NJIT Physics
Department Seminar
December 7th, Monday
Mechanism and Function of
Chromatin Positional Dynamics in Interphase
Prof. Alexandra Zidovska
Center for Soft Matter
Research, Dept. of Physics, NYU
(Biophysics, Host: Prodan)
Time: 11:45am-12:45pm with 11:30am tea time
Room: ECE202
Chromatin structure and
dynamics control all aspects of DNA biology yet are poorly understood. In
interphase, time between two cell divisions, chromatin fills the cell nucleus
in its minimally condensed polymeric state. Chromatin serves as substrate to a
number of biological processes, e.g. gene expression and DNA replication, which
require it to become locally restructured. These are energy-consuming processes
giving rise to non-equilibrium dynamics. Chromatin dynamics has been
traditionally studied by imaging of fluorescently labeled nuclear proteins and
single DNA-sites, thus focusing only on a small number of tracer particles.
Recently, we developed an approach, displacement correlation spectroscopy (DCS)
based on time-resolved image correlation analysis, to map chromatin dynamics
simultaneously across the whole nucleus in cultured human cells [1]. DCS
revealed that chromatin movement was coherent across large regions (4–5μm)
for several seconds. Regions of coherent motion extended beyond the boundaries
of single-chromosome territories, suggesting elastic coupling of motion over
length scales much larger than those of genes [1]. These large-scale, coupled
motions were ATP-dependent and unidirectional for several seconds. Following
these observations, we developed a hydrodynamic theory of active chromatin
dynamics, using the two-fluid model and describing the content of cell nucleus
as a chromatin solution, which is subject to both passive thermal fluctuations
and active (ATP-consuming) scalar and vector events [2]. In this work we
continue in our efforts to elucidate the mechanism and function of the
chromatin dynamics in interphase by investigating the dynamic contribution of
major nuclear motors such as DNA polymerase, RNA polymerase II, and
topoisomerase II combining DCS and molecular perturbations.
[1] Zidovska,
Weitz, Mitchison, Micron-scale coherence in interphase
chromatin dynamics, PNAS, 110, 15555 (2013)
[2] Bruinsma,
Grosberg, Rabin, Zidovska, Chromatin Hydrodynamics, Biophys. J., 106, 1871 (2014)