Perinuclear localization of chromatin facilitates transcriptional silencing.
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.
Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794-5215, USA.
E D
ED
Andrulis
A M
AM
Neiman
D C
DC
Zappulla
R
R
Sternglanz
D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D018390:Gene Targeting; D005800:Genes, Fungal / Q000235:genetics; D049770:Genes, Mating Type, Fungal; D006655:Histone Deacetylases; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
D002843:Chromatin; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C084121:SIR1 protein, S cerevisiae; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D014157:Transcription Factors; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases