title: High-resolution mapping of changes in histone-DNA contacts of nucleosomes remodeled by ISW2.
abstract: The imitation switch (ISWI) complex from yeast containing the Isw2 and Itc1 proteins was shown to preferentially slide mononucleosomes with as little as 23 bp of linker DNA from the end to the center of DNA. The contacts of unique residues in the histone fold regions of H4, H2B, and H2A with DNA were determined with base pair resolution before and after chromatin remodeling by a site-specific photochemical cross-linking approach. The path of DNA and the conformation of the histone octamer in the nucleosome remodeled or slid by ISW2 were not altered, because after adjustment for the new translational position, the DNA contacts at specific sites in the histone octamer had not been changed. Maintenance of the canonical nucleosome structure after sliding was also demonstrated by DNA photoaffinity labeling of histone proteins at specific sites within the DNA template. In addition, nucleosomal DNA does not become more accessible during ISW2 remodeling, as assayed by restriction endonuclease cutting. ISW2 was also shown to have the novel capability of counteracting transcriptional activators by sliding nucleosomes through Gal4-VP16 bound initially to linker DNA and displacing the activator from DNA.
authors.affiliation: Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901-4413, USA.
authors.forename: Stefan R
authors.initials: SR
authors.lastname: Kassabov
authors.forename: Nathalia M
authors.initials: NM
authors.lastname: Henry
authors.forename: Martin
authors.initials: M
authors.lastname: Zofall
authors.forename: Toshio
authors.initials: T
authors.lastname: Tsukiyama
authors.forename: Blaine
authors.initials: B
authors.lastname: Bartholomew
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001483:Base Sequence; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli; D006657:Histones / Q000737:chemistry* / Q000378:metabolism; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009707:Nucleosomes / Q000737:chemistry* / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D002843:Chromatin; C070633:Gal-VP16; D006657:Histones; C086468:ISWI protein; D009707:Nucleosomes; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA; D000251:Adenosine Triphosphatases