title: Net1, a Sir2-associated nucleolar protein required for rDNA silencing and nucleolar integrity.
abstract: The Sir2 protein mediates gene silencing and repression of recombination at the rDNA repeats in budding yeast. Here we show that Sir2 executes these functions as a component of a nucleolar complex designated RENT (regulator of nucleolar silencing and telophase exit). Net1, a core subunit of this complex, preferentially cross-links to the rDNA repeats, but not to silent DNA regions near telomeres or to active genes, and tethers the RENT complex to rDNA. Net1 is furthermore required for rDNA silencing and nucleolar integrity. During interphase, Net1 and Sir2 colocalize to a subdomain within the nucleous, but at the end of mitosis a fraction of Sir2 leaves the nucleolus and disperses as foci throughout the nucleus, suggesting that the structure of rDNA silent chromatin changes during the cell cycle. Our findings suggest that a protein complex shown to regulate exit from mitosis is also involved in gene silencing.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115-5730, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Straight
authors.forename: W
authors.initials: W
authors.lastname: Shou
authors.forename: G J
authors.initials: GJ
authors.lastname: Dowd
authors.forename: C W
authors.initials: CW
authors.lastname: Turck
authors.forename: R J
authors.initials: RJ
authors.lastname: Deshaies
authors.forename: A D
authors.initials: AD
authors.lastname: Johnson
authors.forename: D
authors.initials: D
authors.lastname: Moazed
mesh_terms: D001483:Base Sequence; D002466:Cell Nucleolus / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000378:metabolism*; D006655:Histone Deacetylases; D046911:Macromolecular Substances; D008938:Mitosis; D009687:Nuclear Proteins / Q000378:metabolism*; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases