Chromatin: a tunable spring at work inside chromosomes.
This paper focuses on mechanical aspects of chromatin biological functioning. Within a basic geometric modeling of the chromatin assembly, we give a 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 wormlike 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.
Ben-Haïm
E
E
Laboratoire de Physique Théorique des Liquides, Université Pierre et Marie Curie, Case Courrier 121, 4 Place Jussieu, 75252 Paris Cedex 05, France.
Lesne
A
A
Victor
J M
JM
D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D002843:Chromatin / Q000737:chemistry*; D002875:Chromosomes / Q000737:chemistry*; D004247:DNA / Q000737:chemistry; D004548:Elasticity; D006657:Histones / Q000737:chemistry; D008954:Models, Biological; D008968:Molecular Conformation; D009707:Nucleosomes / Q000737:chemistry
D002843:Chromatin; D006657:Histones; D009707:Nucleosomes; D004247:DNA