Nutrient-Driven O-GlcNAcylation Controls DNA Damage Repair Signaling and Stem/Progenitor Cell Homeostasis

Stem/progenitor cells exhibit high proliferation rates, elevated nutrient uptake, altered metabolic flux, and stress-induced genome instability. O-GlcNAcylation is an essential post-translational modification mediated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which act in a nutrient- and stress-responsive manner. The precise role of O-GlcNAc in adult stem cells and the relationship between O-GlcNAc and the DNA damage response (DDR) is poorly understood. Here, we show that hyper-O-GlcNacylation leads to elevated insulin signaling, hyperproliferation, and DDR activation that mimic the glucose- and oxidative-stress-induced response. We discover a feedback mechanism involving key downstream effectors of DDR, ATM, ATR, and CHK1/2 that regulates OGT stability to promote O-GlcNAcylation and elevate DDR. This O-GlcNAc-dependent regulatory pathway is critical for maintaining gut homeostasis in Drosophila and the DDR in mouse embryonic stem cells (ESCs) and mouse embryonic fibroblasts (MEFs). Our findings reveal a conserved mechanistic link among O-GlcNAc cycling, stem cell self-renewal, and DDR with profound implications for stem-cell-derived diseases including cancer.

Systematic screen of chemotherapeutics in Drosophila stem cell tumors

Here we report the development of an in vivo system to study the interaction of stem cells with drugs using a tumor model in the adult Drosophila intestine. Strikingly, we find that some Food and Drug Administration-approved chemotherapeutics that can inhibit the growth of Drosophila tumor stem cells can paradoxically promote the hyperproliferation of their wild-type counterparts. These results reveal an unanticipated side effect on stem cells that may contribute to tumor recurrence. We propose that the same side effect may occur in humans based on our finding that it is driven in Drosophila by the evolutionarily conserved Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway. An immediate implication of our findings is that supplementing traditional chemotherapeutics with anti-inflammatories may reduce tumor recurrence.