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  • Title: Perinuclear localization of chromatin facilitates transcriptional silencing.
    Author: Andrulis ED, Neiman AM, Zappulla DC, Sternglanz R.
    Journal: Nature; 1998 Aug 06; 394(6693):592-5. PubMed ID: 9707122.
    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.
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