THE NUCLEAR ENVELOPE DIFFUSION BARRIER IS REQUIRED FOR CORRECT MOTHER-DAUGHTER ASYMMETRY IN YEAST

LUCÍA DURRIEU; ALAN BUSH; ALEJANDRO COLMAN-LERNER

Villa Carlos Paz, Córdoba, Argentina

Congreso; XLIV Reunión Anual SAIB; 2008

SAIB

Saccharomyces cerevisiae reproduces by budding, a process that is intrinsically asymmetric. Mother cells form buds that separate to become daughters. Daughters and mothers are genetically identical but constitute distinct cell types. Three asymmetric processes have been studied the most: the mating type switch, the aging process, and the Ace2-driven daughter cell-specific gene expression. However, the event that triggers de asymmetry remains unknown, and the molecular mechanism that leads to the activation of daughter cell-specific gene expression is not fully understood. Recently, it has been described that during budding a septin-dependent lateral diffusion barrier forms in the nuclear envelope and limits the translocation of pre-existing nuclear pores into the bud (Scheprova 2008). In that work they found that the barrier defective delta Bud6 mutants fail to segregate age determinants asymmetrically. Here we show that delta Bud6 mutants also fail to establish mother- daughter asymmetric gene expression correctly. These results involve for the first time the nuclear envelope diffusion barrier in the mechanism responsible for the mother- daughter expression polarity in the budding yeast.