title: Asymmetric unwrapping of nucleosomes under tension directed by DNA local flexibility.
abstract: Dynamics of the nucleosome and exposure of nucleosomal DNA play key roles in many nuclear processes, but local dynamics of the nucleosome and its modulation by DNA sequence are poorly understood. Using single-molecule assays, we observed that the nucleosome can unwrap asymmetrically and directionally under force. The relative DNA flexibility of the inner quarters of nucleosomal DNA controls the unwrapping direction such that the nucleosome unwraps from the stiffer side. If the DNA flexibility is similar on two sides, it stochastically unwraps from either side. The two ends of the nucleosome are orchestrated such that the opening of one end helps to stabilize the other end, providing a mechanism to amplify even small differences in flexibility to a large asymmetry in nucleosome stability. Our discovery of DNA flexibility as a critical factor for nucleosome dynamics and mechanical stability suggests a novel mechanism of gene regulation by DNA sequence and modifications.
authors.affiliation: Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA.
authors.forename: Thuy T M
authors.initials: TT
authors.lastname: Ngo
authors.affiliation: Department of Physics, Center for Physics in Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA.
authors.forename: Qiucen
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Physics, Center for Physics in Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA.
authors.forename: Ruobo
authors.initials: R
authors.lastname: Zhou
authors.affiliation: Department of Physics, Center for Physics in Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA. Electronic address: jyodh@illinois.edu.
authors.forename: Jaya G
authors.initials: JG
authors.lastname: Yodh
authors.affiliation: Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA; Department of Physics, Center for Physics in Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA; Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2902, USA; Howard Hughes Medical Institute, University of Illinois, Urbana, IL 61801-2902, USA. Electronic address: tjha@illinois.edu.
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
mesh_terms: D000818:Animals; D010582:Bacteriophage lambda / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006657:Histones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism*; D052898:Optical Tweezers; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D006657:Histones; D009707:Nucleosomes; D029867:Xenopus Proteins; D004247:DNA