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  • The EMBO Journal (1997) 16, 3243 - 3255
  • doi:10.1093/emboj/16.11.3243

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

Monica Gotta1, Sabine Strahl-Bolsinger2,3, Hubert Renauld1, Thierry Laroche1, Brian K. Kennedy4, Michael Grunstein3 and Susan M. Gasser1

  1. Swiss Institute for Experimental Cancer Research, Chemin des Boveresses 155, CH-1066 Epalinges/Lausanne, Switzerland
  2. Department of Biological Chemistry, University of California at Los Angeles, School of Medicine and the Molecular Biology Institute, Los Angeles, CA 90095, USA
  3. Present address: Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, Universitätstrasse 31, D-93053 Regensburg, Germany
  4. Present address: MGH Cancer Center, Building 149, 13th Street, Charlestown, MA 02129, USA

Received 2 January 1997; Revised 12 February 1997

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.

  • Keywords:

    • nuclear organization,
    • nucleolus,
    • Sir2p,
    • Sir3p,
    • telomere