title: Conformational flexibility in the chromatin remodeler RSC observed by electron microscopy and the orthogonal tilt reconstruction method.
abstract: Chromatin remodeling complexes (remodelers) are large, multisubunit macromolecular assemblies that use ATP hydrolysis to alter the structure and positioning of nucleosomes. The mechanisms proposed for remodeler action on nucleosomes are diverse, and require structural evaluation and insights. Previous reconstructions of remodelers using electron microscopy revealed interesting features, but also significant discrepancies, prompting new approaches. Here, we use the orthogonal tilt reconstruction method, which is well suited for heterogeneous samples, to provide a reconstruction of the yeast RSC (remodel the structure of chromatin) complex. Two interesting features are revealed: first, we observe a deep central cavity within RSC, displaying a remarkable surface complementarity for the nucleosome. Second, we are able to visualize two distinct RSC conformers, revealing a major conformational change in a large protein "arm," which may shift to further envelop the nucleosome. We present a model of the RSC-nucleosome complex that rationalizes the single molecule results obtained by using optical tweezers and also discuss the mechanistic implications of our structures.
authors.affiliation: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA. aeleschziner@berkeley.edu
authors.forename: Andres E
authors.initials: AE
authors.lastname: Leschziner
authors.forename: Anjanabha
authors.initials: A
authors.lastname: Saha
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Wittmeyer
authors.forename: Yongli
authors.initials: Y
authors.lastname: Zhang
authors.forename: Carlos
authors.initials: C
authors.lastname: Bustamante
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Cairns
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D002843:Chromatin / Q000648:ultrastructure*; D042002:Chromatin Assembly and Disassembly; D008854:Microscopy, Electron; D008954:Models, Biological; D008968:Molecular Conformation; D009707:Nucleosomes / Q000648:ultrastructure; D015003:Yeasts / Q000378:metabolism*
chemical_list: D002843:Chromatin; D009707:Nucleosomes; D000255:Adenosine Triphosphate