title: Spatial contacts and nucleosome step movements induced by the NURF chromatin remodeling complex.
abstract: The nucleosome remodeling factor NURF is a four-subunit, ISWI-containing chromatin remodeling complex that catalyzes nucleosome sliding in an ATP-dependent fashion, thereby modulating the accessibility of the DNA. To elucidate the mechanism of nucleosome sliding, we have investigated by hydroxyl radical footprinting how NURF makes initial contact with a nucleosome positioned at one end of a DNA fragment. NURF binds to two separate locations on the nucleosome: a continuous stretch of linker DNA up to the nucleosome entry site and a region asymmetrically surrounding the nucleosome dyad within the minor grooves, close to residues of the histone H4 tail that have been implicated in the activation of ISWI activity. Kinetic analysis reveals that nucleosome sliding occurs in apparent increments or steps of 10 bp. Furthermore, single nucleoside gaps as well as nicks about two helical turns before the dyad interfere with sliding, indicating that structural stress at this region assists the relative movement of DNA. These findings support a sliding model in which the position-specific tethering of NURF forces a translocating ISWI ATPase to pump a DNA distortion over the histone octamer, thereby changing the translational position of the nucleosome.
authors.affiliation: Laboratory of Molecular Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
authors.forename: Ralf
authors.initials: R
authors.lastname: Schwanbeck
authors.forename: Hua
authors.initials: H
authors.lastname: Xiao
authors.forename: Carl
authors.initials: C
authors.lastname: Wu
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry* / Q000378:metabolism*; D004331:Drosophila melanogaster; D017665:Hydroxyl Radical / Q000378:metabolism; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D009707:Nucleosomes / Q000737:chemistry* / Q000378:metabolism*; D011755:Pyrophosphatases / Q000737:chemistry / Q000378:metabolism; D056505:Retinoblastoma-Binding Protein 4
chemical_list: C110251:Caf1-55 protein, Drosophila; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; C437989:E(bx) protein, Drosophila; D018832:Molecular Chaperones; D009707:Nucleosomes; D056505:Retinoblastoma-Binding Protein 4; D017665:Hydroxyl Radical; D000255:Adenosine Triphosphate; D004247:DNA; D011755:Pyrophosphatases; C115568:Nurf-38 protein, Drosophila