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EMBO J. 2001 Jan 15;20(1-2):197-209.

A cytosolic NAD-dependent deacetylase, Hst2p, can modulate nucleolar and telomeric silencing in yeast.

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  • 1Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, CH-1066 Epalinges/Lausanne, Switzerland.

Abstract

In budding yeast, the silent information regulator Sir2p is a nuclear NAD-dependent deacetylase that is essential for both telomeric and rDNA silencing. All eukaryotic species examined to date have multiple homologues of Sir two (HSTs), which share a highly conserved globular core domain. Here we report that yeast Hst2p and a mammalian Hst2p homologue, hSirT2p, are cytoplasmic in yeast and human cells, in contrast to yHst1p and ySir2p which are exclusively nuclear. Although yHst2p cannot restore silencing in a sir2 deletion, overexpression of yHst2p influences nuclear silencing events in a SIR2 strain, derepressing subtelomeric silencing while increasing repression in the rDNA. In contrast, a form of ySir2p carrying a point mutation in the conserved core domain disrupts both telomeric position effect (TPE) and rDNA repression at low expression levels. This argues that non-nuclear yHst2p can compete for a substrate or ligand specifically required for telomeric, and not rDNA repression.

PMID:
11226170
[PubMed - indexed for MEDLINE]
PMCID:
PMC140183
Free PMC Article

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