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A defined terminal region of the E. coli chromosome shows late segregation and high FtsK activity.

Deghorain M, Pagès C, Meile JC, Stouf M, Capiaux H, Mercier R, Lesterlin C, Hallet B, Cornet F - PLoS ONE (2011)

Bottom Line: Displacement of replication termination outside the FtsK high activity region had no effect on FtsK activity and deletion of a part of this region was not compensated by its extension to neighbouring regions.By observing the fate of fluorescent-tagged loci of the ter region, we found that segregation of the FtsK high activity region is delayed compared to that of its adjacent regions.Our results show that a restricted terminal region of the chromosome is specifically dedicated to the last steps of chromosome segregation and to their coupling with cell division by FtsK.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Microbiologie et de Génétique Moléculaire, CNRS, Toulouse, France.

ABSTRACT

Background: The FtsK DNA-translocase controls the last steps of chromosome segregation in E. coli. It translocates sister chromosomes using the KOPS DNA motifs to orient its activity, and controls the resolution of dimeric forms of sister chromosomes by XerCD-mediated recombination at the dif site and their decatenation by TopoIV.

Methodology: We have used XerCD/dif recombination as a genetic trap to probe the interaction of FtsK with loci located in different regions of the chromosome. This assay revealed that the activity of FtsK is restricted to a ∼400 kb terminal region of the chromosome around the natural position of the dif site. Preferential interaction with this region required the tethering of FtsK to the division septum via its N-terminal domain as well as its translocation activity. However, the KOPS-recognition activity of FtsK was not required. Displacement of replication termination outside the FtsK high activity region had no effect on FtsK activity and deletion of a part of this region was not compensated by its extension to neighbouring regions. By observing the fate of fluorescent-tagged loci of the ter region, we found that segregation of the FtsK high activity region is delayed compared to that of its adjacent regions.

Significance: Our results show that a restricted terminal region of the chromosome is specifically dedicated to the last steps of chromosome segregation and to their coupling with cell division by FtsK.

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Related in: MedlinePlus

Specificity of the FtsK high activity region.Same legend as Figure 2 and 3. Green dots: strains were mutated for the tus gene. The position of the tus gene is indicated on the X-axis. Red dots: An additional replication terminator, psrA* (A*), was inserted at position 1390. The resulting restricted replication fork trap (RFT) is shown in red bellow the X-axis. Blue dots: strains were deleted of the 1364–1589 fragment (Materials and methods). The deleted fragment is shown as the blue bar. Positions of a subset of loci are shown on the graph. PJ indicates the junction of KOPS polarity (i.e., the endpoints of the deletion in the Δ(1364–1589) strain and the natural position of dif in the other strains. The yellow zone indicates extend of the FtsK high activity region and the grey zone the FtsK-independent recombination background (see Figure 2).
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pone-0022164-g005: Specificity of the FtsK high activity region.Same legend as Figure 2 and 3. Green dots: strains were mutated for the tus gene. The position of the tus gene is indicated on the X-axis. Red dots: An additional replication terminator, psrA* (A*), was inserted at position 1390. The resulting restricted replication fork trap (RFT) is shown in red bellow the X-axis. Blue dots: strains were deleted of the 1364–1589 fragment (Materials and methods). The deleted fragment is shown as the blue bar. Positions of a subset of loci are shown on the graph. PJ indicates the junction of KOPS polarity (i.e., the endpoints of the deletion in the Δ(1364–1589) strain and the natural position of dif in the other strains. The yellow zone indicates extend of the FtsK high activity region and the grey zone the FtsK-independent recombination background (see Figure 2).

Mentions: The FtsK high activity region is the last chromosome region replicated. Half of it is contained in the replication fork trap (the zone between TerA and TerC, Figure 2). In most cells, replication terminates in the vicinity of the TerC terminator, which is located near the natural dif position [39], [40]. We examined a possible role for termination of replication in the control of FtsK activity by inserting an extra replication terminator, psrA*, at position 1390 kb (Materials and methods). This restricts termination to a 50 kb zone located outside the FtsK high activity region (Figure 5). Insertion of psrA* affected only slightly if at all the recombination frequencies at the loci assayed (red dots in Figure 5). In particular, the ydbK locus is located inside the replication fork trap in wt strains and outside it in psrA* strains whereas the pyrF locus is far from most termination events in wt strains and close to them in strains harbouring psrA* (Figure 5). Insertion of psrA* did not significantly change the recombination frequencies at these two loci. Moreover, inactivation of the Tus protein, which is required for termination at terminator sites, had no significant effect on recombination frequencies (green dots in Figure 5). We conclude that the high activity of FtsK does not result from the location of replication termination in the concerned region but rather is linked to its post-replicative processing.


A defined terminal region of the E. coli chromosome shows late segregation and high FtsK activity.

Deghorain M, Pagès C, Meile JC, Stouf M, Capiaux H, Mercier R, Lesterlin C, Hallet B, Cornet F - PLoS ONE (2011)

Specificity of the FtsK high activity region.Same legend as Figure 2 and 3. Green dots: strains were mutated for the tus gene. The position of the tus gene is indicated on the X-axis. Red dots: An additional replication terminator, psrA* (A*), was inserted at position 1390. The resulting restricted replication fork trap (RFT) is shown in red bellow the X-axis. Blue dots: strains were deleted of the 1364–1589 fragment (Materials and methods). The deleted fragment is shown as the blue bar. Positions of a subset of loci are shown on the graph. PJ indicates the junction of KOPS polarity (i.e., the endpoints of the deletion in the Δ(1364–1589) strain and the natural position of dif in the other strains. The yellow zone indicates extend of the FtsK high activity region and the grey zone the FtsK-independent recombination background (see Figure 2).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3140498&req=5

pone-0022164-g005: Specificity of the FtsK high activity region.Same legend as Figure 2 and 3. Green dots: strains were mutated for the tus gene. The position of the tus gene is indicated on the X-axis. Red dots: An additional replication terminator, psrA* (A*), was inserted at position 1390. The resulting restricted replication fork trap (RFT) is shown in red bellow the X-axis. Blue dots: strains were deleted of the 1364–1589 fragment (Materials and methods). The deleted fragment is shown as the blue bar. Positions of a subset of loci are shown on the graph. PJ indicates the junction of KOPS polarity (i.e., the endpoints of the deletion in the Δ(1364–1589) strain and the natural position of dif in the other strains. The yellow zone indicates extend of the FtsK high activity region and the grey zone the FtsK-independent recombination background (see Figure 2).
Mentions: The FtsK high activity region is the last chromosome region replicated. Half of it is contained in the replication fork trap (the zone between TerA and TerC, Figure 2). In most cells, replication terminates in the vicinity of the TerC terminator, which is located near the natural dif position [39], [40]. We examined a possible role for termination of replication in the control of FtsK activity by inserting an extra replication terminator, psrA*, at position 1390 kb (Materials and methods). This restricts termination to a 50 kb zone located outside the FtsK high activity region (Figure 5). Insertion of psrA* affected only slightly if at all the recombination frequencies at the loci assayed (red dots in Figure 5). In particular, the ydbK locus is located inside the replication fork trap in wt strains and outside it in psrA* strains whereas the pyrF locus is far from most termination events in wt strains and close to them in strains harbouring psrA* (Figure 5). Insertion of psrA* did not significantly change the recombination frequencies at these two loci. Moreover, inactivation of the Tus protein, which is required for termination at terminator sites, had no significant effect on recombination frequencies (green dots in Figure 5). We conclude that the high activity of FtsK does not result from the location of replication termination in the concerned region but rather is linked to its post-replicative processing.

Bottom Line: Displacement of replication termination outside the FtsK high activity region had no effect on FtsK activity and deletion of a part of this region was not compensated by its extension to neighbouring regions.By observing the fate of fluorescent-tagged loci of the ter region, we found that segregation of the FtsK high activity region is delayed compared to that of its adjacent regions.Our results show that a restricted terminal region of the chromosome is specifically dedicated to the last steps of chromosome segregation and to their coupling with cell division by FtsK.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Microbiologie et de Génétique Moléculaire, CNRS, Toulouse, France.

ABSTRACT

Background: The FtsK DNA-translocase controls the last steps of chromosome segregation in E. coli. It translocates sister chromosomes using the KOPS DNA motifs to orient its activity, and controls the resolution of dimeric forms of sister chromosomes by XerCD-mediated recombination at the dif site and their decatenation by TopoIV.

Methodology: We have used XerCD/dif recombination as a genetic trap to probe the interaction of FtsK with loci located in different regions of the chromosome. This assay revealed that the activity of FtsK is restricted to a ∼400 kb terminal region of the chromosome around the natural position of the dif site. Preferential interaction with this region required the tethering of FtsK to the division septum via its N-terminal domain as well as its translocation activity. However, the KOPS-recognition activity of FtsK was not required. Displacement of replication termination outside the FtsK high activity region had no effect on FtsK activity and deletion of a part of this region was not compensated by its extension to neighbouring regions. By observing the fate of fluorescent-tagged loci of the ter region, we found that segregation of the FtsK high activity region is delayed compared to that of its adjacent regions.

Significance: Our results show that a restricted terminal region of the chromosome is specifically dedicated to the last steps of chromosome segregation and to their coupling with cell division by FtsK.

Show MeSH
Related in: MedlinePlus