Chromatin Dynamics in Interphase Cells Revealed by Tracking in a

VALERIA LEVI, QIAOQIAO RUAN, MATTHEW PLUTZ, ANDREW S. BELMONT, AND ENRICO GRATTON

BIOPHYSICAL JOURNAL

Año: 2005 vol. 89 p. 4275 - 4285

0006-3495

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