FIG 2.

Transient heat shock leads to transgenerational transmission of derepressed subtelomeric chromatin. (A) Wild-type cells were exposed to heat shock (39°C) for a period of 40 min and then returned to 30°C. They were allowed to grow for 10 days as described in Results. The SIR2 transcript profile was monitored after 2 h and on the 4th, 6th, and 7th days and compared with that of the control cells, which were not exposed to heat shock. The experiment was repeated three times; the results from one representative semiquantitative RT-PCR are presented. (B) Relative mRNA levels of SIR2 in normal and heat-stressed cells at different time points (as indicated on the x axis) were plotted. Error bars indicate SD (n = 3 experiments); asterisks indicate values significantly different from the control, as follows: **, P < 0.01, and *, P < 0.05. N.S., not significant. ACT1 was used as the normalization control. (C) A Western blot was developed with control and heat-stressed samples at different time intervals using anti-Sir2, anti-Hsp82, and antiactin antibodies. (D) Densitometric measurements of Hsp82 from three independent Western blots were plotted for control and heat-treated samples at the indicated time points. Error bars indicate SD. (E) Densitometric measurements of Sir2 from three independent Western blots were plotted with control (before heat shock) and heat-treated samples at the indicated time points. Error bars indicate SD. (F) Relative mRNA levels of HMLα in MATa haploids before and after heat shock at the time points given in the x axis are plotted. Error bars indicate SD (n = 3). *, P < 0.05. (G) Relative mRNA levels of YFR057w in wild-type cells and cells exposed to heat shock (39°C for 40 min) at different time points are shown. Error bars indicate SD (n = 3). *, P < 0.05. (H) Growth kinetics of wild-type and heat-stressed cells were monitored for 7 days. The graph represents a comparison between their growths on the 1st, 4th, 6th, and 7th days.