title: Nonhistone Scm3 and histones CenH3-H4 assemble the core of centromere-specific nucleosomes.
abstract: The budding yeast histone H3 variant, Cse4, replaces conventional histone H3 in centromeric chromatin and, together with centromere-specific DNA-binding factors, directs assembly of the kinetochore, a multiprotein complex mediating chromosome segregation. We have identified Scm3, a nonhistone protein that colocalizes with Cse4 and is required for its centromeric association. Bacterially expressed Scm3 binds directly to and reconstitutes a stoichiometric complex with Cse4 and histone H4 but not with conventional histone H3 and H4. A conserved acidic domain of Scm3 is responsible for directing the Cse4-specific interaction. Strikingly, binding of Scm3 can replace histones H2A-H2B from preassembled Cse4-containing histone octamers. This incompatibility between Scm3 and histones H2A-H2B is correlated with diminished in vivo occupancy of histone H2B, H2A, and H2AZ at centromeres. Our findings indicate that nonhistone Scm3 serves to assemble and maintain Cse4-H4 at centromeres and may replace histone H2A-H2B dimers in a centromere-specific nucleosome core.
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 37, Room 6068, Bethesda, MD 20892-4255, USA.
authors.forename: Gaku
authors.initials: G
authors.lastname: Mizuguchi
authors.forename: Hua
authors.initials: H
authors.lastname: Xiao
authors.forename: Jan
authors.initials: J
authors.lastname: Wisniewski
authors.forename: M Mitchell
authors.initials: MM
authors.lastname: Smith
authors.forename: Carl
authors.initials: C
authors.lastname: Wu
mesh_terms: D002453:Cell Cycle; D002503:Centromere / Q000737:chemistry*; D002868:Chromosomal Proteins, Non-Histone / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D019281:Dimerization; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D018386:Kinetochores / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D008957:Models, Genetic; D009707:Nucleosomes / Q000737:chemistry*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D013696:Temperature
chemical_list: C092746:CSE4 protein, S cerevisiae; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D006657:Histones; D009707:Nucleosomes; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C521684:Scm3 protein, S cerevisiae