caa a22 4500 477083064 CHVBK 20180405111455.0 cr unu---uuuuu 170330e19961201xx s 000 0 eng 10.1007/BF01952113 doi (NATIONALLICENCE)springer-10.1007/BF01952113 Nuclear organization and transcriptional silencing in yeast [Elektronische Daten] [M. Gotta, S. Gasser] Transcriptional repression at the yeast silent mating type loci requires the formation of a nucleoprotein complex at specific cis-acting elements called silencers, which in turn promotes the binding of a histone-associated Sir-protein complex to adjacent chromatin. A similar mechanism of long-range transcriptional repression appears to function near telomeric repeat sequences, where it has been demonstrated that Sir3p is a limiting factor for the propagation of silencing. A combined immunofluorescence/in situ hybridization method for budding yeast was developed that maintains the three-dimensional structure of the nucleus. In wild-type cells the immunostaining of Sir3p, Sir4p and Rap1 colocalizes with Y′ subtelomeric sequences detected by in situ hybridization. All three antigens and the subtelomeric in situ hybridization signals are clustered in foci, which are often adjacent to, but not coincident with, nuclear pores. This colocalization of Rap1, Sir3p and Sir4p with telomeres is lost insir mutants, and also when Sir4p is overexpressed. To test whether the natural positioning of the twoHM loci, located roughly 10 and 25 kb from the ends of chromosome III, is important for silencer function, a reporter gene flanked by wild-type silencer elements was integrated at various internal sites on other yeast chromosomes. We find that integration at internal loci situated far from telomeres abrogates the ability of silencers to repress the reporter gene. Silencing can be restored by creation of a telomere at 13 kb from the reporter construct, or by insertion of 340 bp of yeast telomeric repeat sequence at this site without chromosomal truncation. Elevation of the internal nuclear pools of Sir1p, Sir3p and Sir4p can relieve the lack of repression at theLYS2 locus in an additive manner, suggesting that in wild-type cells silencer function is facilitated by its juxtaposition to a pool of highly concentrated Sir proteins, such as those created by telomere clustering. Birkhäuser Verlag, 1996 Silencing nationallicence Sir nationallicence yeast mating type nationallicence telomere position effect nationallicence subnuclear organization nationallicence chromatin nationallicence Gotta M. Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, CH-1066, Epalinges/Lausanne, (Switzerland) aut Gasser S. Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, CH-1066, Epalinges/Lausanne, (Switzerland) aut Experientia Birkhäuser-Verlag 52/12(1996-12-01), 1136-1147 0014-4754 52:12<1136 1996 52 18 https://doi.org/10.1007/BF01952113 text/html Onlinezugriff via DOI 1 review-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF01952113 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Gotta M. Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, CH-1066, Epalinges/Lausanne, (Switzerland) aut NATIONALLICENCE 700 1- Gasser S. Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, CH-1066, Epalinges/Lausanne, (Switzerland) aut NATIONALLICENCE 773 0- Experientia Birkhäuser-Verlag 52/12(1996-12-01), 1136-1147 0014-4754 52:12<1136 1996 52 18 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer