Uip4 governs nuclear shape by modulating the Saccharomyces cerevisiae lipidome

Cell survival under nutrient stress requires coordinated changes in metabolism and organelle function, yet the molecular mechanisms governing these adaptations remain poorly understood. In budding yeast, the protein Uip4 regulates nuclear morphology during the stationary phase, but its regulation and broader cellular roles are unknown. Here, we investigated how Uip4 expression is controlled and its effects on cellular homeostasis. We found that Uip4 expression is regulated by the transcription factor Msn2, downstream of Sch9 signalling, and responds to nutrient availability and energy state. Cells lacking Uip4 show poor stationary phase survival, dysregulated lipid profiles and aberrant organelle morphology. These defects are rescued by overexpressing the lipin Pah1, indicating that Uip4 functions in lipid homeostasis. Our findings reveal that such mechanisms linking nutrient signalling to lipid metabolism and organelle architecture are conserved, with implications for understanding cellular stress responses from yeast to humans.