Synthetic circuit identifies subpopulations with sustained memory of DNA damage

Differential responses to stimuli can affect how cells succumb to disease. In yeast, DNA damage can create heterogeneous responses. To delineate how a response contributes to a cell's future behavior, we constructed a transcription-based memory circuit that detects DNA repair to isolate subpopulations with heritable damage responses. Strongly responsive cells show multigenerational effects, including growth defects and iron-associated gene expression. Less-responsive cells exhibit increased mutation frequencies but resume wild-type behavior. These two subpopulations remain distinct for multiple generations, indicating a transmissible memory of damage. Collectively, this work demonstrates the efficacy of using synthetic biology to define how environmental exposure contributes to distinct cell fates. Cells containing the HUG1 memory device (Burrill, 2011) were exposed to 0.3% EMS for 24 h and recovered for 36 h, at which point cells were sorted based on YFP expression, i.e. memory and non-memory cells. These two sorted populations were then grown for another 12 h, at which point transcriptional profiling was performed.