Abstract
Heat Shock Factor 1 (HSF1) is a critical transcription factor for cellular proteostasis, but its role in sleep regulation remains unexplored. We demonstrate that nuclear HSF1 levels in the mouse brain fluctuate with sleep-wake cycles, increasing during extended wakefulness and decreasing during sleep. Using CUT&RUN and RNA-seq, we identified HSF1-regulated transcriptional changes involved in synaptic organization, expanding its known functions beyond traditional heat shock responses. Both systemic and brain-specific Hsf1 knockout mice exhibit altered sleep homeostasis, including increased delta power after sleep deprivation and upregulation of sleep-related genes. However, these knockouts struggle to maintain sleep due to disrupted synaptic organization. In Drosophila , knockout of HSF1's ortholog results in fragmented sleep patterns, suggesting a conserved role for HSF1 in sleep regulation across species. Our findings reveal a novel molecular mechanism underlying sleep regulation and offer potential therapeutic targets for sleep disturbances.