title: DNA bridging and looping by HMO1 provides a mechanism for stabilizing nucleosome-free chromatin.
abstract: The regulation of chromatin structure in eukaryotic cells involves abundant architectural factors such as high mobility group B (HMGB) proteins. It is not understood how these factors control the interplay between genome accessibility and compaction. In vivo, HMO1 binds the promoter and coding regions of most ribosomal RNA genes, facilitating transcription and possibly stabilizing chromatin in the absence of histones. To understand how HMO1 performs these functions, we combine single molecule stretching and atomic force microscopy (AFM). By stretching HMO1-bound DNA, we demonstrate a hierarchical organization of interactions, in which HMO1 initially compacts DNA on a timescale of seconds, followed by bridge formation and stabilization of DNA loops on a timescale of minutes. AFM experiments demonstrate DNA bridging between strands as well as looping by HMO1. Our results support a model in which HMO1 maintains the stability of nucleosome-free chromatin regions by forming complex and dynamic DNA structures mediated by protein-protein interactions.
authors: Department of Physics, Northeastern University, Boston, MA 02115, USA.
authors: Divakaran
authors: D
authors: Murugesapillai
authors: Department of Physics, Northeastern University, Boston, MA 02115, USA.
authors: Micah J
authors: MJ
authors: McCauley
authors: Department of Physics, Northeastern University, Boston, MA 02115, USA.
authors: Ran
authors: R
authors: Huo
authors: Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors: Molly H
authors: MH
authors: Nelson Holte
authors: Department of Physics, Northeastern University, Boston, MA 02115, USA.
authors: Armen
authors: A
authors: Stepanyants
authors: Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors: L James
authors: LJ
authors: Maher
authors: Department of Physics, Northeastern University, Boston, MA 02115, USA.
authors: Nathan E
authors: NE
authors: Israeloff
authors: Department of Physics, Northeastern University, Boston, MA 02115, USA mark@neu.edu.
authors: Mark C
authors: MC
authors: Williams
mesh_terms: D002843:Chromatin / Q000737:chemistry*; D004247:DNA / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D006609:High Mobility Group Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D002843:Chromatin; C103154:HMO1 protein, S cerevisiae; D006609:High Mobility Group Proteins; D009707:Nucleosomes; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA