title: Localization of Sir2p: the nucleolus as a compartment for silent information regulators.
abstract: In wild-type budding yeast strains, the proteins encoded by SIR3, SIR4 and RAP1 co-localize with telomeric DNA in a limited number of foci in interphase nuclei. Immunostaining of Sir2p shows that in addition to a punctate staining that coincides with Rap1 foci, Sir2p localizes to a subdomain of the nucleolus. The presence of Sir2p at both the spacer of the rDNA repeat and at telomeres is confirmed by formaldehyde cross-linking and immunoprecipitation with anti-Sir2p antibodies. In strains lacking Sir4p, Sir3p becomes concentrated in the nucleolus, by a pathway requiring SIR2 and UTH4, a gene that regulates life span in yeast. The unexpected nucleolar localization of Sir2p and Sir3p correlates with observed effects of sir mutations on rDNA stability and yeast longevity, defining a new site of action for silent information regulatory factors.
authors.affiliation: Swiss Institute for Experimental Cancer Research, Chemin des Boveresses, Epalinges/Lausanne, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Gotta
authors.forename: S
authors.initials: S
authors.lastname: Strahl-Bolsinger
authors.forename: H
authors.initials: H
authors.lastname: Renauld
authors.forename: T
authors.initials: T
authors.lastname: Laroche
authors.forename: B K
authors.initials: BK
authors.lastname: Kennedy
authors.forename: M
authors.initials: M
authors.lastname: Grunstein
authors.forename: S M
authors.initials: SM
authors.lastname: Gasser
mesh_terms: D000908:Antibodies, Fungal; D000918:Antibody Specificity; D002451:Cell Compartmentation; D002466:Cell Nucleolus / Q000235:genetics / Q000648:ultrastructure*; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D019204:GTP-Binding Proteins / Q000276:immunology / Q000302:isolation & purification; D006655:Histone Deacetylases; D008954:Models, Biological; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000648:ultrastructure*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D016615:Telomere; D015534:Trans-Activators / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D020668:rap GTP-Binding Proteins
chemical_list: D000908:Antibodies, Fungal; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins