Dynamic Nuclear Structure Emerges from Chromatin Cross-Links and Motors

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 physical mechanisms, we develop model an active, crosslinked Rouse chain bound polymeric shell. System-sized motions occur but require both activity {\it and} crosslinks. Contractile motors, in particular, enhance by driving anomalous density fluctuations. Nuclear depend on strength, crosslinking, chromosome-lamina binding. Therefore, complex chromatin emerge minimal, active system.