Temporal coordination of the transcription factor response to HO stress.

Oxidative stress from excess HO activates transcription factors that restore redox balance and repair oxidative damage. Although many transcription factors are activated by HO, it is unclear whether they are activated at the same HO concentration, or time. Dose-dependent activation is likely as oxidative stress is not a singular state and exhibits dose-dependent outcomes including cell-cycle arrest and cell death. Here, we show that transcription factor activation is both dose-dependent and coordinated over time. Low levels of HO activate p53, NRF2 and JUN. Yet under high HO, these transcription factors are repressed, and FOXO1, NF-κB, and NFAT1 are activated. Time-lapse imaging revealed that the order in which these two groups of transcription factors are activated depends on whether HO is administered acutely by bolus addition, or continuously through the glucose oxidase enzyme. Finally, we provide evidence that 2-Cys peroxiredoxins control which group of transcription factors are activated.