  The cell nucleus houses the chromosomes, which are linked to a soft shell of
lamin filaments. Experiments indicate that correlated chromosome dynamics and
nuclear shape fluctuations arise from motor activity. To identify the physical
mechanisms, we develop a model of an active, crosslinked Rouse chain bound to a
polymeric shell. System-sized correlated motions occur but require both motor
activity {\it and} crosslinks. Contractile motors, in particular, enhance
chromosome dynamics by driving anomalous density fluctuations. Nuclear shape
fluctuations depend on motor strength, crosslinking, and chromosome-lamina
binding. Therefore, complex chromatin dynamics and nuclear shape emerge from a
minimal, active chromosome-lamina system.

Subcellular Processes