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Biophys J. 2005 Dec;89(6):4275-85. Epub 2005 Sep 8.

Chromatin dynamics in interphase cells revealed by tracking in a two-photon excitation microscope.

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Laboratory for Fluorescence Dynamics, and Department of Cell and Structural Biology, Chemical and Life Science Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA.


Increasing evidence points to a dynamical compartmentalization of the cell nucleus, yet the mechanisms by which interphase chromatin moves and is positioned within nuclei remain unclear. Here, we study the dynamics of chromatin in vivo applying a novel particle-tracking method in a two-photon microscope that provides approximately 10-fold higher spatial and temporal resolutions than previous measurements. We followed the motion of a chromatin sequence containing a lac-operator repeat in cells stably expressing lac repressor fused with enhanced green fluorescent protein, observing long periods of apparent constrained diffusion interrupted by relatively abrupt jumps of approximately 150 nm lasting 0.3-2 s. During these jumps, the particle moved an average of four times faster than in the periods between jumps and in paths more rectilinear than predicted for random diffusion motion. Additionally, the jumps were sensitive to the temperature and absent after ATP depletion. These experimental results point to an energy-dependent mechanism driving fast motion of chromatin in interphase cells.

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