Quantitative study of Ace2 mother‐daughter asymmetry

LUCÍA DURRIEU; GUNNAR CEDERSUND; ALEJANDRO COLMAN-LERNER

Hetel Sofitel, Campana, Pcia BsAs, Argentina

Congreso; Exciting Biologies: Biology in Balance; 2009

Cell Press

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: mating type switching, replicative aging, and Ace2‐driven daughter cell‐specific gene expression. The cause for the asymmetry in the third process still remains unknown, and the molecular mechanism that leads to the activation of daughter cell‐specific gene expression is not fully understood. Ace2 asymmetric localization to the nucleus of daughters implies that import and/or export rates are different in the two cell types. In order to quantify these differences we performed fluorescence recovery after photobleaching (FRAP) experiments. To interpret the resulting data, and distinguish import from export, we constructed a model that considers import and export as simple mass action kinetic reactions. We proved that using this model it is possible to extract the import and export rate constants. We have also shown that the solutions are unique, and that the uncertainties acceptable. We show that predominantly nuclear Ace2 is constantly shuttling in and out of the nucleus at the end of mitosis, that mother cells have slower kinetics that daughters, and we explored the dynamic properties of some of the mutants. These results are presented as an introduction to a new approach for the study of Ace2 asymmetry and a method for measuring import and export rates.