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Identifier uch.biology.msc//2008zacharioudakis
Title Ένα καταβολικό ένζυμο του σακχαρομύκητα ρυθμίζει τη μεταγραφική μνήμη
Author Ζαχαριουδάκης, Ιωάννης
Thesis advisor Τζαμαρίας, Δημήτρης
Abstract Budding yeast (S.cerevisiae) has several genes that are highly induced in the presence of galactose. Upon exposure to this metabolite the genes that encode for the enzymes responsible for the metabolism of galactose (GAL1,GAL7 and GAL10 genes) and the galactose specific permease (encoded by GAL2) are higly induced. The transcription factor responsible for the activation of these genes is Gal4. When glucose grown yeast cells are exposed for the first time with galactose, they activate these genes slowly. Controrary if galactose grown cells are transfered to glucose media for several generations and then back to galactose containing medium, the induction of the Gal4 regulated genes is much faster. This phenomenon is known as galactose memory. It had been observed previously that chromatin modifications are implicated in the phenomenon of galactose memory. However, by performing a heterokaryon experiment it was shown that cytoplasmic (or membrane) factors are responsible for this phenomenon. Furthermore, the major factor responsible for the maintenance of memory was found to be Gal1, the yeast galactokinase, which besides being an enzyme, it has a Gal3-like activity. Gal3’s function is to sequester Gal80 from the nucleus in the presence of galactose, thus freeing Gal4 from the Gal80 mediated inhibition. Gal1 protein is an abundant cytoplasmic protein during extended culture in galactose. So even after 15h Gal1 protein is still present in the cells thus allowing the faster induction kinetics of the Gal4 regulated genes.
Language Greek
Issue date 2008-04-07
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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