent complex can undergo strand exchange with intact duplex dif in the absence of ATP. FtsK Cmediated stimulation of BSN cleavage by XerD requires synaptic complex formation. Mutational impairment of the XerD-FtsK C interaction leads to reduction in the in vitro stimulation of BSN cleavage by XerD and a concomitant deficiency in the resolution of chromosomal dimers at dif in vivo , although other XerD functions are not affected.

Synthetic Lethality with the dut Defect in Escherichia coli Reveals Layers of DNA Damage of Increasing Complexity Due to Uracil Incorporation

“…While it is unclear why XerC overproduction could be detrimental to the cell, overproduction of FtsK might titrate the recombinase away from the septum. Strong interaction between FtsK and XerD (but not XerC) is observed in vitro (79).…”

Synchronization of Chromosome Dynamics and Cell Division in Bacteria

“…Apart from its role in synapse formation, FtsK C was shown to interact directly with XerD and thereby stimulate XerD to perform a first pair of strand exchanges, resulting in the generation of a Holliday junction. This intermediate is subsequently converted to a crossover by a second pair of strand exchanges, catalyzed by XerC in an FtsK C -independent manner (Grainge and Sherratt 1999;Barre et al 2000;Aussel et al 2002;Massey et al 2004;Yates et al 2006). Given that successive rounds of XerCD-mediated recombination can unlink catenated DNA molecules in vitro, FtsK may also have a direct role in chromosome decatenation that is independent of its interaction with Topo IV (Ip et al 2003;Grainge et al 2007).…”

Two DNA Translocases Synergistically Affect Chromosome Dimer Resolution inBacillus subtilis

“…Since the mutant strains used here differ only slightly in generation time (see Table S2 in the supplemental material), one can infer that k reflects mainly the number of nonviable cells produced in each cell division. E. coli mutants with mutations in xerD or ftsK␥ show reduced fitness when competing with the wild-type strain (2,28). However, when recA is deleted additionally, double mutants have no disadvantage compared to the ⌬recA single mutant, because in the absence of RecA-dependent homologous recombination, no chromosome dimers are formed and dimer resolution is dispensable.…”

“…By KOPS-guided directed DNA translocation, FtsK arranges the duplicated dif sites in close proximity at the division septum and thereby facilitates dimer resolution (4). Additionally, FtsK directly activates the catalytic state of XerD and is therefore essential for effective chromosome dimer resolution (1,28).…”