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Calorie restriction effects on silencing and recombination at the yeast rDNA
Authors:Daniel L Smith Jr  Chonghua Li  Mirela Matecic  Nazif Maqani  Mary Bryk  Jeffrey S Smith
Institution:1. Department of Biochemistry and Molecular Genetics, University of Virginia Health System, School of Medicine, Charlottesville, VA 22908, USA;2. Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
Abstract:Aging research has developed rapidly over the past decade, identifying individual genes and molecular mechanisms of the aging process through the use of model organisms and high throughput technologies. Calorie restriction (CR) is the most widely researched environmental manipulation that extends lifespan. Activation of the NAD+‐dependent protein deacetylase Sir2 (S ilent I nformation R egulator 2) has been proposed to mediate the beneficial effects of CR in the budding yeast Saccharomyces cerevisiae, as well as other organisms. Here, we show that in contrast to previous reports, Sir2 is not stimulated by CR to strengthen silencing of multiple reporter genes in the rDNA of S. cerevisiae. CR does modestly reduce the frequency of rDNA recombination, although in a SIR2‐independent manner. CR‐mediated repression of rDNA recombination also does not correlate with the silencing of Pol II‐transcribed noncoding RNAs derived from the rDNA intergenic spacer, suggesting that additional silencing‐independent pathways function in lifespan regulation.
Keywords:aging  calorie restriction  rDNA  recombination  silencing  Sir2  yeast
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