Localization of Sir2p: the nucleolus as a compartment for silent information regulators

EMBO J. 1997 Jun 2;16(11):3243-55. doi: 10.1093/emboj/16.11.3243.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antibodies, Fungal
  • Antibody Specificity
  • Cell Compartmentation
  • Cell Nucleolus / genetics
  • Cell Nucleolus / ultrastructure*
  • DNA, Ribosomal*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / immunology
  • DNA-Binding Proteins / isolation & purification*
  • Fluorescent Antibody Technique
  • Fungal Proteins / genetics
  • Fungal Proteins / immunology
  • Fungal Proteins / isolation & purification
  • GTP-Binding Proteins / immunology
  • GTP-Binding Proteins / isolation & purification
  • Histone Deacetylases*
  • Models, Biological
  • Polymerase Chain Reaction
  • Precipitin Tests
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / ultrastructure*
  • Silent Information Regulator Proteins, Saccharomyces cerevisiae*
  • Sirtuin 2
  • Sirtuins
  • Telomere*
  • Trans-Activators / genetics
  • Trans-Activators / immunology
  • Trans-Activators / isolation & purification*
  • rap GTP-Binding Proteins


  • Antibodies, Fungal
  • DNA, Ribosomal
  • DNA-Binding Proteins
  • Fungal Proteins
  • SIR3 protein, S cerevisiae
  • SIR4 protein, S cerevisiae
  • Silent Information Regulator Proteins, Saccharomyces cerevisiae
  • Trans-Activators
  • SIR2 protein, S cerevisiae
  • Sirtuin 2
  • Sirtuins
  • Histone Deacetylases
  • GTP-Binding Proteins
  • rap GTP-Binding Proteins