A Polymer Chain with Dipolar Active Forces in Connection to Spatial Organization of Chromatin

TL;DR

This paper models chromatin as a polymer chain with dipolar active forces to understand how cellular activity influences its large-scale organization and dynamics, revealing that activity type significantly alters chromatin behavior.

Contribution

It introduces a novel polymer model incorporating dipolar active forces to study chromatin dynamics, highlighting differences from passive chains with renormalized elasticity.

Findings

Extensile activity accelerates loci dynamics and increases correlation length.

Contractile activity slows down loci motion and decreases correlation length.

Dipolar active forces significantly alter the chain's elasticity and organization.

Abstract

A living cell is an active environment where the organization and dynamics of chromatin are affected by different forms of activity. Optical experiments report that loci show subdiffusive dynamics and the chromatin fiber is seen to be coherent over micrometer-scale regions. Using a bead-spring polymer chain with dipolar active forces, we study how the subdiffusive motion of the loci generate large-scale coherent motion of the chromatin. We show that in the presence of extensile (contractile) activity, the dynamics of loci grows faster (slower) and the spatial correlation length increases (decreases) compared to the case with no dipolar forces. Hence, both the dipolar active forces modify the elasticity of the chain. Interestingly in our model, the dynamics and organization of such dipolar active chains largely differ from the passive chain with renormalized elasticity.