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.
Andrulis
E D
ED
Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794-5215, USA.
Neiman
A M
AM
Zappulla
D C
DC
Sternglanz
R
R
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