LOH is suppressed (Figure 4; Fob1 Off). Critically, after the TET-FOB1 strain is aged over a 65-hour time course in the presence of doxycycline, removal of the repressor results in a rapid ∼5-fold increase in LOH levels within 5 hours (Figure 4; Fob1 Off → On). This result suggests that the process responsible for increased LOH rates in aging cells occurs independently of Fob1, but that Fob1 activity is required in old cells for this aging process to generate LOH events.
