title: Distinct strategies to make nucleosomal DNA accessible.
abstract: One hallmark of ATP-dependent remodeling complexes is the ability to make nucleosomal DNA accessible to regulatory factors. We have compared two prominent human ATP-dependent remodelers, BRG1 from the SWI/SNF family and SNF2h from the ISWI family, for their abilities to make a spectrum of nucleosomal sites accessible. By measuring rates of remodeling at seven different sites on a mononucleosome and at six different sites on the central nucleosome of a trinucleosome, we have found that BRG1 opens centrally located sites more than an order of magnitude better than SNF2h. We provide evidence that this capability of BRG1 is caused by its ability to create DNA loops on the surface of a nucleosome, even when that nucleosome is constrained by adjacent nucleosomes. This specialized ability to make central sites accessible should allow SWI/SNF family complexes to facilitate binding of nuclear factors in chromatin environments where adjacent nucleosomes might otherwise constrain mobility.
authors.affiliation: Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Hua-Ying
authors.initials: HY
authors.lastname: Fan
authors.forename: Xi
authors.initials: X
authors.lastname: He
authors.forename: Robert E
authors.initials: RE
authors.lastname: Kingston
authors.forename: Geeta J
authors.initials: GJ
authors.lastname: Narlikar
mesh_terms: D000255:Adenosine Triphosphate / Q000235:genetics*; D000818:Animals; D002467:Cell Nucleus / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000235:genetics*; D004265:DNA Helicases; D004268:DNA-Binding Proteins / Q000235:genetics*; D005057:Eukaryotic Cells / Q000378:metabolism*; D005809:Genes, Regulator / Q000235:genetics; D006801:Humans; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics*; D009707:Nucleosomes / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D009707:Nucleosomes; C499336:SMARCA1 protein, human; C084011:SMARCA2 protein, human; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D004247:DNA; C084108:SMARCA4 protein, human; D004265:DNA Helicases