Roles for sphingolipid biosynthesis in mediation of specific programs of the heat stress response determined through gene expression profiling

Previous studies have demonstrated roles for de novo production of sphingolipids in Saccharomyces cerevisiae in the regulation of the transient cell cycle arrest and nutrient permease degradation associated with the heat stress response, suggesting multiple functions for yeast sphingolipids in this response. We, therefore, sought to determine the generalized involvement of sphingolipids in the heat stress response by using microarray hybridization of RNA isolated from heat-stressed cultures of the mutant strain lcb1-100, which is unable to produce sphingolipids in response to heat. Approximately 70 genes showed differential regulation during the first 15 min of heat stress in the lcb1-100 strain compared with the wild type strain, indicating a requirement for de novo sphingolipid biosynthesis for proper regulation of these genes during heat stress. Grouping these genes into functional categories revealed several pathways, including some in which sphingolipids were previously suspected to play a role, such as stress response pathways and cell cycle regulation. Hierarchical clustering analysis revealed sphingolipid involvement in regulation of tRNA synthesis and metabolic genes and transporters. Additionally, the microarray results demonstrated novel sphingolipid involvement in transcriptional regulation of pathways of translation and cell wall organization and biogenesis. Our results demonstrate a broad-reaching effect of sphingolipids in the yeast heat stress response and suggest that the mechanism of sphingolipid involvement in several cellular pathways occurs via sphingolipid-mediated regulation of message levels.