6th Annual Judith Ramaley Celebration of Research and Creative Scholarship
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Poster #84 Dynamics of Stress Granule Formation in Response to Physiological Stress in Saccharomyces cerevisiae Jacqueline Peterson, Christopher Bullard, Katelin Albers, Kylie Oliverius Faculty Mentor: Scott Segal An important response to physiological stress, such as glucose deprivation, is translational repression of mRNA. Under physiological stress, in most cases seen, most mRNA in the cell become unbound by ribosomes and is translationally repressed. These mRNA do not remain free in the cytoplasm, but instead localize to one of two RNA-based cytoplasmic structures: P-bodies or stress granules. Both structures require translationally repressed mRNA for their assembly and contain a number of RNA binding proteins. Whereas, P-bodies contain RNA degradation enzymes, and stress granules contain translation initiation factors. These differences suggest that P-bodies function is to degrade RNA and stress granules store mRNA that is poised for translation once the stress is removed. Significant work showed that under glucose deprivation (0% glucose) translation is almost non-existent and mRNA is subsequently localized mainly to stress granules. However, the physiological dynamics of this relationship are yet to be understood. In this study, we took yeast and suspended them in media containing various glucose concentrations from 0%-2% and examined the dynamics of P-body and stress granule formation. Initially, we examined the localization of Dcp2p, which is one subunit of the mRNA decapping enzyme and localizes to both P-bodies and stress granules. Upon following Dcp2p, we found minimal localization in RNA-based cytoplasmic structures in cells suspended in media containing 2% glucose. Interestingly, as we reduced the amount of glucose in the media, the amount of Dcp2p localization increased, suggesting an increased amount of translational repression. These RNA-based cytoplasmic structures could either be P-bodies or stress granules, Given that Dcp2p localizes to both. To further understand the dynamics of P-body and stress granule formation, we also followed the localization of the stress granule specific proteins Pub1p, Ngr1p, and the translational initiation factors eIF4G/4E. Interestingly, eIF4E, eIF4G, and Pub1p showed only minimal localization to stress granules in cells suspended in 0.5% glucose and significant localization at 0% glucose. However, Ngr1p showed only minimal stress granule localization, even in cells suspended in 0% glucose. These observations are providing new insight into how stress granules are assembled during stress and they suggest that stress granule formation correlates with general translational repression. |
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