Effect of Overexpression of LAS17 on Stress Tolerance and the Stability of Extrachromosomal DNA in Saccharomyces cerevisiae.

Abstract

The effects of the overexpression of LAS17/BEE1, which encodes a yeast protein exhibiting sequence homology to the Wiscott-Aldrich syndrome protein, on the cell growth of Saccharomyces cerevisiae were examined. Sake yeast strain UT-1 grows at a faster rate as a result of the overexpression of LAS17 than control cultures under various stresses such as high temperature, high ethanol concentration, and oxidative stress, and the tolerance to these stresses was increased compared with the control. Moreover, a high cell survival rate was attained with overexpression of LAS17, when cells in the stationary phase of the growth cycle were subjected to heat killing (48 degrees C) or ethanol killing (20% v/v). In addition, the rate of induction of rho- was markedly reduced by overexpression of LAS17 when serine, tyrosine, and aspartic acid were used as N sources and the yeast was cultured at 35 degrees C, while rho- strains in control cultures were induced at a high frequency. After the incubation of cells harboring a multicopy vector in YPD or synthetic complete medium, almost all of the cells inherited the vector at about 15 copies per cell as a result of the overexpression of LAS17, whereas the cells harboring the control vector accounted for only 15% of the total number of cells. These results suggest that Las17p might be a multifunctional protein involved in cell growth regulation, extrachromosomal DNA transportation and stress responses.