Interplay between reactive oxygen species (ROS) and transcriptional regulation in the control of circadian rhythms

Circadian clocks synchronize an organism’s behaviour and physiology with daily environmental fluctuations. The timekeeping apparatus operates within individual cells through a conserved mechanism involving a transcription/translation feedback loop (TTFL). Circadian rhythms in NADPH and cellular redox state have recently been identified as additional cogs of the cellular clock. These circadian oscillations in the cellular redox state have recently received much attention in the context of metabolic cycles and ageing but their mechanistic basis and implications for organismal behaviour remain unclear. Furthermore, mutations in the TTFL, which abolish behavioural rhythms, can cause ROS accumulation suggesting a fundamental interplay between ROS and gene expression loops. This work will examine the role of a potential new regulator that brings together ROS signals and gene expression.

The project will investigate how ROS control cellular and organismal clocks through a newly identified AP-1 binding partner in Drosophila whose mRNA levels display a circadian profile. In response to elevated ROS, AP-1 initiates transcription of antioxidant genes such as sulfiredoxin to bring down ROS. We will test the hypothesis that AP-1 dependent gene expression is rhythmic and that this completes a feedback loop generating cycling cellular ROS levels to drive behavioural rhythms.

The student will use cellular and biochemical techniques to investigate for rhythmic production of several cellular ROS species and AP-1 transcriptional activity in mammalian cell lines and neurons and in Drosophila. Through modern genetic manipulations, including CAS9/CRISPR, the student will assess the contribution of AP-1 induced genes in circadian rhythms. The student will also have the opportunity to develop novel genetically encoded sensors for ROS species and ROS scavengers that will allow real time measurements in transgenic flies and mammalian cells. Cellular changes will be compared to circadian rhythms of locomotor activity in Drosophila.