title: Analysis of epigenetic stability and conversions in Saccharomyces cerevisiae reveals a novel role of CAF-I in position-effect variegation.
abstract: Position-effect variegation (PEV) phenotypes are characterized by the robust multigenerational repression of a gene located at a certain locus (often called gene silencing) and occasional conversions to fully active state. Consequently, the active state then persists with occasional conversions to the repressed state. These effects are mediated by the establishment and maintenance of heterochromatin or euchromatin structures, respectively. In this study, we have addressed an important but often neglected aspect of PEV: the frequency of conversions at such loci. We have developed a model and have projected various PEV scenarios based on various rates of conversions. We have also enhanced two existing assays for gene silencing in Saccharomyces cerevisiae to measure the rate of switches from repressed to active state and vice versa. We tested the validity of our methodology in Δsir1 cells and in several mutants with defects in gene silencing. The assays have revealed that the histone chaperone Chromatin Assembly Factor I is involved in the control of epigenetic conversions. Together, our model and assays provide a comprehensive methodology for further investigation of epigenetic stability and position effects.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada, Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Guelph, Ontario, Canada and Department of Genome Medicine, Genome Dynamics Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Daniel C B
authors.initials: DC
authors.lastname: Jeffery
authors.forename: Brandon A
authors.initials: BA
authors.lastname: Wyse
authors.forename: Muhammad Attiq
authors.initials: MA
authors.lastname: Rehman
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Brown
authors.forename: Zhiying
authors.initials: Z
authors.lastname: You
authors.forename: Roxanne
authors.initials: R
authors.lastname: Oshidari
authors.forename: Hisao
authors.initials: H
authors.lastname: Masai
authors.forename: Krassimir Y
authors.initials: KY
authors.lastname: Yankulov
mesh_terms: D056504:Chromatin Assembly Factor-1 / Q000502:physiology*; D055012:Chromosomal Position Effects; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D008957:Models, Genetic; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics; D012264:Ribonucleotide Reductases / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics; D016615:Telomere / Q000235:genetics
chemical_list: D056504:Chromatin Assembly Factor-1; C546594:POL30 protein, S cerevisiae; D018809:Proliferating Cell Nuclear Antigen; C533589:RLF2 protein, S cerevisiae; C084121:SIR1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C554167:URA3 protein, S cerevisiae; D012264:Ribonucleotide Reductases