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Summary: 930 Research Paper
Interphase chromosomes undergo constrained diffusional
motion in living cells
W.F. Marshall*, A. Straight, J.F. Marko, J. Swedlow§, A. Dernburg*°,
A. Belmont¶, A.W. Murray, D.A. AgardĄ* and J.W. Sedat*
Background: Structural studies of fixed cells have revealed that interphase
chromosomes are highly organized into specific arrangements in the nucleus,
and have led to a picture of the nucleus as a static structure with immobile
chromosomes held in fixed positions, an impression apparently confirmed by
recent photobleaching studies. Functional studies of chromosome behavior,
however, suggest that many essential processes, such as recombination,
require interphase chromosomes to move around within the nucleus.
Results: To reconcile these contradictory views, we exploited methods for
tagging specific chromosome sites in living cells of Saccharomyces cerevisiae
with green fluorescent protein and in Drosophila melanogaster with
fluorescently labeled topoisomerase II. Combining these techniques with
submicrometer single-particle tracking, we directly measured the motion of
interphase chromatin, at high resolution and in three dimensions. We found that
chromatin does indeed undergo significant diffusive motion within the nucleus,
but this motion is constrained such that a given chromatin segment is free to
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