Deteriorated Stress Response in Stationary-Phase Yeast: Sir2 and Yap1 Are Essential for Hsf1 Activation by Heat Shock and Oxidative Stress, Respectively
Figure 7
Activation of Hsf1 by heat shock is mimicked by excess Sir2 and improved by the NAD+ precursor.
(A) Wild-type BY4741 cells harboring HSE2-LacZ plasmid were transformed with an empty vector (−) or a centromeric pSIR2 plasmid (+). Cells grown at 30°C either exponentially (EG) or to stationary-phase (SP) were either incubated for 20 min at 30°C (−) or subjected to a 20 min HS at 42°C (+). (B) Wild-type BY4741 cells harboring HSE2-LacZ plasmid were transformed with an empty vector (−) or a pSIR2 plasmid (+). Cells grown at 30°C to the indicated growth phase were incubated for 30 min with (+) or without (−) NR (10 µM) prior to the heat shock. Cells were either incubated further for 20 min at 30°C (−) or subjected to a 20 min heat shock (HS) at 42°C (+). (C) Activity in SP yeast from (B) drawn to a smaller scale. Hsf1 activity was measured as β-galactosidase specific activity. The data are mean plus standard error of at least 3 independent experiments.