title: Domain organization and quaternary structure of the Saccharomyces cerevisiae silent information regulator 3 protein, Sir3p.
abstract: The silent information regulator protein 3 (Sir3p) functions in the initiation, propagation, and maintenance of transcriptionally silenced chromatin in Saccharomyces cerevisiae. To better understand the physicochemical basis for its effects on chromatin architecture, recombinant full-length S. cerevisiae Sir3p has been purified to near homogeneity on the large-scale and characterized by circular dichroism, limited protease digestion, and analytical ultracentrifugation. Results indicate that the Sir3p monomer has a unique tripartite domain organization, including a nearly 300-amino-acid residue stretch of intrinsically disordered residues that lies internal to its structured N- and C-terminal regions. Sir3p self-associates extensively in moderate salt and at micromolar protein concentrations producing a broad range of oligomers that sediment from 8 to in excess of 85 S. These results provide new insight into Sir3p domain organization and quaternary structure and support a nucleosome bridging model for Sir3p-dependent regulation of chromatin architecture.
authors.affiliation: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: McBryant
authors.forename: Christine
authors.initials: C
authors.lastname: Krause
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Hansen
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D002843:Chromatin / Q000737:chemistry / Q000502:physiology; D009707:Nucleosomes / Q000737:chemistry / Q000502:physiology; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000502:physiology; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000737:chemistry* / Q000502:physiology; D018411:Spodoptera / Q000235:genetics
chemical_list: D002843:Chromatin; D009707:Nucleosomes; D011994:Recombinant Proteins; C084122:SIR3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae