Regulation of Nuclear Positioning and Dynamics of the Silent Mating Type Loci by the Yeast Ku70/Ku80 Complex |
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Authors: | Kerstin Bystricky Haico Van Attikum Maria-Dolores Montiel Vincent Dion Lutz Gehlen Susan M. Gasser |
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Affiliation: | Laboratoire de Biologie Moléculaire Eucaryote, Université de Toulouse, 118 Route de Narbonne, F-31062 Toulouse, France,1. UMR5099, CNRS, IFR109, Toulouse, France,2. Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland,3. Leiden University Medical Center, Department of Toxicogenetics, Einthovenweg 20, 2333 ZC, Leiden, The Netherlands4. |
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Abstract: | We have examined the hypothesis that the highly selective recombination of an active mating type locus (MAT) with either HMLα or HMRa is facilitated by the spatial positioning of relevant sequences within the budding yeast (Saccharomyces cerevisiae) nucleus. However, both position relative to the nuclear envelope (NE) and the subnuclear mobility of fluorescently tagged MAT, HML, or HMR loci are largely identical in haploid a and α cells. Irrespective of mating type, the expressed MAT locus is highly mobile within the nuclear lumen, while silent loci move less and are found preferentially near the NE. The perinuclear positions of HMR and HML are strongly compromised in strains lacking the Silent information regulator, Sir4. However, HMLα, unlike HMRa and most telomeres, shows increased NE association in a strain lacking yeast Ku70 (yKu70). Intriguingly, we find that the yKu complex is associated with HML and HMR sequences in a mating-type-specific manner. Its abundance decreases at the HMLα donor locus and increases transiently at MATa following DSB induction. Our data suggest that mating-type-specific binding of yKu to HMLα creates a local chromatin structure competent for recombination, which cooperates with the recombination enhancer to direct donor choice for gene conversion of the MATa locus. |
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