Adaptive elastic properties of chromatin fiber

TL;DR

This paper models the elastic properties of chromatin fibers, linking DNA mechanics to chromatin structure, and suggests elasticity tuning as a key factor in gene regulation and chromatin functions.

Contribution

It provides a quantitative framework to relate DNA elastic properties to chromatin fiber elasticity, highlighting the tunability of chromatin mechanics for biological functions.

Findings

Elastic constants depend on fiber architecture

Elasticity influences transcription regulation

Framework aids interpretation of micromanipulation studies

Abstract

Chromatin is a complex of DNA and specific proteins forming an intermediary level of organization of eukaryotic genomes, between double-stranded DNA and chromosome. Within a generic modeling of the chromatin assembly, we investigate the interplay between the mechanical properties of the chromatin fiber and its biological functions. A quantitative step is to relate the mechanics at the DNA level and the mechanics described at the chromatin fiber level. It allows to calculate the complete set of chromatin elastic constants (twist and bend persistence lengths, stretch modulus and twist-stretch coupling constant), in terms of DNA elastic properties and geometric features of the fiber. These elastic constants are strongly sensitive to the local architecture of the fiber and we argue that this tunable elasticity might be a key feature in chromatin functions, for instance in the initiation and regulation of transcription. Moreover, this analysis provides a framework to interpret micromanipulations studies of chromatin fiber and suggests further experiments involving intercalators to scan the tunable elasticity of the fiber.