P‐body Formation Increases Upon Exposure to Heat Shock Conditions

Global translational repression of mRNA is an important response to physiological stress. Under physiological stress, mRNA in the cell becomes unbound from ribosomes, and localizes to P‐bodies. P‐bodies are distinct sites in the cell containing non‐translating mRNA, proteins involved in translational repression as well as mRNA degradation enzymes. Under physiologically favorable conditions, P‐bodies are small in size, as most mRNA in the cell is actively translated. However, under physiological stress, P‐bodies become large, due to the fact that most mRNA within the cell becomes translationally repressed. This phenomenon has been observed after exposing the budding yeast, S. cerevisiae to a number of different physiological stresses, including glucose deprivation. In this work, we determined that exposure to heat shock also resulted in increased P‐body formation, indicative of global translational repression under physiological stress. Exposing yeast to heat shock conditions (42 C) resulted in increased formation of P‐bodies, as compared to control (30 C). This effect was rapid, as it occurred within 5 minutes. The increased P‐body formation could also be seen with a less severe heat treatment (33 C or 37 C), provided that exposure lasted for at least 15 min. Additionally, we found that proteins involved in translational repression also localize to P‐bodies upon exposure to heat shock conditions.