Chromatin: a tunable spring at work inside chromosomes

Abstract

This paper focuses on mechanical aspects of chromatin biological functioning. Within a basic geometric modeling of the chromatin assembly, we give for the first time the complete set of elastic constants (twist and bend persistence lengths, stretch modulus and twist-stretch coupling constant) of the so-called 30-nm chromatin fiber, in terms of DNA elastic properties and geometric properties of the fiber assembly. The computation naturally embeds the fiber within a current analytical model known as the ``extensible worm-like rope'', allowing a straightforward prediction of the force-extension curves. We show that these elastic constants are strongly sensitive to the linker length, up to 1 bp, or equivalently to its twist, and might locally reach very low values, yielding a highly flexible and extensible domain in the fiber. In particular, the twist-stretch coupling constant, reflecting the chirality of the chromatin fiber, exhibits steep variations and sign changes when the linker length is varied. We argue that this tunable elasticity might be a key feature for chromatin function, for instance in the initiation and regulation of transcription.

38 pages 15 figures

References in corpus (2)

• DNA folding: structural and mechanical properties of the two-angle model for chromatin
• Helical close packings of ideal ropes

Cited by in corpus (7)

• Structural plasticity of single chromatin fibers revealed by torsional manipulation
• Nucleosome interactions in chromatin: fiber stiffening and hairpin formation
• How does the chromatin fiber deal with topological constraints?
• How short-ranged electrostatics controls the chromatin structure on much larger scales
• Intercalation and buckling instability of DNA linker within locked chromatin fiber
• Adaptive elastic properties of chromatin fiber
• Strain dependent twist-stretch elasticity in chiral filaments