title: A yeast catabolic enzyme controls transcriptional memory.
abstract: It has been postulated that chromatin modifications can persist through mitosis and meiosis, thereby securing memory of transcriptional states. Whether these chromatin marks can self-propagate in progeny independently of relevant trans-acting factors is an important question in phenomena related to epigenesis. "Adaptive cellular memory" displayed by yeast cells offers a convenient system to address this question. The yeast GAL genes are slowly activated by Gal4 when cells are first exposed to galactose, but their progeny, grown in glucose media, exhibit a fast activation mode upon re-exposure to this sugar. This "galactose memory" persists for several generations and was recently proposed to involve chromatin modifications and perinuclear topology of the GAL genes cluster. Here, we perform a heterokaryon assay demonstrating that this memory does not have a chromatin basis but is maintained by cytoplasmic factor(s) produced upon previous galactose induction. We show that Gal3, the cytoplasmic rate-limiting factor that releases the Gal4 activator, is dispensable for preserving galactose memory. Instead, the important memory determinant is a close Gal3 homolog, the highly expressed Gal1 galactokinase, the residual activity of which preserves memory in progeny cells by rapidly turning on the Gal4 activator upon cells' re-exposure to galactose.
authors.affiliation: Institute of Molecular Biology & Biotechnology-Foundation of Research and Technology, 71110 Heraklion, Crete, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Zacharioudakis
authors.forename: Thomas
authors.initials: T
authors.lastname: Gligoris
authors.forename: Dimitris
authors.initials: D
authors.lastname: Tzamarias
mesh_terms: D003470:Culture Media; D005686:Galactokinase / Q000235:genetics / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D003470:Culture Media; C099289:Gal3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C524219:GAL1 protein, S cerevisiae; D005686:Galactokinase; D005947:Glucose; D005690:Galactose