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Mapping the driving forces of chromosome structure and segregation in Escherichia coli.

Kuwada NJ, Cheveralls KC, Traxler B, Wiggins PA - Nucleic Acids Res. (2013)

Bottom Line: In this article, we use automated cell cycle imaging to quantitatively analyse the cell cycle dynamics of the origin of replication (oriC) in hundreds of cells.We exploit the natural stochastic fluctuations of the chromosome structure to map both the spatial and temporal dependence of the motional bias segregating the chromosomes.The observed map is most consistent with force generation by an active mechanism, but one that generates much smaller forces than canonical molecular motors, including those driving eukaryotic chromosome segregation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Department of Bioengineering, University of Washington, Seattle, WA 98195, USA, Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA and Department of Microbiology, University of Washington, Seattle, WA 98195, USA.

ABSTRACT
The mechanism responsible for the accurate partitioning of newly replicated Escherichia coli chromosomes into daughter cells remains a mystery. In this article, we use automated cell cycle imaging to quantitatively analyse the cell cycle dynamics of the origin of replication (oriC) in hundreds of cells. We exploit the natural stochastic fluctuations of the chromosome structure to map both the spatial and temporal dependence of the motional bias segregating the chromosomes. The observed map is most consistent with force generation by an active mechanism, but one that generates much smaller forces than canonical molecular motors, including those driving eukaryotic chromosome segregation.

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(A) Spatiotemporal dependence of the drift velocity of oriC. During the Pre-Replication and cohesion intervals of locus motion, there is a restoring drift velocity to the equilibrium position of the locus at mid-cell. Immediately after the oriC loci split, the mid-cell position becomes unstable and equilibrium positions  appear at the quarter cell positions. This velocity profile remains qualitatively unchanged for the remainder of the cell cycle. (B) Spatiotemporal dependence of locus occupancy. Higher mean velocity is observed in the Rapid-Translocation interval than in the Post-Segregation interval of motion since the peak occupancies (maxima of the occupancy curves) are further from the equilibrium positions (vertical dotted lines). (Shaded regions represent standard error).
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gkt468-F3: (A) Spatiotemporal dependence of the drift velocity of oriC. During the Pre-Replication and cohesion intervals of locus motion, there is a restoring drift velocity to the equilibrium position of the locus at mid-cell. Immediately after the oriC loci split, the mid-cell position becomes unstable and equilibrium positions appear at the quarter cell positions. This velocity profile remains qualitatively unchanged for the remainder of the cell cycle. (B) Spatiotemporal dependence of locus occupancy. Higher mean velocity is observed in the Rapid-Translocation interval than in the Post-Segregation interval of motion since the peak occupancies (maxima of the occupancy curves) are further from the equilibrium positions (vertical dotted lines). (Shaded regions represent standard error).

Mentions: The drift velocity as a function of segregation interval and relative cellular position is shown in Figure 3A. Before the oriC split, there is a restorative drift velocity profile that returns oriC to mid-cell. For instance, oriC loci to the right (x > 0) of mid-cell have a negative drift velocity that moves them back towards mid-cell (x = 0) on average. The restoring velocity is approximately linear in the displacement of the locus from the equilibrium position, reminiscent of a damped linear spring.Figure 3.


Mapping the driving forces of chromosome structure and segregation in Escherichia coli.

Kuwada NJ, Cheveralls KC, Traxler B, Wiggins PA - Nucleic Acids Res. (2013)

(A) Spatiotemporal dependence of the drift velocity of oriC. During the Pre-Replication and cohesion intervals of locus motion, there is a restoring drift velocity to the equilibrium position of the locus at mid-cell. Immediately after the oriC loci split, the mid-cell position becomes unstable and equilibrium positions  appear at the quarter cell positions. This velocity profile remains qualitatively unchanged for the remainder of the cell cycle. (B) Spatiotemporal dependence of locus occupancy. Higher mean velocity is observed in the Rapid-Translocation interval than in the Post-Segregation interval of motion since the peak occupancies (maxima of the occupancy curves) are further from the equilibrium positions (vertical dotted lines). (Shaded regions represent standard error).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3753618&req=5

gkt468-F3: (A) Spatiotemporal dependence of the drift velocity of oriC. During the Pre-Replication and cohesion intervals of locus motion, there is a restoring drift velocity to the equilibrium position of the locus at mid-cell. Immediately after the oriC loci split, the mid-cell position becomes unstable and equilibrium positions appear at the quarter cell positions. This velocity profile remains qualitatively unchanged for the remainder of the cell cycle. (B) Spatiotemporal dependence of locus occupancy. Higher mean velocity is observed in the Rapid-Translocation interval than in the Post-Segregation interval of motion since the peak occupancies (maxima of the occupancy curves) are further from the equilibrium positions (vertical dotted lines). (Shaded regions represent standard error).
Mentions: The drift velocity as a function of segregation interval and relative cellular position is shown in Figure 3A. Before the oriC split, there is a restorative drift velocity profile that returns oriC to mid-cell. For instance, oriC loci to the right (x > 0) of mid-cell have a negative drift velocity that moves them back towards mid-cell (x = 0) on average. The restoring velocity is approximately linear in the displacement of the locus from the equilibrium position, reminiscent of a damped linear spring.Figure 3.

Bottom Line: In this article, we use automated cell cycle imaging to quantitatively analyse the cell cycle dynamics of the origin of replication (oriC) in hundreds of cells.We exploit the natural stochastic fluctuations of the chromosome structure to map both the spatial and temporal dependence of the motional bias segregating the chromosomes.The observed map is most consistent with force generation by an active mechanism, but one that generates much smaller forces than canonical molecular motors, including those driving eukaryotic chromosome segregation.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Department of Bioengineering, University of Washington, Seattle, WA 98195, USA, Biophysics Graduate Group, University of California, Berkeley, CA 94720, USA and Department of Microbiology, University of Washington, Seattle, WA 98195, USA.

ABSTRACT
The mechanism responsible for the accurate partitioning of newly replicated Escherichia coli chromosomes into daughter cells remains a mystery. In this article, we use automated cell cycle imaging to quantitatively analyse the cell cycle dynamics of the origin of replication (oriC) in hundreds of cells. We exploit the natural stochastic fluctuations of the chromosome structure to map both the spatial and temporal dependence of the motional bias segregating the chromosomes. The observed map is most consistent with force generation by an active mechanism, but one that generates much smaller forces than canonical molecular motors, including those driving eukaryotic chromosome segregation.

Show MeSH
Related in: MedlinePlus