Abstract
Transcriptional silencing in Saccharomyces cerevisiae at the HM mating-type loci and telomeres occurs through the formation of a heterochromatin-like structure. HM silencing is regulated by cis-acting elements, termed silencers, and by trans-acting factors that bind to the silencers. These factors attract the four SIR (silent information regulator) proteins, three of which (SIR2-4) spread from the silencers to alter chromatin, hence silencing nearby genes. We show here that an HMR locus with a defective silencer can be silenced by anchoring the locus to the nuclear periphery. This was accomplished by fusing integral membrane proteins to the GAL4 DNA-binding domain and overproducing the hybrid proteins, causing them to accumulate in the endoplasmic reticulum and the nuclear membrane. We expressed the hybrid proteins in a strain carrying an HMR silencer with GAL4-binding sites (UAS(G)) replacing silencer elements, causing the silencer to become anchored to the nuclear periphery and leading to silencing of a nearby reporter gene. This silencing required the hybrids of the GAL4 DNA-binding domain with membrane proteins, the UAS(G) sites and the SIR proteins. Our results indicate that perinuclear localization helps to establish transcriptionally silent chromatin.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Binding Sites
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Cell Nucleus / metabolism*
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Chromatin / metabolism*
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DNA, Fungal / metabolism
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism
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Fungal Proteins / genetics
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Fungal Proteins / metabolism
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Gene Expression Regulation, Fungal*
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Gene Targeting
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Genes, Fungal / genetics
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Genes, Mating Type, Fungal
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Histone Deacetylases*
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Nuclear Envelope / metabolism*
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae Proteins*
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Silent Information Regulator Proteins, Saccharomyces cerevisiae*
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Sirtuin 2
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Sirtuins
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Trans-Activators / genetics
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Trans-Activators / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism
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Transcription, Genetic
Substances
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Chromatin
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DNA, Fungal
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DNA-Binding Proteins
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Fungal Proteins
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GAL4 protein, S cerevisiae
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Membrane Proteins
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Recombinant Fusion Proteins
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SIR1 protein, S cerevisiae
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SIR3 protein, S cerevisiae
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SIR4 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Silent Information Regulator Proteins, Saccharomyces cerevisiae
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Trans-Activators
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Transcription Factors
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SIR2 protein, S cerevisiae
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Sirtuin 2
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Sirtuins
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Histone Deacetylases