Belmont University Research Symposium (BURS)

Publication Date

Spring 2023


Sciences and Mathematics, College of


Biology, Department of

BURS Faculty Advisor

Rebecca Adams

Presentation Type

Poster Presentation


Eukaryotic cells like Saccharomyces cerevisiae facilitate mRNA export via a pathway of protein interactions that allow mature mRNA to leave the nucleus in order to be translated into proteins in the cytoplasm. Under stressful conditions like heat-shock (42°C), S. cerevisiae selectively exports mRNA: most mRNA is retained in the nucleus while specific transcripts are permitted to export for their translation. Specifically, heat-shock-induced transcripts such as SSA4 are carried through the nuclear pore complex to exit into the cytoplasm by interacting with the protein Mex67. Mex67 is then removed by the action of proteins Dbp5 and Nup42. It is unknown how Mex67 is specifically recruited to interact with SSA4 transcripts under heat-shock conditions. I hypothesize there is an unknown adaptor protein that recruits Mex67 to selectively export SSA4 transcripts. To identify this putative adaptor, our original goal was to perform a genetic screen for those that permit selective export. Specifically, we anticipated that nup42Δ and mex67-5 mutants, which don’t allow for SSA4 export during heat shock would have reduced recovery in response to cell stress. We furthermore thought that this could be used as a phenotype to screen for rescuing genes. Thus, to test our initial assumptions, I tested wild-type, nup42Δ and mex67 mutants in a thermotolerance assay for recovery from stress. To our surprise, we observed that mutant cells had the ability to survive heat-shock conditions even better than wild-type cells under a variety of tested conditions. I subsequently hypothesized that mutant cells have an increased level of basal SSA4 production at 25°C. This hypothesis is currently being tested in wild-type and mutant strains with a GFP reporter that has SSA4 regulatory elements. We expect these results to shed light on conditions that lead to SSA4 expression.