Evidence for silencing compartments within the yeast nucleus: a role for telomere proximity and Sir protein concentration in silencer-mediated repression

Laurent A Maillet (1) , Cécile Boscheron (2) , Monica Gotta (3) , Stéphane Marcand (4) , Eric Gilson (5) , Susan M Gasser (3)

1 ENS de Lyon - École normale supérieure de Lyon
2 GIN - Grenoble Institut des Neurosciences
3 ISREC - Swiss Institute for Experimental Cancer Research - Lausanne
4 JACOB - Institut de Biologie François JACOB
5 IRCAN - Institut de Recherche sur le Cancer et le Vieillissement

Transcriptional repression at the silent mating-type loci in yeast requires the targeting of silent information regulator (Sir) proteins through specific interactions formed at cis-acting silencer elements. We show here that a reporter gene flanked by two functional silencers is not repressed when integrated at >200 kb from a telomere. Repression is restored by creation of a new telomere 13 kb from the integrated reporter or by elevated expression of SIRl, SIRS, and/or SIR4. Coupled expression represses in an additive manner, suggesting that all three factors are in limiting concentrations. When overexpressed, Sir3 and Sir4 are dispersed throughout the nucleoplasm, in contrast to wild-type cells where they are clustered in a limited number of foci together with telomeres. Efficient silencer function thus seems to require either proximity to a pool of concentrated Sir proteins, that is, proximity to telomeres, or delocalization of the silencing factors.

Mots clés: yeast mating type; telomere position effect; SIR; subnuclear organization; Silencing

Domaines: Génomique, Transcriptomique et Protéomique [q-bio.GN]

Laurent A Maillet, Cécile Boscheron, Monica Gotta, Stéphane Marcand, Eric Gilson, et al.. Evidence for silencing compartments within the yeast nucleus: a role for telomere proximity and Sir protein concentration in silencer-mediated repression. Genes and Development, 1996, 10 (14), pp.1796-1811. ⟨10.1101/gad.10.14.1796⟩. ⟨hal-02448182⟩