THE DYNAMICS OF FOXO NUCLEAR/CYTOPLASMIC SHUTTLING AS A MECHANISM FOR CONTROLLING CELL FATE
We use CRISPR/Cas9 to fluorescently tag FOXO proteins and measure their nuclear/cytoplasmic shuttling in live cells in response to cellular stress. Shuttling dynamics varies with different types of stress; some stresses lead to pulses of nuclear FOXO proteins (top left movie) while others lead to an "all or none" burst of FOXO in the nucleus (bottom left movie). We are testing the hypothesis that different dynamic patterns lead to the expression of different target genes. Similar dynamic control mechanisms have been identified in other transcription factors including the p53 and NF-KB pathways.
MECHANISMS FOR INPUT/OUTPUT SPECIFICITY IN THE FOXO TRANSCRIPTION FACTOR NETWORK
The FOXO transcription factors are critical for maintaining both cellular and tissue level homeostasis and have an evolutionarily conserved role in prolonging animal lifespan. FOXO proteins are activated by a range of different stresses and when active upregulate hundreds of genes in diverse and often conflicting cellular processes. For example, during quiescence, Foxo3a upregulates ROS scavenger and autophagy genes required for long-term viability of stem cells. In contrast, Foxo3A activity following oncogene inhibition by targeted cancer therapies can lead to programmed cell death or apoptosis. Our goal is to determine how FOXO’s “decide” between these disparate cellular processes.